CONICET | Buscador de Institutos y Recursos Humanos

Abstract. The present contribution involves deposits of continental Neogeneage that outcrop in the Bahía Blanca region. The studies that were carried out inorder to contribute to the paleoenvironmental and chronostratigraphicalknowledge involve sedimentological, paleomagnetic and magnetic susceptibilityanalyses. One of the outcrops studied (Cueva de Los Leones) is mainly composedof facies of fine to thick sandstones, largely pedogenized and withimportant amounts of calcrete, whereas the other (Loma Sarmiento) has a predominanceof loess-like silt facies, reddish brown in colour, an abundance ofrhizoconcretions and evidence of pedogenic processes. Both outcrops culminatein an important layer of calcrete of regional scope, with particular morphologiesat each of the sites. The paleomagnetic analysis leads to the conclusion that thesedimentation of the deposits underlying the calcareous crust at the two siteswas not synchronous. Reverse polarity was recorded in the Cueva de LosLeones in contrast to Loma Sarmiento, where normal polarity is predominant.The paleomagnetic samples of calcareous crust on the top presented anomalouspolarity directions in both sections, with very high values of magnetic intensity.The reverse directions in the Cueva de Los Leones can be assigned to the Gilbert Cron (6.0?3.6 Ma), without discarding younger ages in the Pliocene. In contrast, Loma Sarmiento seems to be older (Late Miocene). The susceptibility records also indicated differences between the two sites that would be linked to pedogenic development; they were higher in Loma Sarmiento and judging by the F%factor, in Cueva de los Leones the superparamagnetic particles contribution ishigher. Petrographic, X-Ray difractometry, paleontological and soil Micromorphology analyses, in some places at the studied sites, also contributed to the paleoenvironmental/paleoclimatic reconstruction carried out.Keywords: Neogene Bahía blanca Sedimentology Magnetostratigraphy