New insights into the graptolite biostratigraphy of the Floian (Lower Ordovician) Acoite Formation at El Moreno, Cordillera Oriental of Argentina

Abstract Two assemblages of Floian graptolites from the Acoite Formation at a new section on the western flank of the Cordillera Oriental, Jujuy Province, referred to as El Moreno, are presented. The first assemblage includes Acrograptus spp., Baltograptus jacksoni Rushton, Baltograptus cf. jacksoni Rushton, Baltograptus sp. and poorly preserved tetragraptids. The second assemblage comprises Baltograptus deflexus ? (Elles & Wood) and Baltograptus minutus (Törnquist). The presence of Baltograptus jacksoni and Baltograptus minutus allows for the identification of the eponymous biozones, indicating a middle to late Floian age for the studied strata. This contribution confirms the occurrence of Baltograptus jacksoni in Argentina. In addition, previous records of Floian graptolites from northwestern Argentina are revised, thus supporting the proposal to use the Baltograptus jacksoni and Baltograptus minutus zones in the Cordillera Oriental of Argentina. This enables regional correlations with equivalent levels throughout the Central Andean Basin, as well as more precise intercontinental correlation.