Thick-skinned tectonics in the Oriente foreland basin of Ecuador

Abstract

Abstract The Oriente Basin is part of the retro-arc foreland basin system that developed in the zone of transition between the Central Andes and the Northern Andes since Late Cretaceous times. It is deformed by thick-skinned tectonics related to the inversion of pre-Cretaceous extensional fault systems, which have broken the basin into three tectonic domains during three mean periods of inversion (Late Cretaceous–Palaeocene, Early Eocene and Miocene). The northern part of the present-day Sub-Andean wedge-top corresponded, during the Late Cretaceous, to the forebulge depozone. The NNE–SSW Sacha–Shushufindi Corridor (SSC) extends from the northern region of the Oriente foredeep to the Sub-Andean Cutucú Cordillera. It results from inversion of the Late Triassic–Early Jurassic rifting. The eastern Capiron–Tiputini Inverted System (CTIS) results from the inversion of the normal faults of the Late Jurassic back-arc basin. The Ishpingo–Tambococha–Tiputini (ITT) trend is located in the present-day forebulge depozone of the basin. This position presents favourable conditions for oil biodegradation. Source rocks throughout the Oriente Basin are immature or poorly mature. A large part of oil accumulations must be explained by long-distance migration from the west, before the Eocene uplift of the Cordillera Real, or from the south.