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The first day of the Cenozoic

Tijdschriftbijdrage - Tijdschriftartikel

Highly expanded Cretaceous–Paleogene (K-Pg) boundary sectionfrom the Chicxulub peak ring, recovered by International Ocean DiscoveryProgram (IODP)–International Continental Scientific DrillingProgram (ICDP) Expedition 364, provides an unprecedented windowinto the immediate aftermath of the impact. Site M0077 includes∼130 m of impact melt rock and suevite deposited the first day ofthe Cenozoic covered by <1 m of micrite-rich carbonate depositedover subsequent weeks to years. We present an interpreted series ofevents based on analyses of these drill cores. Within minutes of theimpact, centrally uplifted basement rock collapsed outward to formapeak ring capped in melt rock. Within tens of minutes, the peak ringwas covered in ∼40 m of brecciated impact melt rock and coarsegrainedsuevite, including clasts possibly generated by melt–waterinteractions during ocean resurge. Within an hour, resurge crestedthe peak ring, depositing a 10-m-thick layer of suevite with increasedparticle roundness and sorting. Within hours, the full resurge depositformed through settling and seiches, resulting in an 80-m-thickfining-upward, sorted suevite in the flooded crater. Within a day,the reflected rim-wave tsunami reached the crater, depositing across-bedded sand-to-fine gravel layer enriched in polycyclic aromatichydrocarbons overlain by charcoal fragments. Generation ofa deep crater open to the ocean allowed rapid flooding and sedimentaccumulation rates among the highest known in the geologicrecord. The high-resolution section provides insight into the impactenvironmental effects, including charcoal as evidence for impactinducedwildfires and a paucity of sulfur-rich evaporites from thetarget supporting rapid global cooling and darkness as extinctionmechanisms.
Tijdschrift: Proceedings of the National Academy of Sciences of the United States of America
ISSN: 0027-8424
Issue: 39
Volume: 116
Pagina's: 19342-19351
Aantal pagina's: 10
Jaar van publicatie:2019
Trefwoorden:Chicxulub impact crater, suevite, Cretaceous–Paleogene, peak ring, tsunami