HR: 0800h
AN: H41B-0302    [Abstracts]
TI: The Internal Structure and External Morphology of Submarine Landslides: A Causative Link
AU: Kneller, B
EM: ben@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California at Santa Barbara, Mail Code 1100, 1140 Girvetz Hall, Santa Barbara, CA 93106-1100 United States
AU: * Dykstra, M
EM: dykstram@umail.ucsb.edu
AF: Institute for Crustal Studies, University of California at Santa Barbara, Mail Code 1100, 1140 Girvetz Hall, Santa Barbara, CA 93106-1100 United States
AB: The internal structure of submarine landslide deposits has been described in detail by relatively few workers, and thus our understanding of them is very incomplete. General internal characteristics include zones of brittle and ductile deformation; normal and listric-normal faults and fault zones, reverse and thrust faults, folds, cleavages, and mixed or homogenized horizons and zones. The large variety of structures internal to landslide deposits implies that stress and strain are partitioned in a very complicated fashion, often varying greatly over short vertical and horizontal distances and differently within the various materials making up the mass-failure. Unraveling the structural makeup of these deposits, and linking this to facies variations within them allow us to help determine details of the stress and strain distribution and hence the mechanics of their movement and deposition. Fieldwork has lead to the following preliminary findings. 1) Slide horizons are characterized by coarser-grained facies than the mass-transported material, implicating elevated pore-fluid pressures as a primary lubricant in these mass-movements. 2) Various cleavages bearing consistent relationships to the direction of movement of the slide body, and the orientation of the slide horizons can be present in the landslide deposits. On the microscopic scale, these cleavages take the form of grain-rotation, grain-translation, and brittle fracture of grains or aggregates of grains. 3) The internal partitioning of strain is very complicated, on all scales, often leaving highly deformed strata immediately laterally adjacent to apparently internally undeformed strata. Some of these relationships can be interpreted in terms of failure systematics, which include both retrogressive failures and single event failures, and some are due to strain localization along lines of weakness in the deposit. 4) Outcrop-scale structures mimic seismic-scale structures, and include brittle and ductile deformation. Additionally, high-resolution 3D seismic data and field map relationships indicate that there is a direct physical relationship between the upper morphology, the internal structure, and the basal morphology of many submarine landslide deposits. This implies that the stresses `felt' by the base of a landslide are projected into the internal structure of the deposit, and directly influence the morphology of the resulting deposit (and hence the post-depositional sea-floor).
DE: 3022 Marine sediments--processes and transport
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting