Monterey Bay Aquarium Research Institute
Canyon Processes
K-T impact structure - Campeche

The most profound and dramatic extinction event in the history of the Earth occurred at the transition between the Cretaceous and Tertiary Eras (K-T boundary). A huge proportion of the animal species that existed on Earth went extinct at this time. These extinctions are generally accepted as being the result of an asteroid with a diameter of ~10 km crashing into the Earth in shallow water in what is now the Yucatan Peninsula of Mexico. The energy that was released in this event greatly exceeds the energy released in largest earthquake ever recorded. This sudden catastrophic event vaporized the immediate impact area, shattered strata over a much larger area, blew enormous blocks of the continental margin out into the adjacent ocean basin leaving deposits that are up to 500 m thick locally and ~100 m thick throughout the southern Gulf of Mexico, triggered a colossal tsunami, and injected huge clouds of acidic dust into the atmosphere. The enormous amounts of dust generated a global "nuclear winter" effectively leading to widespread extinctions, the dinosaur extinction being one of the most prominent among them.

The asteroid impact resulted in the formation of the Chicxulub impact crater which has an inner diameter of ~180 km and lies under the continental shelf at the very north end of the Yucatan Peninsula. Examination of the sediments, lithologies and structures more closely affected by this event has proven to be an elusive task. Over the last 65 million years nearly one-kilometer thick deposits of carbonate sediments have accumulated above the crater and the adjacent deformed rocks over a much broader area, making it difficult to actually sample the strata that were altered by or laid down during the impact event. Thus, direct information about the deformation that happened during the event and the recovery after the event is still limited to data obtained via remote sensing tools, from samples from a few boreholes drilled in the Yucatan and from stratigraphic studies of more distant sites elsewhere in North America and the world.

The boundary between the continental margin and the ocean basin on the NE side of the Yucatan Platform is the Campeche Escarpment, which is only ~20 km from the edge of the Chicxulub impact crater. The Campeche Escarpment is a limestone cliff that extends from 100 to 4,200 m water depths at an average slope of ~45°, making this cliff section one of the steepest and tallest morphologic features on the surface of the Earth. For comparison, the Campeche Escarpment is considerably taller and its flank steeper than the sides of the Grand Canyon. The Campeche Escarpment is also an erosional feature that fortuitously exposes a continuous rock section from a large range of ages that are just outside the Chicxulub impact crater site.

The rock exposures on the face of the Campeche Escarpment are a window into time, similar to the exposures on the flanks of the Grand Canyon. Exposed on the Campeche Escarpment is a ~ 4 km tall section where the pre-existing Late Cretaceous strata that were fractured and metamorphosed by the impact shock, are overlain by a massive blanket of ejecta deposited as little as 30 km downstream from the crater, which is in turn buried by the thick sequence of unaltered Tertiary sediments. All these sediments are sequentially exposed atop of each other and document in exquisite detail the environment and geological events before, during and after the asteroid impact.

In March 2013 MBARI researchers lead by Dr. Charles Paull, in collaboration with Drs. Jaime Urrutia Fucugauchi from the Universidad Autonoma de Mexico and Mario Rebolledo Vieyra of the Centro de Investigacion Cientifica de Yucatan in Mexico, will conduct surface ship multibeam mapping of the Campeche escarpment aboard the R/V Falkor from the Schmidt Ocean Institute. This is the first step in a multi stage proposal. Planned follow-up cruise(s) would utilize both an autonomous underwater vehicle (AUV) to make very detailed maps of selected areas of the escarpment face and a remotely operated vehicle (ROV) to visualize and sample the strata exposed along the escarpment face, which bound the Cretaceous-Tertiary Boundary. The AUV surveys will provide a localized but higher resolution bathymetry than that obtained from surface vessel multibeam mapping. The higher resolution maps will be instrumental in documenting the fracture textures and finer stratigraphy of the exposed rocks and will guide the ROV sampling in the third phase of this project. Sampling the exposed strata using a remotely operated vehicle (ROV) is the principal and ultimate objective of this multistage project. These rock samples will be analyzed to understand the extent of alterations produced by the thermal metamorphism and shock deformation in the mineral fabric, both laterally along the escarpment and vertically up the escarpment, as well as the extent of regional deformation and larger scale geomorphology changes triggered by the impact.

Last updated: Oct. 15, 2012