Taphonomic and paleoenvironmental reconstruction of the Triassic lacustrine system from the Agua de la Zorra Formation, Mendoza, Argentina

BENAVENTE, CECILIA ANDREA; PEDERNERA, TOMÁS; OTTONE, EDUARDO GUILLERMO; MANCUSO, ADRIANA CECILIA

Congreso; 11° Congreso de la Asociación Paleontológica Argentina; 2016

Taphonomic studies and paleoenvironmental analysis have a central role in the interpretation and reconstruction of extinct macroflora paleocommunities. The Agua de la Zorra Formation (Triassic) crops out at the Paramillos de Uspallata locality (Cuyana Basin, Mendoza, Argentina) and represents a deltaic-lacustrine system. This work presents the paleoenvironmental reconstruction of the unit using sedimentologic and taphonomic data provided by vegetal remains. Fossil plant remains were collected and identified recording their taphonomic attributes. We identified six taphofacies defined by lithology of the rocks and taphonomy attributes like density, packing, sorting and orientation of the fossils. The taphofacies represent different sedimentary subenvironments within the deltaic-lacustrine system. Four of them are characterized by siltstone deposits and represent a proximal-distal gradient from the margin to the prodelta. The other two taphofacies are associated with mudstones and represent the lake center. One of this taphofacies shows more deltaic influence (mudrock with diffuse lamination) and articulated vegetal remains; and the other has less deltaic influence (massive mudstone) with disarticulated and broken relative smaller fragments of fossil plants. In the Agua de la Zorra paleolake we identify two depositional subenvironments, one with more input of sediment and oxygenated linked to a delta; and another one dominated by anaerobic conditions linked to the center of the water body.