HR: 1340h
AN: T33B-1375    [Abstracts]
TI: BOLIVAR: Onshore-Offshore Seismic Transect of the Caribbean/South American Plate Boundary at Barcelona, Venezuela
AU: * Sawyer, D S
EM: dale@rice.edu
AF: Rice University, Dept. of Earth Science, Houston, TX 77005 United States
AU: Levander, A
EM: alan@rice.edu
AF: Rice University, Dept. of Earth Science, Houston, TX 77005 United States
AU: Zelt, C A
EM: czelt@rice.edu
AF: Rice University, Dept. of Earth Science, Houston, TX 77005 United States
AU: Christeson, G L
EM: gail@ig.utexas.edu
AF: University of Texas at Austin, Jackson School of Geosciences, Institute for Geophysics, Austin, TX 78759 United States
AU: Mann, P
EM: paulm@ig.utexas.edu
AF: University of Texas at Austin, Jackson School of Geosciences, Institute for Geophysics, Austin, TX 78759 United States
AU: Schmitz, M
EM: mschmitz@funvisis.org.ve
AF: Fundacion Venezolana de Investigaciones Sismologicas, Prolongacion Calle Mara, Caracas, 76880 Venezuela
AB: In April-June, 2004, scientists from Venezuela and the USA acquired a series of marine multi-channel, ocean bottom seismograph, land seismic recorder profiles across the boundary between the Caribbean (CAR) and South American (SA) plates on and off shore northern Venezuela. The ocean bottom seismographs and land recorders recorded the marine airgun-array shots as well as two land explosive shots. This presentation focuses on results from a transect acquired along a roughly north-south line which passes near Barcelona, Venezuela, and extends 175 km inland and 330 km seaward from the coast. Features imaged along the transect (from the seaward end) include the Venezuela Basin, the South Caribbean Deformed Belt, a zone of underthrusting north of the ABC Islands, the Los Roques Canyon, an incipient subduction zone that extends eastward to Grenada, the El Pilar strike-slip fault zone and the associated Cariaco pull-apart basin, the Pilar strike slip fault, the coast, the Serrania Del Interior fold-thrust belt and the Maturin foreland basin. The location of the transect corresponds to a number of important changes in the tectonics of the plate boundary. It lies just to the west of the intersection of the Aves Ridge and the CAR/SA boundary. Associated with this intersection is a roughly 100 km southward shift in the location of the zone of underthrusting marking the southern extent of the Venezuela basin. The shift appears to be a key to understanding the process by which volcanic arc crust of the Aves Ridge is transferred to the SA plate. A carbonate platform, including the Venezuelan islands Isla Blanquilla and Isla la Orchila and possibly overlying Aves Ridge volcanic rocks, lies between the 2 branches of the subduction system. This area of thickened crust may be choking off the eastern branch of subduction, causing subduction to step 100 km northward. We present marine reflection seismic data, and marine and land long-offset seismic refraction data, together providing structure and velocity control on the geology along the transect.
UR: http://earthscience.rice.edu/BOLIVAR.html
DE: 8105 Continental margins and sedimentary basins
DE: 7205 Continental crust (1242)
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting