HR: 0800h
AN: T11B-0389    [Abstracts]
TI: BOLIVAR: Seismic Structure of the Leeward Antilles Arc and Growth of the South American continent
AU: * Arogunmati, A T
EM: aadeyemi@rice.edu
AF: Earth Science Department, Rice University, 6100 Main Street, MS-126, Houston, TX 77005 United States
AU: Zelt, C A
EM: czelt@rice.edu
AF: Earth Science Department, Rice University, 6100 Main Street, MS-126, Houston, TX 77005 United States
AU: Levander, A
EM: alan@rice.edu
AF: Earth Science Department, Rice University, 6100 Main Street, MS-126, Houston, TX 77005 United States
AU: Niu, F
EM: niu@rice.edu
AF: Earth Science Department, Rice University, 6100 Main Street, MS-126, Houston, TX 77005 United States
AU: Working Group, T
EM: geol@rice.edu
AF: Earth Science Department, Rice University, 6100 Main Street, MS-126, Houston, TX 77005 United States
AB: The most widely believed theory for the growth of continents is the magmatic arc accretion process. Arguments against this idea include the difference between continental crustal composition and island arc crustal composition because the average continental crust is known to be intermediate in composition while island arc crusts have been shown to be generally mafic in composition. The boundary between the Caribbean plate and the South American plate is an oblique transpressional zone along part of which the Caribbean is observed to be subducting beneath South America. A magmatic arc related to the subduction, the Leeward Antilles, developed on an ancient oceanic ridge giving a bulk intermediate crustal composition in this area. Given the large volume of material in this zone, a substantial amount of continent could be formed in 50 million years. This study is part of the BOLIVAR project aimed at examining arc-continent collision and accretion, HP/LT rock exhumation and the development of folded belts and sedimentary basins. The seismic refraction data used in this study was obtained in 2004 using 49 WHOI and Scripps OBS units, 9 RefTek 130 PASSCAL seismographs and approximately 40,000 airgun shots. Results in the form of a minimum-structure 3-D seismic velocity model calculated from approximately 21,000 first arrival traveltime picks using regularized seismic traveltime inversion show that the Leeward Antilles arc generally has a high velocity lower crust and that at all depths above the Moho, velocities are higher than those of the accretionary wedge just north of it. Moho depth beneath the arc ranges from 22 to 26 km below sea level. At depths greater than 11km, velocities below the arc are greater than 6.5 km/s and are generally less than 6.0 km/s below the Venezuelan basin at depths shallower than 16 km. An average 1-D velocity-depth function through the preliminary model suggests the average continental crust profile could be derived from a profile through the arc.
UR: http://cohesion.rice.edu/naturalsciences/earthscience/research.cfm?doc_id=5031
DE: 8100 TECTONOPHYSICS
DE: 8108 Continental tectonics: compressional
DE: 8125 Evolution of the Earth (0325)
DE: 8150 Plate boundary: general (3040)
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005