LATE CENOZOIC VERTEBRATE BIOSTRATIGRAPHY AND GEOLOGICAL EVOLUTION OF THE LA CRUZ VALLEY, CORDOBA, ARGENTINA

The aim of this paper is to analyse the stratigraphic sequence, the age of the deposits, vertebrate fossils and geological evolution of the La Cruz valley, Cordoba Province, Argentina, and how they relate to the Andean deformation of the eastern Sierras Pampeanas. In order to do so, twenty-four stratigraphic profiles were studied throughout the valley and seven species of mammals and one amphibian were recorded. Four facies associations were identified, correlated with the Brochero, Estancia Belgrano, Pampean, Chocancharava, Rio Primero and La Invemada fonnations. According to this analysis the following main conclusions were reached: (i) the basal Neogene sediments of the La Cruz river represent new paleontological sites belonging to the late Pliocene (Chapadmalalan Stage/Age); (ii) the sedimentary sequence present in the La Cruz valley began to deposit during the late Pliocene; (iii) the gathered evidence allows to verify that the sedimentary record starts with older deposits from the western part of the Sierras Pampeanas (Montehermosan Stage/ Age) extending to the eastern sector (Chapadmalalan Stage/Age). This coincides with the direction of the propagation of the Andean crustal deformation during the subduction of the low-angled Nazca tectonic plate; (iv) the registered vertebrate fossils suggest a clear paleobiogeographic connection between the La Cruz river basin and the Pampean Region, during the late Pliocene; (v) this connection indicates, a priori, that it would have been much more evident since the Chapadmalalan Stage/Age, instead of the Montehermosan Stage/Age; (vi) the paleobiogeographical distribution of the species Microcavia chapalmalensis, Eucelophorus chapalmalensis and Pseudorypotherium hystatum have been expanded.