First record of Bochianites neocomiensis (Ancyloceratina, Bochianitidae) from the Valanginian of the Neuquén Basin, Argentina: Significance of the fauna and global correlation

Abstract

A new Valanginian ammonoid fauna from the Vaca Muerta Formation in the Neuquén Basin is described and illustrated. It includes Bochianites neocomiensis (d’Orbigny), which is recorded for the first time in the lower Valanginian Lissonia riveroi Zone where it is associated with the Andean species L. riveroi (Lisson), and less commonly with Raimondiceras gerthi (Weaver) and Neocomites subtenuis Sayn. Above these levels, the Olcostephanus atherstoni and Karakaschiceras attenuatus subzones, comparatively poorly known in southern Mendoza, are recorded. Bioevents record the transition between CC3-B nannofossils Subzone of the lower Valanginian and the CC4-A nannofossils Subzone of the upper Valanginian. The finding of B. neocomiensis and N. subtenuis associated with endemic Andean faunas, and their calibration with calcareous nannofossils, allows establishing a much more accurate long-distance correlation between the Neuquén Basin and the West Mediterranean Province of the Tethys.