Análisis de facies y paleoambiental de alta resolución de la Aloformación Punta San Andrés (Plio-Pleistoceno), provincia de Buenos Aires, Argentina

the continental deposits of the punta san andrés alloformation (plio-pleistocene) crop out in the marine cliffs of south eastern buenos aires province (fig. 1). the deposits of this unit have been assigned to different continental sub-environments such as floodplains, fluvial channels and temporary water bodies (zárate, 1989). the aim of this work is to perform a high-resolution facies and facies association analysis as well as an architectural characterization of the sedimentary bodies cropping out in baliza san andrés and complejo turístico chapadmalal (fig. 1). this information will be used to elaborate a conceptual and dynamic model of the depositional environments present in the punta san andrés alloformation and to define main controlling factors over its accumulation. the study area is located in a typical passive margin controlled by transversal extensional systems that originated rift basins (aulacogens) with very little basaltic magmatism (ramos, 1996; parker et al. 2008). this area experienced block rotation due to isostatic equilibrium and sedimentary overload. accumulation of post-miocene deposits was favored by a high sedimentary dynamic associated with the rise of the andean cordillera (turic et al. 1996; parker et al. 2008). more specifically, the study area is located in the southeastern part of the tandilia geological province (rolleri, 1975, fig. 1). the pioneer papers on stratigraphy of the mar del plata and miramar marine cliffs were carried out by ameghino (1908), frenguelli (1921) and kraglievich (1952, 1953, 1959) (figs.2, 3). the sedimentological characterization of these deposits was made by teruggi et al. (1956) and zárate (1989). this last author also proposed an allostratigraphic framework which intended to unify and simplify the late cenozoic stratigraphy (fig. 2). the rich vertebrate fauna present in the punta san andrés alloformation and related units was studied since the first contributions by ameghino (1908). these studies were the