Abstract: The Southern South American Margin Basins and Petroleum Systems

Urien, C. - U&A, Argentina; Gamundi, O. L. - Texaco; Fryklund, B. - Union Texas Petroleum; Kozlowski, E. - Panam, Argentina

The margin underwent repeated deformations as a result of plate activity over the course of geologic time. Suturing of microcontinents produced, toward the end of the Paleozoic, extended orogeny through the Cape province and Buenos Aires Southern Hills. Different tectonic alignments were superimposed on previously deformed basement rock, so that today, the margin is a mosaic of earlier plate fragmentation and accretions. Continued sinistral displacement along east-west- trending sutures, broke the broad "platform" into multiple structural basins. Sedimentation in these basins, as in the proto-Atlantic, may have begun in small sag ponds that evolved into pull-apart basins and half-grabens, as transform segments passed each other in crustal extension episodes which had a major role in localizing the Atlantic rifted margins and the Late Jurassic-Neocomian basins. By the end of the Rio Grande orogeny (150 Ma.), the Gondwana Platform began to be dissected by a series of E-W trending, left lateral fractures. Subsequent continental breakup is influenced largely by tensional forces along the proto-Atlantic axis, displaying both sheared and rifted structures, compensated by wrench tectonics in the northern Malvinas Plateau and Agulhas, and by extension into Patagonia, up to the south Brazilian Shield. Its stratigraphic history is reconstructed from the sedimentary record in the rift-postrift basins, extending across the Patagonian Margin. Since the breakup, the continent went through the following stages: (1) rift, continental detritic, (2) sag, continental-coastal-shallow marine, (3) passive margin stages, marginal. neritic-slope. These basins and the underlying terranes, provide important clues for interpreting the onshore-offshore Mesozoic and Cenozoic Petroleum Systems and their distribution.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil