Cenozoic stratigraphy of the southern Salar de Antofalla region, northwestern Argentina

Abstract

In the region of the southern Salar de Antofalla (Catamarca Province, northwestern Argentina), Late Eocene to Pliocene/(?)Pleistocene successions are exposed with thicknesses of up to 1,600 m. They consist of fluvial, lacustrine and eolian sediments with intercalations of pyroclastic rocks and lava flows. The sedimentary deposits represent 'alluvial fan-playa-complexes' accumulated under a semi-arid to arid climate. From the Late Eocene to the Early Miocene, the sedimentation took place in broken-foreland basins, while from the Early Miocene to the Late Pliocene/(?)Early Pleistocene, the sediments mainly accumulated within compressional retroarc basins in which volcanoes partly formed additional basin boundaries. Seven stratigraphic units can be differentiated on the basis of different lithofacies, angular unconformities and different regional distributions: the Late Eocene to Early Miocene Quiñoas Formation, which can be subdivided into the Campo Negro Member, the Cadillo Member and the Aguada Member, the Early/(?)Middle Miocene Potrero Grande Formation, the Late Miocene Antofalla Formation, which can be subdivided into the Cajeros Member and Bordo Blanco Member, the Late Miocene Salina beds, the Late Miocene Pozuelos Formation (Orilla Member), the (?)Late Miocene/Early Pliocene Sijes Formation (Uncal Grande Member) and the Late Pliocene/(?)Early Pleistocene Singuel Formation (Agua Escondida Member). While the Quiñoas Formation, the Potrero Grande Formation, the Antofalla Formation and the Salina beds have been newly introduced, the strata which represent the other formations can be assigned to the existing stratigraphic division of the southern Puna. Owing to the fact that these strata had no lateral connection to the strata of their type localities, which crop out near the Salar Pastos Grandes, they were defined as lateral members.