AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Subduction-to-Strike-Slip Transition in the Southeastern Caribbean Imaged Using Deeply Penetrating Seismic Reflection Lines and Tomography
(1) Jackson School of Geosciences; The University of Texas at Austin, Austin, TX.
(2) Departamento de Geociencias, Universidad Nacional de Columbia, Bogota, Colombia.
(3) Seismic Research Centre, The University of the West Indies, St. Augustine, Trinidad and Tobago.
(4) Department of Petroleum Engineering, University of Stavanger, Stavanger, Norway.
The subduction-to-strike-slip transition (SSST) zone of the southeastern Caribbean is one of thirty identified locations where active subduction and strike-slip tectonic styles transition along strongly curved and seismogenic plate boundaries. This SSST zone provides a field laboratory for understanding how sedimentary basins, faults, basement areas and subducted slabs change from an area of dominantly westward-directed subduction beneath the Lesser Antilles arc to an area of dominantly east-west strike-slip faulting along northern South America.
We use two geophysical data types to image the lithosphere and study the relationships between lithospheric scale deformation and basin scale response to the transitional tectonic configuration. Interpretation of deeply-penetrating seismic reflection lines recorded down to 16 seconds two-way time, or depths of about 18 km, is combined with tomographic slices of the upper mantle and lower crust which were constructed using the coda method on ~ 700 earthquakes in the depth range of 70-250 km.
Results from the tomographic study are compared with nine seismogenic zones in the southeast Caribbean SSST zone which are defined based on the depth, and focal mechanism of earthquake events. These zones include: (1) the Paria slab tear region; (2) Caribbean/South American strike-slip zone; (3) Hinge area separating continental margin in Trinidad from Tobago forearc basin; (4) Central Range -strike-slip fault zone, onshore Trinidad; (5) Underthrust zone of South American beneath southern onshore and offshore eastern Trinidad, including the prolific hydrocarbon-bearing Columbus Basin; (6) Venezuela foreland and fold-thrust belt; (7) flexural bulge area of oceanic crust located east of Barbados accretionary prism (BAP); (8) Subducted slab beneath the stabilized and supracomplex zones of the BAP; (9) Inner accretionary prism of the BAP. Primary controls on the seismogenic character of each curving tectonic belt include the strike of the plate boundary faults relative to the plate vector for crustal earthquakes and the location and morphology of the subducted slab for sub-crustal earthquakes.