Stratigraphy and Paleontology of the marine Cenozoic from the Gran Bajo and Salinas del Gualicho, Argentina and description of 17 new species.

Abstract

The stratigraphy of the Gran Bajo del Gualicho Formation is explained by the identification of the new Saladar and Arriola Members. The molluscan fauna comprises 38 genera and 44 species, 17 of which are new: Anadara australis sp. nov., Cubitostrea delrioi sp. nov., Amusium rorii sp. nov., Zygochlamys rizzoloi sp. nov., Pododesmus (Monia) atlantica sp. nov., Tawera canalei sp. nov., Dosinia (Dosinia) salarensis sp. nov., 'Spirocolpus' adapicis sp. nov., Torcula magna sp. nov., Magnatica hansi sp. nov., Eudolium lissiei sp. nov., Sconsia magdai sp. nov., Chicoreus (Chicoreus) guadalupei sp. nov., Penion patagonensis sp. nov., Mitra (Fusimitra) carlosi sp. nov., Austroimbricaria brugnii sp. nov. y Polystira cingula sp. nov. The NVG (Nodipecten sp.-Venericor abasolensis- Glycymerita camaronesia) Molluscan Assemblage in the Saladar Member nov. indicates an age of late early Miocene-earliest middle Miocene. The Saladar Member correlates with the upper section of the Chenque Formation and with the Venericor bearing horizons of the Gaiman and Vaca Mahuida formations. The fauna of this member constitutes another evidence with respect to the weather stripes stated for Patagonia since the late Oligocene-early Miocene. The assemblage recorded in the Arriola Member nov. indicates the probable presence of the Aequipecten parenensis Zone and a stratigraphic relationship with the Puerto Madryn Formation of a late Miocene age, extending the covered area along the Valdesian Province to the Salinas del Gualicho. The fauna of the Saladar Member shows more affinity with that in the Monte Len and Chenque formations, while the fauna in the Arriola Member shares more resemblance with the Paran and Puerto Madryn formations. The Chilean Navidad and Guadal formations have 30% and 10% of genus in common with fauna of the Saladar Member, respectively.