[dinosaur] Chicxulub impact crater core shows start of extinction event

Ben Creisler
[email protected]

A new paper:


Sean P. S. Gulick, Timothy J. Bralower, Jens Ormö, Brendon Hall, Kliti
Grice, Bettina Schaefer, Shelby Lyons, Katherine H. Freeman, Joanna V.
Morgan, Natalia Artemieva, Pim Kaskes, Sietze J. de Graaff, Michael T.
Whalen, Gareth S. Collins, Sonia M. Tikoo, Christina Verhagen, Gail L.
Christeson, Philippe Claeys, Marco J. L. Coolen, Steven Goderis, Kazuhisa
Goto, Richard A. F. Grieve, Naoma McCall, Gordon R. Osinski, Auriol S. P.
Rae, Ulrich Riller, Jan Smit, Vivi Vajda, Axel Wittmann, and the Expedition
364 Scientists (2019)
The first day of the Cenozoic.
Proceedings of the National Academy of Sciences (advance online publication
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1073_pnas.1909479116&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=VLhCUkW-M27hJcVHmrrjDENcAwuEvSXYL3Ccci9ueh8&s=167-h0savO0w7DPu8IlEsanMIMXWNsvAP7wVk8r7h04&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.pnas.org_content_early_2019_09_04_1909479116&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=VLhCUkW-M27hJcVHmrrjDENcAwuEvSXYL3Ccci9ueh8&s=v5GvWhouFDgyJgrvPL-azc_B4ousa26RrCedpStV2Lw&e= 

Significance
Chicxulub impact crater cores from the peak ring include ~130 m of impact
melt rock and breccia deposited on the first day of the Cenozoic. Within
minutes of the impact, fluidized basement rocks formed a ring of hills,
which were rapidly covered by ∼40 m of impact melt and breccia. Within an
hour, ocean waters flooded the deep crater through a northeast embayment,
depositing another 90 m of breccia. Within a day, a tsunami deposited
material from distant shorelines, including charcoal. Charcoal and absence
of sulfur-rich target rocks support the importance of impact-generated
fires and release of sulfate aerosols for global cooling and darkness
postimpact.

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.

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News:

Rocks at Asteroid Impact Site Record First Day of Dinosaur Extinction

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https://urldefense.proofpoint.com/v2/url?u=https-3A__www.inverse.com_article_59122-2Dchicxulub-2Dcrater-2Dstudy-2Dreveals-2Dwildfires-2Dtsunamis&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=VLhCUkW-M27hJcVHmrrjDENcAwuEvSXYL3Ccci9ueh8&s=zPNMmCY85cMlNogFLVXKPCtFNyK4w1VhxTrjKtHyC6s&e= 

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