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Chicxulub impact predates the K-T boundary mass extinction

Sorry if this has been posted before. The article:

Gerta Keller, Thierry Adatte, Wolfgang Stinnesbeck, Mario Rebolledo-Vieyra, 
Jaime Urrutia Fucugauchi, Utz Kramar, & Doris Stüben. 2004. Chicxulub impact 
predates the K-T boundary mass extinction. PNAS, 101(11), 3753-3758.

is available at: 



Since the early l990s the Chicxulub crater on Yucatan, Mexico, has been hailed 
as the smoking gun that proves the hypothesis that an asteroid killed the 
dinosaurs and caused the mass extinction of many other organisms at the 
Cretaceous-Tertiary (K-T) boundary 65 million years ago. Here, we report 
evidence from a previously uninvestigated core, Yaxcopoil-1, drilled within the 
Chicxulub crater, indicating that this impact predated the K-T boundary by 
300,000 years and thus did not cause the end-Cretaceous mass extinction as 
commonly believed. The evidence supporting a pre-K-T age was obtained from 
Yaxcopoil-1 based on five independent proxies, each with characteristic signals 
across the K-T transition: sedimentology, biostratigraphy, magnetostratigraphy, 
stable isotopes, and iridium. These data are consistent with earlier evidence 
for a late Maastrichtian age of the microtektite deposits in northeastern 

Jose Ignacio Ruiz-Omeñaca
Departamento de Ciencias de la Tierra
Area de Paleontologia
Universidad de Zaragoza

tel: (+34) 976 761000 ext. 3160
fax: (+34) 976 761106
e-mail: jigruiz@unizar.es