Early Cretaceous calcareous nannofossils and foraminifera from the Huitrín Formation (La Tosca Member), Neuquén Basin, Argentina, and their biostratigraphic and paleoecological implications

Abstract

The limestones, marlstones and gypsiferous shales of the La Tosca Member of the Huitrín Formation record the end of the last Pacific marine transgression in the Neuquén Basin. Since before this contribution, the presence of microfossils from this unit was restricted to unpublished reports or brief mentions; thus this study aims to present and illustrate for the first time the calcareous nannofossils and foraminifera found at Quebrada del Gastrópodo (S 36°32′14.00′′; W 69°36′47.30′′) and Ranquil 1 (S 36°36′36.80′′; W 69°45′46.50′′) sections, both located in southern Mendoza province, west-central Argentina. The recovered calcareous nannofossils were scarce and of low diversity, nevertheless, the presence of Diloma galiciense constrains the age of the La Tosca Member of the Huitrín Formation to the lower Barremian. In addition to nannofossils, a single sample of marlstones from Quebrada del Gastrópodo provided a relatively rare assemblage of foraminifera that includes calcareous benthic species distributed in three suborders (Spirillinina, Lagenina and Miliolina) corresponding to an inner-middle ramp paleoenvironment. The studied nannofossils and foraminifera indicate partial connections with an open marine environment. Furthermore, the recovered calcareous nannofossils at the La Tosca Member confirm a Barremian age for these deposits and the persistence of the Paleo-Pacific-Tethyan connection through a Tethys-Caribbean seaway (Hispanic Corridor) at this time.