Geomorphology, tectonism and Quaternary landscape evolution of the central Andes of San Juan (30°S-69°W), Argentina

摘要

The north-south trending valley of Iglesia is a regional tectonic depression limited to the west by the Cordillera Frontal Unit and to the east by Precordillera Occidental Mountain Units. The forms of the resulting landscape in the region are the result of glacial, periglacial, fluvial and alluvial action, aggra-dational and deggradational processes, as well as neotectonic activity and climatic changes. The generation of large Quaternary alluvial fan aggradational surfaces is related to previous climatic conditions, colder and more humid than the present ones. Abundant snowfalls and rains during the Pleistocene made possible detritus deposition, generating alluvial covers whose thickness increases toward the east. These climatic conditions alternated with arid periods, during which vertical erosion of streams prevailed, forming a landscape of stepped levels. In addition, the presence of faults with Quaternary tectonic activity indicates, a strong structural control in the evolution of the landscape during the Pleistocene-Holocene periods, effectively starting vertical erosion and finishing a cycle of erosion-accumulation and the beginning of the following one.