Schaefer, Bettina1, Grice, Kliti1, Coolen, Marco J.L.1, Summons, Roger E.2, Cui, Xingqian2, Bauersachs, Thorsten3, Schwark, Lorenz3, Böttcher, Michael E.4,5,6, Bralower, Timothey, J.7, Lyons, Shelby, L.7, Freeman, Kate H.7, Cockell, Charles S.8, Gulick, Sean S.9, Morgan, Joanna V.10, Whalen, Michael T.11, Lowery, Christopher, M.9, Vajda, Vivi.12
1Western Australian – Organic and Isotope Geochemistry Centre (WA-OIGC), School of Earth and Planetary Sciences, The Institute for Geoscience Research, Curtin University, Perth WA, Australia 2 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA 3,1 Department of Organic Geochemistry, Institute of Geoscience, Christian-Albrechts-University, Kiel, 24118, Germany 4Geochemistry & Isotope Biogeochemistry Group, Department of Marine Geology, Leibniz Institute for Baltic Sea Research, 18119 Warnemünde, Germany 5Marine Geochemistry, University of Greifswald, 17489 Greifswald, Germany 6Department of Maritime Systems, Interdisciplinary Faculty, University of Rostock, 18059 Rostock, Germany 7Department of Geosciences, Pennsylvania State University, University Park, PA, USA 8School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK 9Institute for Geophysics, Jackson School of Geosciences, University of Texas, Austin, TX, USA 10Department of Earth Sciences and Engineering, Imperial College London, UK 11Department of Geosciences, University of Alaska, Fairbanks, AK, USA 12Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden
The Chicxulub crater (Yucatán Peninsula, Mexico) was formed by an asteroid impact 66 Ma ago and is thought to have caused the Late Cretaceous mass extinction event (e.g. Schulte et al., 2010, Hildebrand, 1991) which led to 76% loss of species world-wide including non-avian dinosaurs (Sepkoski, 1986). Also a collapse in phytoplankton productivity in the world’s oceans occurred due to a lack of sunlight (Zachos and Arthur, 1986). In 2016, the peak ring of the Chicxulub crater core was recovered by the International Ocean Discovery Program and International Continental Drilling Program Expedition 364 (“Chicxulub: Drilling the K-T Impact Crater”). Samples from this core were extracted and analysed for lipid biomarkers and stable isotopes.
Lipid biomarker profiles were used to reconstruct the origin, recovery and development of non-fossilized microbial life forms and the associated paleoenvironmental conditions in the crater from the days after the impact to up to 4 million years. A tsunami that flooded the crater within a day after the impact (Gulick et al. 2019) deposited the upper part of the suevite sequence and carried debris containing cyanobacteria, archaea, dinoflagellates and all types of anaerobic photosynthetic sulfur bacteria, likely originating from microbialites that inhabited the coast of the carbonate platform prior to impact site. The redeposited coastal cyanobacteria predominantly were diazotrophic heterocystous bacteria of the order Nostocales, as evidenced by their characteristic C26-glycolipids. The coastal anaerobic sulfur bacteria were composed of Chlorobiaceae and Chromatiaceae, revealed by the presence of their specific biomarkers from carotenoid pigments (Schaefer et al., 2020). In addition, re-deposited terrestrial organic matter was degraded in situ in the tsunami layer by fungi, as evidenced by enhanced concentrations of perylene (cf. Grice et al., 2009).
As tsunami energy declined, land-derived material and nutrients fed the crater’s microbial ecosystem for the following ca. 30 kyr and led to non-heterocystous pelagic cyanobacterial blooms, recognized by the presence of 2a-methylhopanes. A major change towards an oligotrophic sea occurred 200 kyr after impact supporting nitrogen-fixing heterocystous cyanobacteria (Schaefer et al., 2020). The cyanophyte community structure by then had changed and diversified, as recognized by the occurrence of C32-heterocystous glycolipids, abundant in cyanophytes of the order Stigonematales. About 300 kyr after the impact with the onset of the Danian-C2 hyperthermal event (~65.7 Ma ago) during deposition of hemipelagic limestones abundant carotenoid biomarkers of photosynthetic sulfur bacteria suggests that the water-column in the crater became episodically stratified allowing for the development of photic zone euxinia.
The microbial life near the Chicxulub crater recovered quickly under harsh conditions post impact and subsequently continued to experience rapid changes in environment.
Gulick, S., et al., 2019. First Days of the Cenozoic PNAS, 116, 19342-19351.
Grice et al., 2009. New insights into the origin of perylene in geological samples. Geochimica et Cosmochimica Acta, 73, 6531-6543.
Hildebrand, A. R. et al., 1991. Chicxulub crater: a possible Cretaceous/Tertiary boundary impact crater on the Yucatan Peninsula, Mexico. Geology 19, 867-871.
Schaefer, B., et al. 2020. Microbial life in the nascent Chicxulub crater. Geology, 48, 328-332.
Schulte, P., et al. 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science 327, 1214-1218.
Sepkoski, J. J., 1996. In: Global events and event stratigraphy in the Phanerozoic. pp. 35-51, Springer.
Zachos, J., Arthur, M., 1986. Paleoceanography of the Cretaceous/Tertiary boundary event: inferences from stable isotopic and other data. Palaeogeography & Palaeoclimatology 1, 5-26.
Kliti Grice holds an Honours degree in Applied Chemistry. She has a PhD from the University of Bristol UK and is a John Curtin Distinguished Professor of Organic and Isotope Geochemistry at Curtin University (Perth, WA, Australia) and is the Founding Director of WA-Organic and Isotope Geochemistry Centre. She is an internationally renowned organic geochemist, a Fellow of the Australian Academy of Science and an Honorary Fellow of the Geochemical Society and European Association of Geochemistry. She creatively combines geological information with data on molecular fossils and their stable isotopic compositions (carbon, hydrogen and sulfur). Research applications are largely concerned with studying the dynamics of microbial, fungal and floral inhabitants to catastrophic events (e.g., wild-fire, tsunamis, volcanism, meteorite impacts) to evaluate the ecological health of ancient (paleoenvironments) and modern environments. Her research has focused on many of the big five mass extinctions: end-Permian, end-Triassic, end-Devonian and end-Cretaceous events. She also investigates the role of microbial communities in exceptional fossil preservation including finding the oldest intact dietary sterols in the geological record.