HR: 1340h
AN: OS33B-0583    [Abstracts]
TI: Relations Between Basement Tectonics, Sediment Deformation and Fluid Flow at the Eastern Juan de Fuca Ridge Flank: Results From Very High Resolution Seismic Data
AU: * Zuehlsdorff, L
EM: lzuehls@uni-bremen.de
AF: Department of Geosciences Bremen University, P. O. Box 330440, Bremen, 28334 Germany
AU: Spiess, V
EM: vspiess@uni-bremen.de
AF: Department of Geosciences Bremen University, P. O. Box 330440, Bremen, 28334 Germany
AB: In summer 2004, IODP Leg 301 was drilled on the eastern flank of the Juan de Fuca Ridge as a successor of ODP Leg 168 (1996). The main subject of the new leg was to study the properties of an active ridge flank hydrothermal system, which is for a big part isolated beneath a low permeable sediment cover. During the Leg 301 seismic pre-site survey, which was carried out during R/V Sonne Cruise SO 149 (2000), this sediment cover was imaged in a multi-frequency seismic data set at high and very high resolution. Folds, faults, and the layer structure were carefully mapped to show that forced folding is a dominant process affecting sediment physical properties and fluid flow. By comparing data from areas of different basement age and integrating seismic and borehole data, the importance of basement tectonics on sediment deformation and fluid flow, depending on crustal age and sedimentation processes is investigated. Preliminary results show that growth faults characterized by upwardly decreasing offsets reflect off-axis tectonic crustal reorganization. Growth fault propagation at Second Ridge ceased about 0.28 Ma ago at the base of a major sediment transport channel, whereas tectonic activity at First Ridge was more recent. Forced folding at First Ridge controls creation and maintenance of a subsurface plumbing system for vertical fluid flow through the sediments. Indications for forced folding are also found at Second Ridge though vertical fluid flow likely is much less affected.
DE: 8010 Fractures and faults
DE: 8135 Hydrothermal systems (8424)
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting