Chicxulub: The third dimension of a multi-ring impact basin

Abstract

The buried 65 Ma Chicxulub impact structure in Mexico is the largest well-preserved impact crater known on Earth. Seismic reflection data have revealed Chicxulub to be a multi-ring basin—it has the morphology of the largest impact craters in the solar system. We use these seismic data to relate surface morphology and near-surface structure to deeper deformation within the crust to provide the first high-resolution look into the third dimension of a multi-ring impact basin. We observe three distinct topographic ring types: crater rims, peak rings, and outer rings; each is associated with a different style of deep deformation. Crater rims are the head scarp of the terrace zone formed during the collapse of the transient cavity. The peak ring at Chicxulub appears to have formed when the central uplift collapsed, overthrusting and overriding the terrace zone. The impact has affected the whole crust; the outer rings at Chicxulub are linked to whole-crustal deformation in which the middle crust and lower crust have moved inward and downward. Strong reflections that dip craterward at ∼35° cut the entire crust and connect normal faulting in the sedimentary section with zones of downthrown Moho at a crater radius of ∼35–55 km. Weakly developed exterior rings appear as thrust faults with small offsets; these appear to be the progenitors of the more significant, normally faulted outer rings in multi-ring basins.