Chapter 6 The Pampean Orogen: Ediacaran-Lower Cambrian Evolutionary History of Central and Northwest Region of Argentina

Abstract

The Ediacaran-Lower Cambrian Pampean Orogen comprises a large area in northwest Argentina, which formed the western margin of Gondwana. This orogen evolved from an aulacogenic structure, which determined the outline of the large ‘Puncoviscana Basin’. This basin was bounded by the Meso- to Neoproterozoic cratonic areas of the Rio de la Plata, Guaporé (West Amazonia), and the ‘Arequipa Terrane’. A thick siliciclastic succession with subordinate carbonates and conglomerates was deposited. Body and trace fossils occurring in the siliciclastic sequence allow to assign it to the Ediacaran-Lower Cambrian. Carbon isotopes show that limestones represent different stratigraphic levels. Radiometric ages show that the deformational event F1 and the metamorphism M1 and M2 range from Lower to Middle Cambrian. Detrital zircon ages indicate a close relationship with the peripheral shield rocks. Current evidence supports an autochthonous origin for the Pampean Orogen, contrasting with other ideas supporting an assumed exotic block that collided with West Gondwana.