EXTENSIVE K-PG BOUNDARY OUTCROPS CLOSEST TO THE CHICXULUB IMPACT CRATER IDENTIFIED IN NEW BATHYMETRIC MAPS OF THE CAMPECHE ESCARPMENT

We present the first detailed bathymetric maps of the Campeche Escarpment, the Mesozoic carbonate platform edge that separates the Yucatán Peninsula of Mexico from the deep Gulf of Mexico basin. The Campeche Escarpment is as little as 130 km from the Chicxulub Crater, one of the largest impact structures on Earth. The meteorite impact that created the crater is generally believed to be the cause of the profound global changes that took place at the Cretaceous-Paleogene (K-Pg) transition. Previous work shows the shock waves generated by the impact had the energy equivalent of a magnitude 12+ earthquake on the Richter Scale, and initiated huge tsunamis, triggered slope failures resulting in profound devastation throughout the North American southeast and Caribbean, and released the Earth’s largest volumetric debris flow in the Gulf of Mexico, leaving deposits that are more than one hundred meters thick at the K-Pg boundary. The location of the Cretaceous-Paleogene boundary has been identified on the escarpment face in the newly collected bathymetry by combining it with existing stratigraphic information from boreholes drilled during DSDP Leg 10. The top of a steep cliff on the lower escarpment, which can be traced along the majority of the escarpment face for ~ 200 km, stratigraphically corresponds with the K-Pg boundary identified in the DSDP boreholes drilled near (< 6 Km) the escarpment and represents the K-Pg boundary known outcrop closest to the Chicxulub impact crater. Whether the pre-Tertiary material recovered in these DSDP boreholes, and exposed along the steep cliff, is composed of impact ejecta or in-place Cretaceous strata is unknown. The morphology of the escarpment combined with seismic data reveals that a significant amount of material is missing from its face. The Campeche Escarpment face is the probable source for a major component of the material carried in the mega debris flow that filled the floor of the Gulf of Mexico as a result of the impact. By inference, several kilometers of lateral retreat occurred when this material was blasted off the platform edge as a result of the impact.