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Tectonics, Basin Evolution and Sediment Distribution Within the Collision to Subduction Transition of the Southeastern Caribbean Plate Boundary Zone in Offshore Trinidad


Dynamic topography, structures and geomorphology at the southeastern Caribbean-northeast South American margin which formed as a result of the convergence and oblique collision between the Caribbean and South American plates exert a dominant control on the timing and location of depositional centers and sediment pathways along this transitional plate boundary margin. We use ∼ 10,000 km of 2D seismic reflection lines which are recorded to depths > 12 seconds TWT and well data to interpret the distribution and continuity of tectono-stratigraphic sequences and to identify and constrain the timing of activity of key structural features. The thick (= 4.5seconds) northward-dipping, passive margin Cretaceous strata document the relatively quiescent conditions which existed prior to deformation heralding the arrival of the Caribbean plate. The transition to active subduction and collision by the Mid-Miocene is recorded by the accretionary prism (BAP); composed of thrusted and deformed Paleogene to recent sediments, and the plate boundary deformation zone which includes the uplifted, thrusted and folded structures that form a 140-km-wide zone between the Darien Ridge composed of southward-verging thrust packages of Cretaceous to Middle Miocene sediments and the metasediments of the Tobago High. Uplift of these structures was accompanied by the progressive subdivision of what was previously a broad offshore basin into segmented depocenters of Plio-Pleistocene sediments (PPS): 1) the broad Columbus foreland basin formed as a result of northward flexure of the South American crust beneath the Caribbean plate with up to 12 km of PPS; 2) the narrow Darien sub-basin formed between the uplifted structures of the Darien Ridge and the most proximal thrusts of the accretionary prism containing up to 8 km of PPS; 3) Barbados Basin; the largest piggy back basin of the BAP and contains up to ∼ 4 km of PPS; and 4) a series of small piggyback basins filled with thin packages of PPS. Sediments sourced from the Orinoco River and Guyana current to the south are distributed through sediment pathways which connect through the Columbus Basin. There is a dominant eastward sediment pathway from the Columbus Basin shelf to slope and out to the piggyback basins of the inner BAP via narrow pathways which step south through time. We also identify a volumetrically-significant northward movement of Pleistocene sediments from the Columbus Basin through the Darien Basin to the Barbados Basin.