Aseptella-Tuberculatella/Rhipidomella-Micraphelia Fauna (late Serpukhovian-Bashkirian), in the Agua del Jagüel Formation: biostratigraphic and paleoenvironmental implications.

STERREN A.F,; CISTERNA, G.A.; LÓPEZ GAMUNDÍ, O.

Congreso; 11º Congreso de la Asociación Paleontológica Argentina.; 2017

The lower section of the Agua del Jagüel Formation (Calingasta-Uspallata Basin, Mendoza Province), exhibits a distinctive glacial-postglacial transition related with the mid Carboniferous glacial episode identified for this part of Gondwana. A very low diversified invertebrate assemblage composed of brachiopods, bivalves, gastropods and corals has been recognised in this section. The fossils appear very scattered in a mudstone interval about 150 m thick located immediately above of the diamictite-rich deposits. The brachiopod Rhipidomella discreta Cisterna, 2016 and Micraphelia indianae Simanauskas and Cisterna, 2001, accompanied by the bivalve Nuculanidae indet., have been herein identified. The brachiopod species are diagnostic of the Aseptella-Tuberculatella/Rhipidomella-Micraphelia Fauna which has been dated as late Serpukhovian?early Bashkirian by palynological studies, and recently defined in postglacial mudstones of the El Paso Formation. The development of this fauna is related with a complex array of abiotic factors (substrate stability, turbidity, nutrient availability,variation in oxygen levels, and poor circulation in the water column), related to glacial retreat dynamics and coastline configuration. A restricted, fjord-like environment has been proposed for several locations along the basin margin, i.e. Agua del Jagüel, El Paso and Ciénaga Larga del Tontal Formations. Thus, the occurrence of the Aseptella-Tuberculatella/Rhipidomella-Micraphelia Fauna has important biostratigraphic and paleoecological and paleoenvironmental implications for this sector of southwestern Gondwana.