HR: 1340h
AN: T33B-1379    [Abstracts]
TI: Crustal Structure of the Southern Lesser Antilles Arc: Integration of BOLIVAR Wide-angle and MCS Data
AU: * Christeson, G L
EM: gail@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, University of Texas at Austin, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AU: Mann, P
EM: paulm@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, University of Texas at Austin, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AU: Aitken, T
EM: trevor@ig.utexas.edu
AF: Jackson School of Geosciences, Institute for Geophysics, University of Texas at Austin, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AB: In April-June 2004 we conducted an active-source seismic survey in the SE Caribbean as part of the NSF Continental Dynamics BOLI-VAR study. Here we present data from a coincident seismic reflec-tion and wide-angle profile extending 550 km from the Aves Ridge in the northwest to the Atlantic Ocean southeast of Trinidad and To-bago. In this region the Lesser Antilles island arc is currently collid-ing with northern South America; further to the west this collision has resulted in the accretion of the Leeward Antilles island arc to the South American continent. Geologic features crossed by the profile include the Aves Ridge, the Grenada back-arc basin, the Lesser Antilles island arc, the Tobago Trough, the Trinidad and Tobago region, and the Lesser Antilles ac-cretionary prism. The Aves Ridge and Lesser Antilles island arc have similar crustal structure: upper basement velocities are 4 km/s, velocities of 6 km/s are reached at depths of 6-7 km, and crustal thicknesses are 18-24 km. The Grenada back-arc basin, which formed when the present-day Lesser Antilles island arc rifted away from the Aves ridge during the Paleocene-early Eocene, contains approximately 9.5 km of sediment overlying crust with a thickness of 9-11 km. This crustal thickness suggests that rifting did not proceed to the generation of oceanic crust. The Tobago trough, which lies south-east of the Lesser Antilles island arc, has similar sediment and crustal thickness to the Grenada basin. Seismic penetration is poor through the metamorphic rocks comprising much of the Trinidad and Tobago system; however our data does indicate that velocities of 6 km/s are reached at depths of 4-5 km. Southeast of Trinidad and Tobago the accretionary prism has sediment thickness greater than 10 km due to its position near the Orinoco Delta.
DE: 8105 Continental margins and sedimentary basins
DE: 3025 Marine seismics (0935)
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting