The 2,468th Meeting of the Society

December 2, 2022 at 8:00 PM

Powell Auditorium at the Cosmos Club

The Latest on the Great Dinosaur Extinction

The K-Pg Chicxulub impact and mass extinction event

Sean Gulick

Research Professor, University of Texas Institute for Geophysics
Department of Geological Sciences
University of Texas at Austin

Sponsored by PSW Science Member Erica Kane


About the Lecture

The most recent of Earth’s five largest mass extinction events occurred 66 million years ago, coeval with the impact of an asteroid roughly 12 kilometers in diameter impacting the earth at approximately 60 degrees. The impact produced the Chicxulub crater, approximately 200 kilometers wide, in what today is the Yucatan Peninsula in Mexico. This impact, by some estimations, caused the extinction of 75% of life on Earth at the genus level, including all non-avian dinosaurs. Proposed kill mechanisms include thermal effects, dust, soot, and sulfate aerosols reducing Earth’s solar insolation.

In 2016, 835 meters of core was recovered from the Chicxulub impact structure through International Ocean Discovery Program-International scientific Continental Drilling Program Expedition 364. Analyses of the cores, downhole logs, and geophysical site survey data have led to a series of advances in our understanding of impact cratering processes, how the Chicxulub impact affected the Earth’s environment leading to the Cretaceous-Paleogene mass extinction, and what ecosystems existed within the newly formed crater.

Key areas of discovery from this work include: (1) clear evidence for the origin of peak rings and crater dynamics in large impacts; (2) highest resolution record to date of impact processes within the crater including deposition of impactites and role of ocean resurgel; (3) rapid recovery of life at ground zero with a key niche being filled by cyanobacteria; and (4) development of a long lived hydrothermal system with astrobiological implications.

The lecture will discuss these findings and their implications for the great extinction and for the origins of life on earth and possibly elsewhere.

Selected Reading & Media References
(1) Gulick, S.P.S., et al., First Day of the Cenozoic: Proceeding of the National Academy of Sciences, 116, 19342-19351, doi: 10.1073/pnas.1909479116, 2019.

(2,3) NOVA/PBS specials: Day the Dinosaurs Died; Dinosaur Apocalypse

About the Speaker

Sean Gulick is Research Professor in the Institute for Geophysics, Associate Chair of the Department of Geological Sciences, and Co-Director of the Center for Planetary Systems Habitability in the Jackson School of Geosciences at the University of Texas at Austin.

Sean and his group use geophysical techniques to understand Earth and planetary processes. Current projects relate to the study of tectonic and climate interactions in glaciated continental margins from Antarctica to Greenland to Alaska; geohazards and margin evolution in Alaska, New Zealand, and Haiti, and geologic processes and environmental effects of the Cretaceous-Paleogene Chicxulub meteor impact.

Sean has been on over 30 research cruises using geophysical data and scientific ocean drilling to test hypotheses ranging from how subduction zones are initiated, to roles of sediment flux in glaciated margins, to incised river valleys as preservers of sea level history and sand resources, to impact cratering processes and their links to life.

Sean earned a BS in Geology with a Minor in Marine Sciences at the University of North Carolina, Chapel Hill and a PhD in Geological Sciences at Lehigh University in Pennsylvania.