Stratigraphy and sedimentology of the Neogene deposits of Puchuzum, San Juan, Argentina

BRACCO, A.; LEÓN, L.; PRÁMPARO, M.B.; CERDEÑO, E; CONTRERAS, V.H.

Cenozoic Geology of the Central Andes of Argentina

Universidad Nacional de Salta

Lugar: Salta; Año: 2009;

The Neogene continental sequence examined in this paper crops out in the Candelaria creek section, Puchuzum area, on the eastern slope of the Frontal Cordillera north of  Calingasta village in San Juan Province. This 350-m-thick sequence is composed of conglomerates, sandstones, pelites, limestones and gypsum levels. Sedimentological and stratigraphical features together with fossil content have allowed recognition of four facies associations, A, B, C and D, developed on alluvial, fluvial, and lacustrine systems deposited during the uppermost late  Miocene to Pliocene. Associations A and B  are related to distal deposits of alluvial fans together with fluvial systems of meandering rivers  and wide flooding plains. Associations C and D correspond to a shallow lacustrine facies. The increase in the gypsum and clay (montmorillonite) rate, as well as the pollynic content of angiosperms suggest arid to semiarid climatic conditions. After the lacustrine facies deposition, detritic sediments of alluvial origin which are not described in this work were deposited. Ichnofacies and paleomicrofloras must be mentioned in order to note their paleoenvironmental significance aside from the biocronoestratigrafic significance of paleomicrofloras.