Yaxcopoil-1 (Yax-1), drilled within the Chicxulub crater, was expected
to yield the final proof that this impact occurred precisely 65 Myr ago
and caused the mass extinction at the Cretaceous-Tertiary (K/T)
boundary. Instead, contrary evidence was discovered based on five
independent proxies (sedimentologic, biostratigraphic,
magnetostratigraphic, stable isotopic, and iridium) that revealed that
the Chicxulub impact predates the K/T boundary by about 300,000 years
and could not have caused the mass extinction. This is demonstrated by
the presence of five bioturbated glauconite layers and planktic
foraminiferal assemblages of the latest Maastrichtian zone CF1 and is
corroborated by magnetostratigraphic chron 29r and characteristic late
Maastrichtian stable isotope signals. These results were first presented
in Keller et al. (2004). In this study, we present more detailed
evidence of the presence of late Maastrichtian planktic foraminifera,
sedimentologic, and mineralogic analyses that demonstrate that the
Chicxulub impact breccia predates the K/T boundary and that the
sediments between the breccia and the K/T boundary were deposited in a
normal marine environment during the last 300,000 years of the
Cretaceous.