Full waveform tomographic images of the peak ring at the Chicxulub impact crater

Morgan, J. V. and Warner, M. R. and Collins, G. S. and Grieve, R. A. F. and Christeson, G. L. and Gulick, S. P. S. and Barton, P. J. (2011) Full waveform tomographic images of the peak ring at the Chicxulub impact crater. Journal of Geophysical Research, 116. 14 PP.. DOI doi: 201110.1029/2010JB008015

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Abstract

Peak rings are a feature of large impact craters on the terrestrial planets and are generally believed to be formed from deeply buried rocks that are uplifted during crater formation. The precise lithology and kinematics of peak ring formation, however, remains unclear. Previous work has revealed a suite of bright inward dipping reflectors beneath the peak ring at the Chicxulub impact crater and that the peak ring was formed from rocks with a relatively low seismic velocity. New two-dimensional, full waveform tomographic velocity images show that the uppermost lithology of the peak ring is formed from a thin (∼100–200 m thick) layer of low-velocity (∼3000–3200 m/s) rocks. This low-velocity layer is most likely composed of highly porous, allogenic impact breccias. Our models also show that the change in velocity between lithologies within and outside the peak ring is more abrupt than previously realized and occurs close to the location of the dipping reflectors. Across the peak ring, velocity appears to correlate well with predicted shock pressures from a dynamic model of crater formation, where the rocks that form the peak ring originate from an uplifted basement that has been subjected to high shock pressures (10–50 GPa) and lie above downthrown sedimentary rocks that have been subjected to shock pressures of <5 GPa. These observations suggest that low velocities within the peak ring may be related to shock effects and that the dipping reflectors underneath the peak ring might represent the boundary between highly shocked basement and weakly shocked sediments.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA62;
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Journal or Publication Title: Journal of Geophysical Research
Volume: 116
Page Range: 14 PP.
Identification Number: doi: 201110.1029/2010JB008015
Depositing User: Sarah Humbert
Date Deposited: 10 Dec 2011 01:11
Last Modified: 23 Jul 2013 10:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/2269

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