Interaction of geological and pedological processes in the genesis of soils with gypsum, Northern Patagonia, Argentina.

Abstract

The origin and classification of gypsum soils, which have been usually treated secondarily with calcareous soils, are discussed. Different types of gypsum soils present in Northern Patagonia associated with gypsum and anhydrite outcrops in the upper part of the related hydrographic basins, and their redistribution in alluvial plains and fans, and Pleistocene and Holocene fluvial terraces, are analyzed. The water chemistry in the Colorado and Neuquén rivers is also considered. Gypsum soils formed on Pleistocene terraces have a higher grade of differentiation, and a good internal drainage. The presence of gypsum soils in Holocene terraces of the Colorado River basin, and their lack in the Neuquén River basin, is linked to the currently higher relative exposure of gypsum and anhydrite deposits, along the upper Colorado River basin. Processes that affect the gypsum soils, as well as the uses of these soils in the region, are also discussed.