--> Abstract: Tectono-Sedimentary Evolution Of The Late Cretaceous Napo Formation, Ecuadorian Oriente Basin, South America, by R. Barragan, H. White, P. Baby, M. Rivadeneira, and F. Ramirez; #90928 (1999).

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BARRAGAN, R.1, H. WHITE1, P. BABY2, M. RIVADENEIRA2, and F. RAMIREZ3
1Oryx Energy, Dallas, TX
2Petroproduccion-Orstom, Quito, Ecuador
3Oryx Ecuador, Quito, Ecuador

Abstract: Tectono-Sedimentary Evolution of the Late Cretaceous Napo Formation, Ecuadorian Oriente Basin, South America

The Cretaceous Napo Formation (Cenomain to Campanian) in the Ecuadorian Oriente Basin can be subdivided into five sequence stratigraphic intervals separated by erosional sequence boundaries. Except for the youngest of these intervals, lithofacies deposition and distribution appear to be controlled by relative sea level changes correlative with the global eustatic sea level chart.

Historically, the strong overprint of Neogene Andean tectonics on all pre-existing structures has impeded appreciation of the importance of late Cretaceous deformation in the Oriente Basin. Seismic profiles reveal key distinguishing features of synsedimentary deposition, such as pinch outs, condensed sections, regional thinning and various types of growth structures. Dramatic lithofacies thickness changes within the youngest depositional sequence above the M2 limestone (post Coniacian to Campanian) attest to a widespread early tectonic event resulting in late Cretaceousaged structural movements and traps related to right-lateral wrench-fault zones in a transpressive regime.

Recent integrated analysis of Napo structures and reservoir facies strongly supports the interpretation of late Cretaceous tectonism. The mechanism believed responsible for the synsedimentary deformation is related to the incipient Andean Orogeny marking the beginning of the transition to an active foreland basin along the western margin of the Oriente shelf in Ecuador.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas