HR: 1330h
AN: T43D-06    [Abstracts]
TI: Magnetic Fabric of the K/T Breccia Sequence from the Yaxcopoil-1 Borehole, Chicxulub Impact Structure, Yucatan Peninsula
AU: * Delgadillo, M
EM: mirierid@hotmail.com
AF: Laboratorio de Paleomagnetismo y Geofisica Nuclear, Instituto de Geofisica, UNAM, Circuito Institutos s/n, Mexico, DF 04150
AU: Velasco-Villareal, M
EM: fatima_miriam@hotmail.com
AF: Laboratorio de Paleomagnetismo y Geofisica Nuclear, Instituto de Geofisica, UNAM, Circuito Institutos s/n, Mexico, DF 04150
AU: Soler-Arechalde, A M
EM: anesoler@geofisica.unam.mx
AF: Laboratorio de Paleomagnetismo y Geofisica Nuclear, Instituto de Geofisica, UNAM, Circuito Institutos s/n, Mexico, DF 04150
AB: We report results of a magnetic fabric study of the malt-rich breccia sequence of the Chicxulub impact crater, Yucatan peninsula, Mexico. The breccia sequence has been sampled as part of the Chicxulub scientific drilling project (CSDP). The Yaxcopoil-1 borehole was drilled in the southern sector of the crater, south of Merida city. CSDP included continuous coring from about 404 m to 1511 m, and provided cores of the Tertiary carbonate sequence, the impact breccias and underlying carbonate megablocks. Ninety-two samples from 855.22 to 894.58 meters from Yaxcopoil-1 were selected for the magnetic fabric study. Measurements were performed using a Kappa-bridge KLY-2, which provided data on the magnetic anisotropy of low-field susceptibility (AMS). About 77 percent of the suevitic breccias had a prolate fabrics, 64 percent of the green monomitic breccia and 50 percent policmitic breccia had oblate fabrics. The values of AMS parameters such as L,F and P' of prolate fabric of the samples of monomitic breccia showed an increase with the depth, the opposite ocurre with the oblate specimens. As it is only possible to determine the upper side of the samples, the analysis of the directional results have to be careful, but tendencies of sedimentary-like fabrics can be determined. Results indicate a relative heterogeneity in the magnetic fabric of the breccia, which is expected from the high energy emplacement within the crater during crater formation; certain sectors provide some evidence for characteristic fabric patterns within the impact breccias.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1519 Magnetic mineralogy and petrology
DE: 1520 Magnetostratigraphy
SC: Tectonophysics [T]
MN: 2005 Joint Assembly