ITER Project: Improving Thermal Efficiency of hoRizontal ground heat exchangers - Di Sipio, Eloisa; Bertermann, David (ESOF CONFERENCE MSCA Satellite Event, 2016)

ITER Project: Improving Thermal Efficiency of hoRizontal ground heat exchangers - Di Sipio, Eloisa; Bertermann, David (Book of Abstracts, General Assembly of the Marie Curie Alumni Association, 2017)

ITER Project: Improving Thermal Efficiency of hoRizontal ground heat exchangers - Di Sipio, Eloisa; Bertermann, David (Book of Abstracts, General Assembly of the Marie Curie Alumni Association, 2016)

Jaws of a large belemnite and an ammonite from the Aalenian (Middle Jurassic) of Switzerland - Klug, Christian; Etter, Walter; Hoffmann, René; Fuchs, Dirk; de Baets, Kenneth (Swiss Journal of Palaeontology, 2020)
Although belemnite rostra can be quite abundant in Jurassic and Cretaceous strata, the record of belemnite jaws was limited to a few specimens from Germany and Russia. Here, we describe and figure three cephalopod jaws from the Middle Jurassic Opalinus Clay of northern Switzerland. Although flattened, the carbonaceous fossils display enough morphological information to rule out an ammonoid, nautiloid or octobrachian origin of the two larger jaws. Their similarities to belemnite jaws from Germany and Russia conforms with our interpretation of these specimens as belemnite jaws. Based on their rather large size, we tentatively assign these two jaws to the megateuthidid Acrocoelites conoideus. The third jaw is a rather small upper jaw of an ammonoid. Since Leioceras opalinum is by far the most common ammonite in this unit in northern Switzerland, we tentatively suggest that the upper jaw belongs to this species.
CRIS-Team Scopus Importer:2020-09-11
Keywords: Body size; Cephalopoda; Graphoceratidae; Megateuthididae; Mouthparts; Opalinus clay

Jurassic shift from abiotic to biotic control on marine ecological success - Eichenseer, Kilian; Balthasar, Uwe; Smart, Christopher W.; Stander, Julian; Haaga, Kristian A.; Kießling, Wolfgang (Nature Geoscience, 2019)
Environmental change and biotic interactions both govern the evolution of the biosphere, but the relative importance of these drivers over geological time remains largely unknown. Previous work suggests that, unlike environmental parameters, diversity dynamics differ profoundly between the Palaeozoic and post-Palaeozoic eras. Here we use the fossil record to test the hypothesis that the influence of ocean chemistry and climate on the ecological success of marine calcifiers decreased throughout the Phanerozoic eon. Marine calcifiers build skeletons of calcite or aragonite, and the precipitation of these calcium carbonate polymorphs is governed by the magnesium-to-calcium ratio and temperature in abiotic systems. We developed an environmental forcing model based on secular changes of ocean chemistry and temperature and assessed how well the model predicts the proliferation of skeletal taxa with respect to calcium carbonate polymorphs. Abiotic forcing governs the ecological success of aragonitic calcifiers from the Ordovician to the Middle Jurassic, but not thereafter. This regime shift coincides with the proliferation of calcareous plankton in the mid-Mesozoic. The deposition of biomineralizing plankton on the ocean floor buffers CO2 excursions and stabilizes Earth’s biochemical cycle, and thus mitigates the evolutionary impact of environmental change on the marine biota.
CRIS-Team Scopus Importer:2019-07-16

Kalk-Mergel-Wechselfolgen - Ein Blick hinter die Kulissen - Munnecke, Axel (Geowissenschaftliche Mitteilungen, 2016)
Keywords: Kalk-Mergel-Wechselfolgen; Kalk; Mergel; Diagenese; Kompaktion

Kalorimetrische und röntgenographische Untersuchungen zur Hydratation von Schnellzementen aus Portland- und Calciumaluminatzement - Götz-Neunhoeffer, Friedlinde; Neubauer, Jürgen (GDCh-Monographie Tagung Bauchemie, 2006)
UnivIS-Import:2015-04-02:Pub.2006.nat.dgeo.IGM.LM.kalori

Karoo Synrift-Sedimentation und ihre tektonische Kontrolle am entstehenden Kontinentalrand Namibias. - Stollhofen, Harald (Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 1999)
UnivIS-Import:2015-03-05:Pub.1999.nat.dgeo.IGM.LG.karoos

Karoo unconformities in NW Namibia and their tectonic implications. - Wanke, Ansgar; Stollhofen, Harald; Stanistreet, Ian G.; Lorenz, Volker (Communications - Geological Survey of Namibia, 2000)
The Karoo-Etendeka depositories in northwestern Namibia can be subdivided into (l) a Carboniferous-Permian, (2) a Triassic-Jurassic and (3) a Cretaceous megasequence, recording successive extensional periods, separated by time-stratigraphic gaps. Close to the present-day Atlantic coastline the Karoo Supergroup is only represented by the Permian succession in the Huab area. This is disconformably overlain by the Lower Cretaceous Etendeka Group. Further east, the Karoo succession becomes successively’ more complete, but correlation with the main Karoo Basin in South Africa and the Brazilian Paraná Basin indicates major gaps in the sedimentary record. The gaps can be attributed to the combined effects of the long-lived South Atlantic rift evolution and orogenic pulses derived from the Samfrau active margin.
UnivIS-Import:2015-03-09:Pub.2000.nat.dgeo.IGM.LG.karoou

Keeping to the set path enhanced storage stability for dry-mix mortars based on calcium aluminate - Estival, Jaques; Taquet, Pascal; Götz-Neunhoeffer, Friedlinde (European Coatings Journal, 2012)
Storage under high humidity can adversely affect the properties of dry mix mortars containing hydraulic binders. A new functionalised Calcium Aluminate Cement (CAC) has been developed with the aim of stabilising mortar reactivity during storage. Both setting kinetics and other properties such as shrinkage, porosity and linear size variations were found more robust over storage in humid conditions.
UnivIS-Import:2015-03-09:Pub.2012.nat.dgeo.IGM.LM.keepin

Keratose sponges in ancient carbonates – A problem of interpretation - Neuweiler, Fritz; Kershaw, Stephen; Boulvain, Frédéric; Matysik, Michał; Sendino, Consuelo; McMenamin, Mark; Munnecke, Axel (Sedimentology, 2022)
Reports of diverse vermiform and peloidal structures in Neoproterozoic to Mesozoic open marine to peritidal carbonates include cases interpreted to be keratose sponges. However, living keratose sponges have elaborate, highly elastic skeletons of spongin (a mesoscopic end-member of a hierarchical assemblage of collagenous structures) lacking spicules, thus have poor preservation potential in contrast to the more easily fossilized spicule-bearing sponges. Such interpreted fossil keratose sponges comprise diverse layered, network, amalgamated, granular and variegated microfabrics of narrow curved, branching, vesicular–cellular to irregular areas of calcite cement, thought to represent former spongin, embedded in microcrystalline to peloidal carbonate. Interpreted keratose sponges are presented in publications almost entirely in two-dimensional (thin section) studies, usually displayed normal to bedding, lacking mesoscopic three-dimensional views in support of a sponge body fossil. For these structures to be keratose sponges critically requires conversion of the spongin skeleton into the calcite cement component, under shallow-burial conditions and this must have occurred prior to compaction. However, there is no robust petrographic–geochemical evidence that the fine-grained carbonate component originated from sponge mummification (automicritic body fossils via calcification of structural tissue components) because in the majority of cases the fine-grained component is homogenous and thus likely to be deposited sediment. Thus, despite numerous studies, verification of fossil keratose sponges is lacking. Although some may be sponges, all can be otherwise explained. Alternatives include: (i) meiofaunal activity; (ii) layered microbial (spongiostromate) accretion; (iii) sedimentary peloidal to clotted micrites; (iv) fluid escape and capture resulting in bird's eye to vuggy porosities; and (v) moulds of siliceous sponge spicules. Uncertainty of keratose sponge identification is fundamental and far-reaching for understanding: (i) microfacies and diagenesis where they occur; (ii) fossil assemblages; and (iii) wider aspects of origins of animal clades, sponge ecology, evolution and the systemic recovery from mass extinctions. Thus, alternative explanations must be considered.
CRIS-Team Scopus Importer:2022-12-23
Keywords: Automicrite; metazoan evolution; microfacies analysis; mummification; sponge taphonomy

Kinematics and mechanism of motion of the profound Cuolm da Vi instability at Graubünden, Switzerland Kinematik und Bewegungsmechanismus der Tiefgründigen Instabilität Cuolm da Vi (Graubünden, Schweiz) - Moser, Michael; et al. (Bulletin fuer Angewandte Geologie, 2006)

Kinetic Interface Sensitive Tracers: Experimental Validation in a Two-Phase Flow Column Experiment. A Proof of Concept - Tatomir, Alexandru; De Vriendt, K.; Zhou, D.; Gao, H.; Duschl, Florian; Sun, F.; Licha, T.; Sauter, Martin (Water Resources Research, 2018)
Keywords: column experiment; fluid-fluid interfacial area; transient flow; kinetic interface sensitive tracers; multiphase flow

Kinetics, mechanism and density functional theory calculations on base hydrolysis of α-amino acid esters catalyzed by [Pd(AEMP)(H2O)2]2+ (AEMP = 2-(2-aminoethyl)-1-methylpyrrolidine) - Shoukry, Mohamed M.; Shehata, Mohamed R.; Ragab, Mona S.; Ćorćić, Dušan; Puchta, Ralph; van Eldik, Rudi (Reaction Kinetics Mechanisms and Catalysis, 2020)
Abstract: Pd(AEMP)Cl2 (AEMP = 2-(2-aminoethyl)-1-methylpyrrolidine) was synthesized and characterized by spectral and thermal measurements.[Pd(AEMP)(H2O)2]2+ reacts with amino acid esters (L) to form mixed ligand [Pd(AEMP)L]2+ complexes. The kinetics of the base hydrolysis of [Pd(AEMP)L]2+ was studied by a pH-stat technique and the corresponding rate constants are reported. The coordinated glycine methyl ester is hydrolyzed efficiently, whereas the coordinated methionine- and histidine- methyl esters undergo hydrolysis with a much lower catalytic activity. The catalytic effect is controlled by the mode of coordination of the ester to the Pd(II) complex. Possible mechanisms for these reactions are considered. Activation parameters were determined experimentally for the hydrolysis of the coordinated glycine methyl ester. DFT calculations (B3LYP/def2svp) were applied to gain further insight into the possible mechanism of the base hydrolysis of the amino acid esters. The calculations are discussed in reference to the reported experimental data. Graphic abstract: [Figure not available: see fulltext.].
CRIS-Team Scopus Importer:2020-02-25
Keywords: 2-(2-Aminoethyl)-1-methylpyrrolidine; Amino acid ester; Catalytic hydrolysis; DFT calculations; Pd(II); pH-stat technique

Klimawandel und Veränderung der Biodiversität in der Erdgeschichte. - Königshof, Peter; Suttner, Thomas J; Kießling, Wolfgang (Natur, Forschung, Museum, 2012)
Keywords: Climate change; Biodiversity; Evolution; Extinction

Krisen als Chance: Lernen aus der Evolution - Kießling, Wolfgang (Darwin meets Business, 2010)
Keywords: Extinctions; Biodiversity; Applied Paleobiology

KTB Oberpfalz - einige Ergebnisse der geowissenschaftlichen Bearbeitung - de Wall, Helga; et al. (Zentralblatt für Geologie und Paläontologie, Teil I, Geologie, 1994)
UnivIS-Import:2015-03-05:Pub.1994.nat.dgeo.IGM.c3tekt.ktbobe

Laboratory device to analyse the impact of soil properties on electrical and thermal conductivity - Bertermann, David; Schwarz, Hans (International Agrophysics, 2017)
Keywords: electrical resistivity; soil properties; thermal conductivity; Wenner array; geology; erneuerbare Energiequelle; Bodenkunde; geophysic

Laboratory Measurements of Gravel Thermal Conductivity: An Update Methodological Approach - Dalla Santa, Giorgia; Peron, Fabio; Galgaro, Antonio; Cultrera, Matteo; Bertermann, David; Müller, Johannes; Bernardi, Adriana (Energy Procedia, 2017)

Laboratory measurements of gravel thermal properties. A methodology proposal - Cultrera, Matteo; Peron, Fabio; Bison, Paolo; Dalla Santa, Giorgia; Bertermann, David; Müller, Johannes; Bernardi, Adriana; Galgaro, Antonio (Geophysical Research Abstracts Vol. 19, 2017)

Laborversuche zur Herstellung von Alinitzementen aus Müllverbrennungsrückständen - Oberste-Padtberg, Rüdiger; Neubauer, Jürgen (Wasser, Luft und Boden, 1989)
UnivIS-Import:2015-03-05:Pub.1989.nat.dgeo.IGM.LM.laborv

Lahar inundated, modified, and preserved 1.88 Ma early hominin (OH24 and OH56) Olduvai DK site - Stanistreet, Ian G.; Stollhofen, Harald; Njau, Jackson K.; Farrugia, Paul; Pante, Michael C.; Masao, Fidelis T.; Albert, Rosa Maria; Bamford, Marion (Journal of Human Evolution, 2018)
Archaeological excavations at the DK site in the eastern Olduvai Basin, Tanzania, age-bracketed between 1.88 Ma (Bed I Basalt) and 1.85 Ma (Tuff IB), record the oldest lahar inundation, modification, and preservation of a hominin “occupation” site yet identified. Our landscape approach reconstructs environments and processes at high resolution to explain the distribution and final preservation of archaeological materials at the DK site, where an early hominin (likely Homo habilis) assemblage of stone tools and bones, found close to hominin specimens OH24 and OH56, developed on an uneven heterogeneous surface that was rapidly inundated by a lahar and buried to a depth of 0.4-1.2 m (originally 1.0-2.4 m pre-compaction). The incoming intermediate to high viscosity mudflow selectively modified the original accumulation of “occupation debris,” so that it is no longer confined to the original surface. A dispersive debris “halo” was identified within the lahar deposit: debris is densest immediately above the site, but tails off until not present >150 m laterally. Voorhies indices and metrics derived from limb bones are used to define this dispersive halo spatially and might indicate a possible second assemblage to the east that is now eroded away. Based upon our new data and prior descriptions, two possibilities for the OH24 skull are suggested: it was either entrained by the mudflow from the DK surface and floated due to lower density toward its top, or it was deposited upon the solid top surface after its consolidation. Matrix adhering to material found in association with the parietals indicates that OH56 at least was relocated by the mudflow.
Keywords: Lahar mudflow; OH24; OH56; Olduvai Gorge Bed I; Pleistocene; Voorhies index

Lake conditions and detrital sources of Paleolake Olduvai, Tanzania, reconstructed using X-ray Diffraction analysis of cores - McHenry, Lindsay J.; Kodikara, Gayantha R.L.; Stanistreet, Ian G.; Stollhofen, Harald; Njau, Jackson K.; Schick, Kathy; Toth, Nicholas (Palaeogeography, Palaeoclimatology, Palaeoecology, 2020)
The Olduvai Basin of northern Tanzania contains well-known Pleistocene archaeological sites in a palaeoenvironmental setting of interfingering paleolake and volcanic fan deposits. This study documents the mineral assemblages, as determined qualitatively through bulk X-ray Diffraction (XRD) of systematically sampled lacustrine sediments from Olduvai Gorge Coring Project (OGCP) Cores 1A, 2A, and 3A, from about 45 m below the surface (mbs) to the base of all three cores. This interval includes fluvio-lacustrine sediments below and between two major progradations of Ngorongoro volcanic deposits recorded in Core 2A, and all of Olduvai Bed I and the lower part of Bed II in all three cores. Changes in mineral assemblage track changes in sediment sources and lake water chemistry. Abundant quartz indicates sediment sources derived from eroded Precambrian basement quartzite and gneiss exposures to the west, southwest, and north. In contrast, the presence of anorthoclase feldspar (sometimes associated with minor augite) indicates southerly and easterly sources, derived from the then active volcanoes (Ngorongoro, Olmoti) of the Ngorongoro Volcanic Highlands. The presence and relative abundance of specific zeolites provides information about Paleolake Olduvai's pH conditions and the relative activities of various dissolved cations (K+, Na+, Ca2+, Si) at the time of alteration, and the presence and abundance of authigenic K-feldspar indicates post-depositional exposure to saline-alkaline pore fluids. The mineral assemblages recorded in the cores reveal both large-scale trends in sediment composition over time, and smaller-scale changes related to fluctuating lake levels. In the lacustrine deposits near the base of Core 2A (interval NSF-1), analcime dominates the zeolite assemblage (with minor clinoptilolite), whereas carbonates and authigenic K-feldspar are rare. This interval is followed by more lacustrine deposits in which phillipsite and chabazite are the dominant zeolites (and analcime is absent). Lacustrine deposition was interrupted by the first of two pulses of coarse Ngorongoro volcaniclastic material (NVF-1). In the lacustrine interval between the two Ngorongoro volcanic pulses (NSF-2, recovered only in Core 2A), chabazite and erionite dominate the zeolite assemblage, carbonate and K-feldspar are rare, and analcime is absent, indicating less extreme saline-alkaline conditions and greater Ca2+ availability for zeolite formation. Volcanic glass is preserved, along with abundant zeolites, including phillipsite, chabazite, and erionite, in altered volcanic materials from the upper Ngorongoro volcanic pulse (NVF-2). In the lacustrine deposits of Lower Bed I (below the Bed I basalts but above NVF-2, only recovered in Core 3A), zeolites and K-feldspar are rare to absent, consistent with wetter conditions and fresher lake waters. Carbonates are ubiquitous throughout the lacustrine intervals of Beds I and II. In lacustrine deposits above the Bed I basalts (in Upper Bed I), phillipsite is the dominant zeolite, and quartz is rare. Alternating intervals of zeolite and K-feldspar-rich and poor sediments suggest variations between wetter and drier conditions throughout Upper Bed I and into Lower Bed II. Aragonite and associated dolomite in Bed I during the deposition of a claystone Mg-anomaly points to high magnesium concentrations and elevated Mg2+/Ca2+ ratios during that time. A major change between lowermost Bed II and overlying Bed II lacustrine sediments includes an abrupt increase in quartz coupled with an increase in the zeolite analcime, consistent with the onset of more saline-alkaline conditions, contemporaneous with overall drier conditions.
CRIS-Team Scopus Importer:2020-07-10
Keywords: East Africa; Mineral assemblage; Pleistocene; Saline-alkaline; Zeolites

Laminated carbonate deposits in Roman aqueducts: origin, processes and implications. - Suermelihindi, Guel; Passchier, Cees W.; Spoetl, Christoph; Kessener, Paul; Bestmann, Michel; Jacob, Dorrit E.; Baykan, Orhan N. (Sedimentology, 2013)
Carbonate deposits in Roman aqueducts of Patara and Aspendos (southern Turkey) were studied to analyse the nature of their regular layering. Optical microscopy and electron-backscattered diffraction results show an alternation of dense, coarsely crystalline, translucent laminae composed of bundles and fans of elongate calcite crystals with their c-axes parallel to the long axis, and porous, fine-grained laminae with crystals at near-random orientation. The δ18O and δ13C data show a strong cyclicity and anti-correlation, whereby high and low δ18O values correspond to dense columnar and porous fine-grained laminae, respectively. Geochemical analyses show similar cyclic changes in carbonate composition. Electron microprobe and laser ablation inductively coupled mass spectrometry analyses show that porous fine-grained laminae are enriched in elements associated with detrital material (Fe, Mg, K, Al and Si), whereas the dense columnar laminae are nearly pure calcite. The gradient in major and trace-element distribution, regular changes in crystal type and in oxygen and carbon-isotope composition from porous fine-grained to dense columnar laminae reflect changes in water chemistry, discharge, temperature and biological activity. Because of the strong bimodal cyclicity of the Mediterranean climate in southern Turkey, the observed laminae can be attributed to calcite deposition during the dry (porous fine-grained) and wet season (dense columnar), respectively. This observation implies that, with proper geochemical and microstructural control, lamination in carbonate deposits in Roman aqueducts can be used for relative dating of aqueduct construction and maintenance and to obtain data on external factors that influenced the aqueducts, such as palaeoclimate and natural hazards. Carbonate deposits in Roman aqueducts show properties of both flowstone speleothems and riverine fresh water tufa. As many aqueducts of nearly identical channel geometry are present in different climate zones and with different source water characteristics, they can be used as natural experiment setups to test and improve existing models of how laminated fresh water carbonates record climate on time scales ranging from seasonal to millennial. © 2012 The Authors. Journal compilation © 2012 International Association of Sedimentologists.
UnivIS-Import:2015-03-09:Pub.2013.nat.dgeo.IGM.c3tekt.lamina
Keywords: Calcareous sinter; Carbonate deposits; Layering; Roman aqueduct; Stable isotopes; Trace elements; Turkey

Landscape Distribution of Oldowan Stone Artifact Assemblages across the Fault Compartments of the Eastern Olduvai Lake Basin during Early Lowermost Bed II Times - Blumenschine, Robert J.; Masao, Fidelis T.; Stollhofen, Harald; Stanistreet, Ian G.; Bamford, Marion K.; Albert, Rosa M.; Njau, Jackson K.; Prassack, Kari A. (Journal of Human Evolution, 2012)
The density and composition of Oldowan stone artifact assemblages deposited during the first ca. 20,000 years of lowermost Bed II times show a recurrent pattern of variation across recognized synsedimentary faults that compartmentalized landscapes of the eastern Olduvai Lake Basin. When active, the faults created minor topographic relief. The upthrown fault footwalls accumulated assemblages with relatively high densities of artifacts, including types retaining potential usefulness, particularly volcanic flaked pieces, manuports, pounded pieces, and split cobbles. Values for these assemblage characteristics decline toward the lower-lying hangingwall of the fault compartments, accompanied by an increase in the proportionate weight of artifact assemblages comprising quartzite, particularly flaking shatter and potentially useful detached pieces. Values reverse once again at faults, either on the downthrown, hangingwall side or on the upthrown side. The patterns are stronger for the volcanic components of the artifact assemblages than for the quartzite components, reflecting the additional influence of distance from the local source on quartzite assemblage characteristics reported previously. The landscape distributions of artifact assemblages are consistent with a landscape-fault model in which minor fault-induced topographic relief at times created a mosaic of vegetation environments repeated within each of the three fault compartments of the lake margin and distal alluvial fan. The fault-compartmentalized landscape model is currently supported only by sediment thickness and facies changes across synsedimentary faults, but it provides predictions for spatial variation in the cover abundance of trees, freshwater reservoirs and associated distributions of resources and hazards associated with stone artifact use and discard that can be tested if sample sizes of key paleoenvironmental indicators are increased. © 2011 Elsevier Ltd.
UnivIS-Import:2015-03-09:Pub.2012.nat.dgeo.IGM.LG.landsc
Keywords: Hominin land use; Landscape paleoanthropology; Olduvai Gorge

Landslide reliability analysis based on transfer coefficient method: A case study from Three Gorges Reservoir - Bi, Renneng; Ehret, Dominik; Xiang, Wei; Schleier, Markus; Jiang, Jiwei; Rohn, Joachim (Journal of Earth Science, 2012)
Keywords: Landslide stability reliability; Monte Carlo method; Three Gorges Reservoir; Transfer coefficient method; Water level fluctuation

Landslides at the Qingjiang River in the downstream area of the Shui Bu Ya dam site, China - Rohn, Joachim; et al. (Journal of China University of Geosciences, 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dgeo.IGM.profes_3.landsl

Landslide susceptibility analysis based on ArcGIS and Artificial Neural Network for a large catchment in Three Gorges region, China - Bi, Renneng; Schleier, Markus; Ehret, Dominik; Xiang, Wei; Rohn, Joachim (Environmental Earth Sciences, 2014)
Keywords: ArcGIS; Artificial Neural Network; Landslide causative factors; Landslide susceptibility; Three Gorges Reservoir

Landsnail shell δ18O records in periglacial loess deposits: New transfer functions for precipitation δ18O and temperature in dry continental settings - Richter, Isabel; Walther, F.; Meng, Stefan; Reip, H.; Schneider, Michael; Joachimski, Michael; Horsák, M. (Quaternary Science Reviews, 2025)
Our knowledge about climate change is based on the availability of climate data from both the present and the past. Accurate reference data are essential for improving Earth System Models, which help us to analyse and predict climatic developments with greater accuracy. In this context, subfossil landsnail shells and their stable isotope compositions are valuable climatic proxies. They are used to derive past precipitation isotopy (δ18Oprecipitation), which represents an important reference parametre for climate reconstruction. However, the interpretability of δ18O shell isotopes in periglacial loess deposits has been questioned, due to the complexity of the hydrological cycle in these environments. Calibration studies investigating the relationship between δ18Oshell and δ18Oprecipitation under continental dry conditions are still lacking. To close this gap, we collected two genera commonly found in European loess deposits (Vallonia and Pupilla) at modern dry periglacial sites in continental Inner Asia. Our results confirm a strong positive relationship between δ18Oshell and δ18Oprecipitation of the growing season period (adjR2 = 0.53, p ≪ 0.001). When only Vallonia samples were considered, the relationship was even stronger (adjR2 = 0.60, p ≪ 0.001) indicating a genus-specific response. Our results support the suitability of landsnail shells as proxy for δ18Oprecipitation in dry continental settings. Furthermore, we provide an empirically derived transfer function to reconstruct δ18Oprecipitation from δ18Oshell for periglacial loess archives as well as a transfer function for temperature approximation. This study demonstrates the high potential of shell isotopes as a quantitative climate proxy also for dry continental environments. However, future studies should focus on the resolution of shell isotope data as well as the synchroneity of calibration data, to increase data precisio
CRIS-Team Scopus Importer:2025-05-30
Keywords: Landsnail; Quantitative proxy; Climate reconstruction; Paleoclimate; Isotope

Large-scale geothermal collector systems for 5th generation district heating and cooling networks - Zeh, Robin; Ohlsen, Björn; Philipp, David; Bertermann, David; Kotz, Tim; Jocić, Nikola; Stockinger, Volker (Sustainability, 2021)
Low temperature district heating and cooling networks (5GDHC) in combination with very shallow geothermal energy potentials enable the complete renewable heating and cooling supply of settlements up to entire city districts. With the help of 5GDHC, heating and cooling can be distributed at a low temperature level with almost no distribution losses and made useable to consumers via decentralized heat pumps (HP). Numerous renewable heat sources, from wastewater heat exchangers and low-temperature industrial waste heat to borehole heat exchangers and large-scale geothermal collector systems (LSC), can be used for these networks. The use of large-scale geothermal collector systems also offers the opportunity to shift heating and cooling loads seasonally, contributing to flexibility in the heating network. In addition, the soil can be cooled below freezing point due to the strong regeneration caused by the solar irradiation. Multilayer geothermal collector systems can be used to deliberately generate excessive cooling of individual areas in order to provide cooling energy for residential buildings, office complexes or industrial applications. Planning these systems requires expertise and understanding regarding the interaction of these technologies in the overall system. This paper provides a summary of experience in planning 5GDHC with large-scale geothermal collector systems as well as other renewable heat sources.
CRIS-Team Scopus Importer:2021-06-25
Keywords: 5GDHC; Large-scale geothermal collector; Very shallow geothermal potential; VSGP

Large scale lateral spreading and related mass movements in the Northern Calcareous Alps - Rohn, Joachim; et al. (Bulletin of Engineering Geology and the Environment, 2004)
Lateral spreading is an important geotechnical phenomenon in the Hallstatt zones of the Northern Calcareous Alps where rigid limestones overlie marls and salt clays. Following the last glaciation, mass movements have developed with a general spreading of limestone blocks resulting in a complicated "jigsaw puzzle" of rock. Two typical examples from Mt. Sandling and Mt. Raschberg in the Northern Calcareous Alps of Austria are discussed. © Springer-Verlag 2004.
UnivIS-Import:2015-03-09:Pub.2004.nat.dgeo.IGM.profes_3.larges
Keywords: Calcareous alps; Hallstatt zones; Lateral spreading; Mt. Raschberg; Mt. Sandling; Undrained loading

Large scale mass movements triggered by the Kashmir earthquake 2005, Pakistan - Basharat, Muhammad; Baig, Mirza Shahid; Khan, Muhammad Rustam; Schleier, Markus; Rohn, Joachim (Journal of Mountain Science, 2014)
Keywords: Coseismic mass movements kHimalayas kMuzaffarabad Fault kGeological and tectonic factors kEarthquake kRock fall

Large-scale porphyry-type mineralization in the Central Asian metallogenic domain: A review - Gao, Jun; Klemd, Reiner; Zhu, Mingtian; Wang, Xin-Shui; Li, Jilei; Wan, Bo; Xiao, Wenjiao; Zeng, Qingdong; Shen, Ping; Sun, Jinggui; Qin, Kezhang; Campos, Eduardo (Journal of Asian Earth Sciences, 2017)
A series of porphyry-type Cu-(Mo)-(Au) deposits including some giant world-class deposits such as Kounrad, Aktogai, Kal’makyr, Oyu Tolgoi and Chalukou occur in the Central Asian metallogenic domain (CAMD). The outline of the CAMD almost overlaps with that of the Central Asian orogenic belt (CAOB), which is located between the East Europe, Siberia, Tarim and North China cratons. The CAMD comprises sparsely exposed tectonic slices of Precambrian high-grade metamorphic basement rocks that are sandwiched between Phanerozoic accretionary complexes and arc rocks. According to geological, metallogenic, geochronological and tectonic setting characteristics, the CAMD comprises three metallogenic provinces: (1) the Kazakhstan Cu-Au-Mo, (2) the Mongolia Cu-Au and (3) the Northeast China Mo-Cu metallogenic provinces. Early Paleozoic (∼490 to 440 Ma) and Late Paleozoic (∼330 to 295 Ma) large scale porphyry-type mineralization in the Kazakhstan metallogenic province is intimately associated with the evolution of the Central Tianshan–Yili–Northern Tianshan–Kokchetav–Chingiz Paleozoic arc system which was terminated by the late Permian closure of the western segment of the Paleo-Asian Ocean. In contrast, the ∼370 Ma and ∼240 Ma porphyry-type mineralization of the Mongolia metallogenic province is related to the Tuva–Mongolia arc collage system that was formed during the evolution of the Paleo-Asian Ocean in the Paleozoic and the Mongol–Okhotsk Ocean in the early Mesozoic. Furthermore, the Northeast China metallogenic province was affected by three distinct geodynamic processes that were associated with the Paleo-Asian, Mongol–Okhotsk and Paleo-Pacific Oceans during the Paleozoic (>250 Ma), the early Mesozoic (>200 Ma) and the late Mesozoic (200–90 Ma), respectively. Except for the Early Paleozoic Cu mineralization at Duobaoshan (∼480 Ma) and Bainaimiao (440 Ma), the porphyry-type mineralization of this metallogenic province is predominantly characterized by widespread Mesozoic Mo mineralization. In general, porphyry-type deposits of the CAMD have geological, structural, metallogenic, alteration and fluid characteristics, which are consistent either with those related to the oceanic subductional arc settings of the Circum-Pacific metallogenic domain or with those of the continental collisional environment in the Tethyan metallogenic domain. The involvement of highly oxidized intermediate to felsic magmas is fundamental for the formation of porphyry deposits. Even though the prevalent MASH and slab melting models can be employed to interpret the genesis of some porphyry Cu deposits in the CAMD, a here newly suggested model, which is based on ‘pre-enriched mafic lower crust and the subduction of a relictic mid-oceanic ridge’, is thought to explain the large scale copper mineralization in the Balkhash–West Junggar metallogenic belt of the Kazakhstan metallogenic province. Nevertheless, most of the porphyritic suites associated with the Mo deposits in the Northeast China metallogenic province have relatively depleted mantle-like neodymium and hafnium isotopic compositions, suggesting that the ore-forming granitic magma may have predominantly been derived from juvenile lower crust. Upwelling of asthenosphere may have triggered the melting of the lower crust during post-collisional extension subsequent to the closure of the Paleo-Asian Ocean in the Triassic, the subduction of the Paleo-Pacific ocean in the Jurassic and the thinning of the lithosphere caused by rollback of the Paleo-Pacific plate in the Cretaceous. Ancient crustal components were only locally found to have been involved in the magma source of several medium-large Mo deposits.
Keywords: Porphyry-type deposits; Porphyry-type mineralization; Central Asian metallogenic domain; Central Asian Orogenic Belt

Laser Ablation ICP-MS - Klemd, Reiner; Brätz, Helene (Process Mineralogy – JKMRC Monograph Series in Mining and Mineral Processing: No. 6, 2017)

Last Glacial deep water corals from the Red Sea - Taviani, Marco; López Correa, Matthias; Zibrowius, Helmut; Montagna, Paolo; McCulloch, Malcolm; Ligi, Marco (Bulletin of Marine Science, 2007)
The present Red Sea deep-sea benthos appears impoverished with respect to the adjacent Indian mother-ocean as a result of severe filters, represented by an extremely shallow sill, high salinity, and high temperature. Today, the Red Sea basin hosts a still poorly known deep-water coral fauna of Indian Ocean affinity. During the Pleistocene, conditions were at times suitable as proven by the findings of last glacial corals (Javania insignis Duncan, 1876, and Trochocyathus virgatus sensu Marenzeller, 1907 (not Alcock, 1902), and, possibly, Guynia annulata Duncan, 1872) from seamounts in the north-central part of the basin. A subfossil J. insignis from the Coral Sea peak has been U-series-dated at 26,590 ± 120 yrs. This represents the first documentation regarding the presence of deep-water corals in the Red Sea during the late Pleistocene and predates the postulated basin-wide extinction of normal marine biota that took place at the Last Glacial Maximum. © 2007 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.
UnivIS-Import:2015-03-09:Pub.2007.nat.dgeo.IGM.LP.lastgl

Late Carboniferous high-pressure metamorphism of the Kassan Metamorphic Complex (Kyrgyz Tianshan) and assembly of the SW Central Asian Orogenic Belt - Mühlberg, Moritz; Hegner, E.; Klemd, Reiner; Pfänder, J. A.; Kaliwoda, Melanie; Biske, Y. S. (Lithos, 2016)
High-pressure (HP) metamorphism of the Kassan Metamorphic Complex (KMC) in the western Kyrgyz Tianshan has been related to either late Ordovician or late Carboniferous-Permian subduction processes. We report Sm-Nd ages for retrogressed eclogite samples and 40Ar/39Ar cooling ages for enclosing garnet-muscovite samples from the KMC as new age constraints on HP metamorphism and rock exhumation. These data will be used for an upgraded paleogeographic model for late Paleozoic crustal consolidation in the southwestern Central Asian Orogenic Belt. The retrogressed eclogite samples have transitional alkaline to tholeiitic affinity and trace-elementpatterns consistent with protoliths derived from garnet-bearing mantle sources at rifting plate margins. Geothermobarometric data for a retrogressed eclogite sample indicate peak-metamorphic conditions of 540 ± 30 °C at 1.6 ± 0.1 GPa. Samples from different lithotectonic units of the KMC provide coherent Sm-Nd garnet-whole rock ages of 317 ± 4 Ma and 316 ± 3 Ma (2σ). The prograde major-element zoning in the mm-sized garnets in combination with the moderate peak-metamorphic temperature, support our interpretation of the Sm-Nd garnet ages as unambiguous evidence for late Carboniferous HP metamorphism. The Sm-Nd garnet growth ages overlap within-error with the 40Ar/39Ar mica cooling ages of 314 ± 2 Ma and 313 ± 2 Ma (2σ) indicating rapid uplift of the subduction complex after peak metamorphism. The ca. 317-313 Ma HP-exhumation event of the KMC is contemporaneous with those of the Atbashi and Akeyazi (ca. 500 km east in NW China) HP complexes and implies similar collision histories at the South Tianshan Suture to the east and west of the Talas-Fergana Fault (TFF). The exhumation of the KMC and Atbashi HP complexes overlaps with the initiation of the TFF (Rolland et al., 2013) suggesting incipient separation of the Chatkal and Atbashi complexes during rock exhumation and early plate collision.<br
Keywords: Tianshan; eclogite; Sm-Nd garnet ages; 40Ar/39Ar mica ages; Talas-Fergana Fault; Central Asian Orogenic Belt

Late Carboniferous hydrocarbon-seep carbonates from the glaciomarine Dwyka Group, southern Namibia. - Himmler, Tobias; Freiwald, André; Stollhofen, Harald; Peckmann, Jörn (Palaeogeography, Palaeoclimatology, Palaeoecology, 2008)
Limestone deposits with columnar to lenticular geometry (max. 3.2 m in height and 1.5 m in diameter) occur within the uppermost part of the Ganigobis Shale Member, a marine mudstone unit capping the second deglaciation sequence of the glaciomarine Dwyka Group in southern Namibia. The limestones mainly consist of four authigenic carbonate phases (microspar, banded/botryoidal cement, yellow calcite, spheroidal calcite). Extremely negative δ13C values (as low as - 51‰ VPDB) indicate a hydrocarbon-derived origin of the carbonates with biogenic methane being the most likely carbon source. The limestones contain a low-diversity but high-abundance faunal assemblage of tubular fossils. These fossils closely resemble the tubes of modern and fossil seep-dwelling vestimentiferan tube worms in terms of size, shape, arrangement, and taphonomical patterns. © 2007 Elsevier B.V. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2008.nat.dgeo.IGM.LG.lateca
Keywords: Hydrocarbon seeps; Karoo; Methane; Pennsylvanian; Vestimentiferans

Late Carboniferous to Late Permian carbon isotope stratigraphy: A new record from post-Variscan carbonates from the Southern Alps (Austria and Italy) - Buggisch, Werner; Krainer, Karl; Schaffhauser, Maria; Joachimski, Michael; Korte, Christoph; Joachimski, Michael (Palaeogeography, Palaeoclimatology, Palaeoecology, 2015)
An integrated study of the litho-, bio-, and isotope stratigraphy of carbonates in the Southern Alps was undertaken in order to better constrain δ13C variations during the Late Carboniferous to Late Permian. The presented high resolution isotope curves are based on 1299 δ13Ccarb and 396 δ13Corg analyses. The carbon isotope record of diagenetically unaltered samples from the Carnic Alps (Austria) and Karavanke Mountains (Slovenia) shows generally high δ13C values, but Late Carboniferous and Early Permian successions are affected by a diagenetic alteration as consequence of glacio-eustatic sea level changes. Negative δ13C excursions are related to low-stand deposits and caused by diagenetic processes during subaerial exposure. The comparison with δ13C records from other parts of the world demonstrate that δ13C values are high in most unaltered samples, an overall negative trend during the Permian, as recently published, is not obvious and negative excursions related to changes in the carbon isotope composition of the global oceanic carbon pool cannot be confirmed, except for the Permian-Triassic boundary interval.
Keywords: Carbon isotopes; Carboniferous; Diagenesis; Permian

Late cretaceous magmatism in the Northern Lhasa subterrane, central Tibet: geodynamic implications - Sun, Miao; Chen, Wei; Klemd, Reiner; Tang, Ju-Xing; Ma, Xu-Dong; Liu, Qing-Ping (International Geology Review, 2022)
Compositional changes of successively emplaced magmatites can be used to infer changes in their petrogenetic evolution and geodynamic setting. The central-northern Lhasa terrane hosts extensive Late Cretaceous magmatism, however, the mechanism that triggered the magmatism and its relationship to the directly preceding Late Cretaceous tectonic transition in the central Tibetan Plateau is still unresolved. Therefore, we conducted a detailed petrological, geochronological, geochemical, and isotopic study on recently identified Late Cretaceous doleritic and granodioritic rocks in the Xiongmei area, northern Lhasa subterrane. The potassic (K2O/Na2O ratios >1) dolerites (ca. 80 Ma) display a post-collisional basaltic shoshonitic signature with uniform moderately enriched whole-rock Sr-Nd and zircon-Hf isotopic compositions ((Sr-87/Sr-86)(t) = 0.7070 to 0.7095, whole-rock epsilon(Nd)(t) = - 2.4 to - 1.3, and zircon epsilon(Hf)(t) = - 5.9 to +1.9), suggesting that they evolved from a similar parental magma and were likely derived by partial melting of an enriched lithospheric mantle metasomatized by hydrous fluids. The granodiorites are geochemically divided into medium-K and high-K calc-alkaline rocks. The medium-K samples (ca. 80 Ma) are generally characterized by low K2O/Na2O ratios <1, whereas the high-K samples (78-76 Ma) display high K2O/Na2O ratios >1. The medium-K samples have positive zircon epsilon(Hf)(t) values from +4.8 to +6.5 and uniform whole-rock e(Nd)(t) values from - 2.4 to - 1.3, which significantly differ from those of the high-K samples that have negative to positive zircon epsilon(Hf)(t) values from - 1.9 to +2.8 and negative whole-rock e(Nd)(t) values from - 8.4 to - 5.1. The medium-K samples are characterized by high Sr contents and Sr/Y ratios, coupled with low Y and HREE contents, similar to adakitic compositions, and were interpreted to have been derived from deep partial melting of the foundering juvenile garnet-bearing mafic lower crust at relatively low temperatures. Compared to the medium-K samples, the high-K samples have lower Sr/Y and (La/Yb)(N) ratios, coupled with flat HREE patterns and distinct negative Eu, Sr and Ti anomalies and are most likely derived from shallower partial melting of the K-rich juvenile lower crust at relatively high temperatures. Considering the occurrence of variable magmatism in the central-northern Lhasa subterrane during the Late Cretaceous, the change in magma composition and lower crustal melting conditions (cold-deep vs. hot-shallow) suggest that the lithospheric mantle keel was partially detached by small-scale mantle convection in response to the low-angle Neo-Tethys-associated subduction between 85 and 70 Ma.
CRIS-Team WoS Importer:2022-07-29

Late Cretaceous tectonothermal evolution of the southern Lhasa terrane, South Tibet: Consequence of a Mesozoic Andean-type orogeny - Dong, Xin; Zhang, Zeming; Klemd, Reiner; He, Zhenyu; Tian, Zuolin (Tectonophysics, 2018)
The Lhasa terrane of the southern Tibetan Plateau participated in a MesozoicAndean-type orogeny caused by the northward subduction of the Neo-Tethyan oceanic lithosphere. However, metamorphic rocks, which can unravel details of the geodynamic evolution, are rare and only exposed in the south-eastern part of the Lhasa terrane. Therefore, we conducted a detailed petrological, geochemical and U–Pb zircon geochronological study of the late Cretaceousmetamorphic rocks and associated gabbros from the Nyemo inlier of the southern Lhasa terrane. The Nyemo metamorphic rocks including gneisses, schists, marbles and calc-silicate rocks, experienced peak amphibolite-faciescontact metamorphism under P–T conditions of 3.5–4.0 kbar and 642–657 °C with a very high geothermal gradient of 45–50 °C/km, revealing a distinct deflection from the steady-state geotherm during low-pressure metamorphism. Inherited magmatic zircon cores from the metamorphic rocks yielded protolithages of 197–194 Ma, while overgrowth zircon rims yielded metamorphic ages of ca. 86 Ma. Whole-rock chemistry and zircon Hf isotopes suggest that the protoliths of the gneisses and schists are andesites and tuffs of the early JurassicSangri Group, which were derived from a depleted mantle source of a continental arc affinity. The coeval intimately-associated gabbro (ca. 86 Ma) crystallized under P–T conditions of 3.5–5.3 kbar and 914–970 °C, supplying the heat flux high enough to cause the contact metamorphism of the Sangri Group rock types. We propose that the intrusion of the gabbro and a simultaneous pressure increase of up to 4.0 kbar, which is related to crustal thickening due to crustal overthrusting and the intrusion of mafic material, resulted in the late Cretaceous metamorphism of the early Jurassic Sangri Group during an Andean-type orogeny. Furthermore the Nyemo metamorphic rocks, which have previously been considered to represent slivers of the Precambrianmetamorphic basement of the Lhasa terrane, are late Cretaceous metamorphic supracrustal rocks.
Keywords: Late Cretaceous contact metamorphism; Gabbroic intrusion; Intrusion-related perturbed geothermal gradient; Andean-type orogeny; Southern Lhasa terrane

Late Devonian carbon isotope chemostratigraphy: A new record from the offshore facies of South China - Zhang, Xinsong; Joachimski, Michael; Over, D. Jeffrey; Ma, Kunyuan; Huang, Cheng; Gong, Yiming (Global and Planetary Change, 2019)
Keywords: Bio-events; Plants; Stable carbon isotopes; Famennian; Frasnian; Tectonics

Late Devonian greenhouse-icehouse climate transition: New evidence from conodont δ18O thermometry in the eastern Palaeotethys (Lali section, South China) - Zhang, Xinsong; Joachimski, Michael; Gong, Yiming (Chemical Geology, 2021)
The Late Devonian is considered as a crucial climatic transition from the Devonian greenhouse to Carboniferous icehouse. Published Late Devonian marine palaeotemperature records are mainly based on conodont δ18Oapatite data from the Rheic Ocean. In order to reconstruct palaeotemperature variations in the eastern Palaeotethys, oxygen isotopes were measured on the latest Givetian to latest Famennian conodonts from the Lali section (South China). Assuming constant seawater δ18O, the early to middle Frasnian is marked by a warming trend (−1.5‰ shift in δ18Oapatite), with warmest temperatures reconstructed in FZ 11 (FZ = Frasnian Zonation). Late Devonian cooling during the middle to late Famennian (velifer to ultimus Zone) is documented by a long-term positive δ18Oapatite shift of +2‰. This increase corresponds to a similar δ18Oapatite increase in the Rheic Ocean and can be explained by cooling as well as the formation of ice masses as evidenced by the occurrence of glacial sediments in Gondwana and Euramerica during the late Famennian. The Late Devonian δ18Oapatite record largely matches 2nd-order T-R cycles. The δ18Oapatite record from the Lali section shows several short-term positive excursions coinciding with Late Devonian bio-events as the Middlesex (+0.5‰ δ18Oapatite), Lower Kellwasser (+1‰ δ18Oapatite) and Upper annulata (+0.8‰ δ18Oapatite) events. However, due to the lower sampling resolution of the F-F (Frasnian-Famennian) boundary interval, we did not recognize a positive shift in δ18Oapatite for the Upper Kellwasser event as reported from other sections.<br
Keywords: Late Devonian; Conodont oxygen isotope; Palaeotemperatures; Climate change; Bio-events; South China

Lateglacial and Holocene environmental changes in Ganga plain, Northern India - Joachimski, Michael; et al. (Quaternary Science Reviews, 2004)
UnivIS-Import:2015-03-09:Pub.2004.nat.dgeo.IGM.LAG.lategl

Late Jurassic fishes from Longing Gap, Antarctic Peninsula - Arratia, Gloria; Scasso, R. A.; Kießling, Wolfgang (Journal of Vertebrate Paleontology, 2004)
Few records of Late Jurassic fishes have been reported previously from Antarctica. They include an indeterminate teleost from the Ameghino (Nordenskjöld) Formation at Longing Gap and two incomplete aspidorhynchiforms from James Ross Island, all of presumed Late Jurassic age. New fish material recently recovered in the Upper Jurassic of Longing Gap is described. The new material consists of one piece of body squamation, which, based on the structure of the scales, corresponds to a new genus and species (Ameghinichthys antarcticus gen. et sp. nov.) of an indeterminate actinopterygian family; one aspidorhynchiform identified as Vinctifer sp. due to the structure and distribution of the scales; and numerous specimens of a new ichthyodectiform, Antarctithrissops seymouri gen. et sp. nov. This new genus differs from European ichthyodectiforms in the shape of the preopercle, the presence of long sensory preopercular branches almost reaching the posterior margin of the bone, and the uncommon structure of the scales, with a fine layer of bone obscuring the circuli. The presence of Vinctifer in the Antarctic is consistent with its other Gondwanan records. The Ichthyodectiformes, previously known from four European genera, extends the distribution of the group to the southernmost part of the Southern Hemisphere during the Late Jurassic. In contrast to most non-teleostean fishes, the known Late Jurassic teleosts apparently are species endemic to restricted areas in the Southern Hemisphere. © 2004 by the Society of Vertebrate Paleontology.
UnivIS-Import:2015-03-09:Pub.2004.nat.dgeo.IGM.LP.lateju

Late Jurassic (Oxfordian-Kimmeridgian) brachiopods of the El Bayadh Area (Central Saharan Atlas, Algeria): biostratigraphy, stratigraphic revision, Paleobiogeography and paleoecology - Mahboubi, Chikh Younes; Radulovic, Barbara V.; Ouali Mehadji, Abdelkader; Ayoub-Hannaa, Wagih; Munnecke, Axel (Historical Biology, 2021)
The Upper Jurassic rocks of the El Bayadh Area (Central Saharan Atlas, Algeria) are composed of mixed siliciclastic-carbonate rocks, which were roughly assigned to a Kimmeridgian-Hauterivian age in previous studies. Based on our studies, the succession can be subdivided into five new formations; from base to top: the Theniet Et-Temar, Ksel, Laguremi, Boualem, and the Sfissifa formations. Brachiopod faunas have been recorded from two levels. The lower one is located in the Theniet Et-Temar Formation, and the upper one in the Sfissifa Formation. Two brachiopod species Lacunosella (Lacunosella) arolica and Moeschia alata from the first level and Xestosina arguta from the second level have been recorded for the first time not only in Algeria but also in Africa. Based on the new findings, the age of the studied section can be restricted to the middle Oxfordian at the base and to the upper Kimmeridgian at the top. The stratigraphic successions between the two levels (70 m) are nearly barren except for dinosaur footprints, which were tentatively assigned to a Lower Cretaceous age by previous workers. However, this succession can be attributed to an upper Oxfordian-lower Kimmeridgian age now based on its brachiopod faunas.
CRIS-Team WoS Importer:2021-02-05

Late Jurassic radiolarians from the Antarctic Peninsula - Kießling, Wolfgang (Micropaleontology, 1999)
Radiolarian faunas from the type section of the mostly Late Jurassic Ameghino Formation (= Nordenskjold Formation) on the Antarctic Peninsula (Longing Gap, northern Graham Land) are described taxonomically, analyzed stratigraphically and interpreted paleoecologically, based on quantitative observations. Three hundred and fifty-nine species have been discovered in total; some two hundred of them are probably new. Twenty-eight new species and three new subspecies are described. The most abundant and characteristic species are used to present a regional radiolarian stratigraphy. The radiolarian faunas show distinct high-latitude characteristics. They are demarcated by high abundances of Parvicingula s.1. and spongy spumellarians, whereas Tethyan taxa like Mirifusus, Ristola, Tethysetta, Tritrabs, Syringocapsidae, Spongocapsulidae, and Xitidae are absent or very rare. The average diversity is high, but significantly lower than in coeval Tethyan samples. Cluster analysis reveals a major change in faunal composition near the early-late Tithonian boundary. The characteristics of the Antarctic radiolarian faunas allow an Austral Province to be defined extending from circum-Antarctica to northeast Australia. The Austral radiolarian province is similar to the Northern Tethys and Southern Boreal Provinces sensu Pessagno and Blome (1986), but exhibits some differences. The new data allow the biogeographic scheme of Pessagno and Blome (1986) to be revised and permit the introduction of a preliminary global paleobiogeographic map for the Tithonia
UnivIS-Import:2015-03-05:Pub.1999.nat.dgeo.IGM.LP.lateju

Late Jurassic temperatures for the southern Tethyan margin based on belemnites δ18O from the Ouarsenis Mountains, northwestern Algeria - Sadji, Radouane; Munnecke, Axel; Benhamou, Miloud; Alberti, Matthias; Belkhedim, Salim; Ramdane, Nabil (Palaeogeography, Palaeoclimatology, Palaeoecology, 2021)
This study presents the first record of stable carbon and oxygen isotopes of well-preserved belemnites and bulk sediment from the Upper Jurassic pelagic carbonates of the Ouarsenis Mountains (northwestern Algeria), which were deposited at the southern margin of the Tethys ocean. Cathodoluminescence and scanning electron microscopy was used to eliminate potentially diagenetically altered specimens (brachiopods, aptychi, and some belemnites). Ultimately, 55 belemnite specimens were used to reconstruct water temperatures for the Middle Oxfordian to the Early Tithonian. Their δ18Ocarb values ranged from −0.35‰ to −3.88‰, suggesting warm and mostly stable temperature conditions during the Late Jurassic. Using a δ18Osea value of 0‰ for the tropical palaeolatitude of 15–20°N, the δ18Ocarb values of the well-preserved belemnite rostra translate into average temperatures of 27.8 °C in the Middle Oxfordian (Gregoryceras transversarium Zone), 27.0 to 27.5 °C in the Late Oxfordian (Epipeltoceras bimmamatum and Idoceras planula zones, respectively), 26.2 °C in the Early Kimmeridgian, and 27.3 °C in the Early Tithonian (Hybonoticeras hybonotum Zone).
CRIS-Team Scopus Importer:2021-01-29
Keywords: Bulk sediment; Palaeoclimate; Pelagic carbonates; Stable isotopes; Tropical palaeolatitude

Late Jurassic (Volgian) radiolarians from Central Spitsbergen - A preliminary study - Nakrem, Hans Arne; Kießling, Wolfgang (Norwegian Journal of Geology, 2012)

Late Neoproterozoic-to-recent long-term t-T-evolution of the Kaoko and Damara belts in NW Namibia - Salomon, Eric; et al. (International Journal of Earth Sciences, 2020)
This research aims to reconstruct the Late Neoproterozoic-to-recent long-term time-temperature-evolution of the NW Namibian Kaoko and Damara belts combining numerical modeling of new thermochronological data with previously published geochronological data, i.e., U-Pb, Sm-Nd, and Rb-Sr analyses, and K/Ar, Ar-40/Ar-39 low-temperature thermochronology. Consequently, we retrieve a coherent long-term time-temperature-evolution of the NW Namibian Neoproterozoic basement rocks including rates of exhumation and subsidence periods over the last 500 Myr. Neoproterozoic basement rocks indicate fast post-Pan African/Brasiliano cooling and exhumation, reheating, or rather subsidence during the development of the Paleozoic-to-Mesozoic SW Gondwana intraplate environment and a significant thermal overprint of the rocks during South Atlantic syn- to post-rift processes, and therefore, resemble the opponent SE Brazilian time-temperature-evolution. We provide an overview of thermochronological data including new apatite and zircon fission-track data derived from Neoproterozoic, Late Paleozoic, and Lower Cretaceous rocks. Apatite fission-track ages range from 390.9 +/- 17.9 Ma to 80.8 +/- 6.0 Ma in the NW Kaoko Belt with youngest ages confined to the coastal area and significant age increase towards the inland. New zircon apatite fission-track data reveal ages between 429.5 +/- 47.8 and 313.9 +/- 53.4 Ma for the rocks of the Kaoko Belt. In the central Damara Belt, new apatite fission-track ages range between 138.5 +/- 25.3 Ma to 63.8 +/- 4.8 Ma. Combined apatite fission-track age distributions from Angola to Namibia and SE Brazil correlate for both sides of the South Atlantic passive continental margin and the reset AFT ages overlap with the lateral Parana-Etendeka dike swarm distribution.
Keywords: Long-term t-T-evolution; Thermochronology; Numerical modeling; South Atlantic passive continental margin of NW Namibia

Late Ordovician microbial reefs in the Lianglitag Formation (Bachu, Tarim, NW China) - Zhang, Yuanyuan; Li, Yue; Munnecke, Axel (Facies, 2014)
Reefs in the Late Ordovician are usually built up by metazoans, whereas in the Early and Middle Ordovician microbial reefs are dominating. In the Late Ordovician (Katian) Lianglitag Formation, at Bachu, Tarim, NW China, however, three distinct stages of thrombolithic microbial reefs are exposed. The lower and upper reef intervals are characterized by widespread microbial carbonates with almost constant thicknesses (biostromes). The middle reef interval exposes dome-like mounds, and shows a higher diversity of reef-building and reef-dwelling organisms. Calcareous algae such as Vermiporella are abundant, but also other components such as fragments of Halysis, brachiopods, molluscs, echinoderms, bryozoans, and trilobites have been found in the microbial reef units. The purpose of this study is to describe for the first time the composition and microfacies of the reefs in this remote area. Especially the question of whether or not these Late Ordovician reefs represent remnants of the Early/Middle Ordovician microbial-dominated reef type just lacking Calathium and lithistid sponge is addressed. The results indicate that the local conditions on the leeward side of the carbonate platform, where waters are less well agitated and thus less well oxygenated, and probably also characterized by temporarily elevated water temperatures hampering the growth of metazoan reefs, were responsible for the proliferation of the Late Ordovician microbial reefs in the Bachu area. © 2014 Springer-Verlag Berlin Heidelber
Keywords: Biotic structures; Katian; Late Ordovician; Microbial reefs; NW China; Tarim

Late Ordovician sponge spicules from the Yangtze Platform, South China: Biostratigraphical and palaeobiogeographical significance - Lixia, Li; Guanzhou, Yan; Xin, Wei; Fangyi, Gong; Lehnert, Oliver; Rongchang, Wu (Journal of Asian Earth Sciences, 2025)
A diverse and abundant isolated sponge spicule assemblage of Late Ordovician age is first reported from the western margin of the Yangtze Platform in South China. The spicule assemblage was recovered from argillaceous limestone sampled for conodonts. It includes 14 types which can be split into two categories: hexactinellid spicules and demosponge spicules. The assemblage primarily comprises hexactines and their derivatives, including not only some distinctive types such as Kometia cruciformis, but also large numbers of morphotypes that are quite common and diagnostic for hexactinellids, e.g. swollen hexactines, curved hexactines, and stauractines. Demosponge spicule types are represented by tetraxons, and various desmas typical for lithistids also occur. A highly modified hexactine, Kometia cruciformis, is recovered from China for the first time. This record represents currently the only recovery of such spicules from strata outside of Australia, and is coeval to the assemblage known from the Malongulli Formation. The presence of such unique modified hexactines (Kometia) in both time-equivalent assemblages suggests that certain spicules may have potential importance in biostratigraphic correlations and palaeobiogeographical interpretations, demonstrating the dispersal of taxa and their migration along the peri-Gondwana shelf areas during the Ordovician, driven by ocean current systems. The Late Ordovician sponge spicule assemblage from the Yangtze Platform provides new perspectives for investigating phylogeny, biostratigraphy, and palaeobiogeography of Palaeozoic sponges, and promotes some understanding of macroevolution in siliceous sponges.
CRIS-Team Scopus Importer:2024-11-15
Keywords: Biostratigraphy; Late Ordovician; Palaeobiogeography; South China; Sponge spicules

Late orogenic faulting and associated vein mineralisation in Saxothuringian metasediments - implications for crustal strength estimates - Dietl, Carl; Donhauser, Ines; Bestmann, Michel; Scharfenberg, Lars; de Wall, Helga (Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2022)
Palaeozoic metasediments, recovered from a well bore at the E' margin of the Franconian Basin in NE Bavaria, give insight into the Variscan basement west of the Bohemian Massif. Quartz veins are abundant in the folded and cleaved pelitic to psammitic sequence. They are mainly restricted to coarse-grained massive metasandstone. The structural inventory of the quartz veins and cross-cutting relationships between them indicates their formation during three brittle deformation phases and corresponding fluid pulses at a depth of ca. 7 km. The metasandstone has a low porosity (1.1 to 1.5 vol-%) and is almost impermeable (permeability = 1.70e-17). Triaxial tests characterise the metasandstone as strong and very cohesive lithology (C0: 185.52 MPa, S0: 52.11 MPa) that can sustain high compressive stresses. Faulting and vein formation seem to be triggered by high fluid pressure which might have built up in the low permeable metasandstone. The most probable timing for fracturing and vein formation is shortly after the transition from compression to extension tectonics late in the orogenic history of the Variscides during orogenic collapse. At this changeover point effective stresses are decreasing, because fluid pressure becomes more effective as driving force for (hydraulic) fracturing. The generated fracture structures (from vein to fault scale) are preferably orientated in N-S and NW-SE directions. Both orientations represent prominent and persistent regional fault trends in the area not only for Variscan structures but also for younger Permo-Mesozoic to Cenozoic strata of the Franconian Basin.
CRIS-Team WoS Importer:2022-12-02

Late Paleozoic and Late Triassic limestones from North Palawan Block (Philippines): Microfacies and paleogeographical implications - Kießling, Wolfgang; et al. (Facies, 2000)
Selected Late Paleozoic and Triassic limestone exposures were studied on northern Palawan Island, Philippines, with regard to microfacies, stratigraphy and facies interpretation. Although some of the outcrops were already reported in literature, we present the first detailed microfacies study. Late Paleozoic carbonates in the El Nido area are represented by widley distributed Permian and locally very restricted Carboniferous limestones. Of particular interest is the first report of Carboniferous limestones in the Philippines dated by fossils. Fusulinids indicate a 'Middle' Carboniferous (Moscovian-Kasimovian) age of the Paglugaban Formation only known from Paglugaban Island. The Permian Minilog Formation consists mostly of fusulinid wackestones and dasycladacean wacke-/packstones. Fusulinid datings (neoschwagerinids and verbeekinids) provide a Guadalupian (Wordian-Capitanian) age. The depositional setting of the Middle Permian carbonates corresponds to a distally steepened ramp with biostromes built by alatoconchid bivalves locally associated with richthofeniid brachiopods. Late Triassic limestones occur in isolated exposures on and around Busuanga Island (Calamian Islands). The age of the investigated carbonates is Rhaetian based on the occurrence of Triasina hantkeni Majzon. Microfacies data indicate the existence of reefs (Malajon Island) and carbonate platforms (Kalampisanan Islands, Busuanga Island, Coron Island). Reef boundstones are characterized by abundant solenoporacean red algae, coralline sponges and corals. Platform carbonates yield a broad spectrum of microfacies types, predominantly wacke- and packstones with abundant involutinid foraminifera and some calcareous algae. These facies types correspond to platform carbonates known from other parts of Southeast Asia (Eastern Sulawesi and Banda Basin; Malay Peninsula and Malay Basin). The Philippine platform carbonates were deposited on and around seamounts surrounded by deeper water radiolarian cherts. The new data on facies and age of the Philippine Permian and Triassic carbonates contradict a close paleogeographical connection between the North Palawan Block and South China and arise problems for the currently proposed origin of the North Palawan Block at the paleomargin of South China. We hypothesize that North Palawan was part of the Indochina Block during the Carboniferous and Permian, separated from the Indochina Block during the Middle Permian and collided with the South China Block in the Late Cretaceous.
UnivIS-Import:2015-03-09:Pub.2000.nat.dgeo.IGM.LP.latepa
Keywords: Carbonate ramps and platforms; Carboniferous; Late Triassic; Microfacies analysis; Middle Permian; Paleogeography; Philippines (Palawan); Reefs

Late Pan-African granite emplacement during regional deformation, evidence from magnetic fabric and structural studies in the Hammamat-Atalla area, Central Eastern desert of Egypt - Greiling, R. O.; de Wall, Helga; Sadek, M. F.; Dietl, C. (Journal of African Earth Sciences, 2014)
Keywords: Ediacaran; Egypt; Escape tectonics; Late orogenic granite; Magnetic fabric (AMS); Pan-African orogeny

Late Pennsylvanian fishes from the Finis Shale of North-Central Texas - Ivanov, Alexander; Seuß, Barbara (54th Annual Meeting, South-Central Section of the GSA, 2020)
The fossil-rich deposits from the Finis Shale (Graham Formation) at the "spillway section" near Jacksboro (North-Central Texas) are dated as early Virgilian (early Gzhelian; Late Pennsylvanian) in age. The Finis Shale is part of a cyclothem and represents the shallowing upwards sequence at this outcrop. The shale deposits are capped by phylloid algae and fusulinid carbonates of the Jacksboro Limestone. Various chondrichthyan macroremains such as Glikmanius, Orodus, Campyloprion, or Petalodus are known from these deposits. A diverse assemblage of fish microremains is now discovered in and described from the Finis Shale deposits. The micro-fossil assemblage includes numerous chondrichthyan teeth and scales, while acanthodian scales and actinopterygian teeth and scales are rare. The chondrichthyan microremains are taxonomically more diverse and represented by teeth of the bransonelliform Bransonella nebraskensis Johnson, by the symmoriiform Denaea cf. williamsi Ginter et Hansen, and yet undetermined stethacanthids. The ctenacanthiforms Heslerodus divergens (Trautschold) and Glikmanius sp., sphenacanthid euselachians, the neoselachian Cooleyella amazonensis Duffin, Richter et Neis, the petalodontids Euglossodus sp. and cf. Tanaodus sp., and eugeneodontid remains are also preserved. Symmoriiform denticles and chondrichthyan scales of various types are also found. The new occurrence of fishes demonstrates the presence of chondrichthyan taxa with different food specialization in the early Virgilian faunal communit

LATE PERMIAN PLUME AND NEOPROTEROZOIC SUBDUCTION-MODIFIED MANTLE INTERACTION: INSIGHTS FROM GEOCHRONOLOGY AND Sr-Nd-O ISOTOPES OF MAFIC DIKES OF THE WESTERN EMEISHAN LARGE IGNEOUS PROVINCE br - Wang, Yanning; Xue, Shengchao; Klemd, Reiner; Yang, Lin; Zhao, Feng; Wang, Qingfei (American Journal of Science, 2022)
Geochronological investigations of mafic dikes along the southwest-ern margin of the Emeishan large igneous province (ELIP) in the South China block display a restricted range of U-Pb zircon, baddeleyite, and apatite isotopic ages rang -ing from 263 to 257 Ma, which overlaps with that of previously studied ELIP basalts and mafic intrusions. The dikes are divided into high-Ti and low-Ti groups, whereby the latter is further divided into two subgroups (low-Ti group-1 and-2). The high-Ti group rocks (Ti/Y > 500) are characterized by ocean island basalt-like trace element patterns with mantle-like zircon 4318O of 5.0 +/- 0.10 parts per thousand and slightly enriched sNd(t) val-ues of -1.0 to +1.0. The low-Ti group-1 rocks (Ti/Y < 500) have trace element pat-terns similar to those of the high-Ti group, yet generally with weak negative Nb-Ta anomalies, lower (Sm/Yb)N ratios, elevated zircon 4318O (6.6 +/- 0.33 parts per thousand), and highly variable sNd(t) values (-3.9 to +3.2). The low-Ti group-2 rocks (Ti/Y < 500) are characterized by pronounced negative Nb-Ta anomalies, more negative sNd(t) (-8.4 to -6.6) values, and higher initial 87Sr/86Sr ratios than those of the other two groups. The compositional variations of the high-Ti group and the low-Ti group-1 rocks, in conjunction with the negative correlation between the sNd(t) values and the (Th/ Nb)N ratios, suggest that the two groups were generated from an isotopically hetero-geneous mantle plume at different depths, and experienced varying degrees of crustal contamination (but < 20 wt.%). The high-Ti group rocks are considered to have originated from a deeper garnet-stable source, and the low-Ti group-1 rocks from a shallower source. Mixing calculations indicate that the highly enriched Sr-Nd isotopes of the low-Ti group-2 rocks cannot be explained by crustal contamination. A subduction-modified mantle source is required to account for the arc-like geochemi-cal characteristics of this group. This is consistent with the spatial overlap of the low-Ti group-2 rocks and previously studied geochemically similar samples with rocks from the Neoproterozoic subduction zone along the western margin of the South China block. Furthermore, a fertilized mantle is also consistent with the variable 4318O values of various mafic-ultramafic rocks of the western and central ELIP due to the involvement of recycled oceanic crustal materials. Our results are in accordance with the model that the western ELIP late Permian magmatism was generated by the interaction of two distinct sources, that is, an isotopically heterogenous mantle plume and a Neoproterozoic subduction-modified, Nd isotope-enriched litho-spheric mantle with distinct heterogenous oxygen isotope characteristics.
CRIS-Team WoS Importer:2022-11-18

Late Permian to Late Triassic Large Igneous Provinces: Timing, Eruptive Style and Paleoenvironmental Perturbations - Boscaini, Andrea; Callegaro, Sara; Sun, Yadong; Marzoli, Andrea (Frontiers in Earth Science, 2022)
The emplacement of the Siberian Traps, the Central Atlantic Magmatic Province (CAMP) and the Wrangellia have been linked to the end-Permian, the end-Triassic mass extinctions, and to the Carnian Pluvial Episode (CPE), respectively. Exploring the timing, eruptive styles, and volatile degassing of these Large Igneous Provinces (LIPs) is crucial to understand their causal link to the catastrophic environmental crises that punctuated the Triassic. In this study we review the main characteristics of these LIPs, emphasizing common features and differences, and discussing aspects that are still in debate. Estimates of CO2 budgets and emissions from the three LIPs are based on the Nb content of little evolved basalts and highlight that early Siberian Traps and CAMP and high-Ti Wrangellia volcanics were quite CO2-rich. On the contrary, other volcanics from the three LIPs probably emitted relatively low amounts of CO2, which reinforces the possibility that thermogenic reactions between sills and sediments were additional fundamental suppliers of climate-modifying gases.
CRIS-Team Scopus Importer:2022-05-06
Keywords: carnian crisis; central atlantic magmatic province (CAMP); large igneous province; mass extinction; siberian traps; triassic; wrangellia LIP

Late Pliocene grassland from Olduvai Gorge, Tanzania. - Bamford, Manon K.; Stanistreet, Ian G.; Stollhofen, Harald; Albert, Rosa M. (Palaeogeography, Palaeoclimatology, Palaeoecology, 2008)
The Olduvai fossil plants documented by us in this paper are the first direct evidence for open grassland in the late Neogene of Africa based on macroplant remains. Silicified remains of herbaceous ground cover are exceptionally well preserved in situ within Late Pliocene sediments below the initial pyroclastic ash surge unit of Tuff IF in the uppermost part of Bed I, Olduvai Gorge, northern Tanzania. Published radiometric and palaeomagnetic dates place this grass layer between 1.839 + 0.005 Ma and 1.785 + 0.01 Ma. Exposed at localities on the south side of the Gorge this herbaceous ground cover grew on a floodplain developed on a dried out lake bed, following pronounced lake retreat of saline-alkaline palaeo-Lake Olduvai during a developing dry climatic phase. Sheathed basal culms, rhizomes and roots are interpreted as those of one or more small mat-forming grasses or less likely, sedges. Small dicotyledonous herbs were probably also present. The proximity of adjacent plants indicates a relatively dense ground cover. Roots extended at least 8 cm below the ground surface. Aerial parts of the plants were absent or were not preserved when the weathered basal culms were covered by a thin layer of brown waxy clay, followed by fallout of pyroclastic ash. Both units were mostly eroded away prior to emplacement of a wet, cool pyroclastic surge which then buried and preserved in situ remnants of the herbaceous ground cover. Preservation of the semi-woody rhizomes implies well-drained soils, otherwise the plant material would have quickly rotted. Collections from discontinuous exposures indicate the grassland covered an area of at least a few hectares. This open grassland would have provided grazing for the Late Pliocene fauna. © 2007 Elsevier B.V. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2008.nat.dgeo.IGM.LG.latepl
Keywords: Grassland; Macrofossils; Olduvai Gorge; Serengeti ecosystem; Terminal Neogene

Late quaternary climate change shapes island biodiversity - Weigelt, Patrick; Steinbauer, Manuel; Cabral, Juliano; Kreft, Holger (Nature, 2016)
Island biogeographical models consider islands either as geologically static with biodiversity resulting from ecologically neutral immigration–extinction dynamics1, or as geologically dynamic with biodiversity resulting from immigration–speciation–extinction dynamics influenced by changes in island characteristics over millions of years2. Present climate and spatial arrangement of islands, however, are rather exceptional compared to most of the Late Quaternary, which is characterized by recurrent cooler and drier glacial periods. These climatic oscillations over short geological timescales strongly affected sea levels3,4 and caused massive changes in island area, isolation and connectivity5, orders of magnitude faster than the geological processes of island formation, subsidence and erosion considered in island theory2,6. Consequences of these oscillations for present biodiversity remain unassessed5,7. Here we analyse the effects of present and Last Glacial Maximum (LGM) island area, isolation, elevation and climate on key components of angiosperm diversity on islands worldwide. We find that post-LGM changes in island characteristics, especially in area, have left a strong imprint on present diversity of endemic species. Specifically, the number and proportion of endemic species today is significantly higher on islands that were larger during the LGM. Native species richness, in turn, is mostly determined by present island characteristics. We conclude that an appreciation of Late Quaternary environmental change is essential to understand patterns of island endemism and its underlying evolutionary dynamics.

Lateral facies heterogeneity and carbonate productivity changes during the Lower Jurassic of the Traras Mountains (NW Algeria): local versus regional controls - Belkhedim, Salim; Munnecke, Axel; Benaaoume, Hachemi Mokhtar; López Correa, Matthias; Nemra, Abdelkrim; Bradai, Mohammed El Amine; Benhamou, Miloud (Facies, 2025)
Lateral facies heterogeneity and carbonate production perturbation within peri-Tethyan platforms were widespread phenomena during the Early Jurassic. These variations were either controlled by local factors affecting small areas or by processes prevailing on a global scale. Three geological sections are investigated in Lower Jurassic outcrops in the Traras Mountains, northwest Algeria, from synrift-settings to disentangle the influence of local and global factors. The detailed sedimentological study reveals 11 facies types, grouped into four facies associations ranging from alluvial fan to outer ramp setting. Whereas thickness variation and lateral facies distribution are mainly controlled on a regional scale by synsedimentary tectonics, resulting from the spreading of the Tethys, the irregular topography inherited from the palaeo-alluvial fan topography of the underlying Beni Menir Formation seems to be the main control on a local scale. This irregular topography which coexisted in very close proximity to the studied carbonate deposits provided a significant amount of siliciclastic input, partially disturbing carbonate production. The local erosion of this detrital material during the initial early Pliensbachian transgression, combined with other local factors such as a low rate of accommodation space renewal and high-energy conditions, resulted in the absence of the otherwise prevalent Lithiotis fauna in the studied sector. Siliciclastic input perturbating carbonate production during the late Pliensbachian to early Toarcian could instead have been induced by a global warming event that increased continental weathering at the global scale during the Pl/To boundary or T-OAE associated with storm intensification. Alternatively, in view of the lack of solid biostratigraphic attribution, high terrigenous input could also have been induced from a cooling event leading to a sea-level fall during the latest Pliensbachian (Emaciatum Zone) and/or the lowermost Toarcian (latest Tenuicostatum Zone). In addition to tectonics, this eustatic sea-level fall could also explain the absence of shallow carbonate production in the Traras Mountains during these periods. In the future, a multidisciplinary basin-scale approach may resolve these uncertainties related to the lack of biostratigraphic dating, thus helping to identify the key factor influencing the perturbation of carbonate production.
CRIS-Team Scopus Importer:2024-11-22
Keywords: Climate change; Eustatic sea-level change; Facies analysis; Jurassic Algeria; Synsedimentary tectonics; Traras Mountains

Late to post-Variscan basement segmentation and differential exhumation along the SW Bohemian Massif, central Europe - Eberts, Andreas; Fazlikhani, Hamed; Bauer, Wolfgang; Stollhofen, Harald; de Wall, Helga; Gabriel, Gerald (Solid Earth, 2021)
The exposed Variscan basement in central Europe is well-known for its complex structural and lithological architecture resulting from multiple deformation phases. We studied the southwestern margin of the Bohemian Massif, which is characterized by major and long-lived shear zones, such as the Pfahl and Danube shear zones, extending over >ĝ€¯100ĝ€¯km and initiated during Variscan tectonics. We integrated Bouguer gravity anomaly and lidar topographic data analyses and combined our results with available data and observations from low-Temperature thermochronology, metamorphic grades, and the exposed granite inventory to detect patterns of basement block segmentation and differential exhumation. Three NW-SE-striking basement blocks are bordered by the Runding, Pfahl, and Danube shear zones from the northeast to the southwest. Basement block boundaries are indicated by abrupt changes in measured gravity patterns and metamorphic grades. By applying high-pass filters to gravity data in combination with lineament analysis, we identified a new NNW-SSE-striking tectonic structure (Cham Fault), which further segments known basement blocks. Basement blocks that are segmented by the Cham Fault differ in the abundance and spatial distribution of exposed late Variscan granites and are further characterized by variations in apparent thermochronological age data. Based on our observations and analyses, a differential exhumation and tectonic tilt model is proposed to explain the juxtaposition of different crustal levels. Block segmentation along the NW-SE-striking Pfahl and Runding shear zones most likely occurred prior, during, and after late orogenic granite emplacement at ca. 320ĝ€¯±ĝ€¯10ĝ€¯Ma, as some of the granites are cross-cut by the shear zones, while others utilized these structures during magma ascent and emplacement. In contrast, activity and block segmentation along the Cham Fault occurred after granite emplacement as the fault sharply truncates the granite inventory. Our study provides evidence of intense and continuous fault activities during late and post-orogenic times and highlights the importance of tectonic structures in the exhumation and juxtaposition of different crustal levels and the creation of complex lithological patterns in orogenic terrains.
CRIS-Team Scopus Importer:2021-10-29

Late Triassic (Norian) strontium and oxygen isotopes from the Baoshan block, southwestern China: Possible causes and implications for climate change - Chen, Yan; Zeng, Weiping; Joachimski, Michael; Wignall, P. B.; Ogg, James G.; Jiang, Haishui; Zhang, Muhui; Lai, Xulong (Palaeogeography, Palaeoclimatology, Palaeoecology, 2024)
The Norian Stage (Late Triassic) has long been regarded as an interval of stable climates, but, in fact, there are only sparse studies of the paleoclimate variations during this longest (>20 Myr) stage of the Phanerozoic. Here, oxygen and strontium isotopes have been measured on conodont apatite from the open-marine shelf succession at the Xiquelin section (Baoshan terrane, Yunnan Province, China). Magnetostratigraphy linked to conodont biostratigraphy indicates that the succession was deposited during the Sevatian substage, upper Norian. The δ18Oapatite values from conodonts indicate that low-latitude average sea-surface temperatures in eastern Tethys were 32 °C during the earliest Sevatian, cooled to 25 °C through the middle Sevatian, and then increased again to 29 °C by the late Sevatian. The seawater 87Sr/86Sr values maintained a high plateau through the entire Sevatian, with very little variation between inferred warm and cool episodes. The possible explanation for the observed trends in sea-surface temperature and 87Sr/86Sr during Sevatian is an enhanced weathering of silicates exposed during the closure of the Paleo-Tethys Ocean at the zenith of Pangea supercontinent assembly.<br
Keywords: Late Triassic; Climate change; Conodont; Geomagnetic polarity time scale; Paleo-Tethys

Late Wenlock carbon isotope excursions and associated conodont fauna in the Podlasie Depression, eastern Poland: a not-so-big crisis? - Jarochowska, Emilia; Munnecke, Axel (Geological Journal, 2016)
The middle Silurian ‘big crisis’ refers to a graptolite extinction event and faunal turnover at the onset of a double-peaked positive carbon isotope excursion. The crisis has been proposed to affect conodonts, giving rise to a sophisticated palaeoecological model of their stepwise extinction, known as the Mulde Event. However, the impact of the event on conodont faunas outside Gotland and the Silurian Baltic Basin remains unknown. Here, it is examined in the Widowo IG-1 core (E Poland). The middle Silurian succession in this core represents foreshoal, shoal, and lagoonal settings on a tropical carbonate ramp on the shelf of the Eastern European Craton. Three positive δC excursions have been identified; the two upper excursions correlate with the Mulde isotope anomaly and with two global eustatic regressions. Conodont species proposed to be affected by the extinction event either were not observed or ranged through the extinction interval. Changes in their frequencies are best explained by the sequence stratigraphic architecture of the late Wenlock strata in the Widowo IG-1 core. The little impact of the ‘big crisis’ may reflect facies homogeneity across the studied interval, supporting the hypothesis that the late Wenlock conodont turnover in epicontinental settings was primarily driven by eustatically controlled facies shifts. Copyright © 2015 John Wiley & Sons, Lt
Keywords: Baltica; extinction; gamma ray stratigraphy; Homerian; lundgreni event; Mulde Event; sequence stratigraphy

Latitudinal trends in Cenozoic reef patterns and their relationship to climate. Carbonate Systems during the Oligocene-Miocene climatic transition - Perrin, Christine; Kießling, Wolfgang (IAS Special Publications, 2010)
UnivIS-Import:2015-03-09:Pub.2010.nat.dgeo.IGM.LP.latitu

Lattice preferred orientation of talc and implications for seismic anisotropy in subduction zones - Lee, Jungjin; Jung, Haemyeong; Klemd, Reiner; Tarling, Matthew S.; Konopelko, Dmitry (Earth and Planetary Science Letters, 2020)
Strong seismic anisotropy is generally observed in subduction zones. Lattice preferred orientation (LPO) of olivine and elastically anisotropic hydrous minerals has been considered to be an important factor causing anomalous seismic anisotropy. For the first time, we report on measured LPOs of polycrystalline talc. The study comprises subduction-related ultrahigh-pressure metamorphic schists from the Makbal Complex in Kyrgyzstan-Kazakhstan and amphibolite-facies metasomatic schists from the Valla Field Block in Unst, Scotland. The here studied talc revealed a strong alignment of (001) planes (sub)parallel to the foliation and a girdle distribution of [100] axes and (010) poles (sub)parallel to the foliation. The LPOs of polycrystalline talc produced a significant P-wave anisotropy (AVp = 72%) and a high maximum S-wave anisotropy (max AVs = 24%). The results imply that the LPO of talc influence both the strong trench-parallel azimuthal anisotropy and positive/negative radial anisotropy of P-waves, and the trench-parallel seismic anisotropy of S-waves in subduction zones.
CRIS-Team Scopus Importer:2020-03-10
Keywords: lattice preferred orientation; seismic anisotropy; subduction zone; talc

Lava penetrating water: Submarine lava flows around the coasts of Pico Island, Azores. - Mitchell, Neil C.; Beier, Christoph; Rosin, Paul L.; Quartau, Rui; Tempera, Fernando (Geochemistry Geophysics Geosystems, 2008)
Bathymetry data collected with a multibeam echo sounder around Pico Island, Azores (Portugal), reveal a remarkable series of lava flows on the island's shelf with a variety of pristine structures that suggest how lava behaves on entering water. Many flows are dendritic in plan view, some with channels and tumuli. Dendritic geometries are interpreted to arise from flow fronts repeatedly arrested by enhanced cooling and magma pressure subsequently causing new breakouts. Cascades of elongated flow fingers also occur, with individual fingers of comparable diameters to the largest known megapillows. Some flows have wide transverse clefts, in cases separating flows into segments, which are interpreted as caused by their upper surfaces having solidified, while their still-fluid cores allowed the surfaces to extend. A number of flows moved onto the shelf as large bodies, stopped, and then sourced smaller lobes forming the dendritic patterns. This two-stage evolution and the tumuli (which lie on a low gradient immediately below a steep nearshore gradient) suggest that, after initial emplacement and development of a crust by cooling, some flows pressurized. Once movements ceased and viscous stresses dissipated, magma static pressure developed from the weight of flow interiors passing over cliffs and nearshore gradients. One group of flows traverses the island's submarine slope, so direct supply of lava to the slopes is possible, although volumetrically how important it is to the island's internal composition is difficult to tell from these data. On the basis of observed strong surf erosion of historical flows, these delicate structures probably could not have survived passage through a moving sea level unmodified by erosion so they are unlikely to be pre-Holocene subaerial flows. They are interpreted to have formed in the Holocene from flows penetrating sea level or possibly some from nearshore tube openings or vents. Such flows and abundant clastic deposits are ephemeral features that become remobilized by surf during times of lower sea level. The shelves of active volcanic islands are therefore active geologically and are far from being simple products of erosional truncation as was once envisaged. Copyright 2008 by the American Geophysical Union.
UnivIS-Import:2015-03-09:Pub.2008.nat.dgeo.IGM.legeo.lavape
Keywords: Lava channel; Submarine lava flow; Tumuli; Volcanic landslides; Volcanic ocean island

Lava/sediment interaction in desert settings; are all peperite-like textures the result of magma-water interaction? - Jerram, Dougal A.; Stollhofen, Harald (Journal of Volcanology and Geothermal Research, 2002)
This study reports on lava-sediment interaction in dry depositional settings focusing on the Early Cretaceous volcano-sedimentary sequence in the Huab Basin, NW Namibia, as a detailed example. Here an active aeolian sand sea (erg) system was progressively engulfed by lavas of the Etendeka Flood Basalt Province 133 Ma BP. This volcanic flooding resulted in: (1) the unprecedented preservation of large parts of the active dune system; (2) the development of a variety of sediment interlayers; and (3) a record of excellent examples of the dynamic interaction between lava and aeolian sand. The lava-sediment interaction happens on a variety of scales from simple sediment interbeds within the lavas at a large scale down to complex breccia horizons and bulbous lava-sediment contacts at small scales. 'Peperite' like textures are found where hot lava has dynamically interacted with unconsolidated aeolian sands. Such interaction could involve lava cascading down the front of dune faces, or active 'aa' style flow fronts 'bulldozing' into and oversteepening dune faces causing rapid influx of sand into the active flow front. Resulting breccia horizons have been found up to 5 m thick. Locally, the aeolian sand is baked to a quartzite by the hot lava. In contrast, on other surfaces, the lava leaves striations in the sand as it flows across it indicating local flow directions and less pronounced interaction. In places, wind ripples and topset beds are preserved on the stoss side of the dune indicating the passive nature of emplacement for some of the lava flows. Peperites are often thought to form due to the presence of water within the unconsolidated sediments that the juvenile magma comes into contact with. However, examples from arid environments demonstrate that peperite-forming processes are diverse and may not always require water. Therefore, it is suggested that the term peperite should be used to describe deposits consisting of sediments mixed with juvenile magmatic components where it is clear that there has been a dynamic interaction between the two. This leaves the presence, or lack, of water as an issue for interpreting the processes by which the peperite formed. © 2002 Elsevier Science B.V. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2002.nat.dgeo.IGM.LG.lavase
Keywords: Aeolian; Etendeka; Lava-sediment interaction; Namibia; Peperite

Leaky top seals - Evidence, rates and mechanisms - Kurtev, Kuncho; Böker, Ulf; Drews, Michael; Abrakasa, Selegha; Aplin, Andrew (3rd International Conference on Fault and Top Seals: From Characterization to Modelling, 2012)

Lernort Geologie - de Wall, Helga; et al. (Hrsg.: Bayerisches Staatsministerium für Umwelt und Gesundheit (StMUG), Staatsinstitut für Schulqualität und Bildungsforschung (ISB) & GeoZentrum Nordbayern der FAU Erlangen-Nürnberg (GZN), 2009)
UnivIS-Import:2017-11-07:Pub.2009.nat.dgeo.IGM.c3tekt.lernor

Lethally hot temperatures during the Early Triassic - Sun, Yadong; Joachimski, Michael; Wignall, Paul B.; Yan, Chunbo; Chen, Yanlong; Jiang, Haishui; Wang, Lina; Lai, Xulong; Sun, Yadong (Science, 2012)
UnivIS-Import:2015-03-09:Pub.2012.nat.dgeo.IGM.LG.lethal

Life's complexity cast in stone - Kießling, Wolfgang (Science, 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dgeo.IGM.LP.lifesc

Limestone-marl alternations: A warm-water phenomenon? - Westphal, Hildegard; Munnecke, Axel (Geology, 2003)
Ancient limestone-marl alternations are concentrated in settings analogous to loci of aragonite accumulation in the modern world. They typically occur on shelves in the tropical-subtropical climate belt, are far more abundant on passive continental margins than on active ones, and are rare in upwelling zones. In recent studies, aragonite was proposed to play an important role in differential diagenesis typical of most limestone-marl alternations. The coincidence of depositional settings of ancient limestone-marl alternations and modern aragonite accumulation is a strong case for this hypothesis. If confirmed, it could provide a valuable tool for broad-scale paleoenvironmental interpretations. An additional, different type of limestone-marl alternations resulted from the Cretaceous explosion in productivity of calcitic plankton: these pelagic ones are fundamentally different in their style of diagenesi
Keywords: Aragonite; Differential diagenesis; Global maps; Limestone-marl alternations; Paleoenvironment; Rhythmites

Limestone - Marl alternations in epeiric sea settings - Witnesses of environmental changes or diagnesis? - Westphal, Hildegard; Munnecke, Axel; Böhm, Florian; Bornholdt, Stefan (2008)
Limestone-marl alternations are widespread and typical sediments of epeiric basins and are present in varying abundance throughout the Phanerozoic. In many cases, their rhythmic appearance has been interpreted as a direct response to orbital forcing. However, it is a challenge to unequivocally prove a sedimentary origin of the rhythmic intercalation of the two lithologies. This difficulty arises from differential diagenesis that alters calcareous beds in different ways than interlayers (marls), causing a loss of comparability between the final lithologies. Differential diagenesis, between other effects, causes passive enrichment of the inert non-carbonate fraction in interlayers, where calcium carbonate is dissolved, as well as passive dilution in limestone beds, which get cemented by imported calcium carbonate. Therefore, reliable information about primary systematic differences in the precursor sediments is preserved only in constituents that are not modified during diagenesis. Such diagenetically inert components include the spectra of organic-walled microfossils (but not their absolute concentration in the bulk sediment) and the ratios of certain trace elements (also not their absolute concentrations). Systematic differences in diagenetically inert components can provide unequivocal proof of primary differences. In the limestone-marl alternations, we have studied however, such aspects do not directly reflect the lithological rhythm, shedding doubt on limestone-marl alternations as direct archives of environmental change. Box-model computer simulations visualize possible effects of early diagenetic change acting on the precursors of limestone-marl alternations, independent of the presence or absence of a primary sedimentary rhythm. The simulations demonstrate that diagenesis has the potential to seriously distort any primary rhythm present in the pristine sediment. In particular, differential compaction acting mainly on the marl interlayers induces distortions of the ratios of the original frequencies. These simulations emphasize the difficulties in conducting frequency analyses on relative carbonate contents in real-world succession
Keywords: anactualism; aragonite; aragonite sea; calcite; calcite sea; cellular automaton; cementation; compaction; computer simulation; diagenesis; differential diagenesis; dissolution; distortion; environmental archive; environmental conditions; insolubles; limestone-marl alternation; Milankovitch; model; overprint; palynomorphs; sedimentary record; self- organization; stratigraphic record; rhythmites

Li/Mg systematics in scleractinian corals: Calibration of the thermometer - Montagna, Paolo; McCulloch, Malcolm; Douville, Eric; López Correa, Matthias; Trotter, Julie; Rodolfo-Metalpa, Ricardo; Dissard, Delphine; Ferrier-Pagès, Christine; Frank, Norbert; Freiwald, André; Goldstein, Steve; Mazzoli, Claudio; et al. (Geochimica Et Cosmochimica Acta, 2014)
We show that the Li/Mg systematics of a large suite of aragonitic coral skeletons, representing a wide range of species inhabiting disparate environments, provides a robust proxy for ambient seawater temperature. The corals encompass both zooxanthellate and azooxanthellate species (Acropora sp., Porites sp., Cladocora caespitosa, Lophelia pertusa, Madrepora oculata and Flabellum impensum) collected from shallow, intermediate, and deep-water habitats, as well as specimens cultured in tanks under temperature-controlled conditions. The Li/Mg ratios observed in corals from these diverse tropical, temperate, and deep-water environments are shown to be highly correlated with temperature, giving an exponential temperature relationship of: Li/Mg (mmol/mol)=5.41 exp (-0.049*T) (r2=0.975, n=49). Based on the standard error of the Li/Mg versus temperature correlation, we obtain a typical precision of ±0.9°C for the wide range of species analysed, similar or better than that of other less robust coral temperature proxies such as Sr/Ca ratios.The robustness and species independent character of the Li/Mg temperature proxy is shown to be the result of the normalization of Li to Mg, effectively eliminating the precipitation efficiency component such that temperature remains as the main controller of coral Li/Mg compositions. This is inferred from analysis of corresponding Li/Ca and Mg/Ca ratios with both ratios showing strong microstructure-related co-variations between the fibrous aragonite and centres of calcification, a characteristic that we attribute to varying physiological controls on growth rate. Furthermore, Li/Ca ratios show an offset between more rapidly growing zooxanthellate and azooxanthellate corals, and hence only an approximately inverse relationship to seawater temperature. Mg/Ca ratios show very strong physiological controls on growth rate but no significant dependence with temperature, except possibly for Acropora sp. and Porites sp. A strong positive correlation is nevertheless found between Li/Ca and Mg/Ca ratios at similar temperatures, indicating that both Li and Mg are subject to control by similar growth mechanisms, specifically the mass fraction of aragonite precipitated during calcification, which is shown to be consistent with a Rayleigh-based elemental fractionation model.The highly coherent array defined by Li/Mg versus temperature is thus largely independent of coral calcification mechanisms, with the strong temperature dependence reflecting the greater sensitivity of the Kd Li/Ca partition coefficient relative to Kd Mg/Ca. Accordingly, Li/Mg ratios exhibit a highly coherent exponential correlation with temperature, thereby providing a more robust tool for reconstructing paleo-seawater temperatures. © 2014 Elsevier Ltd.
UnivIS-Import:2015-03-09:Pub.2014.nat.dgeo.IGM.LP.limgsy

Limited latitudinal mantle plume motion for the Louisville hotspot - Koppers, Anthony A. P.; Yamazaki, Toshitsugu; Geldmacher, Joerg; Gee, Jeffrey S.; Pressling, Nicola; Hoshi, Hiroyuki; Anderson, L.; Beier, Christoph; Buchs, D. M.; Chen, L-H.; Cohen, B. E.; Deschamps, Fabien; et al. (Nature Geoscience, 2012)
Hotspots that form above upwelling plumes of hot material from the deep mantle typically leave narrow trails of volcanic seamounts as a tectonic plate moves over their location. These seamount trails are excellent recorders of Earth's deep processes and allow us to untangle ancient mantle plume motions. During ascent it is likely that mantle plumes are pushed away from their vertical upwelling trajectories by mantle convection forces. It has been proposed that a large-scale lateral displacement, termed the mantle wind, existed in the Pacific between about 80 and 50 million years ago, and shifted the Hawaiian mantle plume southwards by about 15° of latitude. Here we use 40 Ar/ 39 Ar age dating and palaeomagnetic inclination data from four seamounts associated with the Louisville hotspot in the South Pacific Ocean to show that this hotspot has been relatively stable in terms of its location. Specifically, the Louisville hotspot - the southern hemisphere counterpart of Hawai'i - has remained within 3-5° of its present-day latitude of about 51° €‰S between 70 and 50 million years ago. Although we cannot exclude a more significant southward motion before that time, we suggest that the Louisville and Hawaiian hotspots are moving independently, and not as part of a large-scale mantle wind in the Pacific. © 2012 Macmillan Publishers Limited. All rights reserved.

Linking the PETM and North Atlantic volcanism using tellurium in sediments - Baumann, Nils; Regelous, Marcel; Adatte, T.; Thibault, N. R.; Regelous, Anette; Schultz, B. P.; Fantasia, A.; Madsen, H.; Haase, Karsten (Palaeogeography, Palaeoclimatology, Palaeoecology, 2024)
The Paleocene – Eocene Thermal Maximum (PETM) was a short period (∼170 kyr) of global temperature rise starting at 55.93 Ma, which occurred during the breakup of the North Atlantic and the emplacement of the North Atlantic Igneous Province (NAIP). Recently, mercury (Hg) concentrations in sediments have been used in an attempt to connect the eruptive history of the NAIP with environmental change during this period, at a higher resolution than possible using geochronology. Here we present sedimentary tellurium (Te) as a novel proxy to further reconstruct NAIP volcanism at high resolution. We measured 45 trace elements in 401 sediment samples from 3 sections across the PETM in the northern hemisphere. All study sites exhibit an increase in Te concentrations and Te/Th ratios close to the onset of the PETM and remain high until the end of the main North Atlantic ash phase about 1 Myr later. The trace element data indicate that changes in sediment lithology or in environmental conditions do not influence sedimentary Te concentrations suggesting a volcanic source instead. We used existing age models to remove the effect of changes in sedimentation rate and calculated volcanic Te fluxes. Our Te data suggest increased volcanism in the latest Paleocene and early Eocene. This fits existing radiometric ages of the NAIP, which demonstrate that a more than 5 km thickness of lava in eastern Greenland and the Faroes was erupted within about 1 Myr between ∼56 to ∼55 Ma. All our study sites show similar Te flux variations across the PETM. In contrast, sedimentary mercury (Hg) profiles from these and other sites are less consistent. Tellurium in sediments may represent a useful proxy to reconstruct NAIP volcanism.
CRIS-Team Scopus Importer:2024-11-08
Keywords: PETM; Proxy; Tellurium; Volcanism

Lithium and boron isotope systematics in lavas from the Azores islands reveal crustal assimilation - Genske, Felix; Turner, Simon P.; Beier, Christoph; Haase, Karsten; Chu, Mei-Fei; Tonarini, Sonja; Pearson, Norman J. (Chemical Geology, 2014)
The stable isotope systems of Li and B are useful tools for the understanding of ocean island basalt genesis. We have applied both systems to a comprehensive set of well-characterised samples across the Azores islands in order to further evaluate the nature of the mantle source. These ocean islands represent the surface expression of a low-buoyancy mantle plume. The variability of Li and B concentrations and their isotopic compositions across the archipelago builds on recent radiogenic isotope studies from the islands to the west of the Mid-Atlantic Ridge (Flores and Corvo). The results for both systems yield some values that are typical for ocean island basalts; however, the variability of both δLi and δB observed in primitive lavas is most extreme on the western islands of Flores and Corvo (δLi=+3.5 to +8.2‰ and δB=-3.5 to +11.8‰). The large spread in isotopic composition is most likely due to contamination of the magmas during ascent through hydrothermally altered oceanic crust. Models of assimilation fractional crystallisation best explain the variability observed on each island and allow for robust estimates of the mantle source. The implication of these observations is that the interpretation of the radiogenic isotopes and trace elements may have to be treated with care if the stable isotopes record contamination by assimilation of hydrothermally altered material and that the use of Li and B as mantle source tracers may be obscured by shallow level processes. Further, it seems unlikely that the large range observed in Sr and Nd isotopes can reflect variable contributions from recycled low-T materials such as sediment or altered MORB, since there is no correlation between the radiogenic and stable isotope data. © 2014 Elsevier B.V.
Keywords: Assimilation; Azores mantle plume; Lithium-Boron isotopes; Ocean island basalts; Recycling

Lithium isotope evidence shows Devonian afforestation may have significantly altered the global silicate weathering regime - Liu, Xianyi; Krause, Alexander J.; Wilson, David J.; Fraser, Wesley T.; Joachimski, Michael; Brand, Uwe; Stigall, Alycia L.; Qie, Wenkun; Chen, Bo; Yang, Xiangrong; Pogge von Strandmann, Philip A.E. (Geochimica Et Cosmochimica Acta, 2025)
The Devonian period (∼359–419 Ma) documents significant environmental changes and marine species turnover, but whether these changes were linked to terrestrial weathering remains unknown. Here, we use lithium isotopes in brachiopods and bulk marine carbonates (δ7Licarb) from the Devonian period to investigate changes in silicate weathering, which represents the primary long-term atmospheric CO2 sink. A rise of ∼ 10 ‰ in δ7Licarb values (from ∼ 8 ‰ to ∼ 18 ‰) is observed across the Mid-Devonian (∼378–385 Ma), suggesting a major change in the seawater Li cycle. We attribute the rise in δ7Licarb values to an increase in the dissolved riverine Li flux and δ7Liriver values, which likely arose from increases in both weathering intensity and regolith thickness, related to the expansion of deep-rooted plants. However, the presence of such terrestrial ecosystems would also have restricted the continuous weathering of silicate rocks. In order to maintain high δ7Liseawater values in the Late Devonian, we propose that repeated cycles of destruction and regeneration of terrestrial forest ecosystems could have occurred, which would have prevented a supply-limited weathering regime from being permanently established. Such a process would potentially have caused oscillations in marine nutrient availability and redox conditions, thereby contributing to prolonged marine biodiversity loss during the Late Devonia
Keywords: Li isotopes; Devonian; Biosphere; Weathering; Carbonate diagenesis

Litho-climatic influences on groundwater geochemistry in Sri Lanka - Senarathne, Sachintha Lakshan; Barth, Johannes; van Geldern, Robert; Chandrajith, Rohana (Groundwater for Sustainable Development, 2024)
We present a preliminary investigation of geological, climatic and anthropogenic influences on groundwater geochemistry in Sri Lanka. This spatially confined island of about 65,000 km2 offers excellent boundary conditions for such an overview because it can be separated into two major geological and three climatic domains. Summary parameters, including electrical conductivity (EC) and total hardness (TH), were chosen as best proxies because they belong to the most frequently measured parameters of this data set. Groundwater quality data are presented from a total of 1318 groundwater samples. They were grouped into selected geo-climatic domains. Groundwater in the dry zone showed higher median EC and TH values (740 μS cm−1 and 199 mg L−1) when compared to the intermediate (400 μS cm−1 and 120 mg L−1) and wet zones (146 μScm−1 and 53 mg L−1). The sedimentary terrain of the county could be characterized by the highest median EC and TH values (1006 μS cm−1 and 261 mg L−1). In the metamorphic terrain that covers over 90% of the island, EC and TH values showed the strongest spatial variations that likely depend on climatic conditions. A correlation between EC and TH correlated with an r of +0.70. This trend suggests that EC can also serve as a robust indirect indicator of groundwater TH. Excessive evaporation, seawater intrusion and agricultural return flows affect groundwater quality, mostly in coastal regions, where freshwater demand increases. Sustainable groundwater management demands continuous and comprehensive monitoring of spatial and temporal fluctuations of groundwater. We also propose managed aquifer recharge to protect the long-term sustainability of groundwater in both sedimentary and metamorphic domains. This becomes particularly important under projected climate change scenarios in which drier regions in the country are expected to expand.
CRIS-Team Scopus Importer:2024-05-03
Keywords: Climate change; Electrical conductivity; Geo-climatic regions; Groundwater geochemistry; Total hardness

Lithogeochemistry of the Nesjavellir geothermal field, SW Iceland—Implications for elemental mass movement in active geothermal systems - Toro Vivanco, Diego I.; Kleine-Marshall, Barbara; Smit, Maud J.; Gunnarsdóttir, Sveinborg H.; Franzson, Hjalti; Stefánsson, Andri (Geothermics, 2024)
The lithogeochemistry of altered basalts was investigated to assess elemental mass changes in the active meteoric water dominated geothermal system at Nesjavellir, SW Iceland. The study revealed that elemental mass changes upon hydrothermal alteration is rather limited and the extent of metasomatism is controlled by the type of alteration minerals. Large mass movement was detected in volatiles (C and S), likely derived from magma degassing. The geothermal system at Nesjavellir may thus provide an ideal locality to investigate the natural sequestration of deep-sourced volatiles and deliver insights in quantifying the input of mantle degassing on the budget of geothermal systems.
Created from Fastlane, Scopus look-up
Keywords: Elemental mass transfer; Geothermal systems; Lithogeochemistry; Metasomatism; Water-rock interaction

Lithological and structural control of Hattian Bala rock avalanche triggered by the Kashmir earthquake 2005, sub-Himalayas, northern Pakistan - Basharat, Muhammad; Ehret, Dominik; Baig, Mirza Shahid; Rohn, Joachim (Journal of Earth Science, 2012)
Keywords: Kashmir earthquake 2005; mass movement; Muzaffarabad fault; northern Pakistan; rock avalanche

Lithological dependence of aragonite preservation in monospecific gastropod deposits of the Miocene Mainz Basin: Implications for the (dia-)genesis of limestone–marl alternations - Nohl, Theresa; Wetterich, Jannick; Fobbe, Nicholas; Munnecke, Axel (Journal of Sedimentary Research, 2020)

Lithologic, geomorphic, and climatic controls on sand generation from volcanic rocks in the Sierra Nevada de Santa Marta massif (NE Colombia) - Hatzenbühler, Diana; Caracciolo, Luca; Weltje, G. J.; Piraquive, A.; Regelous, Marcel (Sedimentary Geology, 2022)
Tectonics, climate, and lithology are the three main factors controlling the generation and transfer of sediments as well as their textural and compositional signatures. In this paper, we investigate the generation of sands from volcanic rocks in nine drainages with mixed lithological assemblage in a high-relief – subtropical climate setting (Sierra Nevada de Santa Marta, NE Colombia). The integration of geomorphological analysis with sand petrography, and bulk-rock and clay geochemistry allows us to constrain the dynamics regulating the generation of sediments derived from felsic and mafic-intermediate volcanic basement rocks in relation to plutonic and metamorphic lithologies. The petrographic composition of modern fluvial sands from the area is extremely variable (litho-feldspatho-quartzose, feldspatho-quartzose, and quartzose-feldspatho-lithic), but it reveals a strong dilution of (especially mafic) volcanic compositional signals, and a consequent overrepresentation of plutonic and metamorphic lithologies. Traditional chemical weathering indices fail to represent the extent of chemical alteration, but instead seem to favour preservation of provenance signals. Chemical weathering primarily affects feldspars and the ferromagnesian groundmass of mafic volcanic rock fragments. Enrichment of ferromagnesian elements in the clay fraction supports the notion that mafic volcanic rock fragments are unstable relative to plutonic and metamorphic rocks. Drainage features (particularly river network and relief) control the abundance of volcanic lithic fragments and the rates and extent of chemical weathering. A linear log-ratio model permits us to quantify sediment generation from volcanic rocks in this mixed-lithology setting. The results indicate that even in the case where volcanic grains are practically absent in the sand fraction, there could still be up to 20% of volcanic rocks in the drainage basin, and in the case that 50% of the sand grains are volcanic, around 75% of drained lithologies are expected to be volcanic. Our results demonstrate that the contribution of volcanic detritus to modern sands systematically underrepresents the areal proportion of volcanics rocks in mixed source areas. Post-depositional diagenetic modifications are likely to alter and/or dissolve volcanic lithic fragments, making accurate reconstruction of sediment provenance even more difficult. Sediment-generation models based on a range of mixed lithologies in various tectonic and climatic settings will be needed to improve estimates of the abundance of volcanic rocks in drainage basins of ancient sediment routing systems.
CRIS-Team Scopus Importer:2022-03-25
Keywords: Lithological; tectonic; and climatic controls; Quantitative provenance analysis; Sediment budget; Sediment generation; Weathering of volcanic rocks

Lithologierekonstruktion von submarinen Einheiten des Mauna Kea Vulkans mit bohrlochgeophysikalischen Messungen der magnetischen Suszeptibilität, HSDP Bohrung, Hawaii. - de Wall, Helga; et al. (11. Symposium "Tektonik, Struktur- und Kristallingeologie", 2006)
UnivIS-Import:2015-04-16:Pub.2006.nat.dgeo.IGM.c3tekt.lithol

LITHOLOGY CONTROLS AMMONOID SIZE DISTRIBUTIONS - de Baets, Kenneth; Jarochowska, Emilia; Buchwald, Stella Zora; Klug, Christian; Korn, Dieter (Palaios, 2022)
Body-size distributions of organisms across environments in space and time are a powerful source of information on ecological and evolutionary processes. However, most studies only focus on selected parameters of size distributions (e.g., central tendency or extremes) and rarely take into account entire distributions and how they are affected by the collection style and facies. Here we analyze the impact of facies, region, taxonomy, and collection style over size distributions using diameter as a proxy of Late Devonian ammonoids in their entirety using non-metric multidimensional scaling and PERMANOVA based on Kolmogorov distance. The effects are then compared with effects on mean sizes. In all analyses, lithology was the dominant effect, with sizes greater by 59% in marls and by 33% in limestones, as compared to black shales. The effect of complete sampling style was a decrease in size by 11%. Kurtosis was an important parameter differentiating size distributions, with platykurtic distributions in marls and leptokurtic distributions in limestones, suggesting that this parameter may reflect different degrees of time averaging. Most size distributions were positively skewed, but most strongly in marls. Complete sampling led to skewness values close to zero (symmetrical distributions) and high kurtosis.
CRIS-Team WoS Importer:2023-02-10

Lithology-specific influence of particle size distribution and mineralogical composition on thermal conductivity measurements of rock fragments - Kämmlein, Marion; Stollhofen, Harald (Geothermics, 2019)
Thermal conductivity data from reservoir rocks are key parameters for the analysis of heat transfer processes and heat flow patterns in geothermal exploration. Laboratory measurements of regional sample sets still provide the most reliable database. Since well cores are rarely available, rock fragments (e.g., drill cuttings) are the most common sample type for laboratory thermal conductivity measurements. However, the effects of the particle size of the rock fragments on the determination of thermal conductivity have not yet been discussed in a systematic study for different rock types. In this study, we used a line source device to investigate the influence of the particle size distribution of rock fragments and powder samples from different rock types on thermal conductivity measurements. The study focuses on three main objectives: <dl> 1. Does the particle size distribution of rock fragments impact thermal conductivity measurements of sample–water mixtures with a line source? 2. Are there lithology-specific differences in suitable particle sizes for measurements of thermal conductivity? 3. Is there an ‘ideal’ or an inappropriate particle size for measurements of rock fragments? </dl> Our study demonstrates that particle size effects on thermal conductivity determination of rock fragments and powders are unequivocal and that the accuracy of thermal conductivity determination can be improved by consideration of suitable, lithology-specific particle size ranges. The accuracy of measurement is related to the particle size distribution, mineralogical composition, competence under mechanical stress, and porosity of the sample–water mixtures during the measurement. For almost monomineralic limestones without significant clay volume fractions, powder samples with particle sizes ≤0.063 mm are most appropriate. In the case of argillaceous sandstone, powder samples are an inappropriate sample type, and instead, coarse rock fragment samples with mean particle sizes of 0.9–1.3 mm are recommended.
Keywords: Thermal conductivity; Particle size; Rock fragments; Mineralogical composition; Powder; Drill cuttings

Lithospheric control on geochemical composition along the Louisville Seamount Chain - Beier, Christoph; Vanderkluysen, Loyc; Regelous, Marcel; Mahoney, John J.; Garbe-Schoenberg, Dieter (Geochemistry Geophysics Geosystems, 2011)
Major and trace element and Sr, Nd, and Pb isotope data for lavas from 12 seamounts along the western (older) 1500 km section of the Louisville Seamount Chain in the southwest Pacific show remarkably uniform compositions over a ∼30-40 Myr period of volcanism. All 56 samples analyzed are alkalic to transitional in composition. Unlike Hawaiian volcanoes, Louisville volcanoes appear not to pass through a sequence of evolutionary stages characterized by older tholeiitic basalts overlain by incompatible element enriched alkalic and silica-undersaturated lavas. The youngest lavas from a given Louisville seamount tend to have the least enriched incompatible element compositions. This unusual chemical evolution may be the result of re-melting of heterogeneous hot spot mantle that was partially depleted during the earlier, age progressive stages. The oldest Louisville seamounts were constructed close to the extinct Osbourn Trough spreading center, located north of the chain, but age-progressive lavas from these older seamounts are not significantly different to lavas from younger seamounts. This may indicate that spreading at this fossil ridge ceased several tens of millions of years before the oldest Louisville seamounts were constructed. Large fracture zones apparently had no significant effects on the composition of Louisville magmatism. However, lavas from the central part of the Louisville Seamount Chain, where volcanoes are smaller and more widely spaced, tend to have more variable and more enriched compositions. We suggest this may reflect smaller degrees of melting resulting from greater lithosphere thickness, and hence a shorter melting column for this section of the Louisville Seamounts. © 2011 by the American Geophysical Union.
Keywords: lithosphere thickness; Louisville Seamount Chain; melting dynamics; plume evolution; spreading centre

Lithostratigraphy and depositional environments in the Waterberg-Erongo area, central Namibia, and correlation with the main Karoo Basin, South Africa. - Holzförster, Frank; Stollhofen, Harald; Stanistreet, Ian G. (Journal of African Earth Sciences, 1999)
The dissected landscape of the Waterberg-Erongo area, central Namibia, exposes Karoo-equivalent strata deposited in basins that occur throughout sub-Saharan Africa. Although many are of economic interest, including coal-bearing strata, their depositional history is not well understood. This study of the Waterberg-Erongo area provides detailed lithostratigraphical data, which suggest sedimentation from the late Early Triassic to the Early Jurassic in a fault-bounded depository. Subsidence and sediment supply were controlled predominantly by the northeast-southwest trending Waterberg-Omaruru Fault Zone, which defines the northwestern margin of the depository. Facies development and thickness distribution of the Karoo strata in the Waterberg-Erongo area, perhaps the most continuous of any of the Karoo basins, indicate a northeastwardly-migrating depocentre alongside that fault, in response to major extensional movements in the early pre-South Atlantic rift zone. Periodic fault movements repeatedly caused basinward progradation of the alluvial facies, which are reflected by stacked fining-upward cycles in the lithological record. On a broader scale, the results of this study suggest that the northward propagation of the rift zone between Southern Africa and South America, was partially accommodated by transfer lineaments. Local depocentres developed along these lineaments, such as those in the Waterberg-Erongo area, with localised enhanced subsidence greater than that revealed in other Namibian onshore exposures, dominated by the rifting itself.
UnivIS-Import:2015-03-05:Pub.1999.nat.dgeo.IGM.LG.lithos_0

Living to the range limit: Consumer isotopic variation increases with environmental stress - Reddin, Carl James; O'Connor, Nessa; Harrod, Chris (PeerJ, 2016)
Keywords: Diet; Intertidal; Isotopic niche; Littorinid; Physiological condition; Range limit; Stable isotopes; Stress gradient; Trophic niche width; Trophic variation

Local-scale assessment of the displacement pattern of a densely populated landslide, utilizing finite element software and terrestrial radar interferometry: a case study on Huangtupo landslide (P.R. China) - Dumperth, Christian; Fleer, Alexander; Xiang, Wei; Rohn, Joachim (Environmental Earth Sciences, 2016)
Keywords: ArcGIS; Finite element analysis; Huangtupo; Radar interferometry; Susceptibility; Three Gorges Dam

Long-term cement hydration studies with isothermal calorimetry - Linderoth, O.; Wadsö, L.; Jansen, Daniel (Cement and Concrete Research, 2021)
The purpose of this study was to investigate for how long the thermal power of hydration can be measured with isothermal calorimetry, which is a general measurement technique with stable properties that, in many cases, can detect low rates of processes. Measurements were conducted for 365 days on cement paste with Portland cement, fly ash blended Portland cement and different water-to-binder ratios. The results showed that all the tested systems still produced a measureable signal after one year. The samples with Portland cement were also analyzed by XRD after 365 days, and phase composition calculations were made with GEMS. Together with the calorimetric results, these results were used to determine the degree of hydration by five methods, the results of which showed good agreement.
CRIS-Team Scopus Importer:2021-01-15
Keywords: Calorimetry; Cement paste; Hydration; Rietveld analysis; X-ray diffraction

Long-term dynamics of dissolved oxygen and isotopic composition in Lake Erie and Lake Ontario: Implications for eutrophication and ecosystem health - Dordoni, Marlene; Barth, Johannes; Wassenaar, Leonard I. (Journal of Great Lakes Research, 2024)
This study, focusing on Great Lakes Erie and Ontario, Canada, explores dissolved oxygen (DO) dynamics and its stable isotopic composition (δ18ODO) in the Great Lakes. Using historical dissolved oxygen data from 1965 to 2021, combined with synoptic isotopic data collected in the early 2000s, the research examined the spatiotemporal trends in DO and δ18O-DO to assess the effects of biotic and abiotic processes such as photosynthesis, respiration, and atmospheric gas exchange. The study revealed significant seasonal and depth-related variations in DO levels, with hypolimnetic hypoxia and metalimnetic oxygen minima (MOM) observed in both lakes. With its comparatively shallow depth and higher nutrient loads, Lake Erie exhibited more pronounced dissolved oxygen fluctuations, with DO levels reaching as low as 3.65 mg L−1 and δ18ODO values falling below +24.6 ‰. These findings indicated Lake Erie's more dynamic metabolic environment, particularly during the thermally stratified season. In contrast, Lake Ontario showed more stable oxygen concentration levels, with occasional dissolved oxygen depletions down to 6.80 mg L−1 and δ18ODO values up to +32.1 ‰, suggesting more localised influences of external inputs and biological processes. This study provides a long-term perspective on dissolved oxygen status in these lakes and offers essential insights into their ecological health. This work contributes valuable data for managing and protecting the Great Lakes ecosystem.
CRIS-Team Scopus Importer:2024-10-11
Keywords: Dissolved oxygen; Dissolved oxygen isotopes (; Great Lakes; Hypolimnetic hypoxia; Lake Erie; Lake Ontario; Metalimnetic Oxygen Minimum (MOM)

Long-term relationships between ecological stability and biodiversity in Phanerozoic reefs - Kießling, Wolfgang (Nature, 2005)
High biodiversity has been shown to enhance ecological stability on small spatial scales and over intervals of weeks to decades. It remains unclear, however, whether this diversity-stability relationship can be scaled up to regional scales, or to longer timescales. Without empirical validation at larger scales, the implications of the diversity-stability relationship for both ecology and long-term conservation strategies cannot readily be resolved. Here I show that in biogenic reefs, ecological stability is related to taxonomic diversity on million-year timescales. The higher the mean reef diversity in a particular time interval, the smaller the change in skeletal density, style of reef building and biotic reef types in the subsequent time interval. Because the relationships apply to a wide spectrum of disturbance regimes and reef types, these results support the hypothesis that species richness itself promotes ecological stability. Carbonate production by reefs, while closely correlated with reef diversity without temporal lag, is not stabilized by reef diversity over these long timescales. This suggests that ecological stability and productivity may be decoupled in natural ecosystems.
UnivIS-Import:2015-03-09:Pub.2005.nat.dgeo.IGM.LP.longte

Lost in transition – the selective compaction of a halysitid coral and its implications for diagenesis and time - Nohl, Theresa; Munnecke, Axel (GeoBonn2018 - Living Earth, 2018)

Louisville Seamount Chain: Petrogenetic processes and geochemical evolution of the mantle source - Vanderkluysen, Loyc; Mahoney, John J.; Koppers, Anthony A. P.; Beier, Christoph; Regelous, Marcel; Gee, Jeffrey S.; Lonsdale, Peter F.; Haase, Karsten (Geochemistry Geophysics Geosystems, 2014)
The Louisville Seamount Chain is a ∼4300 km long chain of submarine volcanoes in the southwestern Pacific that spans an age range comparable to that of the Hawaiian-Emperor chain and is commonly thought to represent a hot spot track. Dredging in 2006 recovered igneous rocks from 33 stations on 22 seamounts covering some 49 Myr of the chain's history. All samples are alkalic, similar to previous dredge and drill samples, providing no evidence for a Hawaiian-type tholeiitic shield-volcano stage. Major and trace element variations appear to be predominantly controlled by small but variable extents of fractional crystallization and by partial melting. Isotopic values define only a narrow range, in agreement with a surprising long-term source homogeneity - relative to the length scale of melting - and overlap with proposed fields for the "C" and "FOZO" mantle end-members. Trace element and isotope geochemistry is uncorrelated with either seamount age or lithospheric thickness at the time of volcanism, except for a small number of lavas from the westernmost Louisville Seamounts built on young (<20 Ma old) oceanic crust. The Louisville hot spot has been postulated to be the source of the ?120 Ma Ontong Java Plateau, but the Louisville isotopic signature cannot have evolved from a source with isotopic ratios like those measured for Ontong Java Plateau basalts. On the other hand, this signature can be correlated with that of samples dredged from the Danger Islands Troughs of the Manihiki Plateau, which has been interpreted as a rifted fragment of the "Greater" Ontong Java Plateau. Key Points LSC mantle source is surprisingly homogeneous A Hawaiian-type tholeiitic shield-volcano stage is absent from LSC seamounts LSC mantle source is isotopically distinct from Ontong Java source © 2014. American Geophysical Union. All Rights Reserved.
Keywords: geochemistry; hot spot; Louisville; mantle plumes; ocean island basalt; seamount

Lower crustal hot zones as zircon incubators: Inherited zircon antecryts in diorites from a mafic mush reservoir - Lim, Hoseong; Nebel, Oliver; Weinberg, Roberto F.; Nebel-Jacobsen, Yona; Barrote, Vitor R.; Park, Jongkyu; Myeong, Bora; Cawood, Peter A. (Geological Society of London, 2024)
Continental arcs are key sites of granitic magmatism, yet details of the origins of these magmas, including the role and contribution of mafic magma, the timing and location of initial zircon formation and how zircon isotopic signatures relate to granite formation, remain as challenges. Here we use U–Pb dating, trace elements and Hf isotopic systematics of zircon in mafic microgranular enclaves (MMEs), from the convergent plate margin Satkatbong diorite (SKD) in Korea to understand lower arc magmatism and zircon pro-duction. The host granitic body and MMEs display similar major element evolutionary trends and similar ranges of Sr, Nd and Hf isotopes, implying a cognatic relationship. Zircons show a large variability in εHf (t)(c. 6 units) and age (>30 Ma). We propose that the SKD and MMEs originated from the same, long-lasting, lower crustal mush reservoir, enabling long and variable residence times for zircons. Prolonged zircon ages, combined with the Hf isotope variability within a single pluton (SKD and its MME), indicate that not all zircons were instantaneously crystallized in a rapidly cooling shallow magma chamber but were continuously formed in a long-lasting hot source. A low-melt-fraction mush type reservoir in a deep crustal hot zone provides a viable model for the source setting. Continuous replenishment of mafic magmas acts as the main re-activator of the reservoir, and provide a critical role in spawning zircons that record a long age span, because (1) the magma adds Zr into the reservoir, enabling it to reach zircon saturation and (2) the generated zircon grains are trans-ported upward as antecrysts by flow inside of the reservoir. This means that antecrysts with different ages may mix with each other in the ascending magma body. The significance of this model is that a conclusive time of intrusion cannot be constrained by such zircon ages, as these antecrysts constitute inherited grains.
CRIS-Team Scopus Importer:2024-01-19

Lower crustal hydrothermal circulation at slow-spreading ridges: evidence from chlorine in Arctic and South Atlantic basalt glasses and melt inclusions - van der Zwan, Froukje; Devey, Colin; Hansteen, Thor; Almeev, Renat; Augustin, Nico; Frische, Matthias; Haase, Karsten; Basaham, Ali; Snow, Jon (Contributions To Mineralogy and Petrology, 2017)
Keywords: (Ultra)slow-spreading ridges; Chlorine; Crustal assimilation; Crystallization depths; Hydrothermal circulation; MORB

Lower-Middle Ordovician δ 13C chemostratigraphy of western Baltica (Jämtland, Sweden) - Wu, R.; Calner, Michael; Lehnert, Oliver; Petterfy, O.; Joachimski, Michael (Palaeoworld, 2015)
The province of Jämtland, central Sweden, records a well-preserved but very thin suite of the Lower-Middle Ordovician cool-water carbonates. In this study we present the first carbon isotope profile for these strata on the basis of whole-rock samples from the Brunflo 2 core. The studied succession is 41.55m thick and includes, in ascending order, the Bjørkåsholmen Formation, Latorp Limestone, Tøyen Shale, and the Lanna, Holen, and Segerstad limestones. We identify two distinct positive δ13C excursions that can be used for intra- as well as inter-continental correlations. A positive excursion in the Tøyen Shale probably correlates to the mid-late Floian and the Oepikodus evae Zone in Baltica and Precordillera, and the Reutterodus andinus Zone in North America. A continuous increase in δ13C values through the upper Holen Limestone and the preserved part of the overlying Segerstad Limestone is interpreted as the rising limb of the Middle Darriwilian Isotope Carbon Excursion (MDICE), an important tie-point for the global correlation of the Jämtland strata. Negative δ13C values associated with the Latorp Limestone may correlate with similar low values in the late Tremadocian and early Floian of the Argentine Precordillera and the Shingle Pass and Ibex sections in North America.
Keywords: Carbon isotope chemostratigraphy; MDICE; Ordovician; Sweden

Lower Palaeozoic geology of southern Sweden - Calner, Mikael; Erlström, Mikael; Lehnert, Oliver; Ahlberg, Per (The Lower Palaeozoic of southern Sweden and the Oslo Region, Norway. Field Guide for the 3rd Annual Meeting of the IGCP project 591, 2013)
UnivIS-Import:2015-03-09:Pub.2013.nat.dgeo.IGM.LG.lowerp_5

Low-latitude vegetation and climate dynamics at the Paleocene-Eocene transition - A study based on multiple proxies from the Jathang section in northeastern India - Prasad, V.; Utescher, T.; Sharma, A.; Singh, I. B.; Garg, R.; Gogoi, B.; Srivastava, J.; Uddandam, P. R.; Joachimski, Michael (Palaeogeography, Palaeoclimatology, Palaeoecology, 2018)
Keywords: Climate change; Paleotropics; Palynology; PETM; Precipitation; Rainforest

Low water contents in garnet of orogenic peridotite: clues for an abyssal or mantle-wedge origin? - Schmädicke, Esther; Gose, Jürgen (European Journal of Mineralogy, 2019)
Data on water in nominally anhydrous minerals (NAMs) of orogenic garnet-bearing ultramafic rocks (GBU) are extremely rare. In this study, garnet of peridotite and pyroxenite from Erzgebirge (EG), Germany, and two peridotite samples from Alpe Arami (AA), Switzerland, were analyzed by infrared (IR) spectroscopy. Garnet from EG peridotite and pyroxenite yielded IR absorption bands at 3650 +/- 10 cm(-1) (type I) and in the wavenumber range of 3570-3630 cm(-1 )(type II) that are ascribed to structural hydroxyl (colloquially "water"). Additional broad band's centered at <3460 cm(-1), present in about half of the samples, are related to molecular water (MW). The content of structural H2O defined by band types I + II is low (3-68 ppm) in all EG samples. Structural water is negatively correlated to Mg and Ti and positively to Y and HREE in EG garnet. Including molecular water, a pronounced positive correlation between H2O and Li is observed. Because the intensity of the type II band is enhanced in domains with molecular water, the primary, peak metamorphic H2O content in EG garnet was probably as low as 0-11 ppm. Equally low contents of structural water are present in AA garnet (10-13 ppm) in which molecular water is negligible. Such concentrations are distinctly lower than the water storage capacity of garnet at the relevant pressure. Water loss upon decompression cannot serve as an explanation for the low contents because, on the contrary, post-peak-metamorphic influx of H2O led garnet to take up secondary structural water. Hence, the results are interpreted as an indication of severe water deficiency at peak metamorphism. Notably, the obtained data agree with the H2O content of 6 ppm reported in garnet from Cima di Gagnone peridotite, which originated as abyssal peridotite. It remains unknown if these low contents are typical for an abyssal, low-pressure protolith but, if the rocks were part of the lowermost, most hydrated portion of the mantle wedge, they are expected to contain much more water. Given that garnet in basaltic coesite eclogite from the Erzgebirge is equally water-deficient as the GBU samples from the same unit, it is at least a possibility that both rock types share a low-pressure origin in an oceanic setting.
CRIS-Team WoS Importer:2019-11-29

LREE rich perovskite in antiskarn reactions - REE transfer from pyroxenites to carbonatites? - Voropaeva, Daria; Arzamastsev, Andrei A.; Botcharnikov, Roman; Buhre, Stephan; Gilbricht, Sabine; Götze, Jens; Klemd, Reiner; Schulz, Bernhard; Tichomirowa, Marion (Lithos, 2024)
We study three ultrabasic-alkaline carbonatite complexes (UACCs: Afrikanda, Vuorijarvi, Kovdor) from the Kola Alkaline Province to focus on the comparison of REE contents from pyroxenites and carbonatites and the fate of perovskite. Pyroxenites and carbonatites have large REE variations and similar contents in all three complexes. Afrikanda and Vuorijarvi pyroxenites and carbonatites have higher REE contents compared to all Kovdor rocks. Despite their comparable LREE contents, pyroxenites and carbonatites have different REE-carrier minerals. In most studied pyroxenites, perovskite is the main REE-bearing mineral and its abundance controls the LREE enrichment of the whole rock. When perovskite is absent or in low abundance, apatite is the main REE carrier. Instead, in carbonatites and phoscorites, apatite and calcite control REE contents. REE‑carbonates - found in several carbonatite samples - do not play a substantial role in the overall REE budget because of their very low abundance and tiny grain sizes. We found large LREE variations at very low local scales (< 1 mm) in several thin sections. These large variations are related to carbonatite infiltration and associated antiskarn reactions. Perovskite near calcite is replaced by titanite that has much lower LREE contents. Most LREE released from the breakdown of perovskite were probably dissolved in the carbonatite melt because apatite and calcite that crystallized from this melt are highly enriched in LREE. Newly formed apatites and calcites show large LREE variations that probably are controlled by local factors (e.g. variations of Si, Ca, Mg activities). Y/Ho ratios are strongly fractionated in most minerals and often show large variations at local scales (mm) in these antiskarn reactions. The potential of REE remobilization from such perovskite replacement reactions is very high as perovskite contributes about 70% to the REE budget for these three UACCs. Therefore, more attention should be given to perovskite replacement reactions and its role for LREE enrichment of carbonatite melts.
CRIS-Team Scopus Importer:2024-02-02
Keywords: Antiskarn reactions; Apatite; Carbonatite; Kola alkaline province; Perovskite; Rare earth elements

Machine learning-based re-classification of the geochemical stratigraphy of the Rajahmundry Traps, India - Hoyer, Patrick; Regelous, Marcel; Adatte, Thierry; Haase, Karsten (Journal of Volcanology and Geothermal Research, 2022)
The lavas exposed at the Rajahmundry Traps have similar ages and geochemical compositions compared to those from the Ambenali and Mahabaleshwar formations of the Deccan Traps, which is why they are believed to represent their eastern extensions. However recent geochronological data for the lavas crop out in the Rajahmundry quarries and paleontological evidence from the expanded sediment-lava sequences preserved in the Krishna-Godavari Basin indicate that the lower Rajahmundry Flow could represent a flow of the Poladpur formation. Here we present new major and trace element data for lavas of the lower (five samples) and middle (three samples) Rajahmundry Flows exposed in the Gowripatnam Quarry. To test whether the lower Rajahmundry Flow show geochemical similarities to the Poladpur formation, we applied a machine learning-based classification model which is able to predict the most probable formation affiliation for an unknown sample. The classification method we used is the Random Forest algorithm and training as well as testing our model with new and published geochemical data from the Poladpur and Ambenali formations (n = 73) by using Repeated K-Fold Cross Validation yields a prediction accuracy of 86%. According to our model results, the lavas of the lower Rajahmundry Flow were assigned to the Poladpur formation, while those from the middle Rajahmundry Flow show geochemical similarities to the Ambenali formation. Flows of each of the voluminous Deccan formations (Poladpur, Ambenali and Mahabaleshwar) are therefore present at Rajahmundry, confirming that these are an eastward extension of the Deccan Traps.
CRIS-Team Scopus Importer:2022-06-17
Keywords: Continental flood basalts; Cretaceous-Paleogene boundary; Deccan Traps; Machine learning classification model; Rajahmundry Traps

Mafic rocks from Erinpura gneiss terrane in the Sirohi region: Possible ocean-floor remnants in the foreland of the Delhi Fold Belt, NW India - Pandit, M. K.; de Wall, Helga; Daxberger, H.; Just, J.; Bestmann, Michel; Sharma, K. K. (Journal of Earth System Science, 2011)
Keywords: Daba mafic rocks; Geochemistry; Magnetic fabric; Neoproterozoic; NW India; Phulad ophiolite

Magma evolution of the Sete Cidades volcano, São Miguel, Azores. - Beier, Christoph; Hansteen, Thor; Haase, Karsten (Journal of Petrology, 2006)
The Sete Cidades volcano (São Miguel, Azores) is situated at the eastern end of the ultraslow spreading Terceira rift axis. The volcano comprises several dominantly basaltic pre-caldera eruptions, a trachytic caldera-forming stage and a post-caldera stage consisting of alternating trachytic and basaltic eruptions. The post-caldera flank lavas are more primitive (>5 wt % MgO) than the pre-caldera lavas, implying extended fractional crystallization and longer crustal residence times for the pre-caldera, shield-building lavas. Thermobarometric estimates show that the ascending alkali basaltic magmas stagnated and crystallized at the crust-mantle boundary (∼15 km depth), whereas the more evolved magmas mainly fractionated in the upper crust (∼3 km depth). The caldera-forming eruption was triggered by a basaltic injection into a shallow trachytic magma chamber. Lavas from all stages follow a single, continuous liquid line of descent from alkali basalt to trachyte, although slight differences in incompatible element (e.g. Ba/Nb, La/Nb) and Sr isotope ratios imply some heterogeneity of the mantle source. Major and trace element data suggest similar partial melting processes throughout the evolution of the volcano. Slight geochemical differences between post- and pre-caldera stage lavas from the Sete Cidades volcanic system indicate a variation in the mantle source composition with time. The oxygen fugacity increased from the pre-caldera to the post-caldera stage lavas, probably as a result of the assimilation of crustal rocks; this is supported by the presence of crustal xenoliths in the lavas of the flank vents. The lavas from the Sete Cidades volcano generally have low Sr isotope ratios; however, rocks from one post-caldera vent on the western flank indicate mixing with magmas resembling the lavas from the neighbouring Agua de Pau volcano, having higher Sr isotope ratios. The different magma sources at Sete Cidades and the adjacent Agua de Pau volcano imply that, despite their close proximity, there is only limited interaction between them. © 2006 Oxford University Press.
UnivIS-Import:2015-03-09:Pub.2006.nat.dgeo.IGM.legeo.magmae
Keywords: Crystallization depth; Fractionation; Stratigraphy; Terceira rift; Volcanic stages

Magma genesis and crustal contamination of continental intraplate lavas in NW Syria. - Krienitz, Marc-Sebastian; Haase, Karsten; Mezger, Klaus; Eckhardt, Viola; Shaikh-Mashail, M.A. (Contributions To Mineralogy and Petrology, 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dgeo.IGM.legeo.magmag

Magma genesis and mantle dynamics at the Harrat Ash Shamah Volcanic Field (southern Syria). - Krienitz, Marc; Haase, Karsten; Mezger, Klaus; Shaikh-Mashail, M.A. (Journal of Petrology, 2007)
A geochemical and petrological study of Miocene to recent alkali basalts, basanites, hawaiites, mugearites, trachytes, and phonolites erupted within the Harrat Ash Shamah volcanic field was performed to reconstruct the magmatic evolution of southern Syria. The major element composition of the investigated lavas is mainly controlled by fractional crystallization of olivine, clinopyroxene, ± Fe-Ti oxides and ± apatite; feldspar fractionation is restricted to the most evolved lavas. Na2O and SiO2 variations within uncontaminated, primitive lavas as well as variably fractionated heavy rare earth element ratios suggest a formation by variable degrees of partial melting of different garnet peridotite sources triggered, probably, by changes in mantle temperature. The isotopic range as well as the variable trace element enrichment observed in the lavas imply derivation from both a volatile- and incompatible element-enriched asthenosphere and from a plume component. In addition, some lavas have been affected by crustal contamination. This effect is most prominent in evolved lavas older than 3.5 Ma, which assimilated 30-40% of crustal material. In general, the periodicity of volcanism in conjunction with temporal changes in lava composition and melting regime suggest that the Syrian volcanism was triggered by a pulsing mantle plume located underneath northwestern Arabia. © The Author 2007. Published by Oxford University Press. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2007.nat.dgeo.IGM.legeo.magmag
Keywords: Intraplate volcanism; Mantle plume; Partial melting; Syria

Magma genesis by rifting of oceanic lithosphere above anomalous mantle: Terceira Rift, Azores. - Beier, Christoph; Haase, Karsten; Abouchami, Wafa; Krienitz, Marc-Sebastian; Hauff, Folkmar (Geochemistry Geophysics Geosystems, 2008)
The Terceira Rift formed relatively recently (̃1 Ma ago) by rifting of the old oceanic lithosphere of the Azores Plateau and is currently spreading at a rate of 2-4mm/a. Together with the Mid-Atlantic Ridge, the Terceira Rift forms a triple junction that separates the Eurasian, African, and American Plates. Four volcanic systems (São Miguel, João de Castro, Terceira, Graciosa), three of which are islands, are distinguished along the axis and are separated by deep avolcanic basins similar to other ultraslow spreading centers. The major element, trace element and Sr-Nd-Pb isotope geochemistry of submarine and subaerial lavas display large along-axis variations. Major and trace element modeling suggests melting in the garnet stability field at smaller degrees of partial melting at the easternmost volcanic system (São Miguel) compared to the central and western volcanoes, which appear to be characterized by slightly higher melting degrees in the spinel/garnet transition zone. The degrees of partial melting at the Terceira Rift are slightly lower than at other ultraslow mid-ocean ridge spreading axes (Southwest Indian Ridge, Gakkel Ridge) and occur at greater depths as a result of the melting anomaly beneath the Azores. The combined interaction of a high obliquity, very slow spreading rates, and a thick preexisting lithosphere along the axis probably prevents the formation and eruption of larger amounts of melt along the Terceira Rift. However, the presence of ocean islands requires a relatively stable melting anomaly over relatively long periods of time. The trace element and Sr-Nd-Pb isotopes display individual binary mixing arrays for each volcanic system and thus provide additional evidence for focused magmatism with no (or very limited) melt or source interaction between the volcanic systems. The westernmost mantle sources beneath Graciosa and the most radiogenic lavas from the neighboring Mid-Atlantic Ridge suggest a mantle flow from Graciosa toward the Mid-Atlantic Ridge and hence a flux of mantle material from one spreading axis into the other. The Terceira Rift represents a unique oceanic rift system situated within the thickened, relatively old oceanic lithosphere and thus exhibits both oceanic and continental features. © 2008 by the American Geophysical Union.
UnivIS-Import:2015-03-09:Pub.2008.nat.dgeo.IGM.legeo.magmag
Keywords: Azores; Geochemistry; Incompatible elements; Ocean Island Basalts; Radiogenic isotopes; Spreading center

Magmatic and hydrothermal evolution of the Skouries Au-Cu porphyry deposit, northern Greece - Höß, Alica; Haase, Karsten; Keith, Manuel; Klemd, Reiner; Melfos, Vasilios; Gerlach, Lisa; Pelloth, Fabian; Falkenberg, Jan; Voudouris, Panagiotis; Strauss, Harald; Baker, Tim; Tarantola, Alexandre (Ore Geology Reviews, 2024)
The Skouries Au-Cu porphyry deposit is located in northern Greece and hosted by quartz monzonites and monzogranites of early Miocene age (∼20 Myr). The host rocks show geochemical similarities to other mafic to felsic intrusions in the district that have a similar strike direction, but which are 6 Myr older and lack evidence of economic mineralization. The Skouries magmas probably formed by fractional crystallization of mafic mantle-derived melts, from which the ore-forming fluids were released during second boiling accompanied by massive feldspar crystallization at ∼65 wt% SiO2. Drill core samples record the dominant potassic alteration with A- and B-type veins, which are locally overprinted by chlorite-sericite alteration and related C-type veins, transitioning into sericitic alteration assemblages and D-type veins. The ore mineralization is characterized by chalcopyrite, bornite, pyrite, magnetite and accessory minerals, such as tellurides and PGE minerals. Incompatible trace element ratios of the host rocks, that are commonly used as tracers of magma fertility (e.g., Sr/Y, La/Sm), vary between the alteration-types and may therefore not generally provide a record of magmatic processes. Fluid inclusion and Ti-in-quartz thermometry yielded a temperature range of 520 to >600 °C for the A-type veins and 420 to 500 °C for the B-type veins. Decreasing fluid inclusion entrapment pressures suggest relatively rapid uplift of the hydrothermal system during the early- to main porphyry stage. Fluid inclusion compositions indicate that early K- and Cl-rich fluids caused the potassic alteration resulting in a strong mobilization of REEs, following a decrease in fluid salinity and temperature with proceeding porphyry evolution. Systematic variations in trace element contents (e.g., As, Ag, Pb) and ratios (e.g., As/Sb, Zn/Pb) of pyrite record fluid temperature changes and suggest early phase separation as a major ore-forming process. The common occurrence of native Au as inclusions in pyrite and chalcopyrite are indicative of early Au oversaturation in the fluid, which we relate to sulfide precipitation and phase separation, destabilizing the AuHS0 or Au(HS)2- complex, leading to the accumulation of Au particles. The formation of such Au colloids in fluids may thus reflect an important step towards the hydrothermal enrichment of Au in porphyry environments.
CRIS-Team Scopus Importer:2024-09-27
Keywords: Au nanoparticles; Fluid inclusion microthermometry; LA-ICP-MS; Porphyry deposit; Pyrite chemistry; Trace element systematics

Magmatic evidence for carbonate metasomatism in the lithospheric mantle underneath the Ohře (Eger) Rift - Brandl, Philipp; Genske, Felix; Beier, Christoph; Haase, Karsten; Sprung, Peter; Krumm, Stefan (Journal of Petrology, 2015)
Magmas erupted in intracontinental rifts typically form from melting of variable proportions of asthenospheric or lithospheric mantle sources and ascend through thick continental lithosphere. This ascent of magma is accompanied by differentiation and assimilation processes. Understanding the composition of rift-related intracontinental volcanism is important, particularly in densely populated active rift zones such as the Ohře (Eger) Rift in Central Europe. We have sampled and analysed nephelinites from Železná hůrka (Eisenbühl), the youngest (<300 ka) Quaternary volcano related to the Ohře Rift where frequent earthquake swarms indicate continuing magmatic activity in the crust. This nephelinite volcano is part of a larger eruptive centre (Mỳtina Maar) representing a single locality of recurrent volcanism in the Ohře Rift. We present a detailed petrographic, mineralogical and geochemical study (major and trace elements and Sr-Nd-Hf-O isotopes) of Železná hůrka to further resolve the magmatic history and mantle source of the erupted melt. We find evidence for a highly complex evolution of the nephelinitic melts during their ascent to the surface. Most importantly, mixing of melts derived from different sources and of strong chemical contrast controls the composition of the erupted volcanic products. These diverse parental melts originate from a highly metasomatized subcontinental lithospheric mantle (SCLM) source. We use a combined approach based on mineral, glass and whole-rock compositions to show that the mantle underneath the western Ohře Rift is metasomatized dominantly by carbonatitic melts. The nephelinites of Železná hůrka formed by interaction between a carbonatitic melt and residual mantle peridotite, partial crystallization in the lithospheric mantle and minor assimilation of upper continental crust. Thermobarometric estimates indicate that the stagnation levels of the youngest volcanism in this part of the Ohře Rift were deeper than the focal depths of recent earthquake swarms, indicating that those are not directly linked to magma ascent. Furthermore, close mineralogical and geochemical similarities between the Železná hůrka nephelinite and fresh kimberlites may point towards a genetic link between kimberlites, melilitites and nephelinites.
Keywords: Assimilation; Carbonated peridotite; Continental rift; Mantle metasomatism; Nephelinite

Magmatic evolution and source variations at the Nifonea Ridge (New Hebrides Island Arc) - Lima, Selma; Haase, Karsten; Beier, Christoph; Regelous, Marcel; Brandl, P. A.; Hauff, F.; Krumm, Stefan (Journal of Petrology, 2017)
Keywords: Back-arc melting; Mantle heterogeneity; Nb-enriched basalts; New Hebrides island arc

Magmatic evolution of a dying spreading axis: evidence for the interaction of tectonics and mantle heterogeneity from the fossil Phoenix Ridge, Drake Passage - Haase, Karsten; Beier, Christoph; Fretzdorff, Susanne; Leat, Phil; Livermore, Roy; Barry, Tiffany; Pearce, Julian; Hauff, Folkmar (Chemical Geology, 2011)
New <sup style="border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.75em; font-weight: 100; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; vertical-align: super; font-family: Arial, Helvetica, 'Lucida Sans Unicode', 'Microsoft Sans Serif', 'Segoe UI Symbol', STIXGeneral, 'Cambria Math', 'Arial Unicode MS', sans-serif; line-height: 0; ">40Ar–<sup style="border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.75em; font-weight: 100; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; vertical-align: super; font-family: Arial, Helvetica, 'Lucida Sans Unicode', 'Microsoft Sans Serif', 'Segoe UI Symbol', STIXGeneral, 'Cambria Math', 'Arial Unicode MS', sans-serif; line-height: 0; ">39Ar ages of 5.6 to 1.3 Ma for lavas from the fossil Phoenix Ridge in the Drake Passage show that magmatism continued for at least 2 Ma after the cessation of spreading at 3.3 ± 0.2 Ma. The Phoenix Ridge lavas are incompatible element-enriched relative to average MORB and show an increasing enrichment with decreasing age, corresponding to progressively decreasing degrees of partial melting of spinel peridotite after spreading stopped. The low-degree partial melts increasingly tap a mantle source with radiogenic Sr and Pb but unradiogenic Nd isotope ratios implying an ancient enrichment. The post-spreading magmas apparently form by buoyant ascent of enriched and easily fusible portions of the upper mantle. Only segments of fossil spreading ridges underlain by such enriched and fertile mantle show post-spreading volcanism frequently forming bathymetric highs. The Phoenix Ridge lavas belong to the Pacific, rather than the Atlantic, mantle domain in regional Sr–Nd–Pb space. Our new data show that the southern Pacific Ocean mantle is heterogeneous containing significant enriched portions that are preferentially tapped at low melt fractions. Isotopic mapping reveals that Pacific-type upper mantle flows eastward through Drake Passage and surrounds the subducting Phoenix Plate beneath the Bransfield Basin.
UnivIS-Import:2015-03-09:Pub.2010.nat.dgeo.IGM.legeo.magmat
Keywords: Basalt; Incompatible elements; Mantle upwelling; Mid-ocean ridges; Partial melting

Magmatic Evolution of the Fossil Melanesian Island Arc: Evidence From Lower Miocene Lavas of Malekula Island (Vanuatu) - Haase, Karsten; Schneider, K. P.; Pelletier, B.; Ishizuka, O. (Geochemistry Geophysics Geosystems, 2024)
The subduction zones in the SW Pacific Ocean are some of the most dynamic plate boundaries on Earth with changes in subduction polarity and subduction initiation processes. The New Hebrides island arc formed some 10 million years ago after the Melanesian island arc was abandoned due to the cessation of subduction of the Pacific Plate after collision of oceanic plateaus with the island arc. Parts of the Melanesian island arc occur within the New Hebrides island arc and we show that Miocene volcanic rocks exposed on Malekula island in the New Hebrides island arc consist of island arc tholeiites to alkaline basalts with variable slab contribution. The lava erupted between 22.5 and 16.3 Ma, similar to the Wainimala Group lavas on Fiji representing the eastern portion of the Melanesian island arc. Partial melts from subducted sediments affected a Pacific MORB-type mantle, but we do not find evidence for a slab component derived from the Ontong Java Plateau or for assimilation of continental crust. Thus, no Miocene subduction of the Ontong Java Plateau occurred beneath Malekula and the basement of the island probably does not consist of continental crust rifted from Australia. The Malekula lava succession resembles that of other portions of the Miocene Melanesian island arc between New Britain and Fiji, indicating continuous subduction of the Pacific plate along this arc.
CRIS-Team Scopus Importer:2024-03-08
Keywords: Hf-Nd isotope ratios; island arc evolution; New Hebrides island arc; polarity reversal; subduction; Vitiaz island arc

Magmatic evolution of the migrating central Urumieh–Dokhtar arc, Iran: implications for magma production - Babazadeh, Shahrouz; Haase, Karsten; Ghalamghash, Jalil; Regelous, Marcel; Poujol, Marc; Raeisi, Davood; Zhao, Miao (International Journal of Earth Sciences, 2023)
The Cenozoic Avaj volcano-plutonic rocks in central Urumieh-Dokhtar magmatic arc (UDMA) encompass gabbro, and basalt to rhyolite, chemically akin to those from continental arcs. U–Pb geochronology on zircon yielded ages of 23.69 ± 0.48 Ma, 24.71 ± 0.38 Ma, 20.92 ± 0.14 Ma, and 19.25 ± 0.13 Ma for gabbro, basalt, trachyandesite, and rhyolite, respectively. εHf(t) values for zircon grains are ranging from − 1.4 to + 6.2. The data display narrow ranges of initial Pb isotopic ratios and εNd(t) values, implying a fairly homogeneous source. Moderate 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, high 143Nd/144Nd ratios of the mafic samples highlight the role of mantle components. The isotopic ratios–incompatible trace elements modelings reveal 2% of the melt come from the melting sediments in the petrogenesis of Avaj igneous rocks. The central UDMA with ages ranging from 42–38 Ma and 25–18 Ma, respectively, must have experienced two relatively brief periods of important magma production separated by 14–15 M.y. The early period of magma production correlates with the Middle Eocene Climatic Optimum (MECO), while the second magmatic period of the central UDMA is not associated with increasing CO2 contents in the atmosphere. The plutons of the older group are generally located to the east of those from the younger group suggesting a SW-directed migration of the arc following slab rollback. No systematic change of source compositions and magma formation is observed between the older and younger rocks implying similar magma sources and subduction input from the Eocene to Miocene. The potential effect of the UDMA magmatic activity on the global climate apparently does not reflect decreasing subduction of carbonate.
CRIS-Team Scopus Importer:2023-05-19
Keywords: Global climate; Oligocene to Miocene; Sr–Nd–Hf–Pb isotopes; Urumieh–Dokhtar magmatic arc; U–Pb zircon ages

Magmatic evolution of the Schiel Alkaline Complex, Bushveld large igneous province, South Africa - Höß, Alica; Klemd, Reiner; Bolhar, Robert; Haase, Karsten; Ramos, Joshua; Geiger, Elena; Brandt, Sönke; Graupner, Torsten (Lithos, 2024)
The Paleoproterozoic Schiel Alkaline Complex (SAC) in the Limpopo Belt is a composite pluton that coevally formed with the layered intrusion of the Bushveld large igneous province. The SAC is mainly composed of alkaline felsic rocks, pyroxenite, gabbro, syenodiorite/−gabbro, and minor carbonatite and gabbroic dikes. Here we present a new geochemical, geochronological, and isotopic study of the felsic and (ultra)mafic rock suites of the western SAC. The whole rock Sm[sbnd]Nd isotope study of the felsic rocks revealed εNd2059 Ma values between −6.5 and − 3.8, while those of the syenodiorite/−gabbros and gabbros vary from −7.9 to −8.8, and − 4.3 to +1.1, respectively. The pyroxenites have εNd2059 Ma values of +7.4 to +2.7. The Lu[sbnd]Hf isotope study displays εHf2059 Ma values of −15.9 to −9.0 for the syenites, alkali granites and syenodiorite/−gabbros, and significantly higher εHf2059 Ma of −3.1 to +3.4 for the gabbros. LA-SF-ICPMS U[sbnd]Pb zircon dating yields 2079 ± 10 Ma and 2088 ± 30 Ma for the syenodiorite/−gabbros, and 2086 ± 51 Ma and 2107 ± 30 Ma for the gabbros. In conjunction with published data from the eastern SAC, we propose a close petrogenetic link between the mafic and felsic rocks of the SAC. The positive εNd and εHf values of the pyroxenite and gabbro favor a depleted mantle source, while variable εNd and εHf values, and trace element ratios of the gabbros are ascribed to crustal contamination during magma ascent. The felsic rocks, however, mainly formed by fractional crystallization from the gabbros as revealed by major and trace element correlation trends, isotopic data and thermodynamic modelling.
CRIS-Team Scopus Importer:2024-01-05
Keywords: Alkaline complex; Bushveld LIP; Crustal assimilation; Fractional crystallization; Nd-Hf isotope compositions; Rare earth elements

Magmatic evolution of the South Shetland Islands, Antarctica, and implications for continental crust formation - Haase, Karsten; Beier, Christoph; Fretzdorff, Susanne; Smellie, John; Garbe-Schönberg, Dieter (Contributions To Mineralogy and Petrology, 2012)
Lavas from the South Shetland Islands volcanic arc (northern Antarctic Peninsula) have been investigated in order to determine the age, petrogenesis and compositional evolution of a long-lived volcanic arc constructed on 32-km-thick crust, a thickness comparable with average continental crust. New Ar- Ar ages for the volcanism range between 135 and 47 Ma and, together with published younger ages, confirm a broad geographical trend of decreasing ages for the volcanism from southwest to northeast. The migration pattern breaks down in Palaeogene time, with Eocene magmatism present on both Livingston and King George islands, which may be due to a change in both subduction direction and velocity after c. 60 Ma. The lavas range from tholeiitic to calc-alkaline, but there is no systematic change with age or geographic location. The compositions of lavas from the north-eastern islands indicate magma generation in a depleted mantle wedge with relatively low Sr and high Nd isotopic compositions and low U/Nb, Th/Nd and Ba/Nb ratios that was metasomatized by hydrous fluids from subducted basaltic oceanic crust. Lavas from the south-western islands show an additional sedimentary influence most likely due to fluid release from subducted sediments into the mantle wedge. Although magmatic activity in the South Shetland arc extended over c. 100 m. y., there is no evolution towards more enriched or evolved magmas with time. Few South Shetland arc lavas are sufficiently enriched with incompatible elements to provide a potential protolith for the generation of average continental crust. We conclude that even long-established subduction zones with magmatic systems founded on relatively thick crust do not necessarily form continental crustal building blocks. They probably represent only the juvenile stages of continental crust formation, and additional re-working, for example during subsequent arc-continental margin collision, is required before they can evolve into average continental crust. © 2012 Springer-Verlag.
Keywords: Fractionation; Geochemistry; Magmatism; Subduction zone

Magmatic PGE sulphide mineralization in clinopyroxenite from the platreef, bushveld complex, South Africa - Klemd, Reiner; Beinlich, Andreas; Kern, Matti; Junge, Malte; Martin, Laure; Regelous, Marcel; Schouwstra, Robert (Minerals, 2020)
The Platreef, at the base of the northern limb of the Bushveld Complex in South Africa, hosts platinum-group element (PGE) mineralization in association with base-metal sulphides (BMS) and platinum-group minerals (PGM). However, whilst a magmatic origin of the stratiform mineralization of the upper Platreef has been widely confirmed, the processes responsible for the PGE and BMS mineralization and metasomatism of the host rocks in the Platreef are still under discussion. In order to contribute to the present discussion, we present an integrated petrographical, mineral-chemical, whole-rock trace-and major-element, sulphur-and neodymium-isotope, study of Platreef footwall clinopyroxenite drill core samples from Overysel, which is located in the northern sector of the northern Bushveld limb. A metasomatic transformation of magmatic pyroxenite units to non-magmatic clinopyroxenite is in accordance with the petrography and whole-rock chemical analysis. The whole-rock data display lower SiO2, FeO, Na2O and Cr (<1700 ppm), and higher CaO, concentrations in the here-studied footwall Platreef clinopyroxenite samples than primary magmatic Platreef pyroxenite and norite. The presence of capped globular sulphides in some samples, which display differentiation into pyrrhotite and pentlandite in the lower, and chalcopyrite in the upper part, is attributed to the fractional crystallization of a sulphide liquid, and a downward transport of the blebs. In situ sulphur (V-CDT) isotope BMS data show isotopic signatures (δ34S = 0.9 to 3.1 ‰; ∆33S = 0.09 to 0.32‰) close to or within the pristine magmatic range. Elevated (non-zero) ∆33S values are common for Bushveld magmas, indicating contamination by older, presumably crustal sulphur in an early stage chamber, whereas magmatic δ34S values suggest the absence of local crustal contamination during emplacement. This is in accordance with the εNd (2.06 Ga) (chondritic uniform reservoir (CHUR)) values, of −6.16 to −6.94, which are similar to those of the magmatic pyroxenite and norite of the Main Zone and the Platreef in the northern sector of the northern Bushveld limb. Base-metal sulphide textures and S–Se-ratios give evidence for a secondary S-loss during late-to post-magmatic hydrothermal alteration. The textural evidence, as well as the bulk S/Se ratios and sulphide S isotopes studies, suggest that the mineralization in both the less and the pervasively hydrothermally altered clinopyroxenite samples of Overysel are of magmatic origin. This is further supported by the PPGE (Rh, Pt, Pd) concentrations in the BMS and mass-balance calculations, in both of which large proportions of the whole-rock Pd and Rh are hosted by pentlandite, whereas Pt and the IPGE (Os, Ir, Ru) were interpreted to mainly occur in discrete PGM. However, the presence of pentlandite with variable PGE concentrations on the thin section scale may be related to variations in the S content, already at S-saturation during magmatic formation, and/or post-solidification mobilization and redistribution.
CRIS-Team Scopus Importer:2020-07-10
Keywords: Bushveld Complex; Clinopyroxenite; Fluid–rock interaction; Metasomatism; Platreef

Magmatism in the Bransfield Basin: Rifting of the South Shetland Arc? - Fretzdorff, Susanne; Worthington, Tim; Haase, Karsten; Hékinian, Roger; Keller, Randy; Stoffers, Peter (Journal of Geophysical Research D: Atmospheres, 2004)
Bransfield Basin is an actively extending marginal basin separating the inactive South Shetland arc from the northern Antarctic Peninsula. Rift-related volcanism is widespread throughout the central Bransfield Basin, but the wider eastern Bransfield Basin was previously unsampled. Lavas recovered from the eastern subbasin form three distinct groups: (1) Bransfield Group has moderate large-ion lithophile element (LILE) enrichment relative to normal mid-ocean ridge basalt (NMORB), (2) Gibbs Group has strong LILE enrichment and is restricted to a relic seamount interpreted as part of the South Shetland arc, and (3) fresh alkali basalt was recovered from the NE part of the basin near Spanish Rise. The subduction-related component in Bransfield and Gibbs Group lavas is a LILE-rich fluid with radiogenic Sr, Nd, and Pb isotope compositions derived predominantly from subducting sediment. These lavas can be modeled as melts from Pacific MORB source mantle contaminated by up to 5% of the subduction-related component. They further reveal that Pacific mantle, rather than South Atlantic mantle, has underlain Bransfield Basin since 3 Ma. Magma productivity decreases abruptly east of Bridgeman Rise, and lavas with the least subduction component outcrop at that end. Both the eastward decrease in subduction component and occurrence of young alkali basalts require that subduction-modified mantle generated during the lifetime of the South Shetland arc has been progressively removed from NE to SW. This is inconsistent with previous models suggesting continued slow subduction at the South Shetland Trench but instead favors models in which the South Scotia Ridge fault has propagated westward since 3 Ma generating transtension across the basin. Copyright 2004 by the American Geophysical Union.
UnivIS-Import:2015-03-09:Pub.2004.nat.dgeo.IGM.legeo.magmat
Keywords: Back-arc basin; Bransfield Basin; Geochemistry; Volcanic arc

Magnesium quantification in calcites (Ca,Mg)CO_3_ by Rietveld-based XRD analysis: Revisiting a well-established method - Titschack, Jürgen; Götz-Neunhoeffer, Friedlinde; Neubauer, Jürgen (American Mineralogist, 2011)
Mg-calcites commonly occur in natural environments, with Mg-contents ranging between about 0 and 32 mol% (referring to MgCO3). Often, different Mg-calcite phases occur within the same sample. The Mg-content in calcites permits the classification of the diagenetic environment (marine vs. meteoric), or the reconstruction of paleotemperatures from skeletal remains. Since the 1960s, there have been published various calibrations for Mg determination in calcites based on XRD measurements. Recently, this method has come to be superseded by wet chemical, laser ablation, and microprobe analysis, due to their higher accuracy and/or higher sample resolution of these latter methods.This study presents a new calibration for the Mg determination in calcites using XRD measurements analyzed by means of the Rietveld refinement method. The calibration is based on lattice parameters and exhibits a reliable Mg-determination accuracy of more than 0.8 mol% between 0 and 15.5 mol%. The incorporation of the calibration into the Rietveld refinement software TOPAS permits a fast, standardized workflow. This, in turn, enhances the user-friendliness and the reproducibility of results, as well as allows the simultaneous analysis of multiple Mg-calcites in a sample. Mixtures of two Mg-calcites were analyzed using this new method. The Mg-content of two co-occurring Mg-calcite phases can be reliably quantified providing the Mg-calcites differ by at least 4.9 mol% and the minor Mg-calcite phase makes up more than 2.7 wt%. If the Mg-calcite phases differ by 3.4 mol% or less, the reliable identification of different Mg-calcite phases is questionable, due to the fact that differences involved here are too small. If such XRD patterns are refined with only one Mg-calcite phase, then the systematic misfit between measured and refined pattern can be used for the identification of a second Mg-calcite phase down to a difference in the Mg-content of about 3 mol%. However, a reliable phase quantification for these patterns cannot be achieved.
UnivIS-Import:2015-03-09:Pub.2011.nat.dgeo.IGM.LM.magnes

Magnetic characteristics of the Ság-hegy volcanic complex, little Hungerian Plain. - de Wall, Helga; et al. (Physical geology of subvolcanic systems: Laccoliths, Sills, and Dykes. Portree, Isle of Skye, Scotland, 2006)
UnivIS-Import:2015-04-16:Pub.2006.nat.dgeo.IGM.c3tekt.magnet

Magnetic fabric analysis in a mesoscopic fold - Mamtani, M. A.; Chadima, Martin; de Wall, Helga; Greiling, R. O. (International Journal of Earth Sciences, 2012)

Magnetic response contrast of Oligo-Miocene basaltic magmatism and structural control during its ascent at the northern tip of the Red Sea Rift - Maged, Azeeza; Said, Said Mohamed; Shallaly, Nahla Ahmed; Haase, Karsten; Elhussein, Mahmoud (Journal of African Earth Sciences, 2024)
Oligo-Miocene volcanic activity has occurred along the northern Egyptian margin of the Red Sea Rift system, leading to the creation of small-volume monogenetic volcanoes. This research delves into the morphology and setting of these rift-related volcanics by combining aeromagnetic data, remote sensing, and field verification. Basaltic exposures in the study area were mapped using False Color Composite (FCC) and band ratios in Landsat 8 OLI data. In a map view, these mappable volcanic rocks appear as discrete semi-circular basaltic bodies and as discontinuous dikes. The basaltic bodies are aligned along ENE and NW-oriented zones, with most dikes orientated NW-SE. Multiple isolated high magnetic zones with NE and NW orientations were identified. Most basaltic outcrops coincide with high magnetic zones except for Gabal Abu Treifiya along the Cairo-Suez Road. The integration and combination of three layers of surface and subsurface structure patterns reveal an array of variance. The dominant trend of surface and deeper structural lineaments is NW-SE and NE-SW respectively. In contrast, shallow structural lineaments have NW-SE, NE-SW, E-W, and N–S trends. Long linear grabens result from the pairing of NW-SE normal faults. The basaltic occurrences such as Qattamiya and Abu Treifiya are located at the intersection of the NW-SE and E-W normal faults along the NW-SE linear grabens. The field investigation at both locations reveals a polyphase magmatic feeding system manifesting in the surface today as coherent and volcaniclastic rock units. This suggests a diverse range of eruptive styles through a complex feeder system that involves more than one volcanic cone. Though the two areas have good basaltic exposures, yet they have different magnetic responses. The severe alteration of Abu Treifiya's volcanic rocks into nonmagnetic minerals assemblage of zeolite, smectite, calcite, and hydrolysis of basaltic glass diminishes the expected high magnetic anomaly. This study contributes to our knowledge of Rift-related volcanism and the factors influencing the distribution of these volcanic materials.
CRIS-Team Scopus Importer:2024-05-10
Keywords: Basalts; Landsat-8; Northeastern desert; Red sea rift; Reduction to pole; Source parameter imaging; Tilt derivative

Magnetic Supraparticles Capable of Recording High‐Temperature Events - Wolf, Andreas; Sauer, Julian; Hurle, Katrin; Müssig, Stephan; Mandel, Karl (Advanced Functional Materials, 2024)
Superparamagnetic iron oxide nanoparticles (SPIONs) are prone to oxidation at elevated temperatures (>300 °C) and lose their magnetizability upon transition from magnetite/maghemite (γ-Fe2O3 / Fe3O4) to hematite (α-Fe2O3). Silica (SiO2) shells can effectively prevent this undesired effect up to ≈1000 °C. Herein, the study shows how to utilize SPIONs with varying SiO2 shell thickness and thus, different oxidation susceptibility, and how to combine them in micrometers sized assemblies – so-called supraparticles (SPs), to create a structurally emerging magnetic temperature recording functionality. The desired oxidation of non or weakly-protected SPIONs within SPs upon temperature events reduces dipole–dipole interactions of well-protected SPIONs in the confined SP entity. The resulting change of magnetic interactions therefore contains information on the thermal history of the SP, which can be spectrally read out via magnetic particle spectroscopy within seconds. Their working range can be tuned from 400 to 1000 °C on two independent structural hierarchy levels, namely the SiO2 shell thickness and the freely selectable ratios of different building blocks in the SP. The application of such SPs as particulate additives for magnetic recording of high-temperature events, especially relevant in metal, alloy, and ceramic processing, representing a yet unexplored and optically-independent option for bulk temperature recording is proposed.<br
Keywords: high-temperature events; magnetic particle spectroscopy; magnetic recorders; smart additives; supraparticles

Magnetic susceptibility measurements for the petrographic characterization of Granitoids: Comparison of field and laboratory measurements in the Saghro region of the anti-Atlas of Morocco Magnetische Suszeptibilitätsmessungen zur petrographischen Charakterisierung von Granitoiden - Vergleich von Feld-undlabormessungen (Saghro-Gebiet, Anti-Atlas, Marokko) - de Wall, Helga; et al. (Zeitschrift für Angewandte Geologie, 2000)

Magnetic susceptibility variations in carbonates of the La Vid Group (Cantabrian Zone, NW-Spain) related to burial diagenesis - de Wall, Helga; et al. (Sedimentary Geology, 2004)
Keywords: Burial diagenesis; Fe-carbonate cements; Fe-chlorite; La Vid section; Magnetic susceptibility; Pyrite

Magnetic susceptibility zonation of the melilititic Riedheim dyke (Hegau volcanic field, Germany): Evidence for multiple magma pulses? - de Wall, Helga; et al. (Journal of Volcanology and Geothermal Research, 2004)
Keywords: Anisotropy of magnetic susceptibility; Magnetic susceptibility; Magneto-petrology; Riedheim dyke; Titanomagnetite

Magnetische Suszeptibilitätsmessungen an Gängen vom Ostrand des Hauzenberger Granitplutons Bayerischer Wald. - de Wall, Helga; et al. (11. Symposium "Tektonik, Struktur- und Kristallingeologie", 2006)
UnivIS-Import:2015-04-16:Pub.2006.nat.dgeo.IGM.c3tekt.magnet_9

Magnetostratigraphy and 40Ar-39Ar geochronology of the Malwa Plateau region (Northern Deccan Traps), central western India: Significance and correlation with the main Deccan Large Igneous Province sequences - Schöbel, Stefan; de Wall, Helga; Ganerod, Morgan; Pandit, Manoj K.; Rolf, Christian (Journal of Asian Earth Sciences, 2014)
Keywords: Ar-Ar geochronology; Deccan LIP; Deccan tectonomagmatic history; Eruption rate; Magnetostratigraphy; Malwa plateau

Manganous water column in the Tethys Ocean during the Permian-Triassic transition - Müller, Johann; Sun, Yadong; Yang, Fen; Regelous, Marcel; Joachimski, Michael (Global and Planetary Change, 2023)
Ocean anoxia was one of the key killing mechanisms responsible for the end-Permian mass extinction ( 252 Ma). However, the temporal evolution and the triggering mechanisms of the end-Permian anoxia are controversial, with the current view being that the water column deoxygenation was a spatially and temporally heterogeneous event. Here, we use cerium-anomalies, uranium contents and rare earth element and yttrium (REY) compositions measured on the carbonate fraction of samples from two marine sections in Armenia and South China to constrain the evolution of end-Permian marine anoxia. In particular, we attempt to identify intervals of manganous redox conditions (i.e., Mn2+-rich water column). These are characterized by the reduction of Mn(IV)-oxides at a redox potential lower than of nitrate and higher than of Fe(III)-oxide reduction. Most of our samples yield REY patterns with seawater characteristics suggesting the dominance of hydrogenous REYs. While decreasing U concentrations in the C. yini Zone suggest an overall intensification of global marine anoxia in the latest Permian, Ce-anomalies shift from negative to positive above the C. yini Zone, implying a deterioration in the oxygen content of the local water columns. Highly positive Ce-anomalies (Ce/Ce* > 1.3) are firstly reported for the P-T interval, indicating enrichment of Ce in the water column and the establishment of manganous redox conditions at both locations. This change coincided globally with climatic warming, the onset of the marine extinction interval as well as locally with the disappearance of sponge spicules and radiolarians (South China) and the appearance of microbialites (Armenia).<br

Manitouscolex a new palaescolecidan genus from the Lower Ordovician of Colorado - Lehnert, Oliver; Kraft, Petr (Journal of Paleontology, 2006)
UnivIS-Import:2015-03-09:Pub.2006.nat.dgeo.IGM.LG.manito

Mantle dynamics, element re-cycling, and magma genesis beneath the Kermadec ArcHavre Trough. - Haase, Karsten; Worthington, Tim; Garbe-Schönberg, Dieter; Stoffers, Peter; Wright, Ian (Geochemistry Geophysics Geosystems, 2002)
UnivIS-Import:2015-03-09:Pub.2002.nat.dgeo.IGM.legeo.mantle

Mantle heterogeneity controls on small-volume basaltic volcanism - Mcgee, Lucy E.; Millet, Marc-Alban; Beier, Christoph; Smith, Ian E. M.; Lindsay, Jan M. (Geology, 2015)
Eruptions of basaltic material in small-scale volcanic fields located in intraplate settings display a very diverse range in physical and chemical characteristics. Despite its relevance to the understanding of volcanic hazards, the relationship between physical properties of eruptions (explosivity, volume, location) and chemical composition of erupted products has, to date, not been investigated. Here we present a relationship between mantle heterogeneity and extents of partial melting, and both erupted volumes and eruptive style from the Auckland Volcanic Field (New Zealand), and we suggest that this provides a general model for smallscale "monogenetic" magmatic systems globally. Small volcanic centers consistently take the form of nephelinitic tuff rings and scoria cones, whereas larger centers are produced from effusive eruptions of less alkalic magmas. Nephelinitic melts are generated by melting of a deep, carbonated source, whereas less alkalic melts are the products of melting of a shallower, noncarbonated source. U-Th-Ra isotope data from eruptions closely paired in space and time show that mixing between magmas is extremely limited as a consequence of different ascent mechanisms due to differential segregation of melts from varying sources (early, carbonated melts ascending by higher porosity channels, and later, uncarbonated melts by a more diffusive regime). This suggests that extraction of melt is nearly instantaneous in these environments. Our results stress the importance of melting and magma dynamics in determining the size and style of eruptions in small volcanic fields, and suggest that mantle controls should be an important consideration in volcanic hazard assessment.

Mantle plume and rift-related volcanism during the evolution of the Rio Grande Rise - Hoyer, Patrick; Haase, Karsten; Regelous, Marcel; O'Connor, John; Homrighausen, Stephan; Geissler, Wolfram H.; Jokat, Wilfried (Communications Earth & Environment, 2022)
The Rio Grande Rise in the western South Atlantic Ocean has been interpreted as either an oceanic plateau related to the Tristan-Gough mantle plume, or a fragment of detached continental crust. Here we present new major and trace element data for volcanic rocks from the western and eastern Rio Grande Rise and the adjacent Jean Charcot Seamount Chain. The eastern Rio Grande Rise and older parts of the western Rio Grande Rise are comprised of tholeiitic basalt with moderately enriched trace element compositions and likely formed above the Tristan-Gough mantle plume close to the southern Mid-Atlantic Ridge. Younger alkalic lavas from the western Rio Grande Rise and the Jean Charcot Seamount Chain were formed by lower degrees of melting beneath thicker lithosphere in an intraplate setting possibly during rifting of the plateau. There is no clear geochemical evidence that remnants of continental crust are present beneath the Rio Grande Rise.<br

Mantle sources and magma evolution of the Rooiberg lavas, Bushveld Large Igneous Province, South Africa - Günther, Thomas; Haase, Karsten; Klemd, Reiner; Teschner, Claudia (Contributions To Mineralogy and Petrology, 2018)
We report a new whole-rock dataset of major and trace element abundances and Sr-87/Sr-86-Nd-143/Nd-144 isotope ratios for basaltic to rhyolitic lavas from the Rooiberg continental large igneous province (LIP). The formation of the Paleoproterozoic Rooiberg Group is contemporaneous with and spatially related to the layered intrusion of the Bushveld Complex, which stratigraphically separates the volcanic succession. Our new data confirm the presence of low- and high-Ti mafic and intermediate lavas (basaltic-andesitic compositions) with > 4 wt% MgO, as well as evolved rocks (andesitic-rhyolitic compositions), characterized by MgO contents of < 4 wt%. The high- and low-Ti basaltic lavas have different incompatible trace element ratios (e.g. (La/Sm)(N), Nb/Y and Ti/Y), indicating a different petrogenesis. MELTS modelling shows that the evolved lavas are formed by fractional crystallization from the mafic low-Ti lavas at low-to-moderate pressures ( 4 kbar). Primitive mantle-normalized trace element patterns of the Rooiberg rocks show an enrichment of large ion lithophile elements (LILE), rare-earth elements (REE) and pronounced negative anomalies of Nb, Ta, P, Ti and a positive Pb anomaly. Unaltered Rooiberg lavas have negative epsilon Nd-i (- 5.2 to - 9.4) and radiogenic epsilon Sr-i (6.6 to 105) ratios (at 2061 Ma). These data overlap with isotope and trace element compositions of purported parental melts to the Bushveld Complex, especially for the lower zone. We suggest that the Rooiberg suite originated from a source similar to the composition of the B1-magma suggested as parental to the Bushveld Lower Zone, or that the lavas represent eruptive successions of fractional crystallization products related to the ultramafic cumulates that were forming at depth. The Rooiberg magmas may have formed by 10-20% crustal assimilation by the fractionation of a very primitive mantle-derived melt within the upper crust of the Kaapvaal Craton. Alternatively, the magmas represent mixtures of melts from a primitive, sub-lithospheric mantle plume and an enriched sub-continental lithospheric mantle (SCLM) component with harzburgitic composition. Regardless of which of the two scenarios is invoked, the lavas of the Rooiberg Group show geochemical similarities to the Jurassic Karoo flood basalts, implying that the Archean lithosphere strongly affected both of these large-scale melting events.
Keywords: Bushveld Complex; Large igneous province (LIP); Sub-continental lithospheric mantle (SCLM); Assimilation fractional crystallization; Kaapvaal craton

Mantle sources and magma evolution of the Rooiberg lavas, Bushveld Large Igneous Province, South Africa - Günther, Thomas; Haase, Karsten; Klemd, Reiner; Teschner, Claudia (Contributions To Mineralogy and Petrology, 2018)
Keywords: Assimilation fractional crystallization; Kaapvaal craton; Bushveld Complex; Sub-continental lithospheric mantle (SCLM); Large igneous province (LIP)

Mapping intrashell variation in Mg/Ca of brachiopods to external growth lines: Mg enrichment corresponds to seasonal growth slowdown - Müller, Tamás; Tomašových, Adam; López Correa, Matthias; Mertz-Kraus, Regina; Mikuš, Tomáš (Chemical Geology, 2022)
Determining secular changes in seawater temperature and Mg/Ca ratio is of high importance in paleooceanographic, paleoenvironmental and paleoecological studies. On the one hand, intra-shell variation in Mg/Ca in brachiopod shells is used to reconstruct historical changes in temperature and in seasonality. On the other hand, intra-shell analyses show a weak relationship between Mg/Ca and δ18O, but a positive correlation between Mg/Ca and Sr/Ca, and an increase of Mg/Ca at growth lines, indicating that Mg/Ca does not simply track seawater temperature alone. Internal growth lines are rarely visible in brachiopod shells, and the relation between growth lines that mark growth slowdown or cessation and Mg/Ca fluctuation is thus not properly understood. Here, using four species of extant brachiopods from the NE Pacific and the SW Pacific, from environments with low seasonality in seawater temperature (<5 °C), and two species of Late Triassic brachiopods (Western Carpathians), we measure intra-shell ontogenetic variation in Mg/Ca, S/Ca and Sr/Ca with laser ablation ICP-MS and electron microprobe. In contrast to previous studies, we map variation in Mg, S, and Sr to external growth lines. We find that, first, zones of Mg/Ca enrichment in the secondary layer form 10–50 μm-thick discrete bands or clusters of micrometric bands that consistently terminate at major external, predominantly annual growth lines that are associated with distinct notches that correspond to mantle retractions in most species. These bands generate distinct peaks in Mg/Ca that stand above low, more uniformly distributed background Mg/Ca values along laser-ablation and microprobe transects. The magnitude of Mg/Ca in these bands is comparable to Mg/Ca in the primary layer, exceeding background values of Mg/Ca in the secondary layer by 5–20 mmol/mol (by a factor of two to five). Second, Mg enrichment in discrete bands is closely associated with an increase in S concentrations in the secondary layer. Therefore, even when Mg and S uptake is expected to be highest under fast precipitation rate, these empirical observations show that Mg and S enrichment occur in the zones that were precipitated at times of a significant growth reduction (e.g., in cold-temperate brachiopods studied here during winters when primary productivity is low). The mechanisms for this paradox are unclear but can be related to uptake of Mg by amorphous calcium carbonate (ACC) to delay the transformation of ACC to calcite during the formation of growth lines. Therefore, intra-shell variation in Mg/Ca in brachiopods with major growth lines is primarily determined by seasonal decline or cessation in shell growth and not by seasonal changes in seawater temperature.
Keywords: Brachiopoda; Biomineralization; Mg/Ca ratio; S/Ca ratio; Sr/Ca ratio; Growth rate; Seasonality

Mapping of Very Shallow Geothermal Potentials in Rural Areas: a Case Study of Bavaria (Germany) - Bertermann, David; Jocic, Nikola; Rammler, Mario; Schwarz, Hans; Wagner, Jan (Alternative Energy Sources, Materials and Technologies (AESMT’21), 2021)
Shallow geothermal energy is a renewable source for heating and cooling systems and buildings, by which a significant part of the arising energy demand could be covered if it is in widespread use. Especially in rural areas (very) shallow geothermal systems are well applicable due to the availability of spacious unsealed areas. The aim of the study was the examination of geothermal potential maps for utilization of very shallow horizontal applications in the rural areas of Bavaria (Germany). These potential maps should bring a more facilitated access to this issue for heating engineers and planners and with that a more common use of shallow geothermal energy. To develop these potential maps, the relevant parameters were implemented as areal data in a geographical information system (GIS). As database serves a soil map of Bavaria (scale 1:5000) which includes crucial parameters such as soil texture. Additionally, climate data based on degree-day numbers for characteristic regions were implemented. Soil and climate data provided the basis to develop an algorithm for calculation of (very) shallow geothermal potentials. Results are presented in two categories – thermal conductivity on the one hand, and heat extraction on the other. Thermal conductivity is the general parameter which describes local geothermal potentials, dependent on soil texture, bulk density and water content, while heat extraction is given as a system-specific characteristic. This research focused on four different shallow geothermal systems – horizonal ground heat collectors, capillary tube mats, geothermal baskets, and trench collectors. These geothermal potentials were processed in a GIS project enabling the output as potential maps. For validation of the very shallow geothermal potential maps soil data from selected case study municipalities were consulted. Therefore, data from geotechnical surveys and sampled and analysed soils were used. As a result, these maps revealing the very shallow geothermal potential can serve as handy tool for heating engineers and planners for an appropriate design of these horizontal geothermal applications. Afterall, the compilation process is easy to transfer to other regions, just by using respective soil maps and climatic dat
Keywords: Very shallow geothermal potential (vSGP); thermal conductivity; heat extraction; geothermal potential maps; GIS; rural areas

Mapping of very shallow geothermal potentials in rural areas of Bavaria - Bertermann, David; Schwarz, Hans; Rammler, Mario; Jocic, Nikola (Glasnik Srpskog Geografskog Društva, 2024)
Climate change is a rising issue which strongly influences contemporary society. Therefore, the utilization of sustainable non-fossil energy sources is one of the most important goals in order to reduce greenhouse gas emission. Utilization of geothermal energy for heating and cooling buildings or residential units is one of the significant steps in providing sustainable and renewable energy supply. This paper presents very Shallow Geo-thermal Potentials (vSGP) of German federal state Bavaria, with special focus on rural are-as. Main goal of the study was to analyze the potentials for utilization of very shallow geo-thermal systems in terms of thermal conductivity and heat extraction. High-resolution soil maps containing information of grain size conditions served as an area-wide data basis for the research, while the analysis and visualization of the results were conducted by GIS software. Thermal conductivity as well as system-specific heat extraction were calculated depending on soil texture and climate conditions. Thermal conductivity results are intend-ed to be further used as the basic parameter for planning and installing horizontal geo-thermal heating and cooling systems.<br
Keywords: very shallow geothermal potentials (vSGP); thermal conductivity; heat extraction; sustainable cooling; rural area; Bavaria

Mapping paleocoastlines and continental flooding during the Phanerozoic - Kocsis, Ádám; Scotese, Christopher R. (Earth-Science Reviews, 2021)
Sea levels shape the face of the Earth, define processes of sedimentation, and influence the evolution of life via the distribution of habitats. Ancient topographies can be reconstructed using the history and understanding of tectonic processes, lithological evidence, and present-day topographies. Paleogeographic reconstructions must accommodate ever newer sources of geological data, so we can refine and improve our model of ancient topography and bathymetry. Here, we assess the accuracy of a set of Phanerozoic digital paleogeographic maps by testing the proposed distribution of flooded shallow seas and land using fossil occurrence data from the Paleobiology Database. After noting a moderate match, we modified the positions of the coastlines and continental margins of these topographic models to reflect times of maximum transgression. Using the updated paleogeographic maps, we outline the changes of land and shallow marine areas over time and suggest ways they can be used for further investigations of our planet's history.
CRIS-Team Scopus Importer:2021-01-08
Keywords: Coastlines; Continental flooding; Fossils; Global; Paleogeography; Phanerozoic; Reconstruction

Mapping the elemental and crystalline phase distribution in Cu2+ doped 45S5 bioactive glass upon crystallization - Nawaz, Qaisar; De Pablos-Martin, Araceli; Berthold, Lutz; De Souza E Silva, Juliana Martins; Hurle, Katrin; Boccaccini, Aldo R. (CrystEngComm, 2021)
Bioactive glasses (BGs) incorporating metallic ions to impart antibacterial activity and stimulation of osteogenesis and angiogenesis are promising candidates for bone tissue engineering. Silicate BGs of the 45S5 composition (45 SiO2, 24.5 Na2O, 24.5 CaO, 6 P2O5, (wt%)) crystallize readily during the high temperature processing of porous scaffolds. The crystallization slightly suppresses the bioactivity and dissolution of the glass. Structural changes during the high-temperature processing of metal ion-doped 45S5 BGs are challenging since metal ions may affect the formation of crystalline phases during thermal treatment. In this study, we investigated the effect of Cu on structural changes during the sintering of Cu doped 45S5 BG (Cu-45S5). The Cu-45S5 BG was sintered at 900 degrees C and 1050 degrees C for 1 hour, and the resultant microstructures were investigated using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), including elemental distribution mappings from energy-dispersive X-ray spectroscopy (EDXS), and X-ray nano-computed tomography (nano-CT). XRD patterns of thermally treated samples indicate the formation of combeite and rhenanite as crystalline phases. Besides the crystalline fraction, a residual glassy phase is also present, which is enriched with Na and P ions. The results reveal that the crystallinity of Cu-45S5 glass-ceramics can be adjusted over a range of 70-78% by applying appropriate heat treatment profiles. Moreover, the size of the crystals increases with increasing temperature under the investigated conditions. Cu is found to be localized in the residual glassy phase, together with Si and Na, which has an effect on the release of Cu ions in physiological environments.
CRIS-Team WoS Importer:2021-12-10

Mapping the techno-economic potential of closed-loop geothermal systems: A Europe-tested method - Perego, Rodolfo; Pera, Sebastian; Galgaro, Antonio; Dalla Santa, Giorgia; Cultrera, Matteo; de Carli, Michele; Emmi, Giuseppe; Bertermann, David; Müller, Johannes; Mendrinos, Dimitrios; Karytsas, Constantine; Vercruysse, Jacques; et al. (Swiss Geoscience Meeting 2018, 2018)

Marine benthic invertebrates from the Upper Jurassic of northern Ethiopia and their biogeographic affinities - Kießling, Wolfgang; Pandey, Dhirendra; Schemm-Gregory, Mena; Mewis, Heike; Aberhan, Martin (Journal of African Earth Sciences, 2011)
We present the first modern description of corals, brachiopods and bivalves from the Antalo Limestone in the Mekele Outlier of northern Ethiopia. This fauna is largely of Oxfordian age and lived in shallow subtidal environments and in small patch reefs. In combining our new data with fossil occurrence data from the Paleobiology Database, we conducted multidimensional scaling analyses to assess biogeographic patterns and the delineation of the Ethiopian Province for the Callovian to Kimmeridgian stages. Results suggest that an Ethiopian Province is indeed evident for our focal groups, but this is more confined than traditionally assumed. The so defined Ethiopian Province includes Tunisia, the Levant, Arabia and much of East Africa, but excludes Tanzania and India. The special status of India and Tanzania is perhaps due to latitudinal gradients in faunal composition. © 2010 Elsevier Ltd.
UnivIS-Import:2015-03-09:Pub.2011.nat.dgeo.IGM.LP.marine
Keywords: Biogeography; Bivalves; Brachiopods; Corals; Ethiopia; Jurassic

Marine Biodiversity and Geographic Distributions Are Independent on Large Scales - Antell, Gwen S.; Kießling, Wolfgang; Aberhan, Martin; Saupe, Erin E. (Current Biology, 2020)
Fundamental ecological and evolutionary theories, such as community saturation and diversity-dependent diversification, assume that biotic competition restricts resource use, and thus limits realized niche breadth and geographic range size [1–3]. This principle is called competitive exclusion. The corollary (ecological release) posits that, after competitors disappear from a region, species that were previously excluded will invade. Hundreds of field experiments have demonstrated ecological release in living populations. However, few of these studies were conducted in marine environments, and almost no work extended beyond 10 years and 1,000 km2 [4, 5]. In limited investigation of marine taxa at larger spatiotemporal scales, macroecologists and paleobiologists have observed little evidence of competitive exclusion [6–9]. Here, we quantified spatial trends in the rich and densely sampled fossil history of brachiopods and bivalves, while accounting for inconsistent sampling coverage through time using a new method of spatial standardization. The number of potential competitors in a region did not explain the geographic distribution of constituent species or genera. Furthermore, although ecological release predicts species to expand after extinction events, survivors of intervals with net species loss expanded as rarely as species in other intervals. Regression model estimates indicated different spatial responses of brachiopods and bivalves, and of habitat specialists and generalists, but no effect from changes in number of potential competitors. Biotic competition may control the distribution of populations, but, on larger spatiotemporal scales, non-competitive factors may have driven biogeographic patterns of brachiopods and bivalves. Long-standing ecological and evolutionary theories assume that competition between individuals controls the cumulative resource use and geographic ranges of species. Antell et al. demonstrate that spatial distributions of marine invertebrates are incongruent with this expectation throughout the last 485 million years.
CRIS-Team Scopus Importer:2020-01-07
Keywords: bivalves; brachiopods; competition; diversity-dependent diversification; ecological release; fossil record; macroecology; niche partitioning; spatial scale; species distributions

Marine biological responses to abrupt climate change in deep time - Kießling, Wolfgang; Reddin, Carl James; Dowding, Elizabeth; Dimitrijevic, Danijela; Raja, Nussaïbah Begum; Kocsis, Ádám (Paleobiology, 2024)
Ancient changes in the biosphere, from organismic traits to wholesale ecosystem changes, can be aligned with climate forcing across the Phanerozoic. Clear examples of abrupt climate warming causing biodiversity crises are primarily found between the Permian and Paleogene periods. During these times, catastrophic events occurred, resembling the extreme climate scenarios projected for the near future. The paleobiologic literature around these events generally supports the hypothesis that abrupt climate change was a dominant trigger of extinction and/or ecological crisis. When climate change and climate history are considered, virtually all post-Paleozoic global biotic events can be confidently attributed to climatic change, with abrupt warming (hyperthermal events) leaving the most consistent fingerprint. The combined stress of deoxygenation and warming are sufficient to explain marine extinction patterns across most hyperthermal events. Although ocean acidification may have contributed, the direct role of pH on the extinction toll of organisms is not consistently demonstrated. Future research can enhance the correspondence between the magnitudes of climatic changes and their biological impacts, even though observed rates of change cannot currently be compared across different timescales. Mimicking multi-scale approaches in modern ecology, paleontological approaches to climate impact research will benefit from specifically targeting scaling relationships.

Marine carbonate facies in response to climate and nutrient level: The Upper Carboniferous and Permian of central Spitsbergen (Svalbard). - Buggisch, Werner; Joachimski, Michael; et al. (Facies, 2001)
Carbonate-dominated successions of the Gipsdalen and Tempelfjorden Groups from Svalbard record a significant shift from Photozoan to Heterozoan particle associations in neritic settings during the late Palaeozoic. During the Bashkirian, benthic particle associations which included photoautotrophs such as phylloid algae (Chloroforam Association) characterised shallow subtidal environments. Most depositional settings which endured siliciclastic terrestrial input exhibited poorly diversified associations dominated by brachiopods, bryozoans and siliceous sponges (Bryonoderm Association). During the Moscovian to Asselian, highly diversified associations typified by various calcareous green algae, Palaeoaplysina, Tubiphytes, fusulinids, smaller and encrusting foraminifers (Chloroforam Association) prevailed in carbonate sediments from supratidal to shallow subtidal environments. During the Sakmarian and Early Artinskian, oolitic carbonate sands (Chloroforam Association) typified intertidal flats, whereas shallow subtidal environments were occupied by moderately diversified associations with fusulinids, smaller foraminifers, echinoderms and bryozoans (Bryonoderm-extended Association) and poorly diversified associations with echinoderms, brachiopods and bryozoans (Bryonoderm Association). During the Late Artinskian to Kazanian, poorly diversified associations characterised by brachiopods, echinoderms and bryozoans (Bryonoderm Association), and sponge-dominated associations (Hyalosponge Association) reigned within siliceous carbonates of intertidal and shallow subtidal environments. This trend is interpreted as a result of climatic cooling and fluctuations of prevailing levels of trophic resources within shallow-water settings during the studied time period. While raised nutrient levels were restricted to near-shore settings during the Bashkirian, steady mesotrophic conditions arose from the Sakmarian onward and increased to late Permian times.
UnivIS-Import:2015-03-09:Pub.2001.nat.dgeo.IGM.LG.marine_7
Keywords: Climate; Microfacies; Northern pangaea; Permian; Photozoan and heterozoan caronates; Spitsbergen (Svalbard); Trophic resources; Upper carboniferous

Marine carbonate facies of arid to temperate humid climates: Upper Carboniferous to Permian strata from Billefjorden Trough and Nordfjorden Block, Svalbard. - Buggisch, Werner; Joachimski, Michael; et al. (Facies, 2001)

Marine clade sensitivities to climate change conform across timescales - Reddin, Carl James; Nätscher, Paulina; Kocsis, Ádám; Pörtner, Hans Otto; Kießling, Wolfgang (Nature Climate Change, 2020)
Rapid climate change is postulated to cause marine extinctions, especially among climate-sensitive clades, traits and regions1–6. This premise is based on two hypotheses: (1) known individual physiological sensitivities scale up to macroecological selectivity patterns4,7,8 and (2) ancient hyperthermal events are appropriate models to anticipate ecological winners and losers of anthropogenic climate change9. Yet these hypotheses have largely escaped quantitative appraisal. Here we show that experimental responses of modern marine ectotherms to single and combined climate-related stressors (such as seawater warming, hypoxia and acidification) align with Phanerozoic fossil extinction regimes across clades and functional traits. Of climate-related stressors, the synergistic interaction between warming and hypoxia10, encumbering aerobic metabolism, has the greatest potency as a proximate driver of extinction. All else being equal8, this synergy particularly imperils modern warm-water organisms. Modern–fossil agreement is strongest at intermediate–high extinction intensities and hyperthermal events but may fail at extreme extinction events, perhaps due to rising prominences of, and interactions among, additional biotic and abiotic stressors. According to results from marine ectotherms, clade-based sensitivity of individuals to climate-related stressors scales up from subannual experiments and decadal range-shift response magnitudes11, to extinction selectivity patterns at ancient climate-related stressor events and the Phanerozoic durations of genera.
CRIS-Team Scopus Importer:2020-02-25

Marine invertebrate migrations trace climate change over 450 million years - Reddin, Carl James; Kocsis, Ádám; Kießling, Wolfgang (Global Ecology and Biogeography, 2018)
Aim Poleward migration is a clear response of marine organisms to current global warming but the generality and geographical uniformity of this response are unclear. Marine fossils are expected to record the range shift responses of taxa and ecosystems to past climate change. However, unequal sampling (natural and human) in time and space biases the fossil record, restricting previous studies of ancient migrations to individual taxa and events. We expect that temporal changes in the latitudinal distribution of surviving taxa will reveal range shifts to trace global climate change. Location Global. Time period Post‐Cambrian Phanerozoic aeon. Major taxa studied Well‐fossilized marine benthic invertebrates comprising stony corals, bivalves, gastropods, brachiopods, trilobites and calcifying sponges. Methods We track deviations in the latitudinal distribution of range centres of age boundary crossing taxa from the expected distribution, and compare responses across latitudes. We build deviation time series, spanning hundreds of million years, from fossil occurrences and test correlations with seawater temperature estimates derived from stable oxygen isotopes of fossils. Results Seawater temperature and latitudinal deviations from sampling are positively correlated over the post‐Cambrian Phanerozoic. Simulations suggest that sampling patterns are highly unlikely to drive this putative signal of range shifts. Systematically accounting for known sampling issues strengthens this correlation, so that climate is capable of explaining nearly a third of the variance in ancient latitudinal range shifts. The relationship is stronger in low latitude taxa than higher latitude taxa, and in warm ages than cool ages. Main conclusions Latitudinal range shifts occurred in concert with climate change throughout the post‐Cambrian Phanerozoic. Low latitude taxa show the clearest climate‐migration signal through time, corroborating predictions of their shift in a warming future.
Keywords: d18O; fossil; latitude; out of the tropics; Paleobiology Database; Phanerozoic; sampling bias; time series

Marine sepiolite in Middle Permian carbonates of South China: implications for secular variation of Phanerozoic seawater chemistry. - Yan, Jiaxin; Munnecke, Axel; Steuber, Thomas; Carlson, E.H.; Xiao, Yilin (Journal of Sedimentary Research, 2005)
t is now widely accepted that the composition of seawater varied significantly during the Phanerozoic, and that the Mg/Ca ratio of seawater is a major factor in synchronized secular oscillations in the mineralogical composition of marine evaporites and nonskeletal as well as biogenic carbonates. However, the nature of the Mg sink is still subject to debate. We describe early diagenetic sepiolite from the Chihsia Formation (middle Permian) of South China. The Mg incorporated in sepiolite likely was furnished by stabilization of high-Mg calcite, and silica was derived from siliceous fossils. Two factors facilitated the accumulation of sepiolite in the Chihsia Formation. The first is a Chihsian depositional environment of an intra-oceanic carbonate platform that lacked detrital terrestrial input, which enhanced the availability of biogenic silica for sepiolite formation. The second is the chemical composition of Permian seawater, as the precipitation of high-Mg calcite was aided by a high Mg/Ca ratio associated with an aragonite sea. The formation of sepiolite is significant in constraining the recycling flux of Mg during recrystallization of carbonate sediments with a high proportion of high-Mg calcite (periods of aragonite seas). Worldwide, major occurrences of marine sepiolite and palygorskite in the Phanerozoic correlate with periods of aragonite seas. This temporal distribution implies that minerals of the sepiolite-palygorskite group play an important role in the geochemical recycling of Mg, and that major sepiolite and palygorskite deposits indicate episodes of high Mg concentrations in seawater. The formation of sepiolite also was probably related to an abundance of silica-secreting organisms, which interacted with the chemical evolution of Phanerozoic seawater. In addition, authigenic sepiolite and palygorskite are not indicators of arid and semiarid climate
Keywords: Sepiolite; China; Permian; Seawater chemistry

Marine species and assemblage change foreshadowed by their thermal bias over Early Jurassic warming - Reddin, Carl J.; Landwehrs, Jan P.; Mathes, Gregor; Ullmann, Clemens V.; Feulner, Georg; Aberhan, Martin (Nature Communications, 2025)
A mismatch of species’ thermal preferences to their environment may indicate how they will respond to future climate change. Averaging this mismatch across species may forewarn that some assemblages will undergo greater reorganization, extirpation, and possibly extinction, than others. Here, we examine how regional warming determines species occupancy and assemblage composition of marine bivalves, brachiopods, and gastropods over one-million-year time steps during the Early Jurassic. Thermal bias, the difference between modelled regional temperatures and species’ long-term thermal optima, predicts a gradient of species occupancy response to warming. Species that become extirpated or extinct tend to have cooler temperature preferences than immigrating species, while regionally persisting species fell midway. Larger regional changes in summer seawater temperatures (up to +10 °C) strengthen the relationship between species thermal bias and the response gradient, which is also stronger for brachiopods than for bivalves, while the relationship collapses during severe seawater deoxygenation. At +3 °C regional seawater warming, around 5 % of pre-existing benthic species in a regional assemblage are extirpated, and immigrating species comprise around one-fourth of the new assemblage. Our results validate thermal bias as an indicator of immigration, persistence, extirpation, and extinction of marine benthic species and assemblages under modern-like magnitudes of climate change.
CRIS-Team Scopus Importer:2025-02-28

Mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers, Skeleton Coast Erg, Namibia. - Svendsen, Johan; Stollhofen, Harald; Krapf, Carmen; Stanistreet, Ian G. (Sedimentary Geology, 2003)
Channel-shaped deposits of well sorted sand with only 2–4% fine-grained material, being either massive and structureless or upward fining with basal lag, are found interbedded with aeolian sand in the Skeleton Coast Erg, Namibia. Detailed analyses of the channel-shaped deposits suggest that they are formed as hyperconcentrated flows within the erg. Grain-size analysis and whole rock geochemical modeling revealed that some of the fluvial sediments contain up to 70% aeolian sand, interpreted as a result of dune collapse into the fluvial system. In certain cases, this instantaneous supply of sand resulted in generation of sandy mass flows with laminar flow behaviour. The presence of smectite as dominant clay mineral proved to be of crucial importance in formation of mass flow deposits. These mass flows had no erosional capacity, and drape the palaeotopography. They are comparable to those generated by catastrophic collapse of dunes, described in the literature. This paper suggests that all these deposits should be termed intra-erg mass flows, as several of them carry little, if any debris. Based on their origin, intra-erg mass flows can be divided into two groups: (1) Attached intra-erg mass flows, which are formed and found attached to the dune that sourced the flow; (2) Detached intra-erg mass flows, which are not found adjacent to the dune sourcing the flow, and often carry material sourced outside the dune field. A five-stage model is proposed, involving dune damming to explain the observed deposits and the degree of reworking. When the flood basin behind the erg overtops the threshold area, water pours into the erg, giving rise to a complex fluvio aeolian setting. The setting in the Skeleton Coast erg is comparable to recent as well as ancient settings, and reveals valuable information for reservoir characterization and hazard assessment.
UnivIS-Import:2015-03-09:Pub.2003.nat.dgeo.IGM.LG.hyperc

Mass extinctions and clade extinctions in the history of brachiopods: Brief review and a post-paleozoic case study - Vörös, Attila; Kocsis, Ádám; Pálfy, József (Rivista Italiana Di Paleontologia E Stratigrafia, 2019)
Brachiopods are a key group in Phanerozoic marine diversity analyses for their excellent fossil record and distinctive evolutionary history. A genus-level survey of raw diversity trajectories allows the identification of the Brachiopod Big Five, episodes of major genus losses in the phylum which are compared with the established Big Five mass extinctions of Phanerozoic marine invertebrates. The two lists differ in that the end-Cretaceous extinction appears subdued for brachiopods, whereas the mid-Carboniferous is recognized as an event with significant loss of brachiopod genera. At a higher taxonomic level, a review of temporal ranges of rhynchonelliform orders reveals episodes of synchronous termination of multiple orders, here termed clade extinctions. The end-Ordovician, Late Devonian and end-Permian events are registered as both mass extinctions and clade extinctions. The Late Cambrian and the Early Jurassic are identified as the other two clade extinction events. Coincident with the Early Toarcian oceanic anoxic event, the last clade extinction of brachiopods is defined by the disappearance of the last two spire-bearing orders, Athyridida and Spiriferinida. Their diversity trajectory through the recovery after the end-Permian crisis parallels that of the extant terebratulides and rhynchonellides until a Late Triassic peak but diverge afterwards. The end-Triassic diversity decline and Toarcian vanishing of spire-bearers correspond with contraction in their spatial distribution. The observed patterns and extinction selectivity may be explained both ecologically and physiologically. The specialized adaptation of morphologically diverse spire-bearers, as well as their fixed lophophore and passive feeding put them at a disadvantage at times of environmental crises, manifest in their end-Triassic near-extinction and Toarcian demise. Similar analyses of other clade extinctions may further improve our understanding of drivers and processes of extinction.
CRIS-Team Scopus Importer:2019-10-08
Keywords: Biotic crises; Diversity; End-triassic; Rhynchonelliformea; Spire-bearers; Toarcian

Massive corals in Paleocene siliciclastic sediments of Chubut (Patagonia, Argentina) - Kießling, Wolfgang; et al. (Facies, 2005)
UnivIS-Import:2015-03-09:Pub.2005.nat.dgeo.IGM.LP.massiv

Massive volcanism at the Permian-Triassic boundary and its impact on the isotopic composition of the ocean and atmosphere - Korte, Christoph; Pande, Prabhas; Kalia, P.; Kozur, Heinz W.; Joachimski, Michael; Oberhaensli, Hedi (Journal of Asian Earth Sciences, 2010)
Bulk carbonate and conodonts from three Permian-Triassic (P-T) boundary sections at Guryul Ravine (Kashmir), Abadeh (central Iran) and Pufels/Bula/Bulla (Italy) were investigated for δ13C and δ18O. Carbon isotope data highlight environmental changes across the P-T boundary and show the following features: (1) a gradual decrease of ∼4‰ to more than 7‰ starting in the Late Permian (Changhsingian) C. bachmanni Zone, with two superimposed transient positive excursions in the C. meishanensis-H. praeparvus and the M. ultima-S. ? mostleri Zones; (2) two δ13C minima, the first at the P-T boundary and a higher, occasionally double-minimum in the lower I. isarcica Zone. It is unlikely that the short-lived phenomena, such as a breakdown in biological productivity due to catastrophic mass extinction, a sudden release of oceanic methane hydrates or meteorite impact(s), could have been the main control on the latest Permian carbon isotope curve because of its prolonged (0.5 Ma) duration, gradual decrease and the existence of a >1‰ positive shift at the main extinction horizon. The P-T boundary δ13C trend matches in time and magnitude the eruption of the Siberian Traps and other contemporaneous volcanism, suggesting that volcanogenic effects, such as outgassed CO2 from volcanism and, even more, thermal metamorphism of organic-rich sediments, as the likely cause of the negative trend. © 2009 Elsevier Ltd. All rights reserved.
UnivIS-Import:2015-03-09:Pub.2010.nat.dgeo.IGM.LG.massiv
Keywords: Abadeh; Carbon isotopes; Guryul Ravine; Oxygen isotopes; Permian-Triassic boundary; Pufels/Bula/Bulla; Volcanism

Mass movement investigation in the Xiangxi Catchment, Three Gorges Reservoir Area - Ehret, Dominik; Rohn, Joachim; Dumperth, Christian; Eckstein, Susan; Ernstberger, Stefanie; Otte, Karel; Rudolph, Rene; Wiedenmann, Johannes; Wei, Xiang; Renneng, Bi (Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, 2010)
UnivIS-Import:2015-03-09:Pub.2010.nat.dgeo.IGM.profes_3.massmo

Mass occurrence of the large solitary rugose coral Phaulactis angusta at the boundary Lower/Upper Visby Formation in the Silurian of Gotland, Sweden: palaeoecology and depositional implications - Adomat, Friederike; Munnecke, Axel; Kido, Erika (GFF, 2016)
The boundary between the Lower and Upper Visby formations on Gotland (Sweden), which roughly correlates with the Llandovery–Wenlock boundary, is characterised by a mass occurrence of the large solitary rugose coral Phaulactis angusta. This coral-rich layer can be followed for some 50 km along the north-west coast of Gotland. The mass occurrence coincides with the onset of a pronounced, globally recognised δC and δO excursions in the lower Sheinwoodian. Altogether 31 specimens of P. angusta from eight localities were examined. We demonstrate that the corals preferred to grow in an upright position. Attachment structures were not observed, and therefore a liberosessile life strategy is suggested. Some corallites show an abrupt change in growth direction accompanied by a decrease in diameter. These features mostly occur in later growth stages and may be explained by disturbances in the growth due to toppling or tilting of the corals. Many specimens were able to change their growth axes, but finally died after such an event. Most specimens in the outcrops show a flattened upper surface, which is interpreted as a result of post-mortem abrasion. Epibiontic bryozoan encrustation took place mostly while the corals where alive, whereas stromatoporoid encrustation and Trypanites borings occurred post-mortem. The repeated growth, tilting and erosion of the corallites of P. angusta demonstrate that the Phaulactis layer represents a condensed interval, characterised by multiple pulses of sediment accumulation and erosio
Keywords: Gotland; Ireviken event; rugose corals; Silurian

Matera building stones: Chemical, mineralogical and petrophysical characterization of the calcarenite di gravina formation - Bonomo, A. E.; Lezzerini, M.; Prosser, G.; Munnecke, Axel; Koch, Roman; Rizzo, G. (2019 IMEKO TC4 International Conference on Metrology for Archaeology and Cultural Heritage, MetroArchaeo 2019, 2019)
Matera (Basilicata, southern Italy) was awarded the World Heritage Site status by the UNESCO since 1993, and has been named the European Capital of Culture in 2019. It is one of the most ancient towns in the world, whose historical centre was totally built by a weakly lithified and highly porous lower Pleistocene sedimentary building stone, known as Gravina Calcarenite. This easily workable rock was quarried since prehistoric times, and it was used for building different kinds of constructions from the rupestrian settlement to gorgeous historic palaces during the XVIII century. Calcarenite, however, can be an extremely heterogeneous building material depending on the composition of the particles and their characteristics. After a geological survey, it was possible to recognize two main varieties of this building stone, which were in turn subdivided into six lithofacies (corresponding to sub-typologies of building stones). As a first approach, we have characterized, in terms of building stone quality, six lithofacies: basal bioclastic calcarenite, calcirudite-microconglomerate lithofacies, lithoclastic calcarenite, large bivalve bioclastic calcarenite, rhodolith bioclastic calcarenite, and fine bioclastic calcarenite. We focused on the three typologies that were mainly used as building stone (lithoclastic calcarenite, large bivalve bioclastic calcarenite, and fine bioclastic calcarenite). Mineralogical, petrographical and petrophysical analyses have been carried out according to European standard rules to highlight the main characteristics of the different calcarenite types when used as building stones. These three lithofacies show different petrophysical behavior indicating that large bivalve calcarenite and lithoclastic calcarenite lithofacies have slightly different but characteristic mechanical properties related to the primary influence of grain composition, early cementation and micrite contents. Moreover, fine bioclastic calcarenite lithofacies results to be the worst building stone because it is intensely heterogeneous in porosity, cementation and general petrophysical features because of its intense bioturbation.
CRIS-Team Scopus Importer:2021-04-20
Keywords: Building stone; Cultural heritage; Petrographic characterization; Petrophysical properties

Matera building stones: Comparison between bioclastic and lithoclastic calcarenites - Bonomo, Agnese Emanuela; Lezzerini, Marco; Prosser, Giacomo; Munnecke, Axel; Koch, Roman; Rizzo, Giovanna (Building Materials, Materials Design and Applications, 2019)
Matera (Basilicata, southern Italy) was awarded World Heritage Site status by the UNESCO since 1993, and it will be the European Capital of Culture in 2019. It is one of the most ancient towns in the world, whose historical centre was totally built by only a moderately lithified and highly porous sedimentary building stone, known as Gravina Calcarenite. This easily workable rock was quarried since prehistoric times, and it was used for building different kind of constructions from the rupestrian settlement to the gorgeous historic palace during the XVIII century. Calcarenite, however, can be an extremely heterogeneous building material depending on the composition of the particles and their characteristics. After a geological survey, it was possible to recognize two main varieties of this building stone, which were in turn subdivided into six sub-typologies. As a first approach, we have characterized, in terms of building stone quality, the two main varieties: the bioclastic calcarenite and the lithoclastic calcarenite, sampled in the quarrying area to the North of Matera. The bioclastic calcarenite is from a new quarry in the upper part of the Calcarenite Formation, while the lithoclastic calcarenite is from an old quarry, inactive since 1965, in the lower part of the same formation. Mineralogical, petrographic and petrophysical tests have been carried out according to European Standards rules to highlight the main characteristics of different calcarenite types when used as building stone. Despite of their compositional differences, the bioclastic and lithoclastic calcarenite are both pure limestones with slightly different amounts of non-carbonates (silt quartz, clay minerals). The slightly different but characteristic mechanical properties clearly characterize the primary influence of grain composition, early cementation and micrite contents.
CRIS-Team Scopus Importer:2019-11-12
Keywords: Building stone; Italian Unesco site; Petrographic characterization; Physical and mechanical properties

Matera’s Old Quarries: Geological and Historical Archives That Need Protection and Valorization - Bonomo, A. E.; Acito, A. M.; Prosser, G.; Rizzo, G.; Munnecke, Axel; Koch, Roman; Bentivenga, M. (Geoheritage, 2019)
The Sassi of Matera, UNESCO site since 1993, represents a human settlement completely integrated in the natural landscape. There, the development of the community is closely connected to the geology since prehistoric times. The Calcarenite di Gravina, a Pleistocene poorly lithified limestone onlapping a large area of the Apulian foreland in southern Italy, is the building stone that people used to carve their houses inside, and build the town outside. The use of calcarenite for housing began in the prehistory with the first human settlement, deepening natural caves which served as dwellings, while the mining activity began in the third century B.C., increasing until the nineteenth century in connection with the urban development of Matera. The calcarenite was carved out on site and used to build houses. In the eighteenth century, the great urban development of the city gave way to large mining activities in the northern area of Matera. Geomorphological analysis through aerial photographs and a geological survey in this area have been carried out to investigate the historical quarrying activities. In the present study, six quarry areas along the Appia Antica road are valuated: the Madonna delle Vergini topographic high; Cava della Palomba; Parco Scultura–Cava Paradiso; Cava del Sole, the Monumental Quarry Remains; Via Ridola inside the Piano, the highest area of Sassi. They represent peculiar and important examples to be safeguarded and valued. Their geomorphological, geostratigraphical and palaeontological elements provide useful information for understanding the territory evolution in the last two millennia.
CRIS-Team Scopus Importer:2019-11-19
Keywords: Geo-valorization; Geological itinerary; Mining activities; Reused quarries; Soft limestone

Maximizing Cache Memory Usage for Multigrid Algorithms - Douglas, Craig C.; Hu, Jonathan; Iskandarani, Mohamed; Kowarschik, Markus; Rüde, Ulrich; Weiß, Christian (Numerical Treatment of Multiphase Flows in Porous Media. Proc. of the Int. Workshop held at Beijing, China, August 2–6, 1999, 2000)
<p class="Para" style="border: 0px; font-stretch: inherit; font-size: 13px; line-height: 1.6; font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; margin: 0px; padding: 0px; vertical-align: baseline; outline: 0px; width: 580px; color: rgb(51, 51, 51);"> Computers today rely heavily on good utilization of their cache memory subsystems. Compilers are optimized for business applications, not scientific computing ones, however. Automatic tiling of complex numerical algorithms for solving partial differential equations is simply not provided by compilers. Thus, absolutely terrible cache performance is a common result. <p class="Para" style="border: 0px; font-stretch: inherit; font-size: 13px; line-height: 1.6; font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; margin: 0.5em 0px 0px; padding: 0px; vertical-align: baseline; outline: 0px; width: 580px; color: rgb(51, 51, 51);"> Multigrid algorithms combine several numerical algorithms into a more complicated algorithm. In this paper, an algorithm is derived that allows for data to pass through cache exactly once per multigrid level during a V cycle before the level changes. This is optimal cache usage for large problems that do not fit entirely in cache. The numerical techniques and algorithms discussed in this paper can be easily applied to numerical simulation of fluid flows in porous media.
UnivIS-Import:2015-04-16:Pub.2000.tech.IMMD.lsinfs.maximi
Keywords: multigrid; cache; threads; sparse matrix; iterative methods; domain decomposition; compiler optimization

Maximum rates of climate change are systematically underestimated in the geological record - Kießling, Wolfgang; Kemp, David B.; Eichenseer, Kilian (Nature Communications, 2015)
Recently observed rates of environmental change are typically much higher than those inferred for the geological past. At the same time, the magnitudes of ancient changes were often substantially greater than those established in recent history. The most pertinent disparity, however, between recent and geological rates is the timespan over which the rates are measured, which typically differ by several orders of magnitude. Here we show that rates of marked temperature changes inferred from proxy data in Earth history scale with measurement timespan as an approximate power law across nearly six orders of magnitude (102 to >107 years). This scaling reveals how climate signals measured in the geological record alias transient variability, even during the most pronounced climatic perturbations of the Phanerozoic. Our findings indicate that the true attainable pace of climate change on timescales of greatest societal relevance is underestimated in geological archives.
UnivIS-Import:2017-01-09:Pub.2015.nat.dgeo.IGM.LP.maximu

Measurements and analysis of the thermal properties of a sedimentary succession in Yangtze plate in China - Luo, Jin; Qiao, Yu; Xiang, Wei; Rohn, Joachim (Renewable Energy, 2020)
A geological stratum is a rock or soil layer that has internally consistent characteristics and is distinguishable from adjacent layers. A stratigraphic section contains reference information for the strata of an associated sedimentary area. In this paper, the thermal properties of 36 rock formations in a succession of the Yangtze plate in China are studied. Thermal properties are analyzed with an emphasis on rock formations, rock lithological types and dry/saturated conditions. The results show that thermal conductivity varies dramatically with different rock lithological types, which range from 0.72 W m−1 K−1 to 4.49 W m−1 K−1. The analysis of biochemical sedimentary rocks shows that silicate has the highest thermal conductivity, followed by dolomite and limestone; this variation is due to the differences in rock-forming minerals. The thermal conductivity of the clastic rocks is mainly determined by the type of minerals, the porosity and the water content. Compared to dry samples, the thermal conductivity and volumetric heat capacity of saturated samples are higher. Moreover, the thermal conductivity data of nine other locations in the Yangtze plate are compared with the stratigraphic data. This analysis shows that thermal conductivity matches very well for most of the geological formations, with the exception of sandstone, which exhibits a significant deviation across formations. Finally, the thermal properties for the Yangtze plate are mapped for insight on their spatial distribution.
CRIS-Team Scopus Importer:2019-12-10
Keywords: Geothermal energy; Sedimentary succession; Thermal properties; Yangtze plate

Mechanical improvement of calcium carbonate cements by: In situ HEMA polymerization during hardening - Myszka, Barbara; Hurle, Katrin; Zheng, Kai; Wolf, Stephan; Boccaccini, Aldo R. (Journal of Materials Chemistry B, 2019)
Calcium carbonate cements are a promising alternative for calcium phosphate cements. Due to the higher solubility of calcium carbonate compared to apatite, it is expected to have an improved biodegradation rate; a clear advantage for prospective biomedical applications in a clinical context. As of yet, the poor mechanical performance of calcium carbonate cements precludes their exploitation as a bioceramic. Herein, we report a mechanically enhanced calcium carbonate cement, formulated of vaterite and magnesium-doped amorphous calcium carbonate, which was strengthened by in situ polymerization of incorporated 2-hydroxyethylmethacrylate (HEMA) during setting in simulated body fluid (SBF). This approach allowed us to generate a pronouncedly strengthened polymer-ceramic composite whose mechanical properties can be tuned by the monomer fraction. Varying cement compositions were characterized with respect to their mechanical performance, morphology, and quantitative phase composition. HEMA polymer reinforcement strengthened the calcium carbonate cement distinctly in four-point bending test while, in stark contrast, the brittleness of the polymer-free cement simply made such tests impossible. Our results demonstrate that the chosen polymer-enforcement strategy is an efficient and straightforward approach and allows for tuning the mechanical properties of an otherwise brittle and thus unusable calcium carbonate cement towards biomedical application.
CRIS-Team Scopus Importer:2019-06-25

Mechanically activated alite: New insights into alite hydration - Bergold, Sebastian; Neubauer, Jürgen; Götz-Neunhoeffer, Friedlinde (Cement and Concrete Research, 2015)
For superior understanding of alite hydration an investigation of mechanically activated alite (M3 modification) was performed by XRD and heat flow calorimetry. Activation resulted in reduced particle size, a decreased mean crystallite size and partial amorphization. For the samples of activated alite a significantly accelerated and intensified hydration was observed and complete conversion of alite was found after 24 h. The enthalpy of reaction for crystalline alite was determined to be - 548 J/g from measured heat of hydration after 24 h. The enthalpy of reaction of amorphous "alite" was found to be less exothermic (- 386 J/g). The main hydration period is controlled by nucleation of C-S-H, while the transition from acceleration to deceleration period takes place after consumption of the small alite particles. XRD amorphous C-S-H phase is indicated to precipitate in considerable amount even in the highest activated alite before "long-range ordered", XRD detectable C-S-H was observed.
Keywords: Acceleration (A); Amorphous material (B); Ca3SiO5 (D); Calcium-Silicate-Hydrate (C-S-H) (B); Hydration (A)

Mechanisms and drivers of belemnite body-size dynamics across the Pliensbachian–Toarcian crisis - Costa Rita, Patrícia; Nätscher, Paulina; Duarte, Luís V.; Weis, Robert; de Baets, Kenneth (Royal Society Open Science, 2019)
Body-size reduction is considered an important response to current climate warming and has been observed during past biotic crises, including the Pliensbachian–Toarcian crisis, a second-order mass extinction. However, in fossil cephalopod studies, the mechanisms and their potential link with climate are rarely investigated and palaeobiological scales of organization are not usually differentiated. Here, we hypothesize that belemnites reduce their adult size across the Pliensbachian–Toarcian boundary warming event. Belemnite body-size dynamics across the Pliensbachian–Toarcian boundary in the Peniche section (Lusitanian Basin, Portugal) were analysed based on the newly collected field data. We disentangle the mechanisms and the environmental drivers of the size fluctuations observed from the individual to the assemblage scale. Despite the lack of a major taxonomic turnover, a 40% decrease in rostrum volume is observed across the Pliensbachian–Toarcian boundary, before the Toarcian Oceanic Anoxic Event where belemnites go locally extinct. The pattern is mainly driven by a reduction in adult size of the two dominant species, Pseudohastites longiformis and Passaloteuthis bisulcata. Belemnite-size distribution is best correlated with fluctuations in a palaeotemperature proxy (stable oxygen isotopes); however, potential indirect effects of volcanism and carbon cycle perturbations may also play a role. This highlights the complex interplay between environmental stressors (warming, deoxygenation, nutrient input) and biotic variables (productivity, competition, migration) associated with these hyperthermal events in driving belemnite body-siz
Keywords: cephalopods; Lilliput effect; Pliensbachian–Toarcian boundary event; Toarcian oceanic anoxic event; climate warming; computed tomography

Mechanisms of early ettringite formation in ternary CSA-OPC-anhydrite systems - Wolf, Julian; Jansen, Daniel; Götz-Neunhoeffer, Friedlinde; Neubauer, Jürgen (Advances in Cement Research, 2019)
Ternary systems on the basis of calcium sulfoaluminate (CSA), ordinary Portland cement (OPC) and anhydrite are known for their rapid setting and hardening properties, which are mainly attributed to the formation of ettringite. Ettringite is the major hydrate phase precipitated in the early stages of hydration in these systems and may be formed by three different main reaction pathways. To investigate the process of these mechanisms, the hydration of four different ternary blends were examined by means of heat flow calorimetry, in situ X-ray diffraction, and thermogravimetric analysis. For the CSA-rich mixes, it was found that hydration in the first 48 h is only subject to the behaviour of ye'elimite and anhydrite dissolution and the resulting formation of ettringite. In the system with the highest OPC proportion, the initial hydration kinetics were found to be more rapid, leading to very high ettringite quantities in the first couple of hours. With the dissolution of the anhydrous OPC phases, more ettringite is formed by the hydration of C(3)A and the consumption of AH(3) stemming from the hydration of ye'elimite and calcium provided by the dissolution of C3S. In the OPC-rich mixes, more than 50% of the formed ettringite can be attributed to this coupled reaction pathway.
CRIS-Team WoS Importer:2019-04-12

Mechanistic insight on the chemistry of potential Pt antitumor agents as revealed by collaborative research performed in Kragujevac and Erlangen - Petrović, Biljana; Jovanović, Snezana; Puchta, Ralph; van Eldik, Rudi (Inorganica Chimica Acta, 2019)
This personal account reports on the mechanistic insight gained on the chemistry of potential Pt antitumor agents based on the collaborative research between the groups of Živadin Bugarčić in Kragujevac (Serbia) and Rudi van Eldik in Erlangen (Germany). The work focuses on different mononuclear Pt(II) and Pt(IV), as well as dinuclear Pt(II) complexes, the tuning of their lability through steric and electronic (σ-donor and π-acceptor) effects, their interaction with sulfur- and nitrogen-donor bio-relevant nucleophiles, the elucidation of structure-reactivity relationships, and DFT calculations on ground, transition and product state complexes. It presents an overview of the investigated systems and reveals mechanistic information on the basis of spectroscopic and kinetic measurements.
CRIS-Team Scopus Importer:2019-06-21
Keywords: DFT calculations; Di-nuclear Pt(II) complexes; Kinetics; Mechanism; Pt(II) complexes; Pt(IV) complexes

Mechanistic neutral models show that sampling biases drive the apparent explosion of early tetrapod diversity - Dunne, Emma; Thompson, Samuel E.D.; Butler, Richard J.; Rosindell, James; Close, Roger A. (Nature Ecology & Evolution, 2023)
Estimates of deep-time biodiversity typically rely on statistical methods to mitigate the impacts of sampling biases in the fossil record. However, these methods are limited by the spatial and temporal scale of the underlying data. Here we use a spatially explicit mechanistic model, based on neutral theory, to test hypotheses of early tetrapod diversity change during the late Carboniferous and early Permian, critical intervals for the diversification of vertebrate life on land. Our simulations suggest that apparent increases in early tetrapod diversity were not driven by local endemism following the ‘Carboniferous rainforest collapse’. Instead, changes in face-value diversity can be explained by variation in sampling intensity through time. Our results further demonstrate the importance of accounting for sampling biases in analyses of the fossil record and highlight the vast potential of mechanistic models, including neutral models, for testing hypotheses in palaeobiology.
CRIS-Team Scopus Importer:2023-08-11

Mediate relation between electrical and thermal conductivity of soil - Schwarz, Hans; Bertermann, David (Geomechanics and Geophysics for Geo-Energy and Geo-Resources, 2020)
Thermal conductivity is a key parameter for many soil applications, especially for dimensioning shallow and very shallow geothermal systems based on the possible heat extraction rate and for modelling heat transfer processes around high voltage underground cables. Due to the limited purview of direct thermal conductivity measurements, for an investigation of extensive areas, usually other geophysical methods like electrical resistivity tomography measurements are applied. To derive thermal conductivity of soil from geoelectrical measurements a relation between electrical and thermal conductivity is needed. Until now only few approaches worked on a direct correlation between both conductivities. Due to the difficulties of a direct relation, within this study a modular approach of a mediate correlation between electrical and thermal conductivity was investigated. Therefore, a direct relationship between a corrected electrical conductivity and water content as well as the standard and simple thermal conductivity model of Kersten (Bull of the Univ Minnesota 28:1–227, 1949) was used. To develop this concept soil types of sand, silt loam and clay were investigated where different saturation steps and pressure loads were applied. For each configuration electrical and thermal conductivity as well as water content and bulk density was determined. To refine the results of the calculated water content a corrective factor was applied. Furthermore, bulk density as an inlet parameter of the Kersten equation was also derived based on electrical conductivity. The suggested proceeding enables the determination of thermal conductivity solely based on electrical conductivity without prior soil property information.
CRIS-Team Scopus Importer:2020-08-07
Keywords: Bulk density; ERT; Heat transfer; Kersten model; Water content

Meeresschildkrötenschutz - Schulbert, Christian; Römheld, Julia (Vogelschutz, 2007)
UnivIS-Import:2015-03-09:Pub.2007.nat.dgeo.IGM.LP.meeres

Mega El Niño instigated the end-Permian mass extinction - Sun, Yadong; Farnsworth, Alexander; Joachimski, Michael; Wignall, Paul B.; Krystyn, Leopold; Bond, David P.G.; Ravidà, Domenico C.G.; Valdes, Paul J. (Science, 2024)
The ultimate driver of the end-Permian mass extinction is a topic of much debate. Here, we used a multiproxy and paleoclimate modeling approach to establish a unifying theory elucidating the heightened susceptibility of the Pangean world to the prolonged and intensified El Niño events leading to an extinction state. As atmospheric partial pressure of carbon dioxide doubled from about 410 to about 860 ppm (parts per million) in the latest Permian, the meridional overturning circulation collapsed, the Hadley cell contracted, and El Niños intensified. The resultant deforestation, reef demise, and plankton crisis marked the start of a cascading environmental disaster. Reduced carbon sequestration initiated positive feedback, producing a warmer hothouse and, consequently, stronger El Niños. The compounding effects of elevated climate variability and mean state warming led to catastrophic but diachronous terrestrial and marine losses.
Created from Fastlane, Scopus look-up

Mega El Nino primed the end-Permian world for mass extinction - Sun, Yadong; Farnsworth, Alexander; Joachimski, Michael; WIGNALL, PAUL B.; Krystyn, Leopold; Bond, David P. G.; Ravidà, Domenico C.G.; Valdes, Paul J. (Chinese Science Bulletin, 2024)
CRIS-Team Scopus Importer:2025-02-04

Meiobenthos and ocean acidification: Effects on meiobenthic communities inhabiting Mediterranean cold shallow CO2-vents - Cocozza di Montanara, A.; Baldrighi, E.; López Correa, Matthias; Chianese, E.; Appolloni, L.; Simoncini, N.; Sandulli, R.; Zeppilli, D.; Semprucci, F.; Gambi, M. C.; Ferrigno, F.; Donnarumma, L. (Estuarine Coastal and Shelf Science, 2024)
Ocean acidification is causing major changes in marine ecosystems, with varying levels of impact, depending both on the habitat and the studied organisms. Here, we investigated for the first time the meiobenthos and nematode fauna inhabiting the sediments around Castello Aragonese (Ischia, Italy), characterized by variable pH values due to coastal volcanic CO2 venting. In this scenario, nematode functional diversity changed according to different pH levels and grain size: maturity index was higher at most acidic stations and trophic composition spanned from the dominance of predators in the acidic stations, to the high abundance of non-selective deposit feeders and epistrate feeders in the ambient-pH stations. Overall, the present study revealed a relatively high tolerance of meiobenthos and nematodes to lower pH conditions. However, an in-depth analysis of nematode fauna showed differences in their assemblages at different pH levels with few nematode genera rather adapted to the extreme environmental conditions at the acidic stations.
CRIS-Team Scopus Importer:2024-04-05
Keywords: CO; Community composition; Functional diversity; Ischia vents; Mediterranean sea; Meiofauna; Nematodes

Melt generation beneath Arctic Ridges: Implications from U decay series disequilibria in the Mohns, Knipovich, and Gakkel Ridges - Elkins, Lynne; Sims, Ken W.W.; Prytulak, Julie; Blichert-Toft, Janne; Elliott, Tim; Blusztajn, Jerzy; Fretzdorff, Susanne; Reagan, Mark; Haase, Karsten; Humphris, Susan; Schilling, Jean-Guy (Geochimica Et Cosmochimica Acta, 2014)
We present new U-Th-Ra-Pb, U-Pa, and Nd, Sr, Hf, and Pb isotope data for the slow- to ultraslow-spreading Mohns, Knipovich, and Gakkel Ridges. Combined with previous work, our data from the Arctic Ridges cover the full range of axial depths from the deep northernmost Gakkel Ridge shallowing upwards to the Knipovich, Mohns, and Kolbeinsey Ridges north of Iceland. Age-constrained samples from the Mohns and Knipovich Ridges have (Th/U) activity ratios ranging from 1.165 to 1.30 and 1.101 to 1.225, respectively. The high Th excesses of Kolbeinsey, Mohns, and Knipovich mid-ocean ridge basalts (MORB) are erupted from ridges producing relatively thin (Mohns, Knipovich) to thick (Kolbeinsey) oceanic crust with evidence for sources ranging from mostly peridotite (Kolbeinsey) to eclogite-rich mantle (Mohns, Knipovich). Age-constrained lavas from 85°E on the Gakkel Ridge, on the other hand, overlie little to no crust and range from small ( 5%) Th excesses to small U excesses ( 5%). The strong negative correlation between (Th/U) values vs. axial ridge depth among Arctic ridge basalts is controlled not only by solidus depth influence on U-Th disequilibria, but also by variations in mantle source lithology and depth to the base of the lithosphere, which is expected to vary at ultra-slow spreading ridges. Small Pa excesses (65% excess) in age-constrained basalts support the presence of eclogite in the mantle source for this region. Conversely, the ultraslow-spreading Gakkel Ridge basalts are homogeneous, with Sr, Nd, and Hf radiogenic isotopic signatures indicative of a long time-averaged depleted mantle source. The Gakkel samples have minimum (Ra/Th) ratios ranging from 3.07 to 3.65±3%, which lie along and extend the global negative correlation between Ra and Th excesses observed in MORB. The new Th-Ra data support a model for global MORB production in which deep melts record interaction with shallower materials. This scenario requires either mixing with shallow-derived melts, or melt-rock reaction with shallower rocks in the lithosphere or crust. © 2013 Elsevier Ltd.

Melting versus contamination effects on 238U-230Th-226Ra and 235U-231Pa disequilibria in lavas from São Miguel, Azores - Prytulak, Julie; Avanzinelli, Riccardo; Koetsier, Govert; Kreissig, Katharina; Beier, Christoph; Elliott, Tim (Chemical Geology, 2014)
The island of São Miguel, Azores piques geochemical interest due to a strikingly large range in the long-lived radiogenic isotope ratios of its lavas. The 'enriched' signatures (e.g., radiogenic Sr/Sr and unradiogenic Nd/Nd) observed in lavas found in the east of the island have been proposed to originate from recycled crustal components in their mantle sources. Such fertile lithologies should have higher melt productivities (amount of melt generated per decrement in pressure) than peridotitic mantle and this heritage ought to be evident in the U-series signatures of melts derived from such materials. Specifically, combined U-Th and U-Pa disequilibria in erupted lavas should identify significant differences in the melting rate and/or the mineralogical makeup of their sources (e.g., the amount of garnet). To this end, new U-Th-Ra and U-Pa disequilibria are presented for sixteen mafic lavas (<50wt.% SiO) that encompass the full range of São Miguel's long-lived radiogenic isotope variability. However, primary U-series signatures of mafic lavas can be influenced by assimilation of more differentiated products. Notably, syenite nodules and cumulate alkali feldspar xenocrysts have been identified in São Miguel basalts. We argue that secondary contamination of basalts is most evident in the hugely variable Th-Ra disequilibria ( 18% deficits to >300% excesses of Ra) that strongly correlate with Ba/Th ratios. The longer-lived U-series nuclides are only slightly perturbed in a number of the more enriched lavas, resulting in increased noise in the dataset. In apparently uncontaminated samples, isotopically depleted lavas from the west of São Miguel display slightly higher Th and Pa excesses than the enriched samples from the east. The U-series signature of the enriched lavas can be modeled with a combination of higher absolute values of D-UU and D-Th, coupled with higher melting rates compared to the depleted western source. These parameters are consistent with a peridotite source enriched with contributions from more fusible lithologies such as eclogite and/or pyroxenite in the eastern source, but not with direct derivation from such fusible lithologies. The only subtle variations in U-series isotopes coupled with large, systematic variations in radiogenic isotope compositions suggest that enriched components and/or their melts are well-mixed with mantle peridotite, thus masking their distinctive melting behavior. Finally, basalts from Sete Cidades volcano in the west of São Miguel have very similar long-lived isotope compositions and U-series disequilibria to basalts from the island of Pico, Azores. The geochemical similarity of lavas from islands at the center and periphery of the archipelago argue against systematic differences in melting behavior related to sampling different portions of an underlying plume structure. © 2014 Elsevier B.V.
Keywords: Contamination; Dynamic melting; Pyroxenite/eclogite; São Miguel; U-series

Melts from hydrous depleted back-arc mantle at a young boninitic volcano on the flank of Valu Fa Ridge (Lau basin, SW Pacific) - Myeong, Bora; Regelous, Marcel; Haase, Karsten; Lim, Hoseong; Park, Jongkyu (Contributions To Mineralogy and Petrology, 2023)
Volcano S3 is a young seamount located 5 km east of the Valu Fa Ridge (VFR) in the Lau Basin, which has erupted boninitic lavas. We present new data for whole-rock compositions, minerals and olivine‐hosted melt inclusions, and propose a new model for low-Si boninite (LSB) petrogenesis in a subduction-related setting. The whole-rock compositions reflect mixing of less primitive melt with variable amounts ( 30%) of minerals, whereas quenched glass compositions result from ( 60%) crystal fractionation of a primitive boninitic magma which is preserved as melt inclusions hosted in olivine crystals. The compositions of primitive olivine and spinel from S3 are more refractory than those from MORB and back-arc basin (BAB) lavas. Lower Fe8 and Na8 values of S3 than those of BAB lavas reflect melting of relatively depleted mantle at high temperature and low pressure. The mantle beneath S3, and the adjacent VFR and Ata is more depleted than those of BAB located further from the arc, and S3 and Ata lavas have similar slab input ( 1%). The geochemical differences between S3 and BAB lavas imply that the boundary between dry and wet mantle is located beneath VFR. We suggest that a vertical mantle flow beneath VFR brings depleted mantle containing slab components from deeper within the wedge. This depleted and wet mantle probably experienced a high degree of partial melting at low pressure to form LSB magmas beneath S3. The LSB lavas can be formed at back-arc spreading centers which are located close enough to an active arc.
CRIS-Team Scopus Importer:2023-09-29
Keywords: Crustal thickness; Low-Si boninite; Off-axis seamount; Partial melting; Refractory mantle; Subduction input

Melts of sediments in the mantle wedge of the Oman ophiolite - Haase, Karsten; Freund, Sarah; Koepke, Jürgen; Hauff, Folkmar; Erdmann, Martin (Geology, 2015)
The rocks in the crustal section of the Oman ophiolite show an increasing input of a subduction component with time, most likely reflecting the generation of the ophiolite above a subducting slab. Field relations, new geochemical data, and Nd-Hf isotope data for felsic to mafic intrusive rocks in the mantle harzburgite from the Haylayn block in the Oman ophiolite suggest late magmatic events in a mantle wedge shortly before obduction of the ophiolite. Incompatible element contents and low ε and ε of the felsic rocks exclude differentiation from mafic magmas, but are consistent with an origin by partial melting of pelagic sediments similar to leucogranites in continental collision zones. These melts apparently mixed with mafic magmas resembling enriched late-stage lavas from the ophiolite. The leucogranitic intrusions into the mantle wedge confirm the transfer of melts of sediments from the subducted plate into the mantle at subduction zones. We suggest that the enrichment of Rb, K, and Pb observed in the Oman boninites is caused by addition of melts of sediments similar to those from the Haylayn block to the boninite source in the mantle wedge.

Mesoproterozoic continental arc magmatism and crustal growth in the eastern Central Tianshan Arc Terrane of the southern Central Asian Orogenic Belt: Geochronological and geochemical evidence - He, Zhenyu; Klemd, Reiner; Zhang, Zeming; Zong, Keqing; Sun, Li-Xin; Tian, Zuolin; Huang, Bo-Tao (Lithos, 2015)
Numerous microcontinents are known to occur in the Central Asian Orogenic Belt (CAOB), one of the largest accretionary orogens and the most significant area of Paleozoic crustal growth in the world. The evolution of the Precambrian crust in these microcontinents is central to understanding the accretionary and collisional tectonics of the CAOB. Here, we present systematic zircon U–Pb dating and Hf isotope studies of Mesoproterozoic gneissic granitoids from the eastern Central Tianshan Arc Terrane (CTA) of the southern CAOB. The investigated intermediate to felsic (SiO2 = 60.48–78.92 wt.%) granitoids belong to the calcic- to calc-alkaline series and usually have pronounced negative Nb, Ta and Ti anomalies, relative enrichments of light rare earth elements (LREEs) and large ion lithophile elements (LILEs) while heavy rare earth elements (HREEs) and high field strength elements (HFSEs) are depleted, revealing typical active continental margin magmatic arc geochemical characteristics. These spatially-distant rocks show consistent zircon U–Pb crystallization ages from ca. 1.45 to 1.40 Ga and thus constitute a previously unknown Mesoproterozoic continental magmatic arc covering hundreds of kilometers in the eastern segment of the CTA. Furthermore the high and mainly positive zircon εHf(t) values between − 1.0 and + 8.6 and the zircon Hf model ages of 1.95 to 1.55 Ga, which are slightly older than their crystallization ages, suggest that they were mainly derived from rapid reworking of juvenile material with a limited input of an ancient crustal component. Therefore, the formation of these granitoids defines an extensive Mesoproterozoic intermediate to felsic, subduction-related intrusive magmatic arc activity that was active from at least 1.45 to 1.40 Ga, involving significant juvenile continental growth in the eastern segment of the CTA. Furthermore the zircon U–Pb and Hf isotopic data challenge the common belief that the CTA was part of the Tarim Craton during Paleo- to Mesoproterozoic times. However, the southern Beishan microcontinents and the CTA have similar zircon U–Pb and Hf isotopic signatures, indicating a similar Precambrian tectonothermal evolution for both. This finding provides new and important constraints on the Precambrian crustal evolution of the microcontinents in the southern CAOB.<br
Keywords: Zircon U–Pb geochronology and Hf isotopes; Crustal growth; Mesoproterozoic continental magmatic arc; Chinese Eastern Tianshan; Central Asian Orogenic Belt

Mesoproterozoic dyke swarms in foreland and nappes of the central Scandinavian Caledonides: structure, magnetic fabric, and geochemistry - de Wall, Helga; et al. (Geological Magazine, 2007)
As an example of microstructural and magnetic fabric evolution, and geochemistry of mafic dykes during a Subsequent orogenic overprint, a major Mesoproterozoic dyke complex in Scandinavia, the Vasterbotten complex of the Central Scandinavian Dolerite Group, is traced westwards into the crystalline nappes of the early Phanerozoic Caledonian orogen. Using geophysical, field, microscopic, magnetic and geochemical information, dykes and sills are characterized, and their overprint during Caledonian orogeny documented. The Vasterbotten complex is composed of sets of dykes, trending NE-SW, NW-SE and WNW-ESE, respectively. Similar dykes are exposed in allochthonous positions (Lower and Middle allochthons) in the Caledonian fold-and-thrust belt. The autochthonous dykes are generally undeformed and retain both their primary texture and mineralogy Chilled margins are well preserved. In the Caledonian Lower and Middle allochthons, similar dykes in crystalline basement rocks are progressively faulted and sheared when proceeding from the marginal to the interior parts of the orogen. Dyke margins are more likely to be sheared than the interior parts of dykes. In the Lower Allochthon, under very low- and low-grade metamorphic conditions, dykes are distinctly less competent than granitic host rocks. Thick dykes are more competent than gneisses; thin dykes do not show such competence contrasts. In the Middle Allochthon, metre-scale dykes with patches of altered plagioclase phenocrysts can still be discerned in low-strain domains. Highly sheared dykes are drawn out to thin layers of centimetre thickness. Dykes are deformed together with the crystalline country rocks under greenschist-grade metamorphic conditions without major competence contrasts. Magnetic fabrics show an evolution similar to the silicate mineral fabrics. The magnetic fabrics in the dykes are transformed successively from ferromagnetic-magmatic in the Autochthon to ferromagnetic deformational in the Lower Allochthon and, finally, paramagnetic deformational in the Middle Allochthon. As a consequence, the magnetic susceptibility decreases for several orders of magnitude. Geochemically, the dykes are dominantly sub-alkaline basalts typical for continental tholeiites and can be distinguished from the Neoproterozoic dykes in the Sarv-Nappe equivalents (highest part of the Middle Allochthon), which show a more MORB-like (E-MORB) magmatic signature. Preliminary age information from a dyke in the Lower Allochthon of the Borgefiell area and the Middle Allochthon is consistent with the assumption that these dykes are time equivaient with the Central Scandinavian Dolerite Group. Therefore, the studied dykes may represent an extension of the Vasterbotten complex or a new complex of the Central Scandinavian Dolerite Group. According to section restorations, the Caledonian allochthons were situated further WNW relative to their present position, and, originally, the mafic dykes cut across all of the Fennoscandian lithosphere, at least to the present Atlantic margin and the earlier passive margin of the Baltica terrane. As a consequence, these dykes may provide a link for pre-Caledonian and pre-Grenvillian plate reconstructions.
Keywords: dykes; microstructure; magnetic anisotropy; geochemistry; dolerite; Caledonides; Scandinavia

Mesoproterozoic juvenile crust in microcontinents of the Central Asian Orogenic Belt: evidence from oxygen and hafnium isotopes in zircon - He, Zhenyu; Klemd, Reiner; Yan, Li-Li; Lu, Tianyu; Zhang, Zeming (Scientific Reports, 2018)
We report in situ O and Hf isotope data of zircon grains from coeval Mesoproterozoic (ca. 1.4 Ga) igneous metamafic (amphibolite) and granitic rocks of the Chinese Central Tianshan microcontinent (CTM) in the southern Central Asian Orogenic Belt (CAOB). Zircon grains from amphibolite have mantle-like δ18OVSMOW values of 4.7–5.6‰ and juvenile Hf isotopic compositions (εHf(t) = 8.4–15.3; TDMC = 1.57–1.22 Ga), whereas those from granitic rocks have δ18OVSMOW values of 5.6–7.0‰ and evolved Hf isotopic compositions (εHf(t) = −1.0–8.2; TDMC = 2.09–1.62 Ga). Zircon O–Hf isotopic compositions of the metamafic and granitic rocks provide evidence for Mesoproterozoic (ca. 1.4 Ga) crustal growth and a substantial Palaeoproterozoic supracrustal component in the CTM. These findings and previous studies, reporting ca. 1.4 Ga magmatic rocks from other microcontinents of the CAOB, suggest that a large belt of Mesoproterozoic (ca. 1.4 Ga) juvenile continental crust formed in a continental terrane, fragments of which now occur over a distance of more than a thousand kilometres in the southern CAOB.<br
Keywords: Geochemistry; Petrology; Precambrian geology

Mesoscopic-scale structure and dynamics near the morphotropic phase boundary of (1-x)PbTiO3-xBiScO3 - Datta, Kaustuv; Richter, Andreas; Göbbels, Matthias; Neder, Reinhard; Mihailova, Boriana (Physical Review B - Condensed Matter and Materials Physics, 2015)
A range of compelling information on the local structure and dynamics of the ferroelectric perovskite-type (ABO3) system (1-x)PbTiO3-xBiScO3 has been revealed through analyzing room-temperature x-ray pair distribution functions and temperature-dependent Raman scattering data for compositions ranging across the morphotropic phase boundary (MPB). Raman scattering data have provided exclusive evidence for distinct dynamical responses from the A-site Pb/Bi and the B-site Ti/Sc cations as a function of composition and temperature. Both pair distribution function and Raman scattering analyses indicate improved coherence between the A-site and B-site off-center displacements for x above the MPB composition. The distinguishable dynamical features were spotted between two sets of compositional range from which x=0.34 could be assigned as a critical composition of "local" MPB: the composition at which the pathway of mesoscopic-scale temperature-driven coupling and transformation processes changes. This differs from the previous reports based on the analysis of the average structure, suggesting the response function of a system may not necessarily follow the evolution of the average structure from which however the MPB has so far been ascribed for a particular system. The individual features of the cations revealed here will further help in understanding the structure-property correlations for similar ferroelectric solid solutions.

Mesozoic–Cenozoic bioevents - Kießling, Wolfgang; Lazarus, David; Zeller, Ulrich (Palaeogeography, Palaeoclimatology, Palaeoecology, 2004)
Keywords: Biodiversity; Evolution; Extinctions

Metabolic activity of Planktothrix rubescens and its consequences on oxygen dynamics in laboratory experiment: A stable isotope study - Dordoni, Marlene; Tittel, Jörg; Rosenlöcher, Yvonne; Rinke, Karsten; Barth, Johannes (Journal of Phycology, 2024)
Fluctuations in dissolved oxygen (DO) contents in natural waters can become intense during cyanobacteria blooms. In a reconnaissance study, we investigated DO concentrations and stable isotope dynamics during a laboratory experiment with the cyanobacterium Planktothrix rubescens in order to obtain insights into primary production under specific conditions. This observation was extended to sub-daily timescales with alternating light and dark phases. Dissolved oxygen concentrations and its isotopes (δ18ODO) ranged from 0.02 to 0.06 mmol · L−1 and from +9.6‰ to +23.4‰. The δ18ODO proved to be more sensitive than concentration measurements in response to metabolic variation and registered earlier shifts to dominance by respiration. Oxygen (O2) contents in the headspace and its isotopes (δ18OO2) ranged from 2.62 to 3.20 mmol · L−1 and from +9.8‰ to +21.9‰. Headspace samples showed less fluctuations in concentration and isotope trends because aquatic processes were hardly able to alter signals once the gas had reached the headspace. Headspace δ18OO2 values were corrected for gas–water equilibration and were determined to be higher than the mean δ18OH2O of −8.7‰. This finding suggests that counteracting respiration was important even during the highest photosynthetic activity. Additionally, headspace analyses led to the definition of a fractionation factor for respiration (αR) of this cyanobacterium with a value of 0.980. This value confirms the one commonly used for cyanobacteria. Our findings may become important for the management of water bodies where decreases in DO are caused by cyanobacteria.
CRIS-Team Scopus Importer:2024-05-03
Keywords: cyanobacteria; dissolved oxygen; dissolved oxygen stable isotopes; Planktothrix rubescens; standing water bodies

Metal-induced malformations in early Palaeozoic plankton are harbingers of mass extinction - Vandenbroucke, Thijs R.A.; Emsbo, Poul; Munnecke, Axel; Nuns, Nicolas; Duponchel, Ludovic; Lepot, Kevin; Quijada, Melesio; Paris, Florentin; Servais, Thomas; Kießling, Wolfgang (Nature Communications, 2015)
Glacial episodes have been linked to Ordovician-Silurian extinction events, but cooling itself may not be solely responsible for these extinctions. Teratological (malformed) assemblages of fossil plankton that correlate precisely with the extinction events can help identify alternate drivers of extinction. Here we show that metal poisoning may have caused these aberrant morphologies during a late Silurian (Pridoli) event. Malformations coincide with a dramatic increase of metals (Fe, Mo, Pb, Mn and As) in the fossils and their host rocks. Metallic toxins are known to cause a teratological response in modern organisms, which is now routinely used as a proxy to assess oceanic metal contamination. Similarly, our study identifies metal-induced teratology as a deep-time, palaeobiological monitor of palaeo-ocean chemistry. The redox-sensitive character of enriched metals supports emerging 'oceanic anoxic event' models. Our data suggest that spreading anoxia and redox cycling of harmful metals was a contributing kill mechanism during these devastating Ordovician-Silurian palaeobiological event
Keywords: Metal-induced; Mass extinction; Silurian; Palaeozoic plankton; Palaeobiological events

Metallogenesis of the Zhibo and Chagangnuoer volcanic iron oxide deposits in the Awulale Iron Metallogenic Belt, Western Tianshan orogen, China - Zhang, Xi; Klemd, Reiner; Gao, Jun; Dong, Lian-Hui; Wang, Xin-Shui; Haase, Karsten; Jiang, Tuo; Qian, Qing (Journal of Asian Earth Sciences, 2014)
The Zhibo and Chagangnuoer iron ore deposits occur at the same volcanic edifice and are situated along the eastern segment of the Awulale Iron Metallogenic Belt in the Western Tianshan orogen of China. The former deposit is exposed near the caldera and the latter lies on the northwestern flank of the volcanic structure. The ore mineralization, the ore texture, the ore bodies structures, the trachytic to trachy andesitic host rocks and the geological characteristics of the Zhibo and Chagangnuoer deposits indicate a magmatic source for the iron oxide mineralization. This is supported by the observation that the vast majority of the Zhibo and Chagangnuoer magnetites have δ18O values between >+0.9‰ and <+4.00‰ consistent with a precipitation from 'normal' subduction type intermediate to felsic magmas or high-temperature magmatic fluids. However some magnetites with low δ18O values (<+0.9‰) are thought to have formed in equilibrium with a low to moderate temperature hydrothermal fluid as is evidenced by pervasive and vein-type controlled (skarn-type) alteration of the ore and host volcanic rocks. Furthermore, the trace element composition of the equilibrium ortho-magmatic magnetites was reset during this hydrothermal alteration event. Major and trace element characteristics indicate that the volcanic rocks, the granitoids and the iron ore bodies were formed in a continental arc setting during the Early Carboniferous. The ore-hosting volcanic rocks probably originated from melting of a mantle wedge that was metasomatized during subduction. Laser ablation-ICPMS (LA-ICPMS) U-Pb zircon ages of 350 ± 2 Ma and 361 ± 7 Ma were obtained for zircon from the trachy andesitic host rock of the iron ore exposed near the caldera of the volcano and the highly altered fine grained garnet-dominated host rock on the flank of the volcano, respectively. A U-Pb zircon age of 321 ± 2 Ma was gained for the rhyolite overlying the ore bodies at the Chagangnuoer deposit, which were intruded by a granitic pluton with a U-Pb zircon age of 319 ± 2 Ma. Furthermore, the minerals of the skarn-type alteration zone at the Chagangnuoer deposit yield an Sm-Nd isochron age of 313 ± 7 Ma (Grt-Act-Epi-whole rock). Considering previous geochronological studies, a 350-330 Ma age range as observed in the host rocks of the Zhibo mine is believed to display a period of continuous volcanic activity and associated ortho-magmatic, high-temperature iron oxide mineralization during subduction. The iron oxide mineralization in both deposits is thought to have been derived from the same magma source, as the ore-hosting volcanic rocks are similar to 'Kiruna-type' iron oxide ores. Subsequently, the volcanic host rocks and the iron ore bodies were variably hydrothermally altered during subduction (ca. 319-313 Ma). The alteration zones were probably facilitated by the infiltration of hydrothermal fluids along faults, which were created by the intrusion of a granitic pluton. © 2014 Elsevier Ltd. All rights reserve
UnivIS-Import:2015-03-09:Pub.2014.nat.dgeo.IGM.c3geoc.metall
Keywords: Magmatic iron oxide ore deposits; Magnetite trace elements and O-isotopes; Metallogenesis; Tianshan; U-Pb zircon ages

Metallogenesis of the Zhibo and Chagangnuoer volcanic iron oxide deposits in the Awulale Iron Metallogenic Belt, Western Tianshan orogen, China - Zhang, Xi; Klemd, Reiner; Gao, Jun; Dong, Lian-Hui; Wang, Xin-Shui; Haase, Karsten; Jiang, Tuo; Qian, Qing (Journal of Asian Earth Sciences, 2015)
The Zhibo and Chagangnuoer iron ore deposits occur at the same volcanic edifice and are situated along the eastern segment of the Awulale Iron Metallogenic Belt in the Western Tianshan orogen of China. The former deposit is exposed near the caldera and the latter lies on the northwestern flank of the volcanic structure. The ore mineralization, the ore texture, the ore bodies structures, the trachytic to trachy andesitic host rocks and the geological characteristics of the Zhibo and Chagangnuoer deposits indicate a magmatic source for the iron oxide mineralization. This is supported by the observation that the vast majority of the Zhibo and Chagangnuoer magnetites have δ18O values between >+0.9‰ and <+4.00‰ consistent with a precipitation from ‘normal’ subduction type intermediate to felsic magmas or high-temperature magmatic fluids. However some magnetites with low δ18O values (<+0.9‰) are thought to have formed in equilibrium with a low to moderate temperature hydrothermal fluid as is evidenced by pervasive and vein-type controlled (skarn-type) alteration of the ore and host volcanic rocks. Furthermore, the trace element composition of the equilibrium ortho-magmatic magnetites was reset during this hydrothermal alteration event. Major and trace element characteristics indicate that the volcanic rocks, the granitoids and the iron ore bodies were formed in a continental arc setting during the Early Carboniferous. The ore-hosting volcanic rocks probably originated from melting of a mantle wedge that was metasomatized during subduction. Laser ablation-ICPMS (LA-ICPMS) U–Pb zircon ages of 350 ± 2 Ma and 361 ± 7 Ma were obtained for zircon from the trachy andesitic host rock of the iron ore exposed near the caldera of the volcano and the highly altered fine grained garnet-dominated host rock on the flank of the volcano, respectively. A U–Pb zircon age of 321 ± 2 Ma was gained for the rhyolite overlying the ore bodies at the Chagangnuoer deposit, which were intruded by a granitic pluton with a U–Pb zircon age of 319 ± 2 Ma. Furthermore, the minerals of the skarn-type alteration zone at the Chagangnuoer deposit yield an Sm-Nd isochron age of 313 ± 7 Ma (Grt-Act-Epi-whole rock). Considering previous geochronological studies, a 350–330 Ma age range as observed in the host rocks of the Zhibo mine is believed to display a period of continuous volcanic activity and associated ortho-magmatic, high-temperature iron oxide mineralization during subduction. The iron oxide mineralization in both deposits is thought to have been derived from the same magma source, as the ore-hosting volcanic rocks are similar to ‘Kiruna-type’ iron oxide ores. Subsequently, the volcanic host rocks and the iron ore bodies were variably hydrothermally altered during subduction (ca. 319–313 Ma). The alteration zones were probably facilitated by the infiltration of hydrothermal fluids along faults, which were created by the intrusion of a granitic pluton.<br
Keywords: Metallogenesis; Magmatic iron oxide ore deposits; Magnetite trace elements and O-isotopes; U–Pb zircon ages; Tianshan

Metamorphic and Structural Evolution of the Southern Shackleton Range during the Ross Orogeny. - Buggisch, Werner; Kleinschmidt, Georg; Kreuzer, Hans; Krumm, Stefan (Polarforschung, 1994)
UnivIS-Import:2015-03-05:Pub.1994.nat.dgeo.IGM.LG.metamo

Metamorphic evolution of (ultra)-high-pressure subduction-related transient crust in the South Tianshan Orogen (Central Asian Orogenic Belt): Geodynamic implications - Klemd, Reiner; Gao, Jun; Li, Jilei; Meyer, Melanie (Gondwana Research, 2015)
The study of subduction-related high-pressure- and ultra-high-pressure metamorphic rocks exposed in orogenic belts is critical for unraveling the tectonothermal evolution of an orogen. The South Tianshan Orogen of the southwestern Central Asian Orogenic Belt, one of the world's largest accretionary orogens, contains several Paleozoic (ultra-)high-pressure ((U)HP) metamorphic terranes. (U)HP eclogites, blueschists and associated (U)HP metasedimentary rocks of continental and oceanic origin were reported from two localities in the Northern Tianshan (NTS) of Kazakhstanand Kyrgyzstan, namely from the Ordovician Aktyuz and Makbal metamorphic terranes. Furthermore Lower Carboniferous (U)HP eclogites and blueschists of oceanic origin are located in the Southern Tianshan Accretionary Complex (STAC) of southern Kyrgyzstan (Atbashi) and northwestern China (Akeyazi). The continentally-derived Aktyuz eclogite is considered to have experienced a continuous clockwise prograde P–T path with peak metamorphic conditions of ca. 1.6–2.1 GPa at 610–670 °C, corresponding to a burial depth of about 70 km. A peak metamorphic Lu–Hf garnet isochron age of 474 ± 2 Ma for the retrogressed eclogite of continental origin is in accordance with a Sm–Nd garnet isochron age of 462 ± 7 Ma interpreted as time of cooling and decompression of the metamorphic rock assemblage below 650 to 600 °C. Quantitative P–T pseudosection modeling for peripheral Makbal HP garnet amphibolites of continental origin also revealed a continuous clockwise P–T path with peak-metamorphic conditions of ca. 1.4 GPa at ca. 620 °C followed by an isothermal uplift to ca. 0.7 GPa. Furthermore, prograde P–T paths of oceanically-derived central Makbal high-pressure metabasic rocks revealed peak metamorphic conditions between 520 °C and 560 °C at 2.2 GPa to 2.5 GPa with subsequent isothermal decompressions. The metamorphic (P–T) evolution of a garnet–chloritoid–talc schist is exhibited by a P–T trajectory starting ca. 480 °C at 2.5 GPa, followed by peak pressures of ca. 2.85 GPa at 525 °C and peak temperatures of ca. 580 °C at 2.4 GPa. A Lu–Hf peak metamorphic age of 470.1 ± 2.5 Ma for a peripheral garnet amphibolite is in accordance with a garnet-growth Sm–Nd age of 475 ± 4 Ma of the UHP garnet–chloritoid–talc schist. Different and variable P–T paths show that former oceanic and continental crust at Makbal was subducted to different maximum depths (HP versus UHP conditions). The (U)HP metamorphism of oceanic and continental mafic rocks from the Aktyuz and Makbal metamorphic terranes is assumed to have occurred in a similar time frame of between 500 and 460 Ma. The proposed geodynamic model for the HP Aktyuz metamorphic terrane incorporates the deep northeast-directed subduction of NTS continental crust under the Ankrakhai block of Paleo-Kazakhstan subsequent to the closure of the Djalair–Naiman Basin. At Makbal the final consumption of the oceanic crust of the Terskey Ocean to the northeast was immediately followed by the deep subduction of a (thinned) passive continental margin of the Central Tianshan Arc Terrane (CTA). Both scenarios are in accordance with continental-type subduction geodynamics producing the subduction-related (U)HP rocks during continental–continental collision processes. The exhumation of detached oceanic material by channel flow may have been initiated by the transient subduction of oceanic and subsequent continental crust. The Lower Carboniferous (U)HP metamorphic terranes (Atbashi and Akeyazi) in the Southern Tianshan Accretionary Complex are mainly composed of metasediments which host some lenses and boudins of oceanically-derived blueschists and eclogites. Most eclogites, blueschists and metasediments have experienced peak high-pressure metamorphism (480–580 °C at 1.4–2.1 GPa), while some slices display UHP-conditions (2.7–3.3 GPa at 570–630 °C). Multi-point Lu–Hf and Sm–Nd isochrons from several eclogite and blueschist samples from the Atbashi and Akeyazi metamorphic terranes revealed consistent ages of ca. 320–315 Ma for the peak of metamorphism, thereby confirming that (U)HP metamorphism occurred during a single subduction event. The highly variable peak metamorphic conditions displayed by the (U)HP rocks imply that metamorphism of the metasediments and the various metabasic rocks occurred in different depths of the subduction zone. (U)HP metabasites and metasediments exhibit different P–T paths, which is consistent with the chaotic incorporation in a subduction channel resulting in the eventual exhumation as a mélange. This scenario is much in agreement with initial subduction of oceanic crust and accretionary wedge sediment removal by subduction erosion and thus is similar to accretionary-type subduction terranes, although, with higher peak P–T conditions than previously recorded. The absence of significant melting, in combination with the variable peak pressure metamorphic conditions and the intimate interlayering of high- and ultrahigh-pressure rocks, suggests that the (U)HP rocks were derived from varying depths within the subduction zone and then juxtaposed during exhumation in the subduction channel. This is in accordance with exhumation of the (U)HP rocks by channel flo
Keywords: South Tianshan Orogen; (Ultra-)high-pressure metamorphism; Geochronology; Accretionary- and continental-type subductions; Channel flow exhumation

Metamorphic evolution of (ultra)-high-pressure subduction-related transient crust in the South Tianshan Orogen (Central Asian Orogenic Belt): Geodynamic implications - Klemd, Reiner; Gao, Jun; Li, Ji-Lei; Meyer, Melanie (Gondwana Research, 2015)
UnivIS-Import:2015-03-09:Pub.2015.nat.dgeo.IGM.c3geoc.metamo

Metamorphic petrology of a high-T/low-P granulite terrane (Damara belt, Namibia) – Constraints from pseudosection modelling and high-precision Lu–Hf garnet-whole rock dating - Jung, Stefan; Brandt, Sönke; Bast, Rebecca; Scherer, Erik E.; Berndt, Jasper (Journal of Metamorphic Geology, 2019)
Migmatites comprise a minor volume of the high-grade part of the Damara orogen of Namibia that is dominated by granite complexes and intercalated metasedimentary units. Migmatites of the Southern Central Zone of the Damara orogen consist of melanosomes with garnet+cordierite+biotite+K-feldspar, and leucosomes, which are sometimes garnet- and cordierite-bearing. Field evidence, petrographic observations, and pseudosection modelling suggest that, in contrast to other areas where intrusion of granitic magmas is more important, in situ partial melting of metasedimentary units was the main migmatite generation processes. Pseudosection modelling and thermobarometric calculations consistently indicate that the peak-metamorphic grade throughout the area is in the granulite facies ( 5 kbar at 800°C). Cordierite coronas around garnet suggest some decompression from peak-metamorphic conditions and rare andalusite records late, near-isobaric cooling to <650°C at low pressures of 3 kbar. The inferred clockwise P–T path is consistent with minor crustal thickening through continent–continent collision followed by limited post-collisional exhumation and suggests that the granulite facies terrane of the Southern Central Zone of the Damara orogen formed initially in a metamorphic field gradient of 35–40°C/km at medium pressures. New high-precision Lu–Hf garnet-whole rock dates are 530 ± 13 Ma, 522.0 ± 0.8 Ma, 520.8 ± 3.6 Ma, and 500.3 ± 4.3 Ma for the migmatites that record temperatures of 800°C. This indicates that high-grade metamorphism lasted for c. 20–30 Ma, which is compatible with previous estimates using Sm–Nd garnet-whole rock systematics. In previous studies on Damara orogen migmatites where both Sm–Nd and Lu–Hf chronometers have been applied, the dates (c. 520–510 Ma) agree within their small uncertainties (0.6–0.8% for Sm–Nd and 0.1–0.2% for Lu–Hf). This implies rapid cooling after high-grade conditions and, by implication, rapid exhumation at that time. The cause of the high geothermal gradient inferred from the metamorphic conditions is unknown but likely requires some extra heat that was probably added by intrusion of magmas from the lithospheric mantle, i.e., syenites that have been recently re-dated at c. 545 Ma. Some granites derived from the lower crust at c. 545 Ma are the outcome rather than the cause of high-T metamorphism. In addition, high contents of heat-producing elements K, Th, and U may have raised peak temperatures by 150–200°C at the base of the crust, resulting in the widespread melting of fertile crustal rocks. The continuous gradation from centimetre-scale leucosomes to decametre-scale leucogranite sheets within the high-grade metamorphic zone suggests that leucosome lenses coalesced to form larger bodies of anatectic leucogranites, thereby documenting a link between high-grade regional metamorphism and Pan-African magmatism. In view of the close association of the studied high-T migmatites with hundreds of synmetamorphic high-T granites that invaded the terrane as metre- to decametre-wide sills and dykes, we postulate that crystallization of felsic lower crustal magma is, at least partly, responsible for heat supply. Late-stage isobaric cooling of these granites may explain the occurrence of andalusite in some samples.
CRIS-Team Scopus Importer:2019-10-11
Keywords: Damara orogen; granulite facies metamorphism; Lu–Hf garnet dating; migmatites; Namibia

Metamorphic P–T–t evolution of mafic HP granulites in the northeastern segment of the Tarim Craton (Dunhuang block): Evidence for early Paleozoic continental subduction - He, Zhenyu; Zhang, Zeming; Zong, Keqing; Xiang, Hua; Klemd, Reiner (Lithos, 2014)
The Dunhuang block, which constitutes the northeastern segment of the Tarim Craton, is located between the Central Asian Orogenic Belt (CAOB) to the north and the Altyn-Qilian Orogenic Belt to the south. The present study reveals that the early Paleozoic HP mafic granulites from the Dunhuang block underwent four stages of metamorphism: prograde amphibolite-facies (M1), peak high-pressure (HP) granulite-facies (M2) and two late stages of amphibolite-facies retrograde metamorphism. Based on phase equilibrium modeling, P-T conditions of the four stages of metamorphism are estimated at 720-750. °C and 11-13. kbar, 760-800. °C and 14-16. kbar, 690-720. °C and 8-8.5. kbar, and at <. 6. kbar and <. 640. °C respectively. Peak granulite-facies metamorphism is characterized by a low geothermal gradient of ca. 16. °C/km. Zircon U-Pb dating shows that the HP granulite-facies metamorphism occurred at ca. 431. Ma and the early retrograde amphibolite-facies overprint at ca. 403. Ma. Thus the investigated mafic rocks here reveal a clockwise P-T-t path involving burial heating before peak granulite-facies metamorphism and subsequent decompression-cooling with an uplift rate of ca. 0.8. km/Ma. This, together with a continental affinity of the HP metamorphic rocks, indicates that the Dunhuang block experienced a collisional orogenesis during the early Paleozoic. © 2014 Elsevier B.V.
UnivIS-Import:2015-03-09:Pub.2014.nat.dgeo.IGM.c3geoc.metamo
Keywords: Beishan orogenic collage; CAOB; Dunhuang block; Early Paleozoic; HP granulite; P-T-t path

Metamorphic Response to Alpine Thrusting of a Crustal-scale Basement Nappe in Southern Calabria (Italy) - Brandt, Sönke; Schenk, V. (Journal of Petrology, 2020)
Structural, geophysical and age data indicate that the tilted cross-section of the Variscan continental crust exposed in the Serre of southern Calabria forms the uppermost Alpine nappe ('Serre nappe') of three Variscan basement slices derived from the southern European margin. This Alpine nappe stack is a fragment of the western Mediterranean Alps and rests now, after Miocene emplacement, on top of the Apennine carbonate platform. We report for the first time a P-T path for prograde Alpine metamorphism, which is restricted to the two lower nappes (Castagna and Bagni nappes) that are squeezed between cooler tectonic units, the Serre nappe above and the Apennine platform below. Therefore, we attribute their metamorphism to tectonic loading and concomitant shear heating during Eocene south-directed overthrusting of the crustal-scale Serre nappe. In the underlying Castagna nappe, Alpine metamorphism is only locally recorded, mainly by new growth of garnet, forming at the expense of retrogressed Variscan biotite dated at 43 Ma. The local existence of Alpine besides relict Variscan mineral assemblages in the strongly but heterogeneously overprinted rocks allows for characterization of metamorphic evolutions during both the Alpine and Variscan orogeneses in the former intermediate level of the Variscan crust of Calabria. The metamorphic evolutions have been reconstructed through P-T pseudosection modelling for Al-rich metasediments. In the Castagna nappe, rarely preserved Variscan garnet-sillimanite-biotite-ilmenite-plagioclase-quartz (+/- K-feldspar Si-poor white mica) assemblages formed under amphibolite-facies subsolidus conditions (650 +/- 60 degrees C, 4.0 +/- 0.5 kbar). During subsequent decompression and cooling to greenschist-facies conditions garnet was replaced by biotite-sillimanite and later by white mica-chlorite intergrowths. Retrogression of Variscan biotite is evidenced by the exsolution of ilmenite along grain boundaries and cleavages, textures that were subsequently overgrown by Alpine garnet coexisting with Si-rich white mica, rare chloritoid (in metapelites), and hornblende (in metagreywackes). Alpine garnet shows prograde zoning and is Ca-rich, and thus is distinct from unzoned and Ca-poor Variscan garnet porphyroblasts. Estimated conditions (520 +/- 40 degrees C, 8.0 +/- 1.0 kbar) record elevated pressures during Alpine lower amphibolite-facies metamorphism. In the lowermost Bagni nappe, rare prograde-zoned, Ca-rich garnet in strongly retrogressed mylonitic quartz-phyllites allows isopleth thermobarometry, which indicates lower amphibolite-facies conditions (555 +/- 10 degrees C, 7.4 +/- 0.3 kbar) resembling those for Alpine garnet growth in the Castagna nappe. The similar clockwise P-T paths for prograde Alpine metamorphism and the consistent peak pressures of 7-9 kbar in the Castagna and Bagni nappes point to a joint short-lived metamorphism during overthrusting of the crustal-scale Serre nappe within the south European margin during the north-directed subduction of the Alpine Tethys. South-directed overthrusting of the now tilted Variscan crustal section of the Serre along the up to 500 m thick mylonite horizon of the Curinga-Girifalco Line is in agreement with seismic data indicating an extended, few kilometres thick low-velocity zone (Bagni and Castagna nappes and mylonites of the Curinga-Girifalco Line) below the exposed lower crustal section of the Serre nappe.
CRIS-Team WoS Importer:2021-05-14

Meteoritic Molybdenum and Ruthenium Isotopic Abundances Document Nucleosynthetic p-process Components - Marti, Kurt; Fischer-Gödde, Mario; Proksche, Carina (Astrophysical Journal, 2023)
Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s-process component. We report isotopic relations of ϵ 92Mo versus ϵ 100Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s-process abundance variations. We show that two p-process isotopes 92Mo and 94Mo require the presence of distinct p-process components in meteoritic materials. The nucleosynthetic origin of abundant magic (N = 50) p-process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp-antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p-process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p-nuclides.
CRIS-Team Scopus Importer:2023-11-03

Metre-scale effective flow properties of heterogeneous fine-grained sediments - Kurtev, Kuncho; Drews, Michael; Ma, Jingsheng; Aplin, Andrew (EAGE Shale Workshop 2010: Shale - Resource and Challenge, 2010)

Mg-C-O isotopes and elements reveal the origin of dolostone in the Middle Jurassic Buqu Formation - Li, Xi; Shen, An Jiang; Hao, Ruilin (Petroleum Science, 2025)
The origin of dolostone in the Middle Jurassic Buqu Formation of the Plateau Basin has been a subject of prolonged debate. This study combines detailed petrological observations with analyses of Mg-C-O isotopes and elements to constrain the origin of dolostones in the Buqu Formation. Petrography and cathodoluminescence (CL) examination identified three types of matrix dolostones: very finely to finely crystalline dolostone (D1), finely to medium crystalline dolostone (D2), and medium to coarsely crystalline dolostone (D3). The analysis of the diagenesis sequence reveals that D1 originated from the dolomitization of grainstone in the early diagenetic phase, whereas D2 and D3 resulted from the recrystallization of D1 during the later burial phase. The presence of high Na (>100 ppm), low Fe (<1000 ppm), low Mn (<250 ppm), positive Ce anomaly, LREE enrichment, stable δ26Mg (−2.28‰ to −2.04‰), and δ13C (1.02‰–2.95‰) indicates that the early dolomitization fluid was oxidized seawater. As the crystal size increases (D1→D2→D3), the progressively rising Mn content and significantly negative δ18O (−10.72‰ to −7.81‰) suggest that the dolostone has experienced modification and alteration by buried pore water in the later stages. The fluctuations in relative sea level during the sedimentary deposition of the Buqu Formation were reconstructed through the utilization of Na, Sr/Cu, Sr/Ba, Rb/Sr, ∑REE, and δ13C. It was observed that the δ26Mg of dolostone closely mirrored the variations in sea level. The consistent trend of change confirms that sea level fluctuations control the formation and distribution of early dolostone. Frequent sea level rise and fall prompted the limestone deposited on the carbonate platform to be continuously transformed into dolostone, which accumulates over a long period to form large-scale thick dolostone. After the formation entered the burial stage, under the combined action of high Mg/Ca ratio pore water, high temperature, and high pressure, the early dolostone experienced the adjustment of burial dolomitization. This research offers a typical case study on the application of Mg-C-O isotope and elements to determine the origin of dolostone. This will aid in a more comprehensive understanding of the formation process of dolostone in ancient rock records.
CRIS-Team Scopus Importer:2025-02-17
Keywords: Buqu formation; Burial adjustment dolomitization; Mg-C-O isotopes; Origin of dolostone; Plateau basin; Sea level changes

Miaolingian (Cambrian) trilobite biostratigraphy and carbon isotope chemostratigraphy in the Tingskullen drill core, Öland, Sweden - Ahlberg, Per; Lundberg, Frans; Calner, Michael; Lehnert, Oliver; Dahlqvist, Peter; Joachimski, Michael (Estonian Journal of Earth Sciences, 2021)
The Cambrian succession of the Tingskullen drill core from northern Öland comprises Cambrian Series 2 and Miaolingian (Wuliuan Stage) siliciclastic strata. The major portion of the succession is represented by the Miaolingian Borgholm Formation, which, in ascending order, is subdivided into the Mossberga, Bårstad and Äleklinta members. The Äleklinta Member is barren of body fossils, whereas the Mossberga and Bårstad members are moderately to highly fossiliferous and biostratigraphically reasonably well constrained. Trilobites and agnostoids from the Bårstad Member are indicative of the Acadoparadoxides pinus Zone. The Mossberga Member has not yielded any zonal guide fossils but is tentatively assigned to the Eccaparadoxides insularis Zone. A δ13Corg curve throughout the Borgholm Formation shows a general positive trend up-section without any distinctive excursion, suggesting that the Wuliuan Acadoparadoxides (Baltoparadoxides) oelandicus Superzone (the ‘Oelandicus beds’) of Öland is younger than the negative Redlichiid–Olenellid Extinction Carbon isotope Excursion (ROECE), which is known from near the top of Stage 4 and close to the traditional ‘Lower–Middle Cambrian boundary’ in several parts of the world.<br

Microbial bioerosion of erratic sub-fossil Nautilus shells in a karstic cenote (Lifou, Loyalty Islands, New Caledonia) - Seuß, Barbara; Wisshak, Max; Mapes, Royal H.; Hembree, Daniel I.; Landman, Neil; Lignier, Vincent (Ichnos-An International Journal For Plant and Animal Traces, 2016)
UnivIS-Import:2016-06-01:Pub.2016.nat.dgeo.IGM.LP.microb
Keywords: Bioerosion; Cenote; Holocene; Ichnocoenosis; Karst; Nautilus; New Caledonia; Taphonomy

Microbially induced wrinkle structures in Middle Devonian siliciclastics from the Prague Basin, Czech Republic - Vodrážková, Stanislava; Vodrážka, Radek; Munnecke, Axel; Franců, Juraj; Al‐Bassam, Khaldoun; Halodová, Patricie; Tonarová, Petra (Lethaia, 2018)
The occurrence of wrinkle structures in Middle Devonian deep‐water siliciclastic sequences of the Prague Basin (Roblín Member, Srbsko Formation, Givetian) is reported and interpreted to be microbially induced. Current and/or gravitational forces are considered the simplest explanation of the origin of these structures. Taking into account the tectonic activity linked with ongoing Variscan orogeny, the wrinkle structures could also be interpreted as soft sediment deformation structures originating due to exposure of mat‐bearing sediment to seismic shocks. The distribution of n‐alkanes and isoprenoids suggests two types of prevailing biological sources, namely phytoplankton, representing organic material from the water column, and benthic bacteria. Judging from the sedimentary facies and lack of petrographic characteristics suggestive of light competition, the microbial mats are interpreted to be formed by non‐autotrophic bacteri

Microbial micritic cementation in deep time: Implications for early marine lithification and paleoenvironmental reconstruction - Belkhedim, Salim; Eberli, Gregor P.; López Correa, Matthias; Sadji, Radouane; Nemra, Abdelkrim; Benhamou, Miloud; Munnecke, Axel (Sedimentary Geology, 2024)
Early micritic cementation is important to reconstruct paleoenvironments of sedimentary gaps. However, due to their scarcity in ancient records, their initial mineralogy (low-magnesium calcite (LMC), high-magnesium calcite (HMC), aragonite), as well as their origin (biotic or abiotic) and paleoenvironments are still controversial. Herein, based on fluorescence microscopy (FL), cathodoluminescence microscopy (CL), and microdrilling carbon and oxygen isotope analyses, we investigate well developed micritic cements in lower Pliensbachian limestones from the Traras Mountains, northwestern Algeria. Evidence for a microbiological influence in the formation of these cements is given by their irregular morphology, the presence of clotted micropeloidal structures, as well as their bright fluorescence under FL. Together, they reflect precipitation of the micritic cements under microbial control via active and/or passive mechanisms, in the presence of organic matter. Their orange luminescence and low δ18O signals suggest their initial precipitation by sea-water as HMC before being recrystallized into LMC within the meteoric and/or burial realm. These micritic cements, including anisopachous and meniscus-like cements are thought to be precipitated within the marine phreatic zone, as they are associated mainly with isopachous fibrous cements, which is in contrast to their widespread attribution as typical and indicative fabrics of the marine vadose zone. In addition, it has been shown that crystalline cements are developed always upon the early micritic envelopes and micritic cements. These observations which are in line with recent studies conducted on modern deposits confirm that preservation of marine microbial cements in deep time is crucial not only for early grain stabilization, but also serving as a foundation for the subsequent crystal growth.
CRIS-Team Scopus Importer:2024-09-13
Keywords: Crystal growth; Early micritic cementation; Grain stabilization; Initial mineralogy; Marine phreatic; Microbial control; Organic matter

Microbioerosion in Tahitian reefs: A record of environmental change during the last deglacial sea-level rise (IODP 310) - Heindel, Katrin; Wisshak, Max; Westphal, Hildegard (Lethaia, 2008)
The main motivation for Integrated Ocean Drilling Program Expedition 310 to the Tahitian Archipelago was the assumption that the last deglacial sea-level rise is precisely recorded in the coral reefs of this far-field site. The Tahitian deglacial succession typically consists of coral framework subsequently encrusted by coralline algae and microbialites. The high abundance of microbialites is uncommon for shallow-water coral reefs, and the environmental conditions favouring their development are still poorly understood. Microbioerosion patterns in the three principal framework components (corals, coralline algae, microbialites) are studied with respect to relative light availability during coral growth and subsequent encrustation, in order to constrain the palaeobathymetry and the relative timing of the encrustation. Unexpectedly for a tropical, light-flooded setting, ichnotaxa typical for the deep-euphotic to dysphotic zone dominate. The key ichnotaxa for the shallow euphotic zone are scarce in the analysed sample set, and are restricted to the base of the deglacial succession, thus reflecting the deglacial sea-level rise. At the base of the deglacial reef succession, the ichnocoenoses present in the corals indicate shallower bathymetries than those in the encrusting microbialites. This is in agreement with radiocarbon data that indicate a time gap of more than 600 years between coral death and microbialite formation. At the top of the deglacial reef succession, in contrast, the microbioerosion patterns in the three framework components indicate a uniform palaeobathymetry, and radiocarbon ages imply that encrustation took place shortly after coral demise. An enigma arises from the fact that the ichnocoenoses imply photic conditions that appear very deep for zooxanthellate coral growth. During the deglacial sea-level rise increased nutrients and fluvial influx may have led to (seasonal?) eutrophication, condensing the photic zonation. This would have exerted stress on the coral ecosystem and played a significant role in initiating microbialite development.