Resolving the sinkhole conundrum of the Chicxulub impact crater, Yucatán Peninsula, Mexico, using scaled physical experiments

Karst-induced sinkholes in Pliocene strata, the youngest sequence of Tertiary rocks covering the 66 Ma Chicxulub meteorite impact crater, form a semicircle that is congruent with the underlying crater margin as imaged by gravity anomalies. The causal relationship between the crater margin and the formation of the sinkholes has remained elusive since the discovery of the Chicxulub crater more than 30 years ago. Ground water flow of the northwestern Yucatán aquifer calls for the presence of prominent structural discontinuities in Tertiary strata above the buried crater margin, which likely control sinkhole formation. Based on the analysis of high-resolution satellite scenes, we mapped the ellipticity and respective long axes of some 6500 sinkholes. Assuming that the long axes represent traces of subsurface dilation fractures and, thus, orientations of maximum principal stresses, the angular departures of these stresses from the uniform regional trend point to local stress perturbations above the crater margin. The patterns of these perturbations agree with experimentally produced ones observed in scaled numerical and physical models, in which model craters are embedded in elastic materials and subjected to uniaxial compression. Moreover, concentric fractures preferentially form at model crater margins in physical experiments simulating cratering-induced crustal relaxation on the order of hundreds of thousands of years. We conclude that the localization of sinkholes in Pliocene strata above the Chicxulub crater rim is the combined result of the concentration of ambient stresses at the crater rim and the consequent reactivation of concentric fractures and their propagation into the overlying Tertiary strata.