HR: 0800h
AN: T11B-0386    [Abstracts]
TI: BOLIVAR: Crustal Structure Across the Caribbean-South American Plate Boundary at 70W: Results from Refraction and Reflection Data.
AU: * Guedez, M C
EM: mcguedez@rice.edu
AF: Rice University, 6100 Main St. Earth Science Department MS 126., Houston, TX 77251 United States
AU: Zelt, C A
EM: czelt@rice.edu
AF: Rice University, 6100 Main St. Earth Science Department MS 126., Houston, TX 77251 United States
AU: Magnani, M B
EM: beatrice@rice.edu
AF: Rice University, 6100 Main St. Earth Science Department MS 126., Houston, TX 77251 United States
AU: Levander, A
EM: alan@rice.edu
AF: Rice University, 6100 Main St. Earth Science Department MS 126., Houston, TX 77251 United States
AU: Christeson, G L
EM: gail@utig.ig.utexas.edu
AF: University of Texas, Institute for Geophysics, Austin, TX 78759 United States
AU: Sawyer, D S
EM: dale@rice.edu
AF: Rice University, 6100 Main St. Earth Science Department MS 126., Houston, TX 77251 United States
AB: The active-seismic component of the BOLIVAR project (Broadband Ocean and Land Investigations of Venezuela and the Antilles arc Region) was completed in June 2004. Among the goals of BOLIVAR is to study the structure of the South America-Caribbean plate boundary as a site of likely continental growth by island arc accretion of the Leeward Antilles arc to the South American continent. In the west end of the Venezuelan basin the complex motion across the plate boundary is poorly understood. Other studies have concluded that the Caribbean Plate is subducting beneath the South American Plate and the Leeward Antilles arc is being accreted to older continental crust. Complicating this picture, the Maracaibo block is being displaced northward along the Bocono and Santa Marta strike-slip faults, while the Oca fault is a paleo-strand of the large right-lateral strike-slip system of the plate boundary. We present results of analyses of refraction and reflection seismic data along a 450 km long onshore-offshore profile at 70oW, extending from 10oN to 14.3oN. The refraction data include 40 Ocean Bottom Seismometer (OBS) and 348 Reftek Texan land seismometers that recorded the R/V Ewing airgun shots. The land stations also recorded two large landshots to provide reversed refraction coverage onshore. A 2-D velocity model obtained from travel time inversion of first arrivals shows that the Caribbean crust is anomalously thick, typical of oceanic plateau, ~ 15-20 km. Low velocity sediments, on the Caribbean oceanic plateau, are observed subducting beneath the South-Caribbean deformed belt over a distance of 75-100 km. We also observe low velocities associated with the Paraguana/Falcon basin extending from onshore to offshore depths of 3 km. We observe localized high compressional velocities spatially associated with the Oca fault. Similar high velocity bodies are observed on other BOLIVAR transects (see Avé Lallemant et al., this session). A migrated stack of the marine reflection data will also be presented.
DE: 3025 Marine seismics (0935, 7294)
DE: 3038 Oceanic plateaus and microcontinents
DE: 7205 Continental crust (1219)
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: Fall Meeting 2005