Third party funded individual grant
Start date : 01.03.2022
End date : 28.02.2025
The project aims at developing a new set of analytical and modelling tools to improve the knowledge of three of the most challenging research questions in sedimentary geology: (i) the identification of environmental signals in deep-time, (ii) the reconstruction of the evolution of ancient sediment routing systems, (iii) the effect of climate changes across the Permian-Triassic boundary on sediment production and sediment transfer to the ocean and its impact on life recovery after the most devastating extinction in the history of our planet. The mainstream literature supports a general model indicating increasing arid condition from the Late Permian to the Early Triassic. However, more recent literature indicate increasing sediment flux related to seasonal humid conditions and higher water discharge leaving uncertainty in the interpretation of climate and sediment production unsolved. To tackle such a big challenge, the project relies on an extensive set of analytical tools, paleoclimatic and paleotectonic models, to be applied on sections in Southern Russia and China where high-precision TIMS dating of volcanic layers provide the base to constrain environmental variations in time. The integration of paleoclimatic and paleotectonic models with quantitative provenance analysis, Ne cosmogenic nuclides, Low-T thermochronology, and radiogenic isotope tracers 143Nd / 144Nd (expressed as εNd) and 87Sr / 86Sr in mudstones, will provide the base to link variations in provenance, denudation rates, and sediment flux to climate change and tectonic activity. he implications from proving and especially quantifying an increase in sediment flux are important. Firstly, because the PTB is one of the most critical time intervals in Earth history, and the interplay of tectonics, climate, and changes in the sediment flux are currently poorly understood. Secondly, enhanced silicate weathering could have effectively contributed to the sequestration of atmospheric CO2 emitted by Siberian Trap volcanism instead climate regulation by silicate weathering may have failed in case of no major change in weathering and extensive volcanic degassing.
Two of the biggest challenges in sedimentary geology are (i) the identification of tectonic and climatic perturbations – particularly in relation to down-system propagation in both modern deep-time sedimentary systems, and (ii) the reconstruction of paleo-sediment fluxes in ancient Sediment Routing Systems (SRS) (Caracciolo, 2020). Tectonic and climatic forcings perturbate the steady state of geological landscapes which in turn adapt to the increase/decrease of erosion rates, water discharge, sediment flux, downstream sedimentfining, and sediment partitioning. Furthermore, lithological controls (e.g. how different lithologies react to weathering and sediment production) are commonly overlooked or oversimplified, hence, the calculation of sediment flux in deep-time is often imprecise. Key information relevant to the reconstruction of ancient SRS can be extracted from mineralogy and compositional signatures of sediments. Detrital provenance signatures are possibly the most reliable tool in deep-time research as they faithfully record the provenance of source lithologies. While post-depositional overprinting can destroy pristine, compositionally diagnostic signatures (e.g. mineral dissolution during weathering and/or diagenesis), complete destruction of the compositional signature is unlikely (Caracciolo, 2020, Caracciolo et al., 2020; Chew et al, 2020).
The Permian-Triassic transition is of general interest since it witnessed the most devastating mass extinction in the Phanerozoic (Erwin, 1994; Hallam and Wignall, 1997). About 95% of marine species and 75% of terrestrial species, both plants and animals went extinct.The general models for continental sedimentation converge towards increasing aridity from the Permian to the Early Triassic, with potential increase of sediment flux being related to (i) increase of precipitations in the catchment area, or (ii) increased runoff due to the lack of vegetation (Ward et al., 2000; Newell et al., 2011; Bourquin et al., 2011; Wilson et al., 2019; Zhu et al., 2020). However, several studies suggested that global warming across the P-T transition (Joachimski et al. 2012, 2020) greatly enhanced continental weathering thus providing more nutrients to the ocean. Excessive nutrients are assumed to have stimulated primary productivity, leading to widely observed anoxia-euxinia in Early Triassic oceans (Algeo et al., 2010; Algeo et al., 2011).The implications from proving and especially quantifying an increase in sediment flux are important. Firstly, because the PTB is one of the most critical time intervals in Earth history, and the interplay of tectonics, climate, and changes in the sediment flux are currently poorly understood. Secondly, enhanced silicate weathering could have effectively contributed to the sequestration of atmospheric CO2 emitted by Siberian Trap volcanism instead climate regulation by silicate weathering may have failed in case of no major change in weathering and extensive volcanic degassing (see Kump, 2018).
The main aims of the project are to (i) establish a reliable methodology integrating paleodrainage, cosmogenic nuclides, and Quantitative Provenance Analysis to constrain the evolution of SRS in deep-time, (ii) quantify erosion rates and sediment flux and disentangle the role of tectonics, climate, and drainage lithologies on the generation and transfer of sediments across the PTB, (iii) prove/disprove the climate regulation through silicate weathering across the PTB. In this project, a systematic approach to quantify landscape modifications to climatic and tectonic perturbations, and the correspondent variations in sediment flux is proposed.