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

A major characteristic of the oil industry is that geologic data tend to be kept within each company. In South America, where state-owned companies and exploration monopolies predominate, there are many datasets and many different interpretations. These "virgin" data constitute a valuable basis for assembling a correlation study across the continent. The authors of this paper are making probably the first attempt to put together extensive, previously unavailable information and present it to the geologic community.

The geology of Gondwana is strikingly different from the geology of Laurasia. Gondwana basins tend to be dominated by siliciclastics, whereas northern hemisphere basins are rich in limestones. This largely reflects the cold climate that predominated in Gondwana during most of the Paleozoic. Thick diamictites and sandstones deposited during glaciation in the Carboniferous-Permian are widespread in the Gondwana of South America. These sandstones are the principal reservoirs in the Bolivian and northwestern Argentinian gas fields. Gas and condensate in these fields are sourced from the underlying Devonian black shales.

A regional unconformity on top of the Devonian shales played an important role in oil migration into overlying beds in Bolivia and Argentina. Structural traps created during the Hercynian orogeny, and later during the Andean orogeny, were also important for hydrocarbon accumulation near the Cordillera de Los Andes. A huge area east of the Andes is still a frontier area. This includes the Paraná and Chaco-Paraná basins in Brazil, Paraguay, Uruguay, and Argentina, covering an area larger than 1.7 million km². There are fewer than 200 exploration wells drilled in these basins.