Upper crustal structure of the Chicxulub impact crater from wide-angle ocean bottom seismograph data

We used travel times recorded by 23 ocean bottom seismograph (OBS) receivers to model crustal structure of the Chicxulub impact crater. The OBSs were located along Chicx-A/A1, a deep reflection profile extending as a chord across the offshore portion of the Chicxulub structure. A tomographic inversion of crustal refractions was used to produce the upper crustal structure. The prominent feature in the shallow velocity structure is the low velocities associated with the Tertiary basin. The low velocity section is thickest near the center of the crater, and thins on the flanks. High velocities observed near the surface along several portions of the crater flanks may represent the widespread presence of reefal buildups at the margins of the Tertiary basin. Negative velocity anomalies observed beneath the Tertiary basin within the collapsed transient cavity are interpreted as melt rocks. The largest negative anomaly is located near the center of Chicx-A/A1 (~26 km from the interpreted center of the crater), and extends laterally 50 km. The depth to the top of this anomaly is about 1 km; its average thickness is 1.3 km. Two smaller anomalies are located near the eastern and western margins of the collapsed transient cavity. The average thickness of these three negative velocity anomalies, when averaged over the width of the collapsed transient cavity, is 1 km. Christeson, G. L., Buffler, R. T., and Nakamura, Y., 1999, Upper crustal structure of the Chicxulub impact crater from wide-angle ocean bottom seismograph data, in Dressler, B. O., and Sharpton, V. L., eds., Large Meteorite Impacts and Planetary Evolution II: Boulder, Colorado, Geological Society of America Special Paper 339