Cinturones altitudinales criogénicos en la cuenca del río Bramadero, San Juan, Argentina

Abstract

«Cryogenic altitudinal belts in the Bramadero river basin, San Juan, Argen- tina». The aim of the present study is to delimit and characterize the different altitudinal cryogenic regions or altitudinal belts in the Bramadero river sub-basin (31 º 47’ S to 31 º 57’ 30" S and 70 º 00’ 00" W to 70 º 13’ 30" W), in the province of San Juan, Argentina. This area has one of highest densities of periglacial geoforms in the region. The altitudinal cryogen- ic belts were defined on the basis of the distribution and correlation of periglacial geomorpho- logical units: rock glaciers, protalus ramparts, protalus lobes, embryonic rockglaciers, cryo- forms derived from rockslides, cryoforms derived from moraines, frozen talus slopes and cry- oplanation terraces. The presence of glaciers, debris covered glaciers and perennial snowfields has also been taken into account. With the data a geomorphological periglacial map of the Bramadero river basin, scale 1:125.000 was elaborated. This map was then compared to the position of the MAAT isotherms in order to establish the different categories for the probability of permafrost occurrence for each cryogenic belt. In the following four categories were distinguished: seasonal frost cryogenic belt (without permafrost), Periglacial Cryogenic Belt (likely to display permafrost) and Nival Belt (possible permafrost occurrence).