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Abstract: Sequence Stratigraphy, Facies Architecture and Reservoir Distribution, Cretaceous Lowstand Fan Reservoirs, Southern Basin, Onshore Trinidad

Anthony R. Sprague, David K. Larue, Barbara L. Faulkner, Mark A. Sykes, Leon J. Aden

Thick Albian-Campanian mass-flow sandstones in the Southern Basin Trinidad were deposited within submarine canyons incised into the northern continental slope of South America and as associated down-dip basin-floor lowstand fans. The contemporaneous slope to basin-floor break lay across the Southern Basin area with turbidity current paleoflow being to the northwest.

North of this paleo-slope break graded to massive, channelized, high-density turbidite sandstones occur interstratified with shaly overbank and channel abandonment deposits. A progression of depositional sub-environments from proximal through distal lowstand fan can be recognized. All fine and thin upward but can be discriminated by the occurrence of slumps, debris flows and conglomerates, the grain-size and bedding scale of sandstones and the characteristics of low-density turbidites and mudrocks.

South of the paleo-slope break mass-flow deposits comprise muddy slumps and debris flows rich in granules and pebbles deposited in slope canyons. During periods of turbidity current by-pass or fan abandonment hemipelagic settling processes predominated.

Reservoir distribution maps of these lowstand fans have been constructed utilizing geometric constraints, analogs and paleoslope determinations from oriented core. The interpreted canyon locations and orientations are key to the understanding of reservoir distribution on the basin-floor tract to the north: a vital component in the exploration of the basin.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela