The stratigraphy of Cambrian-Ordovician aged sequences in the Province of Jujuy, northern Argentina, has been controversial due to misinterpretations on the relationship among different units. This succession bear an abundant fauna (conodonts, graptolites and trilobites a.o.) that clarified the previous misinterpretations. Strong environmental controls played an important role during the sedimentation of the Mesdn and Santa Victoria Groups. The biostratigraphic information yielded by the fossils is also analyzed, allowing to correlate this gondwanan succession with Laurentia and Baltica