Stratigraphic and structural evolution of the western Malvinas and southeastern Magallanes basins, Argentina
Galeazzi, Jose Sebastian
Vail, Peter R.
Master of Arts
The area evolved from a Jurassic rifting stage to a Cretaceous sag and a Tertiary foredeep stage. The sedimentary record is subdivided into four tectonostratigraphic units: Jurassic rift deposits, late-Jurassic-Cretaceous sag deposits, latest Cretaceous-Eocene foredeep-transition deposits, and late Eocene-Pliocene foredeep deposits. The rifts are filled with continental volcanics and pyroclastics. The sag deposits form a backstepping marine wedge, which contains the Springhill Formation (main reservoir) and is covered by a muddy and marly aggradational interval deposited in neritic waters of an epeiric sea (main petroleum source and seal). The latest Cretaceous to Eocene is a forestepping-backstepping wedge of glauconitic sandstones and claystones and carbonate buildups of shallow marine origin. The foredeep deepens during the late-Eocene to Oligocene. It is infilled during the Oligocene-late Miocene by a forestepping wedge that prograded from the west and southwest. The age of the foredeep suggests that the southern Andean Orocline formed during the Paleocene-late Eocene interval.