Aspectos sedimentológicos de arenas eólicas del Pleistoceno tardío-Holoceno de la provincia de La Pampa Sedimentologic aspects of eolian sands from the Late Pleistocene-Holocene of the La Pampa Province

El objetivo general de este trabajo es analizar la procedencia, génesis y dinámica de transporte de los depósitos eólicos arenosos del centro-este de la provincia de la Pampa. Para ello, se analizaron el marco geológico-geomorfológico y los aspectos estratigráficos de tres sectores considerados como sendos estudios de casos: cordón medanoso La Pastoril-Santa Isabel, cordón medanoso Toay y cordón medanoso General Acha. Estos cordones se caracterizaron sedimentológicamente (granulometría, mineralogía) a través del análisis de 20 muestras. Se identificaron dos unidades eólicas asociadas a dos ciclos de sedimentación, informalmente denominadas inferior (Pleistoceno tardío-Holoceno medio) y superior (originado por acción antrópica durante el siglo XX) relacionados con vientos del cuadrante O-NO en Santa Isabel y del S y SO en General Acha. Los resultados obtenidos sugieren que la topografía sería un factor de control importante en la distribución de los sedimentos, además de la distancia al sistema fluvial, que determinaría su tama o de grano. Los análisis mineralógicos indicarían un aporte mixto de materiales, tanto distal (sistema fluvial del Bermejo-Desaguadero-Salado-Curacó), como local (afloramientos rocosos de la provincia). The main goal of this paper is to analyze the provenience of sandy eolian deposits of the central eastern part of La Pampa Province. Considering present eolian models proposed by different authors, the hypothesis tested in this paper is that eolian sediments are the result of deflation of alluvial deposits from the Bermejo-Desaguadero-Salado-Curacó fluvial system. With this purpose in mind, three case studies were selected (La Pastoril-Santa Isabel, Toay and General Acha) (Fig. 1). The analysis was made following the concept of spatial scale hierarchy which considered the geological and general environmental setting of the studied areas along with fundamental geomorphological features of the analyzed dune systems. This was complemented by the stratigraphic survey of selected sections from which 20 samples were collected for sedimentological analysis (grain-size and mineralogy). Also, due to the lack of information, three samples were collected from the present Desaguadero fluvial system for general characterization. At the regional scale two main geoforms were identified: an extensive plain and the paleovalley of the Desaguadero fluvial system. The plain grades eastward and includes several longitudinal depressions (longitudinal valleys). A sandy silt mantle is covering the plain, whereas the main dune system is located along the lo