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South America and Southern Africa
Devonian Paleogeography of South America
Principal occurrences of Devonian rocks in South America are: (a) along the Andes, from Venezuela through Colombia, southern Peru, Bolivia, Chile and Argentina; and (b) in the intracratonic basins of Brazil, Paraguay, Uruguay and Argentina. Exposures of Devonian strata usually occur in geographically limited areas widely separated from each other. Most of the Devonian rocks are dated as late Emsian to Givetian.
Lithofacies and faunal patterns suggest that sedimentation occurred around the Precambrian shield areas in an epeiric setting in central South America (Amazon, Parnaiba and Parana Basins) and in an epeiric or marginal-basin setting along the western margin of the continent. Faunal assemblages and lithofacies indicate that most of the Devonian sequences were deposited in subtidal marine environments. The faunas also delineate two major marine biogeographic provinces: a northwestern area (Colombia-Venezuela) with affinities to eastern North America and a southern area (Bolivia-southern Brazil-Argentina) with an endemic, probably cold-water fauna.
The Devonian paleolatitude of the northern part of South America was 30 to 40 degrees south; the southern part of the continent was in south-polar latitudes. Evidence for these paleolatitudes includes paleomagnetic data from other parts of Gondwanaland (of which South America formed the western margin), paleobiogeographic relationships and paleoclimatic indicators.
The tectonic framework of the Devonian western margin is unclear. South of central Chile a compressive margin may have existed, as indicated by a history of intermediate-composition plutonism presumably produced by subduction. However, north of central Chile no evidence (plutonic or volcanic rocks from a magmatic arc, subduction-accretion complexes or ophiolite sequences) exists for a compressive margin during the Devonian. A Late Devonian unconformity, widespread throughout the Andean portion of South America and locally angular, may have a tectonic origin.
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