SPEED, R. C., Northwestern University, Evanston, IL

ABSTRACT: Tectonics and Terranes of the Southeastern Caribbean

The southeastern Caribbean plate (Ca) is comprised of the following terranes: Tobago, Grenada Basin, St. Vincent, Araya-Margarita, and Paria-Trinidad-Barbados (PTB). All are alien relative to South America (SA) east of Caracas except for PTB, which is of continental provenance and parautochthonous and lies within the principal movement zone of the Ca-SA plate boundary. The Tobago terrane extends between the eastern Venezuelan coastline and the Grenada Basin. On its south, the Tobago terrane overrode PTB and the South American passive margin during Neogene oblique collision. The Mesozoic tectonostratigraphy of the Tobago terrane is not unlike that of the Colombian Basin, suggesting the Tobago may belong to the Pacific-derived Caribbean plate. The Grenada Basin terrane consists of Eocen and older oceanic crust that now occupies the southern Lesser Antilles arc platform and the southern Grenada Basin. Such crust abducted southward below the Tobago terrane in mid-Cenozoic time, probably taking up boundary-normal shortening during oblique collision of the Ca and SA plates. The oceanic crust of the GB terrane arose by backarc spreading of unknown orientation. The St. Vincent terrane extends north in the Antilles from St. Vincent; it is defined by thick crust, perhaps an old arc basement. The Araya-Margarita terrane is a probable subduction complex of Mesozoic age of metamorphism that has been transported far eastward from an unknown site with the Ca plate.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.