Exceptional Preservation of Molluscs in the Buckhorn Asphalt

Beitrag bei einer Tagung
(Abstract zum Poster)


Details zur Publikation

Autorinnen und Autoren: Seuß B, Nützel A, Schulbert C
Jahr der Veröffentlichung: 2007
Sprache: Englisch


Abstract

The Late Carboniferous Buckhorn Asphalt Quarry contains the best
preserved Palaeozoic molluscs known world wide. The molluscs are
commonly present in their original aragonitic preservation. Shell
microstructures, larval shells, and colour patterns are commonly
preserved. The good preservation of the fossil molluscs from the
Buckhorn Asphalt was caused by Ordovician oil intruding the sediments
simultaneously to or short after deposition, sealing pore space and
preventing recrystallisation. The oil transformed into asphalt loosing
its volatiles. The fauna of the Buckhorn Asphalt Quarry is dominated by
molluscs, especially by cephalopods and small gastropods. The great
abundance of molluscs and the unique preservation make the Buckhorn
Asphalt one of the most important fossil Lagerstätten for Palaeozoic
molluscs.
The Buckhorn Asphalt Quarry is located near Sulphur, Oklahoma (USA), in
the Arbuckle Mountains. It exposes a suite of clastic Carboniferous
sediments including siliciclastic limestones, mollusc coquinas,
conglomerates, and sandstones. The mollusc bearing sediments from the
Buckhorn Asphalt Quarry are of Late Carboniferous (Desmoinesian, ~308 -
306.5 Ma) age. Deposition of the sediments took place near the
palaeoequator during that time.
For documentation from which facies the fossils derive thin section were
prepared. The high asphalt amount made is necessary to impregnate the
rock samples with synthetic resin before preparing the thin section. To
remove the asphalt of the samples and dissolve them a Soxhlet apparatus
had to be used. Dissolved sediments were further disaggregated with
tensides to remove hydrophobic matter, and then the material was
wet-sieved. The fossils of the Buckhorn Asphalt Quarry allowed us to
study a unique Palaeozoic assemblage of microborers which were studied
in thin sections, casts and etchings. It turned out, that the detected
ichno-fossils represent the most diverse Palaeozoic assemblage of
micro-bioeroders proved yet.
The Buckhorn Asphalt Quarry is an outstanding source of information, as
it is one of the very few Palaeozoic deposits in which mollusc shells
are preserved in almost unaltered composition. Original shell structures
and mineralogy, protoconchs or prodissoconchs are commonly preserved.
Colour preservation of naticopsids is present. Gastropods (~50 species)
are the most diverse group in the faunal assemblage. Ammonites and
nautiloids are very abundant, bivalves are common. Moreover, a rich
marine invertebrate fauna including e.g. brachiopods, echinoderms,
bryozoans, ostracods, foraminifera is present. Vertebrate remains are
rare, remains of land plants are up to several decimetres in size. The
exceptional preservation mollusc shells provides a “preservational
window“ for studying a Late Palaeozoic microboring assemblage revealing a
total of 18 known ichnospecies and the new ichnotaxon Aurimorpha varia –
the most diverse Palaeozoic microboring assemblage known to date. First
results suggest that most fossils including the gastropods lived in
shallow water as is indicated by the diverse assemblage of bioeroders
within the mollusc shells as well as by the presence of large plant
remains. The fossil material was mixed with siliciclastic sediment, some
of them conglomeratic, and transported over a relatively steep slope or
in channels by mass flow events. Data about early ontogenetic mollusc
shells and shell microstructure provide important information for
phylogeny and taxonomy. We can also study heterochronic processes and
compare larval and adult shell morphologies. The fact that shells are
commonly unaltered by diagenesis and are present in their original
mineralogical composition allows the study of original isotope signals
in order to reconstruct palaeo-environmental conditions.


FAU-Autorinnen und Autoren / FAU-Herausgeberinnen und Herausgeber

Schulbert, Christian
Lehrstuhl für Paläoumwelt
Seuß, Barbara Dr.
Lehrstuhl für Paläoumwelt


Einrichtungen weiterer Autorinnen und Autoren

Ludwig-Maximilians-Universität (LMU)


Zitierweisen

APA:
Seuß, B., Nützel, A., & Schulbert, C. (2007). Exceptional Preservation of Molluscs in the Buckhorn Asphalt. Poster presentation at Annual Meeting of the Paläontologische Gesellschaft, Freiberg.

MLA:
Seuß, Barbara, Alexander Nützel, and Christian Schulbert. "Exceptional Preservation of Molluscs in the Buckhorn Asphalt." Presented at Annual Meeting of the Paläontologische Gesellschaft, Freiberg 2007.

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Zuletzt aktualisiert 2018-06-12 um 08:53