Peak-ring formation in large impact craters: geophysical constraints from Chicxulub

A seismic reflection and three-dimensional wide-angle tomographic study of the buried, V200-km diameter, Chicxulub impact crater in Mexico reveals the kinematics of central structural uplift and peak-ring formation during large-crater collapse. The seismic data show downward and inward radial collapse of the transient cavity in the outer crater, and upward and outward collapse within the central structurally uplifted region. Peak rings are formed by the interference between these two flow regimes, and involve significant radial transport of material. Hydrocode modeling replicates the observed collapse features. Impact-generated melt rocks lie mostly inside the peak ring; the melt appears to be clast-rich and undifferentiated, with a maximum thickness of 3.5 km in the center. fl 2000 Elsevier Science B.V. All rights reserved.