Eastbound sublithosphere mantle flow through the Caribbean gap and its relevance to the continental undertow hypothesis

Abstract

Recent evidence indicates that beneath the Caribbean a tongue of sublithosphere mantle is flowing from the Pacific to the Atlantic, dragging the overlying lithosphere eastward: (i) Shear‐wave splitting results from beneath the Andean subduction zone and Venezuela suggest mantle flow eastward through the Caribbean. (ii) Volcanic chemistry in Central America indicates a slab source beneath Nicaragua, but a different source in Costa Rica, above the proposed Pacific outflow. (iii) An extinct volcanic arc accreted to the margins of the Caribbean swept eastward through the Caribbean gap between North & South America. The 1982 ‘continental undertow’ model requires shallow‐mantle flow through the Caribbean gap from the Pacific to the Atlantic, if continents have deep roots and if shallow‐mantle flow beneath oceans is decoupled from convection at deeper levels. The new evidence from the Caribbean is thus compatible with the continental undertow model, and perhaps with other models involving decoupled shallow flow.