Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.    All Rights Reserved.
 

From the Cambrian to Late Jurassic, the basins and arches of southern South America were oriented approximately north-south. Subsequently, southwest-northeast trending stresses related to the breakup of Gondwana and the opening of the South Atlantic imposed new structural alignments, the effects of which were widespread. These two tectonic regimes encompass six stages of basin formation:
 

* Cambrian-Middle Devonian terrigenous clastics, carbonates, and intrusives occurred along the western edge of the Brazilian, Puna, and Pampas shield areas.

* Carboniferous-Late Jurassic sedimentation in the intracratonic rifts was mainly of continental origin. Marine clastics accumulated in a foreland basin in front of a volcanic arc on the western edge of the continent. This period ended with the Late Jurassic breakup of Gondwana and extrusive magmatism.

* Late Jurassic extension marked by widespread marine flooding affected vast regions of the continent. Clastics, evaporites, and acidic volcanics constitute the "Andean foreland" succession which was associated with a volcanic arc system. In Patagonia, acidic volcanics covered the North Patagonia massif and Deseado craton and earlier basins. 

* After breakup, sedimentary prisms formed along the Atlantic margin on the western margin. Thick sequences of shales, limestones, evaporites, and pyroclastics were associated with middle-Late Cretaceous volcanic arc and back-arc settings. New acidic intrusions and the Andean batholith are also dated to this period.

* The Late Cretaceous-early Tertiary (Laramide) was marked by development of the Andean fold and thrust belt and final emplacement of the Andean batholith. A flexural foreland basin formed in front of the Andes. Passive margin sedimentation dominated the eastern margin.

* The Tertiary was a time of Andean mountain building and passive margin subsidence. The thrust belt supplied thick sedimentary fills to the foreland basin. Shallow transgressions covered much of Patagonia and the Pampa plains. 
 

This tectonic evolution is expressed in a complex array of composite basins. These tectonic, structural, and depositional patterns were also responsible for a suite of petroleum systems, many of them commercially significant.