Since the early 1990s 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 approximate to300,000 years and thus
did not cause the end-Cretaceous mass extinction as commonly believed.
The evidence supporting a preK-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 Mexico.