Deep seismic reflection profiles across the Chicxulub crater

The deep seismic reflection profiles acquired during the British Institutions Reflection Profiling Syndicate (BIRPS) survey off the north coast of Yucatan, during September-October 1996, have clarified the geometries of several major features of the Chicxulub impact structure. The most prominent reflectors observed on each of the four radial profiles are related to a Jurassic-Cretaceous stratum at 2-3-km depths and to the Moho at 30-35-km depths. The prominent Mesozoic reflector provides a key marker of near-surface deformation within the preimpact strata at depths great enough to avoid immediate erosion after the impact, and it indicates three major "rings" of impact-related deformation to the upper crust, Prominent reflectors within the lower crust are generally continuous for 1-10 km, The Moho reflectors indicate, in conjunction with the velocity models, variations of only a few kilometers in the thickness of crust beneath the crater. Several crustal reflectors project upward at dips of ca, 30 degrees from Moho depths to the primary deformation zones defined by disruptions to the prominent Mesozoic reflector, suggesting that these reflectors represent shear zones whose reflectivity was enhanced by the rapid injection of impact melt.