HR: 1340h
AN: T33B-1374    [Abstracts]
TI: Tectonic reconstruction of sedimentary basins associated with the proto-Maracaibo and proto-Orinoco Rivers: New constraints from BOLIVAR and GULFREX seismic data
AU: * Escalona, A
EM: escalona@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, The University of Texas at Austin, 4412 Spicewood Springs road, building 600, Austin, TX 78759 United States
AU: Mann, P
EM: paulm@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, The University of Texas at Austin, 4412 Spicewood Springs road, building 600, Austin, TX 78759 United States
AB: The proto-Orinoco River has long been proposed as the single, fluvial source for thick Cenozoic basins along northern Venezuela. The location of these buried and deformed depocenters are significant both for their use as piercing points to reconstruct the amount of Caribbean-South America right-lateral plate motion and because they are excellent source and reservoir rocks for hydrocarbons onland. We have integrated MCS lines of selected BOLIVAR-2004 and GULFREX-1975 data to produce maps of the major depocenters offshore and reconstruct their tectonic history. The two offshore basins in the study area are the Falcon-Bonaire-Grenada basin, a Paleogene backarc basin, and the Tobago trough basin, a Paleogene forearc basin. A plate reconstruction restoring ~1000 km of east-west, right-lateral strike-slip displacement between these Caribbean arc-related basins and the continental margin of South America reunites a ~5-km-thick lobe of marine sediment in the Tobago trough basin with the distal end of a Paleogene river system in western Venezuela that we name the proto-Maracaibo River. It is significant that all sediment associated with the proto-Maracaibo river was confined to the margin and did not reach the deepwater Venezuelan basin west of the Tobago basin. Late Miocene Andean uplift diverted most drainage from the proto-Maracaibo to the proto-Orinoco River south of the Venezuelan coastal ranges. The proto-Orinoco prograded eastward in post-late Eocene time along its E-W-trending corridor between late Eocene to recent time and formed a separate fluvial-deltaic system from the slightly older paleo-Maracaibo system to the north.
DE: 9360 South America
DE: 8105 Continental margins and sedimentary basins
DE: 3010 Gravity
DE: 3022 Marine sediments--processes and transport
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting