# Golfo San Jorge Basin

The Golfo San Jorge Basin (Spanish: Cuenca del Golfo San Jorge) is a hydrocarbon-rich sedimentary basin located in eastern Patagonia, Argentina. The basin covers the entire San Jorge Gulf and an inland area west of it, having one half located in Santa Cruz Province and the other in Chubut Province. The northern boundary of the basin is the North Patagonian Massif while the Deseado Massif forms the southern boundary of the basin. The basin has largely developed under condition of extensional tectonics, including rifting.
The basin is of paleontological significance as it hosts six out of 22 defining formations for the SALMA classification, the geochronology for the Cenozoic used in South America.
At the center of the basin accumulated sediments reach more than 8,000 metres (26,000 ft) of thickness. Oil was first discovered in 1907 and over the years it has become the second most productive hydrocarbon basin in Argentina after Neuquén Basin.

## Stratigraphy

The stratigraphy of the Golfo San Jorge Basin covers the following units:
| Unit | Unit | Age bold is SALMA type | Tectonic regime | Depositional environment | Thickness (m) | Petroleum geology |
| Tehuelche Shingle | Tehuelche Shingle | Pleistocene | | Glacio-fluvial | 40 | |
| Río Mayo | Río Mayo | Mayoan | | | | |
| Santa Cruz | Santa Cruz | Santacrucian | | Fluvio-deltaic | 200 | |
| Patagonia | Patagonia | Santacrucian | | Shallow marine | 280 | |
| Sarmiento Colhué Huapí Mb. Chenque | Sarmiento Colhué Huapí Mb. Chenque | Colhuehuapian | | Fluvio-lacustrine | 120 | |
| Sarmiento Colhué Huapí Mb. Chenque | Sarmiento Colhué Huapí Mb. Chenque | Deseadan | | Fluvio-lacustrine | 120 | |
| Sarmiento Colhué Huapí Mb. Chenque | Sarmiento Colhué Huapí Mb. Chenque | Tinguirirican | | Fluvio-lacustrine | 120 | |
| Río Chico | Koluel Kaike | Divisaderan | | Lacustrine | 42 | |
| Río Chico | Koluel Kaike | Mustersan | | Lacustrine | 42 | |
| Río Chico | Casamayor Las Flores | Casamayoran | | Fluvio-lacustrine | 44 | |
| Río Chico | Peñas Coloradas | Riochican | | Fluvial | 42 | |
| Río Chico | Peñas Coloradas | Itaboraian | | Fluvial | 42 | |
| Río Chico | Las Violetas | Peligran | | Fluvial | 25 | |
| Salamanca | Salamanca | Peligran | | Shallow marine-deltaic-fluvial | 200 | Petroleum reservoir |
| Salamanca | Salamanca | Tiupampan | | Shallow marine-deltaic-fluvial | 200 | Petroleum reservoir |
| Lago Colhué Huapí | Lago Colhué Huapí | Maastrichtian Campanian | | Fluvial | | Petroleum reservoir |
| Yacimiento El Trébol Meseta Espinosa Bajo Barreal Laguna Palacios | Yacimiento El Trébol Meseta Espinosa Bajo Barreal Laguna Palacios | Santonian Aptian | Late sag | Deltaic Fluvio-lacustrine | 4000+ | Petroleum reservoir |
| Cañadón Seco Comodoro Rivadavia Bajo Barreal | Cañadón Seco Comodoro Rivadavia Bajo Barreal | Santonian Aptian | Late sag | Alluvial-fluvial-lacustrine | 4000+ | Petroleum reservoir |
| Mina El Carmen Castillo | Mina El Carmen Castillo | Santonian Aptian | Late sag | Fluvio-lacustrine | 4000+ | Petroleum reservoir |
| Pozo D-129 Matasiete | Pozo D-129 Matasiete | Santonian Aptian | Early sag | Fluvio-lacustrine | 1500+ | Source rock and petroleum reservoir |
| Pozo Cerro Guadal | Pozo Cerro Guadal | Neocomian | Late rift | Fluvio-lacustrine | 560 | |
| Pozo Anticlinal Aguada Bandera | Pozo Anticlinal Aguada Bandera | Neocomian | Late rift | Lacustrine | 1700+ | Source rock |
| Bahía Laura Lonco Trapial | Cerro Carnerero | Mid-Late Jurassic | Early rift | Volcaniclastic | 1300+ | |
| | | Early Jurassic | Pre-rift | Shallow marine | 700+ | |
| Basement | Basement | Paleozoic | | | | |