HR: 1340h
AN: T13B-0458    [Abstracts]
TI: Indications of Fluid Venting Along the Middle American Subduction Zone of Guatemala
AU: * Weinrebe, W
EM: wweinrebe@ifm-geomar.de
AF: SFB-574 and IFM-GEOMAR, Leibniz-Institute of Marine Sciences Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Ranero, C R
EM: cranero@icm.csic.es
AF: ICREA Instituto de Ciencias del Mar, CSIC Paseo Maritimo de la Barceloneta 37-49, Barcelona, 08003 Spain
AU: Grevemeyer, I
EM: igrevemeyer@ifm-geomar.de
AF: SFB-574 and IFM-GEOMAR, Leibniz-Institute of Marine Sciences Wischhofstr. 1-3, Kiel, 24148 Germany
AU: Vannucchi, P
EM: paolav@geo.unifi.it
AF: Dipartimento de Scienze della Terra, Universita di Firenze Via La Pira, 4, Firenze, 50121 Italy
AU: von Huene, R
EM: rhuene@mindspring.com
AF: University of California, Davis, 2910 North Canyon Rd., Camino, CA 95709 United States
AB: A 2003 multibeam bathymetric survey with R/V SONNE mapped the continental margins of Guatemala and El Salvador revealing a detailed image of the continental slope morphology and of the incoming ocean plate. The continental slope displays three morphotectonic units that roughly correspond to upper, middle and lower slope. The upper slope is characterized by numerous small canyons and gullies that begin at the eroded shelf edge high. The middle slope is characterized by a rough terrain of variable width and dip sculptured by pervasive normal faults and mass wasting. The lower slope is formed by en echelon terraces striking parallel to the rough terrain of the incoming plate that mimicks the half graben morphology of the underthrusting plate. The incoming plate morphology, inherited from seafloor spreading processes, is reactivated by bending of the oceanic lithosphere into the subduction zone. Widespread fluid venting has been reported along the adjacent Middle America Margin of Costa Rica and Nicaragua, and was expected off Guatemala and El Salvador. Typical manifestations of fluid venting, such as pockmarks, mud mounds, mud volcanoes or seeps, are difficult to document with swath mapping surveys if only the bathymetry is taken into account, as the size of these features are in the order of the footprint size of one acoustic beam. The backscatter signal, however, resolves different reflectivity of the seafloor and thus gives information on lithology. Fluid venting is often associated with the formation of carbonate structures characterized by high acoustic reflectivity. A detailed analysis of the backscatter data, compiled into a mosaic of the area, revealed several small topographic features (mounds) at mid slope depth characterized by high backscatter indicating carbonate precipitation and thus fluid venting. Several small pinnacles in the trench, showing a mound-like shape and very high backscatter might also indicate fluid venting structures associated with oceanic plate tectonism.
DE: 3002 Continental shelf and slope processes (4219)
DE: 3045 Seafloor morphology, geology, and geophysics
DE: 8104 Continental margins: convergent
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005