Estratigrafía y bioestratigrafía del Ordovícico Medio del río Las Chacritas, Precordillera Central de San Juan

two ordovician carbonate formations are recognized in the las chacritas creek (sierra de la trampa, central precordillera). the lithostratigraphic nomenclature is analyzed and revised, the las aguaditas formation is proposed for the carbonate succession that is overlying the san juan formation. the middle darriwilian conodont faunas recovered from the studied stratigraphic interval allowed the usage of the baltic biostratigraphic chart: the eoplacognathus pseudoplanus and the eoplacognathus suecicus zones. the contact between the san juan and las aguaditas formations is analyzed and correlation is possible with several localities of the central precordillera.