ABSTRACT
This paper presents a geomorphological study of a desertic area in SE San Juan, Argentina. On the basis of the analysis and interpretation of field checked satellite images and aerial photographs, a regional geomorphological map has been prepared, including different order ranging from landscapes of regional extent such as alluvial plains, dune fields and the Pampean Ranges mountain system, to local elements such as anticlinal valleys, homoclinal crests and cuestas, shallow depressions with temporary lakes, interdune basins and others. Pre-Quaternary landforms carved on Precambrian-Early Paleozoic metamorphic rocks have been separated from those of Quaternary age. The following surfaces have been identified: (i) an upper pediment surface and a unit of older alluvial fans, both believed to be Early to Mid Pleistocene in age; (ii) a lower pediment and a unit of younger fans, both probably dating from the Mid-Late Pleistocene. Salines and mud-flats also occur. Four fluvial terraces have been eroded by ephemeral streams on the pediments and fans.
The area shows an ancient, strong fluvial action. Increasing dryness is inferred from extensive dune fields partially covering the plains.
