HR: 15:30h
AN: U33A-07    [Abstracts]
TI: Deep Drilling Into the Chicxulub Impact Crater: Pemex Oil Exploration Boreholes Revisited
AU: * Fucugauchi, J U
EM: juf@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Laboratorio de Paleomagnetismo, Instituto de Geofisica, UNAM, Ciudad Universitaria, Del. Coyoacan, Mexico, 04510, Mexico
AU: Perez-Cruz, L
EM: perezcruz@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Programa Universitario de Perforaciones en Oceanos y Continentes, Instituto de Geofisica, UNAM, Coyoacan, Mexico, 04510, Mexico
AB: The Chicxulub structure was recognized in the 1940īs from gravity anomalies in oil exploration surveys by Pemex. Geophysical anomalies occur over the carbonate platform in NW Yucatan, where density and magnetic susceptibility contrasts with the carbonates suggested a buried igneous complex or basement uplift. The exploration program developed afterwards included several boreholes, starting with the Chicxulub-1 in 1952 and eventually comprising eight deep boreholes completed through the 1970s. The investigations showing Chicxulub as a large impact crater formed at the K/T boundary have relayed on the Pemex decades-long exploration program. Despite frequent reference to Pemex information, original data have not been openly available for detailed evaluation and incorporation with results from recent efforts. Logging data and core samples remain to be analyzed, reevaluated and integrated in the context of recent marine, aerial and terrestrial geophysical surveys and the drilling/coring projects of UNAM and ICDP. In this presentation we discuss the paleontological data, stratigraphic columns and geophysical logs for the Chicxulub-1 (1582m), Sacapuc-1 (1530m), Yucatan-6 (1631m) and Ticul-1 (3575m) boreholes. These boreholes remain the deepest ones drilled in Chicxulub and the only ones providing samples of the melt-rich breccias and melt sheet. Other boreholes include the Y1 (3221m), Y2 (3474m), Y4 (2398m) and Y5A (3003m), which give information on pre-impact stratigraphy and crystalline basement. We concentrate on log and microfossil data, stratigraphic columns, lateral correlation, integration with UNAM and ICDP borehole data, and analyses of sections of melt, impact breccias and basal Paleocene carbonates. Current plans for deep drilling in Chicxulub crater focus in the peak ring zone and central sector, with proposed marine and on-land boreholes to the IODP and ICDP programs. Future ICDP borehole will be located close to Chicxulub-1 and Sacapuc-1, which intersected the impact breccias at about 1 km and the melt and melt- rich breccias at some 1.3-1.4 km.
DE: 0915 Downhole methods
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 3036 Ocean drilling
DE: 5420 Impact phenomena, cratering (6022, 8136)
DE: 8136 Impact phenomena (5420, 6022)
SC: Union [U]
MN: 2007 Joint Assembly