MODELLO

The southern margin of the Caribbean plate, cropping out in the Venezuela belt, consists of an assemblage of four main terranes: the Dutch-Venezuelan Islands, Margarita Island, Cordillera de la Costa and Serrania del Interior. These terranes have been located, since the mid-Cretaceous, along the transform boundary between the Caribbean and South American plates.
The magmatic, tectonic, and metamorphic histories of these terranes are able to provide valuable constrains for the evolution of the southern Caribbean. The collected data suggests a Middle Jurassic-Early Cretaceous location of these elements in a westernmost, "near mid-America" position, almost at the north-western corner of the South American plate. Starting from the mid-Cretaceous, the elements have been affected by a right-oblique convergence along the transform boundary connecting the two oppositely-dipping subduction zones of the Andes and Aves-Lesser Antilles. According to the geological constraints, three possible geodynamic scenarios can be proposed for the beginning of the convergence during mid-Cretaceous, taking into account the different locations of the free boundaries in the geodynamic setting of the southern Caribbean. The collisional belt, resulting from the mid-Cretaceous tectonics, have been dissected in different terranes, progressively rotated clockwise, juxtaposed to each other, and then eastward displaced. The geodynamic framework was closely related to the progressive eastward motion of the Caribbean plateau which, in turn, was associated with the development of a W/S-W dipping, intra-oceanic subduction of the proto-Caribbean oceanic crust below the plateau, and related island-arc calc-alkaline magmatism, today preserved in the Dutch-Venezuelan Islands and Aves-Lesser Antilles. At that time, the terranes were already emplaced onto the South America continental margin. Northward, the dextral strike-slip tectonics of the Caribbean southern margin increasingly involved the southern part of the magmatic arc, which gradually became inactive, and underwent a progressive rotation clockwise. Since the Late Paleocene, the whole marginal belt was already completely identifiable with the large shear zone occurring today at the transform boundary between the Caribbean and South American plates.