| Los Colorados Formation | |
|---|---|
| Stratigraphic range: Norian ~ | |
 Los Colorados massif, La Rioja Province, Argentina | |
| Type | Geological formation |
| Unit of | Agua de la Peña Group |
| Underlies | Cerro Rajado Formation |
| Overlies | Ischigualasto Formation |
| Thickness | 600 m (2,000 ft) |
| Lithology | |
| Primary | Sandstone, siltstone, mudstone |
| Other | Conglomerate, gypsum |
| Location | |
| Coordinates | 29°48′S 67°54′W / 29.8°S 67.9°W |
| Approximate paleocoordinates | 38°54′S 31°24′W / 38.9°S 31.4°W |
| Region | San Juan Province La Rioja Province |
| Country | Argentina |
| Extent | Ischigualasto-Villa Unión Basin |
| Type section | |
| Named for | Los Colorados Massif |
  Los Colorados Formation (Argentina) | |
The Los Colorados Formation is a sedimentary rock formation of the Ischigualasto-Villa Unión Basin, found in the provinces of San Juan and La Rioja in Argentina. The formation dates back to the Norian age of the Late Triassic.
The up to 600 metres (2,000 ft) thick formation comprises sandstones, siltstones, mudstones and conglomerates with gypsum layers deposited in a fluvial to lacustrine environment. The formation is the uppermost stratigraphic unit of the Agua de la Peña Group, overlying the Lagerstätte of the Ischigualasto Formation. Los Colorados Formation is partly covered by the Cretaceous Cerro Rajado Formation, separated by an unconformity.
The formation is known for its fossils of early dinosaurs, including the coelophysoid Zupaysaurus and the "prosauropods" Coloradisaurus, Lessemsaurus, and Riojasaurus.[1] Magnetostratigraphic analysis suggests that the Los Colorados Formation was deposited between 227 and 213 million years ago.[2]