Abstract

The Malvinas Basin is one of the few basins on the Argentine continental shelf that contains a proven petroleum system; however, uneconomical oil discoveries keep the basin at a frontier exploration status. The Malvinas Basin evolved through three main tectonic phases: rift, sag, and foredeep. The sedimentary fill of the basin is closely related to its tectonic history. Middle Jurassic rifting resulted in north-northwest-oriented grabens that filled with volcanic and pyroclastic continental rocks. Diminished faulting and generalized subsidence during the Late Jurassic-Neocomian early sag phase were accompanied by deposition of a basal transgressive marine wedge. The Aptian-Maastrichtian interval was characterized by tectonic quiescence and deposition of offshore mud-prone sediments. Southerly localized early Paleogene transtensional tectonism accompanied the early development of a foredeep trough. Outer shelf glauconite-rich sandstones, basinal claystones, and localized carbonate buildups partially filled the basin. By the middle Eocene-Oligocene, a strong deepening event marked the initiation of the foredeep sensu stricto phase. This phase resulted in the full development of the Malvinas foredeep and the formation of compressional structures in the foreland. The foredeep basin was replenished by a westerly derived offlapping siliciclastic wedge of Oligocene-Miocene age. Noncommercial hydrocarbon discoveries in 5 of the 17 wells drilled in the basin suggest the presence of an undercharged Lower Inoceramus-Springhill petroleum system.

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