Lower and midle paleozoic from Volcancito, Sierra de Famatina, La Rioja Province, Argentina

Abstract

?Lower and midle paleozoic from Volcancito, Sierra de Famatina, La Rioja Province, Argentina?. The Formation units of lower and midle paleozoic age aoutcrop on the oriental slope of Sierra de Famatina. The ordovician Formation Volcancito is formed by dark pelites and psammites of marine origin. It holds a fossil fauna pertaining to the Parabolina argentina (Kayser) ? Kainella meridionalis Kobayashi and Dictyonema flabelliforme Turner biozones. From the ordovician sensu lato are presumed the slates, metagraywackes, slate shales, claystones, and cordieritic semihornfels from the Negro Peinado Formation. The upper ordovician ? lower silurian Ñuñorco Formation appears as a big batholith with monzogranitic composition and tonalitic-granitic diodorite stocks. These formations are affected by intrusive dikes of variable composition dated from upper silurian ? lower devonian.