HR: 16:20h
AN: U34A-01 INVITED     [Abstracts]
TI: Drilling at Impact Structures: Some observations and the case for Chicxulub.
AU: * Grieve, R
EM: rgrieve@nrcan.gc.ca
AF: Earth Sciences Sector, Natural Resources Canada, 580 Booth Street, Ottawa, ON K1A 0E4, Canada
AU: Morgan, J
EM: j.v.morgan@imperial.ac.uk
AF: Department of Earth Sciences and Engineering, Imperial College, London, SW7 2AZ, United Kingdom
AU: Urrutia, J
EM: juf@tonatiuh.igeofcu.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico City, 04510, Mexico
AB: Approximately 40% of known terrestrial impact structures have been drilled for scientific purposes. This has produced a wealth of information on their individual basis lithological and structural characteristics in the third dimension, as well as defined set of commonalities for specific morphological types of impact structures. Drilling has also contributed to the current understanding of important conceptual aspects of cratering processes, e.g., the concept of transient cavity formation and subsequent collapse at simple impact structures in rooted in the results of a systematic drilling campaign at the 3.8 km diameter Brent structure, Canada. This is, however, a singular set of observations. Similarly, constrained estimates of the vertical rate of shock wave attenuation in structural uplifts at complex impact structures are founded solely on drilling of the Puchezh-Katunki structure, Russia. The full characterization of the vertical variations in the character of coherent impact melt sheets are similarly limited, e.g., by drilling results from Boltysh, Ukraine and Sudbury, Canada. Given, however, their difference in size, the results are not directly comparable. Recent computational models suggest that peak rings form at the confluence of the collapsed material from the transient cavity rim area and collapsed material form an over heightened structural uplift. Observational data from the three largest terrestrial impact structures (Vredefort, Sudbury and Chicxulub) will be presented that generally supports this working hypothesis. Chicxulub, Mexico, however, is unique, as it provides the only opportunity within the known record of terrestrial impact cratering to physically test this working hypothesis. Such testing can only be achieved by drilling. Similarly, drilling targeted at the coherent impact sheet at Chicxulub will present a direct comparison with the information from Sudbury, given that they are similar size.
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 6022 Impact phenomena (5420, 8136)
DE: 8136 Impact phenomena (5420, 6022)
SC: Union [U]
MN: 2007 Joint Assembly