--> Abstract: Within-Plate Compressional Structures and Oil Occurrence: Western San Jorge Basin, Argentina, by J. Cerdan, L. Legarreta, G. O. Peroni, G. Laffitte, A. Hegedus, and M. A. Uliana; #91012 (1992).

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ABSTRACT: Within-Plate Compressional Structures and Oil Occurrence: Western San Jorge Basin, Argentina

CERDAN, J., L. LEGARRETA, and G. O. PERONI, Astra C.A.P.S.A., Buenos Aires, Argentina, G. LAFFITTE, Yacimientos Petroliferos Fiscales-Exploracion, Buenos Aires, Argentina, and A. HEGEDUS and M. A. ULIANA, Astra C.A.P.S.A., Buenos Aires, Argentina

The San Bernardo ("Bernardides") structural province is a polyphase deformed belt located across the extra-Andean part of the Argentine Patagonia, where it lays distinctly separated from the Patagonian Cordillera, the fold and thrust belt that fringes the western side of the South American plate at 44-48 degrees S. The structured zone encompasses a NNW-SSE-trending band in excess of 600 km long and mostly less than 100 km wide, displaying faults and folds that involve a Precambrian to middle Paleozoic basement, upper Paleozoic to Jurassic sedimentary and volcanic wedges, and the Cretaceous cover. The region is dominated by a structural style featuring discontinuous, narrow and box-shaped folds associated to east- and west-verging reverse faults. Oil finds are restricted to the low-lyi g unbreached segment between the Senguerr and Deseado rivers, where seismic control suggests that the anticlinal structures developed because contractional reactivation of pre-existing normal and strike-slip faults. Dark gray to black Neocomian shales, rich in amorphous organic matter and deposited in saline-alkaline lakes occasionally flooded by marine waters, sourced the Middle-Upper Cretaceous section from beneath, after short distance migration. Pay zones consist of multiple and lenticular fluvial sandstones with modest reservoir properties, regulated by burial diagenesis on volcaniclastic-rich sandstone frameworks.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)