Tectono-Stratigraphic evolution of a study area in the Northern Ecuadorian Forearc Basin

Abstract:

The Cretaceous to Neogene tectonic history of the northwestern margin of South America, involving accretion and interactions between the Caribbean and South American plates, is complex. This history has been widely studied in the central and northern parts of Colombia from subsurface and surface data. In Ecuador, geochemical and geochronological studies have provided a framework for interpretations of 2D paleotectonic evolutions. In spite of this, there is still uncertainty regarding the tectonic history of this margin with anywhere from 1 to 3 collisions having been proposed to occur since the Cretaceous. Even though there are some studies from the Manabi and Progreso basins in the southern Ecuadorian forearc, tectono-stratigraphic studies proposing 4D paleotectonic reconstructions are missing in the literature. In this work we use a dense set of industry seismic lines, combined with well data and outcrop analysis from the northern Ecuadorian forearc basin, specifically from the Esmeraldas and Borbon basins, to carry out such a study. With this data, several sub-basins, some with up to 6 km of strata that form six tectono-stratigraphic sequences have been recognized. We infer that these sequences are related to the following tectonic processes: 1) accretion of an island arc during the Late Cretaceous; 2) formation of strike-slip basins due to a rapid convergence in the active margin during the Middle and Late Eocene; and 3) strong subsidence due to ridge subduction in the Neogene. The results of our study are of great relevance for any future interpretation related to the interactions between the Caribbean, Nazca and South American plates.