First documentation of Late Paleozoic conodonts from Argentina: Biostratigraphic and paleoclimatic constraints for the Late Paleozoic Ice Age in SW Gondwana

Abstract

We present the first discovery of Late Paleozoic conodonts in Argentina, marking the southernmost occurrence of this fossil group in the dominantly cold, high latitudes of Gondwana. Recovered from the siliciclastic Río del Peñón (RDP) Formation at the Rincón Blanco section in the northern Precordillera, La Rioja Province, the fossil assemblage includes Neognathodus colombiensis and Neognathodus “pre-colombiensis,” precisely indicating the early Moscovian (late Atokan in North America) N. colombiensis Zone. Furthermore, the conodont fauna establishes a crucial temporal constraint for the brachiopod Tivertonia jachalensis−Streptorhynchus inaequiornatus (TS) Zone, which is a widely employed biostratigraphic unit in southern South America. The warm-water affinity of Neognathodus is in accordance with the record of typical paleoequatorial faunal elements in the TS Zone in several central western Argentinian basins, thus reinforcing the idea of a climatic amelioration in the southern latitudes of Gondwana during the early Moscovian.