Upraised Caribbean sea floor below acoustic reflector B" at the southern peninsula of Haiti

Abstract

The Dumisseau Formation, is described-as a complex of intercalated mafic and pelagic rocks of Cretaceous age exposed at the southern Peninsula of Haiti. This formation includes a lower member of possibly Early cretaceous age, and the St. Dominique Member of Late cretaceous age. Their thickness exceeds 1,5 km, and the igneous rocks show geochemical affinities for abyssal and island arc tholeiites, which accumulated in a deep eupelagic environment. The formation is here equated to an ophiolite complex described earlier by Miyashiro, and to crustal layers (2A and 2B) described by Houtz & Ewing. Correlations between the Dumisseau Formation and geophysical data concerning the crustal structure and composition of both the Caribbean crust and oceanic crust provide corroborative evidence to suggest that the analog of crustal materials below acoustic reflector B". The Dumisseau Formation thus represents a portion of the Caribbean crust uplifted through block faulting tectonism much similar to the adjacent Beata Ridge.