Gibson, R. G.¹, K. Meisling¹, P. A. Bentham¹
(1) BP America, Houston, TX

ABSTRACT: Plio-Pleistocene Structural Evolution of the Columbus Basin, Offshore Trinidad, West Indies

The late Tertiary Columbus basin is situated along the transpressional plate margin between the South American and Caribbean plates, immediately west of the subduction boundary between the Caribbean and Atlantic plates (Barbados accretionary prism). Major structures within the 40000+’ thick, Miocene-Pleistocene siliciclastic section are regionally detached from an underlying north-dipping Cretaceous passive margin succession.
Structures in the western, shelfal part of the basin include a NW-SE striking extensional fault system and NE-SW trending contractional folds. 2D restoration of the extensional fault system shows that in excess of 35km extension occurred, much of it accommodated on a counter-regional fault system situated near the depositional shelf edge as it prograded northeastward since middle Pliocene time. Normal faults in this system are folded and rollover anticlines in the NW part of the basin are locally inverted due to Pleistocene NW-SE shortening.
Farther NE, on the present-day slope, NNE-SSW oriented dextral strike-slip zones are the dominant structures and were active during shelf extension. 3D restoration illustrates that these faults partitioned the counter-regional footwall into large blocks, thus accommodating the large extension on the shelf. The strike-slip zones appear to transfer displacement from the extensional fault system basinward into NNE-SSW trending contractional structures of the Barbados accretionary prism.
The Plio-Pleistocene Columbus basin is interpreted as a thin-skinned pull-apart basin formed during the southeastward transfer of dextral displacement from the Caribbean-South American plate boundary into the Caribbean-Atlantic subduction complex.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.