The Cambrian System in Northwestern Argentina: stratigraphical and palaeontological framework

Abstract

Cambrian sequences are widespread in the early Paleozoic of the Central Andean Basin. Siliciclastic sediments dominate these sequences although several minor occurrences of carbonates and volcanic rocks have been observed. The rocks assigned to the Cambrian System in NW Argentina are recognized in the Puna, Eastern Cordillera, Subandean Ranges and the Famatina System. This paper gives a general overview of the Cambrian formations outcropping in the northern provinces of Jujuy, Salta, Tucumán, Catamarca and La Rioja. Special emphasis has been given to the stratigraphical and biostratigraphical framework of the sequences. Late Precambrian-Early Cambrian thick sedimentary wackes dominate the basal Puncoviscana Formation (s.l.), characterized by a varied ichnofauna that includes the Precambrian-Cambrian transitional levels. Thick packages of sandstone facies characterize the overlying highly ichnofossiliferous Mesón Group. A rich shelly fauna included in sandstones, shales and volcaniclastics, dominate in the Cambrian-Ordovician transitional levels of the overlying Cambro-Ordovician Santa Victoria and Cachiyuyo Groups. Palaeogeographic aspects dealing with the position and development of Cambrian basins are discussed. Several synthetic biostratigraphic tables are presented displaying the known record for the Cambrian System, including the transitional levels to the lowermost Ordovician in the above-mentioned regions.