Geometría y estructuras de la cuenca neógena de Loja a partir de datos gravimétricos (Andes Ecuatorianos)

Abstract

The recent tectonic evolution of the central Andes is driven by the subduction of the oceanic Nazca plate below the South America continental crust. This process has produced relief uplift and the isolation and deformation of intramontane retroarc foreland basins. In this setting, the Loja Basin is a N-S elongated and asymmetrical syndine infilled by sediments since the Middle-Late Miocene. While the western area only has undergone eastwards tilting with low dips, the eastern sector is affected by large open N-S folds and by an eastward verging reverse fault zone, several hundreds of meters wide. New gravity measurements constraints the geometry of the sedimentary infill, indicating maximum thickness displaced eastwards in respect to the central axis of the basin, probably as consequence of the activity of reverse faults. These data reveals the progressive development of eastwards verging structures at the shallow crustal Andean orogenic wedge since the Miocene