Palaeocene–Eocene miospores from the Chicxulub impact crater, Mexico. Part 1: spores and gymnosperm pollen

Abstract

In the summer of 2016, the International Ocean Discovery Program (IODP) Expedition 364 cored through the post-impact strata of the end-Cretaceous Chicxulub impact crater, Mexico. Core samples were collected from the post-impact successions for terrestrial palynological analysis, yielding a rare Danian to Ypresian high-resolution palynological assemblage. This record constitutes one of the first Palaeocene and Ypresian palynological assemblages from Central America or Mexico, representing a more coastal lowland palaeoenvironment than previous studies from mainland Mexico. Although the abundance of pollen and spores is very low in the Palaeocene carbonates, abundance increases in the more organic-rich shale layers representing the Palaeocene–Eocene Thermal Maximum (PETM) and later Ypresian. The spores and gymnosperm pollen identified from IODP 364, although rare compared to the angiosperm pollen, are a diverse mix of cosmopolitan taxa, as well as some characteristic of fossil Central American assemblages (e.g. Selaginellaceae), and others previously identified from the Paleogene northern Gulf of Mexico coastal plain. The assemblage generally indicates the presence of nearby moist to seasonally dry lowland tropical forest, with some taxa suggestive of higher elevation forests. Ephedroid pollen grains may be indicative of the presence of more arid conditions.

Keywords:

• Mexico
• miospores
• Palaeocene
• Eocene
• Cretaceous–Paleogene boundary

Acknowledgements

The authors would like to thank the International Ocean Discovery Program (IODP) for granting access to sample the IODP 364 core, as well as the IODP 364 Scientific Party for invaluable help and advice throughout the research process. This research would not have been possible without the financial support of the Center for Excellence in Palynology (CENEX) Endowed Chair fund, which funded lab supplies and sample processing for the initial set of palynological samples. The lead author would also like to thank Louisiana State University for providing financial support in the form of tuition exemptions, salary in the form of a teaching assistantship, and scholarship funding. Finally, we would like to thank The Paleontological Society, which awarded funding for this research in the form of the 2018 James M. and Thomas J. M. Schopf Award Student Research Grant. The authors gratefully thank the peer reviewers, Dr Chris Clowes and Dr Carlos Jaramillo, for their helpful suggestions for improvement of the manuscript. Special thanks to Dr James B. Riding for his expertise and patience throughout the review process, which has greatly improved the original draft of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Vann Smith

VANN SMITH is a PhD student in the Department of Geology and Geophysics at Louisiana State University in Baton Rouge. He completed his undergraduate degree in geology at Louisiana State University in 2011, and an MS degree in earth and environmental sciences at Tulane University in 2015. After graduating from Tulane University, he worked in the oil industry as a nannofossil biostratigrapher from 2015 to 2016. His research interests include tropical Paleogene terrestrial palynology, the K–Pg impact event, morphometrics, Cenozoic nannofossil palaeontology, and quantitative biostratigraphy.

Sophie Warny

SOPHIE WARNY is an associate professor of palynology in the Department of Geology and Geophysics and a curator at the Museum of Natural Science at Louisiana State University (LSU) in Baton Rouge. She has a long history with AASP as she won the AASP Student Award in 1996, served as Director-At-Large on the AASP board from 2006 to 2007, was the AASP newsletter editor from 2006 until 2015 and is now the AASP Chair in Palynology. She received her PhD from the Université Catholique de Louvain in Belgium, working with Dr Jean-Pierre Suc on the Messinian Salinity Crisis. In 2011, she received an NSF career award to conduct palynological research in Antarctica. Since being hired at LSU in 2008, she has directed 18 graduate students’ theses on various Cretaceous to Cenozoic sections. Her students are now employed with the oil and gas industry (Hess, BP, Devon, Chevron, BHP Billiton Petroleum and EOG), with the US Department of Homeland Security, with environmental companies, with IODP, or as instructors.

David M. Jarzen

DAVID M. JARZEN is a research associate at the Cleveland Museum of Natural History, in palaeobotany and palaeoecology. He earned his BS degree in 1967 from Kent State University, and two years later received his MA degree in botany from the same institution. In 1973 he was awarded a PhD in geology from the University of Toronto. His research interests in the nature of extant and fossil plant life have motivated extensive field work around the world, incorporating a global view aiming to understand the evolution of plant life during Earth’s history, with an emphasis on fossil floras recorded from the Paleogene, Neogene and Cretaceous. His work has been incorporated into several radio and television productions, including CBC’s The Nature of Things with David Suzuki, the PBS NOVA Series, the NHK (Japan) Series The Miracle Planet, and others by the National Film Board of Canada, the Discovery Channel and other North American cable networks. He was elected as Fellow National to the Explorers Club, and in 2005 he was elected Fellow of the Ohio Academy of Science.

Thomas Demchuk

THOMAS DEMCHUK is an adjunct professor in the Department of Geology and Geophysics at Louisiana State University in Baton Rouge. He assists the AASP Chair in Palynology, Dr Sophie Warny, with supervising students, finding appropriate graduate projects, and teaching. He is also a business development manager and a geological consultant with RPS Energy in Houston, Texas, marketing specialist geological and biostratigraphical products to the general exploration community. He received his PhD (1992) from the University of Calgary in both palynology and organic petrography, and earlier received his MSc (1987) from the University of Alberta in Edmonton. He has over 26 years of experience in the oil industry, having spent more than 18 years with ConocoPhillips Co., and prior to that over 4 years with Amoco Corp. His current primary research interests include study of the Palaeocene–Eocene boundary (PETM interval) along the US Gulf Coast, particularly the outcrops and subsurface of central and south Texas, and correlation to the deepwater Wilcox Group reservoirs. Additional research includes the organic petrography of Gulf Coast Palaeocene–Eocene coals and palaeoclimatic/palaeogeographical reconstructions of the region. He is interested in all aspects of organic petrography and organic characterisation of coals, source rocks and unconventional resources, including thermal maturity and vitrinite reflectance studies. He was the AASP-TPS Secretary-Treasurer from 1997 to 2016, and prior to that was a Director-at-Large from 1992 to 1994. He is currently the Chair and Trustee for the AASP Foundation.

Vivi Vajda

VIVI VAJDA is a professor in palaeontology at the Swedish Museum of Natural History in Stockholm, Sweden, and department chair of the Department of Palaeobiology. Her research speciality is palynology, and her projects aim to determine the rate of turnover of plants across the Cretaceous–Paleogene (K–Pg) boundary, based on palynological analyses. Investigations focus on sediments from New Zealand, Colombia and Denmark. She also uses the palynological signal from the K–Pg boundary as a tool to interpret other mass-extinction events, such as the Permian–Triassic and the Triassic–Jurassic (Australia, New Zealand and Sweden) extinction events. Additional research includes chemical mapping of leaf fossils using vibrational microspectroscopic analyses. She is active in national and international geo-related organisations and was for several years chair of the Geological Society of Sweden and the UNESCO sciences programme IGCP. In 2019 she became an elected member of the Royal Swedish Academy of Sciences.