Neuquén Basin
Neuquén Basin () is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The basin bounds to the west with the Andean Volcanic Belt, to the southeast with the North Patagonian Massif and to the northeast with the San Rafael Block and to the east with the Sierra Pintada System. The basin covers an area of approximately . One age of the SALMA classification, the Colloncuran, is defined in the basin, based on the Collón Curá Formation, named after the Collón  Curá River, a tributary of the Limay River. Description. Jurassic and Cretaceous marine transgressions from the Pacific are recorded in the sediments of Neuquén Basin. These marine sediments belong to Cuyo Group, Tordillo Formation, Auquilco Formation and Vaca Muerta. In the Late Cretaceous, conditions in the neighboring Andean orogeny changed. A marine regression occurred and the fold and thrust belts of Malargüe (36°00 S), Chos Malal (37° S) and Agrio (38° S) started to develop in the Andes and did so until Eocene times. This meant an advance of the Andean orogenic deformation since the Late  Cretaceous that made the western part of Neuquén Basin to stack in the Malargüe and Agrio fold and thrust belts. This caused a shift in deposition from Pacific to Early Atlantic. In the south of Mendoza Province, the Guañacos fold and thrust belt (36.5° S) appeared and grew in the Pliocene and Pleistocene consuming the western fringes of the Neuquén Basin. Tectonics. The Huincul basement high or Huincul ridge () is a geological structure that divides Neuquén Basin in two parts. The basement high is one of the most studied features of Neuquén Basin given its importance for hydrocarbon exploration  and exploitation. All over the basement high runs an approximate length of . There have been proposals on the nature of this structure. In the 1970s and 1980s it was proposed by that it was a transpressive fault zone. In 2009, Pángaro described it as being made up of inverted half-grabens. Unconformities have been registered in the basin and were dated at 98, 117, 123, 129, 134 and 154 Ma. Stratigraphy. The basin contains many stratigraphic units from the Triassic onwards, with large regional variations from east to west and north to south, often described as different formations that are  laterally equivalent, this list is a comprehensive overview of described formations: Petroleum geology. The Neuquén Basin is an important oil and gas producing basin in Argentina. Production started in 1918 and accumulated to of oil equivalent in 2004, representing 45% of the oil production in Argentina and 61% of its gas production. The basin is also important for unconventionals, with the Vaca Muerta and Los Molles formations being major shale gas producers. Source rock formations are predominantly the Vaca Muerta, and to a lesser extent the Agrio and Los Molles Formations. Reservoir rocks comprise the Mulichinco and Chachao Formations. Deeper  reservoirs are the Lotena and Barda Negra Formations. Regional seal rocks are the evaporites of the Auquilco and Huitrín Formations, with local seals the Vaca Muerta, Agrio and Catriel Formations.