Sequence Stratigraphy of the Chicxulub Crater Infill and Yucatàn Carbonate Platform Development: Implications for the Evolution of Large Terrestrial Impact Craters

Stratigraphic analysis of the Yaxcopoil-1 core and seismic analysis of offshore 2D seismic data provide insight into the Tertiary infilling and sequence stratigraphy of the Chicxulub impact basin. We have identified 5 lithostratigraphic units and depositional sequences based on our analysis of the Tertiary rocks in the core. Ten lithofacies, that are categorized as either redeposited (gravity flows) or background (suspension deposits) facies, make up the depositional sequences.

Biostratigraphic data indicate that sequences 1-3 are Early Paleocene-Early Eocene in age and depositional environments are along a steep, bathyal slope inside Chicxulub's inner rim. Sequence boundary intervals (sequences 1-4) contain redeposited carbonates interpreted as late highstand-lowstand deposits. Sequences 4-5 consist mainly of background and fine-grained redeposited facies and indicate that neritic outer carbonate ramp environments had prograded over the position of the Yax-1 core.

Seismic analysis identified at least 6 seismic units. The lower 5 units appear to correlate with the 5 depositional sequences in the Yax-1 core. Seismic stratigraphy reveals two major patterns of post-impact deposition in the basin. The earlier one is controlled by the underlying crater morphology where units (A & B) accumulated on both sides of the peak ring and infilled the western and central parts of the basin. Later deposits are controlled by changes in sea level as suggested by clinoform deposits (unit C) and regional unconformities (tops of units C, D, E). If Chicxulub is representative, large marine impacts in tectonically quiescent regions may dominate local depositional environments for up to tens of Ma before eustatic controls are reestablished. Along impact basin margins, successions will likely record shoaling and slope readjustment processes as the instantaneously created basin is filled over geologic timescales. Remarkably, most of the topographic scar along the southern Chicxulub crater appears to have been annealed within 10-15 Ma after the impact.