HR: 0830h
AN: P21A-03    [Abstracts]
TI: Terrace Zone Structure in the Chicxulub Impact Crater Based on 2-D Seismic Reflection Profiles: Preliminary Results From EW&35;0501
AU: * McDonald, M A
EM: matt@ig.utexas.edu
AF: Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Gulick, S P
EM: sean@ig.utexas.edu
AF: Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Gorney, D L
EM: david@ig.utexas.edu
AF: Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Christeson, G L
EM: gail@ig.utexas.edu
AF: Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Rd., Bldg. 600, Austin, TX 78759 United States
AU: Barton, P J
AF: Bullard Laboratories, University of Cambridge, Madingly Road, Cambridge, CB3 0EZ United Kingdom
AU: Morgan, J V
AF: Dept. of Earth Science and Engineering, South Kensington Campus, Imperial College, London, SW7 2AZ United Kingdom
AU: Warner, M R
AF: Dept. of Earth Science and Engineering, South Kensington Campus, Imperial College, London, SW7 2AZ United Kingdom
AU: Urrutia-Fucugauchi, J
AF: Dept. of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona 1629 E. University Blvd., Tucson, AZ 85721 United States
AU: Melosh, H J
AF: Instituto de Geofisica, Universidad Autonoma de Mexico, Ciudad Universitaria Delegacion, Coyoacan, Mexico City, CP 04510 Mexico
AU: Vermeesch, P M
AF: Dept. of Earth Science and Engineering, South Kensington Campus, Imperial College, London, SW7 2AZ United Kingdom
AU: Surendra, A T
AF: Bullard Laboratories, University of Cambridge, Madingly Road, Cambridge, CB3 0EZ United Kingdom
AU: Goldin, T
AF: Instituto de Geofisica, Universidad Autonoma de Mexico, Ciudad Universitaria Delegacion, Coyoacan, Mexico City, CP 04510 Mexico
AU: Mendoza, K
AF: Dept. of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona 1629 E. University Blvd., Tucson, AZ 85721 United States
AB: Terrace zones, central peaks, and flat floors characterize complex craters like the Chicxulub impact crater located near the northeast coast of the Yucatan Peninsula. The subsurface crater structure was studied using seismic reflection surveying in Jan/Feb 2005 by the R/V Maurice Ewing. We present 2-D seismic profiles including constant radius, regional, and grid profiles encompassing the 195 km width of the crater. These diversely oriented lines clearly show the terrace zones and aid in the search for crater ejecta as we investigate the formation of the crater including the incidence angle and direction of the extraterrestrial object that struck the Yucatan Peninsula 65 million years ago (K-T boundary). Terrace zones form in complex craters after the modification stage as a result of the gravitational collapse of overextended sediment back into the crater cavity. The terrace zone is clearly imaged on seismic profiles confirming the complex structure of the Chixculub crater. Recent work on reprocessed 1996 profiles found different sizes and spacing of the terraces and concluded that the variations in radial structure are a result of an oblique impact. A SW-NE profile from this study was the only line to show a concentration of deformation near the crater rim hinting that the northeast was the downrange direction of impact. We confirm this narrowing in terrace spacing using a profile with a similar orientation in the 2005 images. Through integration of the new dense grid of profiles and radial lines from the 1996 and 2005 surveys we map the 3-D variability of the terrace zones to further constrain impact direction and examine the formative processes of the Chixculub and other large impact craters.
DE: 5717 Impact phenomena
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly