HR: 0800h
AN: OS21A-1509    [Abstracts]
TI: Deformation Analyses and Lithologic Characterization in Overpressured Basins Based on Logging While Drilling and Wireline Results from the Gulf of Mexico
AU: * Iturrino, G J
EM: iturrino@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, Borehole Research Group Route 9W, Palisades, NY 10964 United States
AU: Pirmez, C
EM: carlos.pirmez@shell.com
AF: Shell International Exploration and Production Inc, 3737 Bellaire Blvd., Houston, TX 77025 United States
AU: Moore, J C
EM: cmoore@es.ucsc.edu
AF: University of California Santa Cruz, Department of Earth Sciences 1156 High Street, Santa Cruz, CA 95064 United States
AU: Reichow, M K
EM: mkr6@le.ac.uk
AF: University of Leicester, Department of Geology University Road, Leicester, GBR LE1 7RH United States
AU: Dugan, B E
EM: dugan@rice.edu
AF: Rice University, Department of Earth Science 6100 Main Street, Houston, TX 77005 United States
AU: Sawyer, D E
EM: dsawyer@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences 307 Deike Building, University Park, PA 16802-2714 United States
AU: Flemings, P B
EM: flemings@geosc.psu.edu
AF: Pennsylvania State University, Department of Geosciences 307 Deike Building, University Park, PA 16802-2714 United States
AU: Shipboard Scientific Party, I
EM: malone@iodp.tamu.edu
AF: Texas A&M University, Integrated Ocean Drilling Program 1000 Discovery Drive, College Station, TX 77845 United States
AB: IODP Expedition 308 drilled transects along the Brazos-Trinity IV and Ursa Basins in the western and eastern Gulf of Mexico, respectively, for examining how sedimentation, overpressure, fluid flow, and deformation are coupled in passive margin settings. A total of eight holes were logged using either logging while drilling (LWD) or wireline techniques to evaluate the controls on slope stability, understand the timing of sedimentation and slumping, establish the petrophysical properties of shallow sediments, and provide a better understanding of turbidite systems. Overall, the log responses vary for the different lithostratigraphic units and associated regional seismic reflectors. The data acquired also make bed-to-bed correlation between sites possible, which is valuable for the study of sandy turbidites and studies of regional deformation. The thick sedimentary successions drilled at these basins show records of the evolution of channel-levee systems composed of low relief channels that were incapable of confining the turbidity currents causing an overspill of sand and silt. In addition, mass transport deposits at shallow depths, and transitions between interbedded silt, sand, and mud units are common features identified in many of the downhole logging data. In the Ursa Basin sediments, resistivity-at-the-bit images show significant deformation of the overlying hemipelagic drape and distal turbidites that were drilled in these areas. Numerous dipping beds throughout these intervals with dips ranging from 5 to 55 degrees confirm core observations. Steeply deformed beds, with dips as high as 65 degrees, and folded and faulted beds suggest down slope remobilization as mass-transport deposits. Resistivity images also show evidence of these mass-transport deposits where steep dips and folds suggest the presence of overturned beds within a series of cyclic intervals that we interpret as a succession of sand-silt-mud lamina. Preliminary structural analyses suggest that many of the deformation features trend in an E-W direction with the majority dipping to the north.
DE: 3022 Marine sediments: processes and transport
DE: 3036 Ocean drilling
DE: 5114 Permeability and porosity
DE: 8005 Folds and folding
DE: 8045 Role of fluids
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005