Palynostratigraphy of the Lower Cretaceous Río Mayer Formation in the Río Lista Area, Austral Basin, Southwestern Argentina

Palynomorph assemblages were recovered from the upper levels of the Cretaceous Río Mayer Formation in the Río Lista area, Austral Basin, southern Argentina. Thirty spore and eighteen pollen species, including one angiosperm, are identified, along with fourteen dinoflagellate cysts and six acritarch taxa. The presence of Clavatipollenites spp. and the dinoflagellate cysts Muderongia mcwhaei, Diconodinium spp., and Muderongia australis suggest an early Aptian age for these palynological assemblages. Based on the relative abundance of the major groups of palynomorphs, deposition of the Rio Mayer Formation in the Río Lista area probably occurred in a progressively shallowing marine setting, evidenced by the decrease in abundance of marine elements (dinoflagellates) and the increase of Pterospermella in upper levels of the unit. These interpretations concur with sedimentological analyses of the same stratigraphic section.