| Santa Juana Formation | |
| Type: | Geological formation |
| Period: | Carnian |
| Age: | Carnian ~ |
| Prilithology: | Conglomerate, sandstone, siltstone |
| Otherlithology: | Arkosic sandstone, mudstone, volcanic rock, anthracite |
| Namedfor: | Santa Juana |
| Namedby: | Ferraris |
| Year Ts: | 1981 |
| Region: | Bío Bío Region |
| Coordinates: | -37.2°N -73°W |
| Paleocoordinates: | -53.8°N -39.9°W |
| Subunits: | Talcamávida-Gomero, Unihue & Quilacoya Members |
| Overlies: | Coastal Batholith of central Chile |
| Thickness: | Unknown |
Santa Juana Formation a Late Triassic (Carnian stage) sedimentary rock formation near Santa Juana in the lower course of the Biobío River in south-central Chile.[1] Lithologies range from conglomerate sandstone, arkosic sandstone, siltstone and mudstone.[2]
The sediments that consolidate into the rocks of the formation deposited in alluvial, fluvial, lacustrine and playa lake environment. Overall, the formation is rich in plant fossils.[2]
The formation was deposited over the rocks of the Coastal Batholith of central Chile in a sedimentary basin that formed along the Gastre Fault. It has been posited that the basin developed as a rift during the early break-up of Gondwana in the Triassic.[2]
The following fossils have been reported from the formation:[1]