El Pre-Aptense En La Cuenca Oriente Ecuatoriana

The present paper describes the structural, stratigraphic and seismic characteristics of the pre-Aptian units of the Oriente Basin. The analysis of lithologic columns from wells as Sacha Profundo-1, Tambococha-1, etc..., and the interpretation of seismic sections allowed us to identify pre-Aptian formations in the central-northern and eastern parts of the Oriente basin. They consist of four seismic units: Unit 1 (Basement); Unit 2 (Paleozoic); Unit 3 (Upp.Tr. - Lw. J.) and the Unit 4 (Mid. J. - Early K.) that includes a new formation named Tambococha Fm. (eastern of the basin). Structural analysis of some structures has permitted to define the tectonic framework of the pre-Aptian basins. Two longitudinal "Back-arc" basins with different structural styles developed from Middle Jurassic to Early Cretaceous. The first one, known as the Corredor Sacha-Shushufindi, was controlled by normal deep faults and corresponds to an aborted Triassic "Rift". The second, known as Sistema Invertido Capirón- Tiputini, was structured by normal listric fault branched on a decollement located in the basement. The pre- Aptian petroliferous system of the Oriente Basin is poor studied. The Santiago Formation seems to be a good source rock, but its distribution in the Oriente basin is not well defined yet.