Pennsylvanian foraminifera from the Río Nevado Formation, Chibcha Terrane, Colombia: biostratigraphic and paleobiogeographic approach

This study presents the first taxonomic description, biostratigraphic analysis, and paleobiogeographic interpretation of Pennsylvanian Fusulinidae, specifically the genera Fusulinella and Beedeina, from the Río Nevado Formation in the Chibcha Terrane, Colombia. The investigated section comprises shallow marine deposits, where part of the Paleozoic sequence is exposed and tectonically deformed by the Andean Orogeny. This outcrop has previously been dated from the Pennsylvanian to the Lower Permian based on invertebrate fossil assemblages such as brachiopods, trilobites, and ammonoids, which provide lower biostratigraphic resolution compared to foraminifera. As part of an accreted terrane, determining the original paleogeographic position of this crustal block has posed significant challenges. The fusulinid assemblage described herein provides a refined biostratigraphic framework, allowing for high-resolution correlation with the Moscovian Stage. The data also align with recent conodont studies from the same samples, supporting both biostratigraphic and paleobiogeographic correlations with fusulinid and conodont faunas from the North American Midcontinent region. These results reinforce the hypothesis that the Chibcha Terrane may have originated from a region within North America prior to its accretion to northwestern South America.