Deep crustal structure and tectonic origin of the Tobago-Barbados ridge

The north-south-trending Tobago-Barbados ridge (TBR) extends 250 km from its southern end at the island of Tobago to its northern end at the island of Barbados. On Tobago, exposed metasedimentary and metaigneous rocks have been identified as fragments of a Mesozoic primitive island arc, whereas on Barbados, exposed sedimentary rocks record Paleogene development of the Barbados accretionary prism (BAP). We integrate gravity data with seismic refraction data, well constraints, and seismic reflection data to improve our understanding of the TBR's crustal structure, uplift mechanism, along-strike compositional variations in the crust, and tectonic origin. Three 2D gravity models suggest that the TBR is underlain by a pop-up crustal block uplifted in the trench between the overriding Caribbean plate and the westwardly subducting South American plate. At approximately 11.75 degrees N, the character of the TBR changes over a distance of 60 km from a symmetrical and more elevated, crystalline, thrust fault-bounded structure to a west-verging thrust belt that is less elevated. The symmetrical pop-up and asymmetrical, west-verging thrust belt accommodate east-west, subduction-related shortening that deforms the westernmost edge of the BAP. We think that the crystalline basement of the southern and central TBR is the buried, northeastern continuation of Mesozoic intraoceanic-arc crust and metamorphic belt of Tobago that accreted along the eastern margin of the Great Arc of the Caribbean during its subduction polarity reversal in the early Cretaceous.