Lower plate retreat and opening of a Cretaceous forearc basin, Northern Andes

The tectonic setting of the Northern Andes is delineated fundamentally by a western oceanic terrane that was juxtaposed to the continental margin along the now fossilized interandean Romeral suture since the Early Cretaceous. This constellation and the connection to the Caribbean Large Igneous province have been attributed to a far-travelled and now partially subducted, formerly coherent terrane with a trailing edge represented by the Panama-Choco block. A former disconnection between oceanic terrane and South American plate may, however, be contended by considering continental provenance data of siliciclastic and volcanic rock units and a widely distributed geochemical arc signature of the effusive rock series. Moreover, the emplacement of the basic igneous sequences was strongly controlled by extensional tectonics and subduction correlates in its lifetime with the production of oceanic crust, suggesting a coupling between intrusive activity and convergence. In this contribution, we examine apparently conflicting structural deformations that may be reconciled, however, with the opening of a forearc basin and a deformational imprint that affected extensively the continental margin, supposing the existence of a subduction system composed of two continentward dipping slabs.