URUGUAYAN OFFSHORE BASINS
Three basins are recognized in offshore Uruguay: Punta del Este, Pelotas (southern portion) and Oriental del Plata. These basins are genetically related to the Western Gondwana breakup, produced near 130 Ma ago, and the subsequent development of the Atlantic Ocean.
The Punta del Este Basin is a NW-SE trending aborted rift, perpendicular to the continental margin, whereas the Pelotas Basin belongs to the flexural border of a precursor rift structure. Since the Paleocene both basins start functioning as a single sedimentary environment. The Oriental del Plata Basin develops in ultradeep waters, over a basement of transitional and oceanic crust.
The fifteen new areas defined for Uruguay Round II range from shallow to ultradeep waters, in the three Uruguayan offshore basins.
TECTONIC AND STRATIGRAPHIC EVOLUTION
The stratigraphy of Uruguayan offshore basins is represented by large depositional sequences, which overly both Paleozoic sedimentary rocks and Precambrian crystalline basement rocks. The synrift sequence (Jurassic-Neocomian) include aluvio-fluvial and lacustrine deposits, interbedded with volcanic rocks. The post-rift sequence starts with a transgressive transitional sequence (Barremian-Aptian), followed by regressive deposits (Late Cretaceous). During the Cenozoic the sedimentation is controlled by eustatic oscillations of sea level, corresponding to regressive and transgressive deposits in the Paleocene, regressive deposits in the Eocene-Oligocene, transgressive deposits in the Miocene, deltaic progradations in the Mio-Pliocene, and transgressive deposits since the Pleistocene.
DEPOCENTER MIGRATION
Recently it has been realized that, during the Cretaceous-Paleogene evolution of the basins, there was an important depocenter migration, which has bearings in the petroleum system and hydrocarbon potential of the offshore basins. The main depocenter of the Cretaceous postrift sequence is located in the Punta del Este Basin, while the depocenter of the Cenozoic postrift sequence corresponds to the Pelotas Basin.
