| Cerro Negro Formation | |
| Type: | Formation |
| Period: | Ediacaran |
| Age: | Ediacaran < |
| Prilithology: | Shale, sandstone |
| Otherlithology: | Marl |
| Region: | Buenos Aires Province |
| Country: | Argentina |
| Coordinates: | -37.2012°N -60.3467°W |
| Unitof: | La Providencia Group Tandilia System |
| Underlies: | Balcarce Formation |
| Overlies: | Sierra Bayas Group |
| Thickness: | >150m (490feet) |
| Extent: | Río de la Plata Craton |
The Cerro Negro Formation is a sedimentary formation of Ediacaran age in Buenos Aires Province, Argentina. The formation crops out along the Tandilia System, a chain of hills made up by of ancient rocks. Together with the formations of the underlying Sierra Bayas Group it is contains the oldest sedimentary formations in Argentina that have not been subject to significant metamorphism or deformation. In 2015 a complete revision of the formation was proposed.[1]
Soft-bodied discoidal specimens resembling Aspidella are described from the formation, that has been estimated as not older than 565 Ma.[2]