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 fore-deep 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.
