Abstract

The subduction-to-strike-slip transition (SSST) zone of the southeastern Caribbean is one of the thirty identified locations where active subduction and strike-slip tectonic styles transition along strongly curved and seismogenic plate boundaries. We use approximately 10,000 km (6000 mi) of 2-D seismic reflection, well, seismic tomographic, gravity, magnetic, earthquake focal mechanisms, and global positioning system (GPS) data to study the primary structures within the SSST zone. We analyze transitions of subducted slabs, basement areas, sedimentary basins, faults, and other structures from an area of westward-directed subduction of Atlantic oceanic crust beneath the Lesser Antilles arc, to a region of east–west-striking, right-lateral strike-slip faulting along the northern South American margin. Tectonic processes in the arcuate plate boundary zone include (1) oblique collision between the arcuate front of the Caribbean plate and the northern South American margin; (2) propagation of the Subduction-Transform Edge Propagator (STEP) fault as defined by Govers and Wortel (2005); and (3) north-to-northwest flexure of transitional South American lithosphere as the slab detaches from the South American continent, tears apart from the west-dipping segment of the slab to the north, and sinks into the mantle beneath the Caribbean plate. Northwest–southeast-oriented Atlantic oceanic fracture zones, and lithospheric transitional boundaries are a significant control on the evolution of the margin including the location and orientations of STEP faults, slab rollback, detachment, and tearing. Lithospheric deformation associated with STEP tearing and slab detachment influences the position, orientation, and evolution of crustal plate boundary structures and sedimentary basins discussed in more detail in Chapter 5 (Alvarez et al., 2021). Sedimentary basins and structures of the southeastern Caribbean SSST zone are characterized by spatially and temporally complex uplift and subsidence patterns at the surface, which are the result of the multiphase deformational history that includes oblique collision, STEP faulting, and subducted slab dynamics, which are inherent to the bounding tectonic configuration.