Paleoecology vs taphonomy: Unraveling the molecular fossil record of the Mesoproterozoic Lakhanda Lagerstätte (SE Siberia, Russia)
Mineralogy, Petrology and Geochemistry
Final Report Abstract
The emergence and diversification of eukaryotes during the Proterozoic is one of the most fundamental evolutionary developments in Earth’s history. Eukaryotic body fossils reach back into the Paleoproterozoic, unambiguously testifying the long evolutionary history of this domain. Molecular fossils (or biomarkers) indicative for eukaryotes (i.e., regular steranes), however, remain conspicuously low until ca. 820 million years ago. As yet it is not clear whether this mismatch reflects a relative minor importance of eukaryotes in early Precambrian ecosystems and/or nonactualistic taphonomic processes in the ancient environments. The ~1 Ga old Mesoproterozoic Lakhanda Lagerstätte (SE Siberia, Russia) contains a wealth of remarkably well-preserved eukaryotic body fossils and offers an important glimpse into the ecosystem of these organisms. This joint German-Russian project aimed at investigating the geobiology of the Lakhanda Lagerstätte by exploring information encoded within sedimentary organic matter. This included (i) the first systematic assessment of organic matter preservation (biodegradation, thermal maturity, hydrocarbon syngenicity) as well as (ii) the detailed analyses of molecular fossils preserved within bitumens and – for the first time – non-extractable kerogen phases. It was expected that the combination of organic geochemical and paleontological evidence will provide important background information on early eukaryote evolution and shed new light on their ecosystems. The project included the combined application of various analytical techniques (e.g., HyPy GC– MS/MS) and delivered the first robust framework for geobiological studies on the Lakhanda Lagerstätte that involve organic geochemical analyses. Total organic matter contents of the samples ranged between 0.01–1.27 wt.%. Programmed pyrolysis and molecular organic geochemistry suggest that the organic matter in the analyzed samples is about peak oil window maturity (e.g. Tmax = 440–445 °C, MPI-1 bitumen = ~1.0, RC bitumen = ~0.9, Ph/n-C18 and Pr/n-C17 << 1) and thus sufficiently well preserved for detailed molecular fossil studies that include eukaryotic steranes and bacterial hopanes. Together with petrographic evidence as well as compositional similarities of the bitumens and corresponding kerogens, the consistency of different independent maturity parameters establishes that sedimentary hydrocarbons are indigenous and syngenetic to the host rock. The possible presence of trace amounts of hopanes and absence of steranes in samples that are sufficiently well preserved to retain both types of compounds evidences an environment dominated by anaerobic bacteria with no or very little inputs by eukaryotes. In concert with the paleontological record of the Lakhanda Lagerstätte, our study adds to the view that eukaryotes were present but not significant in Mesoproterozoic ecosystems. The findings thus have important consequences for our understanding of early eukaryote evolution.
Publications
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(2019): On mysterious creatures and their enigmatic habitats – exploring carbonate ecosystems with Ediacara-type organisms. 90th Annual Meeting of the Paläontologische Gesellschaft (Paleontological Society), 15 –18 September 2019, Munich, Germany. Extended abstract (ISBN 978-3-946705-07-9)
Duda, J.-P., Love, G.D., Reitner, J., Zhu, M., Grazhdankin, D.V.
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(2019): Reading the Siberian record: Unravelling the geobiology of the Ediacaran Khatyspyt Lagerstätte (Arctic Siberia, Russia). 29th International Meeting on Organic Geochemistry (IMOG), 1–6 September 2019, Gothenburg, Sweden. Extended abstract
Duda, J.-P., Rogov, V.I., Melnik, D.S., Love, G.D., Blumenberg, M., Grazhdankin, D.V.
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(2020). Understanding the geobiology of the terminal Ediacaran Khatyspyt Lagerstätte (Arctic Siberia, Russia). Geobiology 18(6), 643-662
Duda, J.-P., Love, G.D., Rogov, V.I., Melnik, D.S., Blumenberg, M., & Grazhdankin, D. V.
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(2021). Early Eukaryotes in the Lakhanda Biota (Mesoproterozoic, Southeastern Siberia)—Morphological and Geochemical Evidence. Doklady Biological Sciences 500(1), 127-132
Shuvalova, J.V., Nagovitsin, K.E., Duda, J.-P., & Parkhaev, P.Y.
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(2021). Molecular fossils within bitumens and kerogens from the~ 1 Ga Lakhanda Lagerstätte (Siberia, Russia) and their significance for understanding early eukaryote evolution. PalZ 95(4), 577-592
Duda, J.-P., König, H., Reinhardt, M., Shuvalova, J., & Parkhaev, P.
