Abstract
The most immediate effects of the terminal-Cretaceous Chicxulub impact, essential to understanding the global-scale environmental and biotic collapses that mark the Cretaceous–Paleogene extinction, are poorly resolved despite extensive previous work. Here, we help to resolve this by describing a rapidly emplaced, high-energy onshore surge deposit from the terrestrial Hell Creek Formation in Montana. Associated ejecta and a cap of iridium-rich impactite reveal that its emplacement coincided with the Chicxulub event. Acipenseriform fish, densely packed in the deposit, contain ejecta spherules in their gills and were buried by an inland-directed surge that inundated a deeply incised river channel before accretion of the fine-grained impactite. Although this deposit displays all of the physical characteristics of a tsunami runup, the timing (<1 hour postimpact) is instead consistent with the arrival of strong seismic waves from the magnitude M w ∼10 to 11 earthquake generated by the Chicxulub impact, identifying a seismically coupled seiche inundation as the likely cause. Our findings present high-resolution chronology of the immediate aftereffects of the Chicxulub impact event in the Western Interior, and report an impact-triggered onshore mix of marine and terrestrial sedimentation—potentially a significant advancement for eventually resolving both the complex dynamics of debris ejection and the full nature and extent of biotic disruptions that took place in the first moments postimpact.
Original language | English |
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Pages (from-to) | 8190-8199 |
Number of pages | 10 |
Journal | Proceedings of the National Academy of Sciences of the United States of America |
Volume | 116 |
Issue number | 17 |
Early online date | 1 Apr 2019 |
DOIs | |
Publication status | Published - 23 Apr 2019 |
Funding
ACKNOWLEDGMENTS. R.A.D. thanks Terry, Randolph, and Ruth Smith; Ashok Vaish; Dr. Robert DePalma Sr.; Mindy Cox; Triebold Paleontology Inc.; Liam O’Meallie; Kylie Ruble; David, Michael, Matthew, Alex, and Benjamin Burhans; Karyn Chiapella; Cameron Smith; Alex Ruger; the Bowman Regional Public Library; the Frontier Travel Center; Henry and Adie Kriegstein; Katie Lizana; Walter Stein; Sarah Snavely; Bowman Lodge and Conference Center; Miller Land and Livestock LLC; and the Rocky Mountain Dinosaur Resource Center for financial and/or material support. We thank Jeremy Klingler, Douglas Preston, Richard Barnes, Evan Wilkinson, Kirsten Hansen, Stacy Trenary, James Wang, Pim Kaskes, Melanie During, and PBMNH amateur volunteers for field assistance or laboratory preparation. We also thank Neil Landman, Jay Melosh, John Gurche, Anthony Wolcott, Kirk Cochran, Arthur Sweet, Patrick Herendeen, Brian Atwater, Victoria Egerton, Steven Bozarth, Virginia Harvey, Gregory Erickson, Jody Bourgeois, Stephen Hasiotis, Kirk Johnson, Steve Nicklas, Rob Sula, Ron Frithiof, Dean Pearson, Donald Rasmussen, Robert Gawthorpe, David Kring, Sean Gulick, and Zane Jobe for technical assistance and/or critique. Jeffrey Person graciously supplied analytical specimens from Mud Buttes. We thank Cornell University Department of Biotechnologies, Teresa Porri, Global Geolabs Ltd., Activation Laboratories Ltd., the Florida Center for Analytical Electron Microscopy, Karina Brez, the Florida International University Trace Elements Analysis Facility, Tatiana Trejos, Thomas Beas-ley, Steven Bozarth, Sven Holbik, and Russ Harms for analytical work. Analytical data and specimens are archived at Florida Atlantic University (FAU.DGS.ND161) and The University of Kansas (KUVP.T.31X). K.K. is funded by Grant 864.12.005 of the Netherlands Organization for Scientific Research. P.L.M. thanks the United Kingdom Science and Technology Facilities Council for their support (Grant STFC:ST/M001814/1).
Funders | Funder number |
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Ashok Vaish | |
Bowman Regional Public Library | |
Livestock LLC | |
Netherlands Organization for Scientific Research | |
Rocky Mountain Dinosaur Resource Center | |
Ruth Smith | |
Science and Technology Facilities Council | ST/M001814/1 |
Nederlandse Organisatie voor Wetenschappelijk Onderzoek | 864.12.005 |
Keywords
- Chicxulub
- Hell creek formation
- Impact
- KPg extinction
- Tsunami