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Proc Natl Acad Sci U S A. 2019 Sep 24;116(39):19342-19351. doi: 10.1073/pnas.1909479116. Epub 2019 Sep 9.

The first day of the Cenozoic.

Author information

1
Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758; sean@ig.utexas.edu.
2
Department of Geological Sciences, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 79712.
3
Department of Geosciences, Pennsylvania State University, University Park, PA 16801.
4
Centro de Astrobiología Instituto Nacional de Técnica Aeroespacial-Spanish National Research Council (INTA-CSIC), Instituto Nacional de Técnica Aeroespacial, 28850 Torrejon de Ardoz, Spain.
5
Enthought, Inc., Austin, TX 78701.
6
Western Australian Organic and Isotope Geochemistry Centre, The Institute for Geoscience Research, School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia.
7
Department of Earth Science and Engineering, Imperial College London, SW7 2AZ London, United Kingdom.
8
Planetary Science Institute, Tucson, AZ 85719-2395.
9
Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
10
Department of Geosciences, University of Alaska Fairbanks, Fairbanks, AK 99775.
11
Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ 08854.
12
Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758.
13
International Research Institute of Disaster Science, Tohoku University, Sendai 980-8572, Japan.
14
Department of Earth Sciences, University of Western Ontario, London, ON, N6A 3K7, Canada.
15
Institut für Geologie, Universität Hamburg, 20146 Hamburg, Germany.
16
Faculty of Earth and Life Sciences (FALW), Vrije Universiteit Amsterdam, 1081 HV, Amsterdam, The Netherlands.
17
Swedish Museum of Natural History, 114 18 Stockholm, Sweden.
18
Eyring Materials Center, Arizona State University, Tempe, AZ 85287-1704.

Abstract

Highly expanded Cretaceous-Paleogene (K-Pg) boundary section from the Chicxulub peak ring, recovered by International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364, provides an unprecedented window into the immediate aftermath of the impact. Site M0077 includes ∼130 m of impact melt rock and suevite deposited the first day of the Cenozoic covered by <1 m of micrite-rich carbonate deposited over subsequent weeks to years. We present an interpreted series of events based on analyses of these drill cores. Within minutes of the impact, centrally uplifted basement rock collapsed outward to form a peak ring capped in melt rock. Within tens of minutes, the peak ring was covered in ∼40 m of brecciated impact melt rock and coarse-grained suevite, including clasts possibly generated by melt-water interactions during ocean resurge. Within an hour, resurge crested the peak ring, depositing a 10-m-thick layer of suevite with increased particle roundness and sorting. Within hours, the full resurge deposit formed through settling and seiches, resulting in an 80-m-thick fining-upward, sorted suevite in the flooded crater. Within a day, the reflected rim-wave tsunami reached the crater, depositing a cross-bedded sand-to-fine gravel layer enriched in polycyclic aromatic hydrocarbons overlain by charcoal fragments. Generation of a deep crater open to the ocean allowed rapid flooding and sediment accumulation rates among the highest known in the geologic record. The high-resolution section provides insight into the impact environmental effects, including charcoal as evidence for impact-induced wildfires and a paucity of sulfur-rich evaporites from the target supporting rapid global cooling and darkness as extinction mechanisms.

KEYWORDS:

Chicxulub impact crater; Cretaceous–Paleogene; peak ring; suevite; tsunami

PMID:
31501350
PMCID:
PMC6765282
[Available on 2020-03-09]
DOI:
10.1073/pnas.1909479116

Conflict of interest statement

The authors declare no conflict of interest.

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