HR: 0800h
AN: OS41C-0487    [Abstracts]
TI: A New Interpretation of the 1st Storegga Slide: Evidence for an Older Event Unassociated With the Base of the Hydrate Stability Zone
AU: * Brown, H E
EM: hbrown@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, 1000 University Ave., Laramie, WY 82071 United States
AU: Holbrook, W
EM: steveh@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, 1000 University Ave., Laramie, WY 82071 United States
AU: Hornbach, M J
EM: mhornbac@uwyo.edu
AF: Department of Geology and Geophysics, University of Wyoming, 1000 University Ave., Laramie, WY 82071 United States
AB: Large submarine landslides on continental slopes are important geologic features because they cause 1) mass wasting, 2) tsunamis, and most importantly 3) the possible rapid release of methane, a greenhouse gas, into the atmosphere. The Storegga Slide off the coast of Norway is one of the largest underwater slides known covering an area of ~34000 km2 and displacing ~5600 km3 of sediment. We present new pre-stack depth migrated images from a multi-channel seismic data set, which comprise the most detailed profiles to date of the Storegga Slide. These images show strong evidence for multiple slide events, including a much older event, at the northern scarp of the 1st Storegga Slide that has previously been interpreted as one large recent slope failure. On-lapping features, layer thickening, and rotated fault blocks draped with undisturbed sediments support this conclusion. According to sedimentation rates on the edge of the Voring plateau, and previous dating of a layer in the Naust formation, we estimate that this older slide event occurred at a minimum of ~185 ka. We calculate thermal gradients of 54.4 and 50.0oC/km under lithostatic and hydrostatic conditions respectively at the southern edge of the Voring Plateau. Pressure/temperature modeling using these thermal gradients shows that, assuming steady state conditions, the base of the gas hydrate stability zone could not have been involved in initiation of the older event because the BSR would have been deeper than the glide plan at the time of failure.
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3025 Marine seismics (0935)
DE: 1635 Oceans (4203)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting