HR: 0800h
AN: OS41C-0493    [Abstracts]
TI: 3D Seismic Imaging of the Blake Ridge Gas Hydrate Province: Evidence for a Dynamic Gas System
AU: * Hornbach, M J
EM: mhornbac@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics, Laramie, WY 82071 United States
AU: Holbrook, W S
EM: steveh@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics, Laramie, WY 82071 United States
AU: Saffer, D M
EM: dsaffer@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics, Laramie, WY 82071 United States
AU: Gorman, A R
EM: andrew.gorman@stonebow.otago.ac.nz
AF: University of Otago, Department of Geology, Dunedin, NZ 9015 New Zealand
AU: Van Avendonk, H
EM: harm@utig.ig.utexas.edu
AF: The University of Texas Institute for Geophysics, 4412 Spicewood Springs Rd. #600 Austin, Austin, TX 78759-8500 United States
AU: Lizarralde, D
EM: danl@eas.gatech.edu
AF: Georgia Tech, School of Earth and Atmospheric Sciences, Atlanta, GA 30332-0340 United States
AU: Pecher, I
EM: i.pecher@gns.cri.nz
AF: Institute of Geological and Nuclear Science, PO BOX 30 368, Lower Hutt, NZ 9015 New Zealand
AB: New 3D multi-channel seismic reflection images of the Blake Ridge gas hydrate province, located 400 km east of Savannah Georgia, suggest that a dynamic gas-hydrate/free-gas boundary exists. Complex ocean bottom currents above the Blake Ridge Depression create both high rates of sediment deposition (~250m/k.y.) and erosion, resulting in changes in sediment overburden and thermal variability at the bottom simulating reflector (BSR). 3D images combined with heatflow analysis show that the BSR below these sediment waves is not in equilibrium, and that fluctuating ocean currents and sedimentary processes may cause gas overpressure and escape. Amplitude analysis of the 3D volume reveals significant amplitude variability at the BSR, suggesting highly variable free-gas concentrations beneath the Blake Ridge. Specifically, compared with the crest of the Blake Ridge, little gas exists along the eastern erosional flank and within the Blake Ridge Depression where faults extend continuously from the BSR to the seafloor. The results imply faults that outcrop at the seafloor act as primary conduits for gas migration into the water column.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 1600 GLOBAL CHANGE (New category)
DE: 1635 Oceans (4203)
DE: 0350 Pressure, density, and temperature
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting