Abstract: The Palaeogeographical Evolution of the South Atlantic: An Integrated Regional Study Based on South American, African and Antarctic Data

Myron P. Maslanyj, Malcolm P. R. Light, Martin L. Keeley, Carlos M. Urien

With increasing interest in the hydrocarbon prospectivity of offshore South America, Africa and the Falkland/Malvinas Islands a palaeogeographical study of the South Atlantic has been undertaken in order to investigate the development of hydrocarbon bearing basins. The study focuses on integrating geological and geophysical data from South America, Africa and Antarctica. Several problems related to space constraints and conflicting structural trends have hampered reconstructions of the Gondwana supercontinent. These have been compounded by sparse and often conflicting evidence from West Antarctica where large scale movement of crustal blocks has been proposed. Comparison of palaeogeographic trends between the three continents has given new insights into the structural evolution of Wes Gondwanaland and distribution of potential source and reservoir rocks from Cambrian to Recent times. Prior to and during the initial stages of break-up, the supercontinent was dominated by processes related to subduction/accretion. In South America during the Palaeozoic oblique subduction along the Pacific margin facilitated northwest shearing and stacking of terranes. By the Late Carboniferous to early Permian the Main Karoo Basin developed into a contractional foreland basin. A rift system developed east of the Patagonian "Outer Basement Ridge." Continental basins developed when the Patagonia plate underwent dextral strike-slip deformation along northwest fractures prior, during and after the Gondwanide Orogeny. Widespread crustal failure and shearing in central Gondwanaland during th Cape Orogeny is attributed to the effects of an indentor accreting along the Pacific margin of the supercondnent. The abrupt trend changes and shearing in the Gondwanide Fold Belt can be explained by intense deformation generated in the core zones of large concentric folds which also produced regions of uplift represented by the Cape Syntaxis, Falkland Islands, Alexander Island and Ellsworth Mountains-Haag Nunataks.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994