Génesis de pavimentos de desierto en el ambiente pedemontano del Bajo de la Suerte, noreste del Chubut extraandino

BOUZA, P.; DEL VALLE, HÉCTOR FRANCISCO

Revista de La Asociación Geológica Argentina

Revista de la Asociación Geológica Argentina

Lugar: Buenos Aires; Año: 1997 vol. 52 p. 157 - 168

0004-4822

Abstract.- Genesis of desert pavements in a piedmont environment of  Bajo de la Suerte, northeastern Chubut.- The objectives of this paper were to determine the factors and processes of desert pavement formation related to superficial soil properties and morphological features. The study site is located in a shrubby steppe of northeastern Chubut. The microtopographical pattern are represented by mounds beneath shrub clumps and areas of desert  pavements. Taking into account to morphological properties, the surface layers were classified in six superficial soil condition classes. The former four classes represent a degradational sequence from better edaphic conditions to desert pavement development. Classes 5 and 6 are forms of  accumulation and erosion respectively produced by rill erosion. The main processes responsible for the desert pavement formation are considered to be a combination of: 1) hydric erosion of fine particles by detriment of soil stability; 2) upward migration of coarse particles by alterning shrinking and swelling, freezing and thawing of water, and uplifting of coarse particles from surface as eolian fines are accumulated in shrinkage cracks, and 3) coarse particles concentration by sheetflow. The higher exchangeable sodium percentage (>10 %) and the raindrop impact are the causes of the loss of the soil stability. The studied desert pavements are considered of mixed type. The autochthonous pavements are related with the soil properties and are developed by hydric erosion of the fine particles and upward migration of coarse particles. While the allochthonous pavement are formed by importation of coarse particles from elsewhere by sheetflow.