The latest Carboniferous-earliest Permian palynological assemblage from the Sauce Grande Formation, Claromecó Basin, Argentina: Implications for the local palynostratigraphic scheme and correlations in Western Gondwana

Abstract

The Sauce Grande Formation of the Ventania System and Claromeco ´ Basin, east-central Argentina, is a geological unit of glaciomarine origin showing evidence of the glaciation that affected the supercontinent of Gondwana during the late Paleozoic. The age of this unit was previously determined from scarce and poorly preserved fossils, but mainly from radiometric dating and the fossil content of the overlying geological units. This study presents a palynological assemblage obtained from the Sauce Grande Formation in the PANG 0002 borehole, drilled in the Upper Paleozoic Claromeco ´ Basin. Based on the identification of key species, such as Converrucosisporites confluens, Pakhapites ovatus, P. fusus, Vittatina spp., and Weylandites magmus, an age no older than Gzhelian is inferred for the interval studied. The inferred age allows us to relate the glaciomarine deposits of the Sauce Grande Formation to the last episode of the late Paleozoic Ice Age. The palynological assemblage of the Sauce Grande Formation is correlated with the Converrucosisporites confluens-Vittatina vittifera (CV) Biozone of the Claromeco ´ Basin. Based on updated information and new correlations of the CV Biozone with palynostratigraphic schemes established in neighboring basins (Chacoparan´ a, Parana, ´ and central-western Argentina), its age is adjusted to the Gzhelian-late Artinskian interval, encompassing the Carboniferous-Permian boundary. This new information contributes to refining the current biostratigraphic scheme of the late Paleozoic Claromeco ´ Basin.