Advances in the study of the Early Cretaceous gastropod fauna from the Neuquén Basin, west-central Argentina

CATALDO, CECILIA SOLEDAD

Heidelberg

Congreso; 22nd International Coloquium on Latin American Earth Sciences; 2011

The marine Lower Cretaceous of the Neuquén Basin, west-central Argentina, contains a highly diverse and abundant fossil record. Among the invertebrate benthic fauna, gastropods are moderately abundant in several localities. Nonetheless, this group has been subject of scarce taxonomic study, the work of Weaver (1931) being the most significant contribution so far. Moreover, its paleoecologic and paleobiogeographic implications are unknown. Here, as part of a long term project on the Early Cretaceous marine gastropod fauna of Argentina, some advances are presented on the basis of newly collected material from several sections in Neuquén and Mendoza Provinces. Specimens come from more than 30 localities in Neuquén and three localities in Mendoza. In nine of these, detailed stratigraphic sections were measured. The specimens proceed from three units: Mulichinco (Valanginian) and Agrio (Late Valanginian-Late Hauterivian) Formations, belonging to the Mendoza Group, and La Tosca Member of the Huitrín Formation (Barremian), belonging to the Bajada del Agrio Group. The Agrio Formation has yielded most of the material. The stratigraphic interval spanned by these records is Early Valanginian-Barremian. The taxonomic study carried out revealed the presence of 21 gastropod species in the Agrio Formation, of which at least nine have not been reported from this unit until present. From the Mulichinco Formation, five species have been identified, of which none has yet been reported from that unit. The La Tosca Member of the Huitrín Formation has yielded three species, of which two have not been previously reported. The gastropod fauna seems to have a significant proportion of endemic taxa at the species level, although genera show affinity with coeval European faunas. Argentinean gastropods also show close relationships with Cretaceous faunas from Chile and northern South America.