HR: 0800h
AN: T11B-0390    [Abstracts]
TI: Crustal Structure of the Caribbean-South American Diffuse Plate Boundary: Subduction Zone Migration and Polarity Reversal Along BOLIVAR Profile 64W
AU: * Clark, S A
EM: stoney@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AU: Levander, A
EM: alan@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AU: Magnani, M
EM: beatrice@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AU: Zelt, C A
EM: czelt@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AU: Sawyer, D S
EM: dale@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AU: Ave Lallemant, H G
EM: ave@rice.edu
AF: Dept. of Earth Science, Rice Univ., 6100 Main St. MS-126 , Houston, TX 77005
AB: The BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) project is an NSF funded, collaborative seismic experiment in the southeast Caribbean region. The purpose of the project is to understand the diffuse plate boundary created by the oblique collision between the Caribbean and South American plates. Profile 64W of the BOLIVAR experiment, a 450 km-long, N-S transect onshore and offshore Venezuela located at ~64°W longitude, images the deep crustal structures formed by this collision. The active source components of profile 64W include 300 km of MCS reflection data, 33 coincident OBSs, and 344 land seismic stations which recorded 7500 offshore airgun shots and 2 explosive land shots. Results from the reflection and refraction seismic data along 64W show complex crustal structure across the entire span of the diffuse plate boundary. The onshore portion of 64W crosses the fold and thrust belt of the Serrania del Interior, which formed at ~16 Ma by collision of the Caribbean forearc with the northern South American passive margin. Underlying the Serrania del Interior is a south-vergent, remnant Lesser Antillean subduction zone. As this Lesser Antilles subduction impinged on continental crust, it caused a polarity reversal and jump offshore to the north. Convergence was initially localized in the closure and inversion of the Grenada Basin. However, subduction could not develop because of the ~20-km-thick crust of the Aves Ridge; instead, north-vergent subduction initiated further to the north, where ~12-km-thick Caribbean oceanic crust of the Venezuela Basin began to subduct beneath the Aves Ridge in the Pliocene (~4 Ma) and appears to continue subducting today. Between the remnant subduction zone and the modern one, the El Pilar and Coche dextral strike-slip faults accommodate most of the transform motion of the plate boundary. From the Serrania del Interior to the Aves Ridge, ~260 km of accreted orogenic float comprises the diffuse plate boundary.
DE: 3025 Marine seismics (0935, 7294)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8104 Continental margins: convergent
DE: 8106 Continental margins: transform
SC: Tectonophysics [T]
MN: Fall Meeting 2005