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Mann, P.¹ (paulm@ig.utexas.edu), Wood, Lesli², and Sullivan, S.^1,3
1Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, 4412 Spicewood Springs Road, Building 600, Austin, TX 78759, phone: 512-471-0452, fax: 512-471-8844
²Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713
³Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin

The slope of eastern offshore Trinidad trends in a NS to NNW direction and separates a 50-100-km-wide, 50-200-m-deep shelf from a >1000-m-deep basin. Merged 3D seismic data sets and 2D lines define three segments of oppositely-dipping normal faults, many of which form active scarps on the seafloor and control Neogene sand fairways. In the southern area adjacent to the Orinoco delta of Venezuela and north of the Venezuela-Trinidad boundary, a master normal fault is seaward-dipping, listric, and associated with toe thrusts in the deepwater area. An antithetic, landward-dipping fault forms a prominent upslope-facing scarp on the slope that traps young sediments and defines a 4-km-wide "keystone" rift filled by Plio-Pleistocene deltaic sand and shale. In the central area north of the Trinidad-Venezuela border and south of the Darien ridge, the master normal fault is landward-dipping and slightly oblique to the NS trend of the slope. Antithetic faults dip seaward and form the edges of a prominent, 5-km-wide, "keystone" rift and overlying slope channel that focuses sand and debris flows from the shelf into the deeper water area. In a northern area north of the Darien ridge, the master normal fault dips seaward. Antithetic faults form a "keystone" rift similar to those to the south. The Darien ridge, an elongate, bathymetric ridge of right-lateral, transpressive thrusting, forms the boundary between the northern and central normal fault segments. The southern segment boundary is not clear from present data.