Abstract: Tectonic and Stratigraphic Controls of Hydrocarbon Systems of the Sub-Andean Fold-Thrust Belt and Associated Basins of South America

CHUCHLA, RICHARD J., and CARLOS A. DENGO

The Sub-Andean (SA) fold-thrust belt and associated foreland basins, from eastern Venezuela to the southern tip of Argentina, represent one of the world's most prolific hydrocarbon provinces. Common to SA hydrocarbon systems is late Tertiary deformation which is responsible for structural traps, migration pathways and the tectonic load which drove subsidence and source maturation. Classic asymetric foreland basins trapped large volumes of hydrocarbons expelled from the fold-thrust belt. Foreland deformation was controlled by inherited basement fabric, late Tertiary stress orientation and the geometry of the subducted slab.

The local Paleozoic / Mesozoic tectonic histories of the South American continent were important in defining the hydrocarbon systems of the SA. The passive margin setting which developed over a Jurassic to Early Cretaceous rifted margin allowed deposition of oil-prone, Upper Cretaceous source rocks from Venezuela to northern Peru. The central SA segment developed over a west-facing Paleozoic passive margin and foreland basin which accomodated source rocks responsible for large gas-condensate accumulations. Opening of the South Atlantic created half-grabens in the southern segment of the SA in which important Mesozoic lacustrine and marine source rocks were deposited.

SA structural architecture manifests both thin-skinned deformation, from Colombia to central Peru and central to southern Argentina, and basement-involved inversion of Mesozoic grabens. The intervening segment is characterized by more continuous pre-Tertiary stratigraphy resulting in efficient detachment surfaces, thin-skinned deformation and folds of great strike length.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria