HR: 17:35h
AN: U34A-06    [Abstracts]
TI: Sedimentologic and Stable Isotope Response to the PETM at Chicxulub
AU: * Whalen, M T
EM: mtwhalen@gi.alaska.edu
AF: University of Alaska Fairbanks and Geophysical Institute, Dept. of Geology and Geophysics, Fairbanks, AK 99775, United States
AU: Pearson, Z F
EM: ftzfr@uaf.edu
AF: University of Alaska Fairbanks and Geophysical Institute, Dept. of Geology and Geophysics, Fairbanks, AK 99775, United States
AU: Perez Cruz, L
EM: perezcruz@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Insituto de Geofisica, Mexico City, DF 04510, Mexico
AU: Urrutia Fucugauchi, J
EM: juf@geofisica.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Insituto de Geofisica, Mexico City, DF 04510, Mexico
AU: Norris, R
EM: RNorris@ucsd.edu
AF: Scripps Insitution of Oceanography, 301 Vaughan Hall, MS-0244, La Jolla, CA 92093, United States
AU: Bralower, T J
EM: bralower@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences, University Park, PA 16802, United States
AU: Gulick, S P
EM: sean@ig.utexas.edu
AF: University of Texas at Austin Institute for Geophysics , 10100 Burnet Rd. (R2200), Austin, TX 78758, United States
AB: We report results of sedimentologic, biostratigraphic, stable isotope, and magneto-stratigraphic analyses of the Lower Paleogene portion of the Chicxulub impact basin infill from the Yaxcopoil-1 (Yax-1) drill core. This portion of the core records the Paleocene (P) and lower Eocene (E) providing documentation of the P-E thermal maximum (PETM). Foram biostratigraphic and isotopic data provide temporal control and aid in identification of the P-E boundary. Documentation of chrons C29r through C24r support the biostratigraphic data and placement of the P- E boundary within chron C24r. Much of the Lower Paleocene is dominated by coarse-grained redeposited carbonates interbedded with fine-grained, laminated or bioturbated wackestones and marls. A variety of clast types are found in the coarse-grained carbonates including Cretaceous clasts exposed by the impact and deformation associated with transient crater collapse. These facies represent slope deposits from mass wasting, associated with erosion of the crater margin, and suspension settling. The Upper Paleocene records a change to facies dominated by suspension deposits and soft sediment folds and likely indicates shallowing of slope declivity. The uppermost Paleocene is dominantly fine-grained with no indication of wave or current activity and implies deposition mainly from suspension. The P-E interval is characterized by three cycles with marl that grades upward into carbonate wacke/packestones. The base of the third cycle is a chemically corroded surface atop a packstone unit overlain by dark marl. This surface and the carbonate-poor intervals appear to indicate shoaling of the CCD and carbonate dissolution. These facies are overlain by carbonate floatstones interbedded with soft sediment folds that are interpreted to indicate renewed gravity flow deposition. Bulk carbonate samples from lowermost E facies record a negative δ¹³C excursion similar in sign and magnitude to excursions associated with the PETM elsewhere. About 80 m of section separates the base of the excursion with the return to "background" values. The δ¹³C and CCD excursions and overlying gravity flow deposits indicate the profound impact of the PETM in the Chicxulub basin. Carbonate dissolution appears to have destabilized the seafloor leading to renewed gravity flow deposition along the crater margin. The high accommodation space in the impact basin and high rates of sedimentation are indicated by the expanded thickness of the δ¹³C excursion interval compared to other localities. There are few records of the PETM from the tropics and this data raises the potential to further investigate the rapid climate change associated with the PETM through high-resolution analysis of sedimentary records from the Chicxulub basin. A joint IODP- ICDP project to drill an onshore-offshore transect in the crater is underway. This research highlights the importance of stratigraphic targets, such as the P-E boundary, within the Cenozoic sections that will be drilled on the way to the impact deposits.
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 5420 Impact phenomena, cratering (6022, 8136)
SC: Union [U]
MN: 2007 Joint Assembly