The Neuque¤n composite section: magnetostratigraphy and biostratigraphy of the marine lower Jurassic from the Neuque¤n basin (Argentina)

Paleomagnetic and biostratigraphic data from five marine sedimentary sections in the Argentine Neuque¤n basin have allowed to construct the Lower Jurassic Neuque¤n Composite Section. This composite section comprises 14 reversed and 11 normal polarity Zones, in relation to 17 Andean ammonite Assemblage Zones, spanning the Hettangian^Toarcian (Early Jurassic). It represents the first paleomagnetic data of Lower Jurassic marine successions in the Southern Hemisphere. The Neuque¤n composite Section was correlated to the International Mesozoic Polarity Time Scale which, for the Lower Jurassic, comprises 54 polarity Zones and 16 Standard ammonite Zones. The correlation between the regional and the international biomagnetostratigraphic scales supports but also refines the correlation between the Andean and Standard ammonite zonations. Correlation between the Neuque¤n composite Section and the polarity sequences recorded in each section helped to assign several unfossiliferous stratigraphical levels to the correspondin