HR: 16:55h
AN: OS24A-04    [Abstracts]
TI: Pressure, Temperature and Flow in the Ursa Basin Ssediment Ccover, Northeast Gulf of Mexico
AU: * Flemings, P B
EM: flemings@geosc.psu.edu
AF: Penn State University, 307 Deike Building, University Park, PA 16802 United States
AU: Dugan, B E
EM: dugan@rice.edu
AF: Rice University, Department of Earth Sciences 6100 Main St., Houston, TX 77005 United States
AU: Long, H
EM: hlong@geosc.psu.edu
AF: Penn State University, 307 Deike Building, University Park, PA 16802 United States
AU: Germaine, J
EM: jgermain@mit.edu
AF: Massachusetts Institute of Technology, Dept. of Civil & Environmental Engineering Massachusetts Avenue, Room 1-353, Cambridge, MA 02139 United States
AU: Behrmann, J
EM: jan.behrmann@geologie.uni-freiburg.de
AF: Albert-Ludwigs-Universitat Frieburg, Geologisches Institut Albertstrasse 23b, Freiburg, 79104 Germany
AU: John, C M
EM: cjohn@pmc.ucsc.edu
AF: University of California, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Jones, C
EM: cjones@geosc.psu.edu
AF: Penn State University, 307 Deike Building, University Park, PA 16802 United States
AB: Thirty-nine penetrometer measurements define the spatial variation in pressure and temperature in low permeability mudstones in the shallow sedimentary section of the Ursa Basin. Sites U1322 and U1324 were located 10 km apart and were drilled to 226 and 600 meters below seafloor, respectively. Lamda-star (fluid overpressure divided by hydrostatic effective stress) is approximately 0.6 in both locations (i.e. the pore pressure lies 60% of the way between hydrostatic and lithostatic pressure). Overpressure may begin at a shallower depth at Site U1322 than at Site U1324. The temperature gradient is linear, but is 25% greater at Site U1322 than at Site U1324. Thermal conductivities at the two locations are similar (~~1.2 vs 1.15 W/mK), implying a vertical conductive heat flow of ~~22 mW/m² 2 at Site U1324 vs ~~30 mW/m² 2 at Site U1322. The overall sedimentation rate is 2.6 times greater at Site U1324 than at Site U1322 (10 versus 3.8 mm/y). The similar overpressure gradients present at both locations coupled with the almost 3-fold difference in sedimentation rate implies a component of lateral flow between them: this flow increases the pressure at Site U1322 relative to a system with only vertical fluid migration. The Blue Unit underlies the Ursa mudstones and is composed of interbedded sands and mudstones. Fluid overpressures generated by rapid loading at Site U1322 may be partially dissipated by migration of fluid laterally in the deeper part of the Blue Unit. Heat is also advected by this process resulting in the elevated temperature gradient at Site U1322.
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 3094 Instruments and techniques
DE: 4564 Tsunamis and storm surges
DE: 5114 Permeability and porosity
DE: 8045 Role of fluids
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005