Type Stratigraphic group Other Diamictite Region Buenos Aires Province | Overlies Buenos Aires Complex Country Argentina | |
Underlies Cerro Negro Formation
Balcarce Formation Primary Limestone, shale (inc. argillite), quartzite, dolomite, quartz-arkose | ||
Sierra Bayas Group is a sedimentary group of Neoproterozoic age in Buenos Aires Province, Argentina. The group crops out in the central and northwestern parts of the Tandilia System, a chain of hills made up by of ancient rocks. The nearby Cerro Negro Formation aside, Sierra Bayas Group contains the oldest sedimentary formations in Argentina that have not been subject to significant metamorphism or deformation. It was formerly grouped together with Cerro Negro Fromation and the Ordivician Balcarce Formation into La Tinta Group. Sierra Bayas Group and the former La Tinta Group have equivalents in Southern Africa, in La Tinta Group in particular is considered equivalent to the Nama Group found in Namibia and South Africa. From top to bottom Sierra Bayas Group is subdivided Loma Negra, Olavarría, Cerro Largo, Colombo and Villa Mónica formations. Sierra Bayas Group has a thickness of 175 meters and the age its rocks range from Tonian to Ediacaran.