PERMAFROST DISTRIBUTION AND ICE-CONTENT OF BLOCKSLOPES AND TALUSES: CONTRIBUTION TO THE HYDROLOGICAL SYSTEM OF THE AGUA NEGRA BASIN, DRY ANDES OF ARGENTINA

ORTIZ, DIANA AGOSTINA; KOEHLER, TAMARA; STAMMLER, MELANIE; VILLARROEL, CRISTIAN DANIEL; DARÍO TROMBOTTO; LOTHAR SCHROTT

Congreso; VIII Congreso Argentino de Cuaternario y Geomorfología; 2022

In high mountain regions, climatic conditions are a keyfactor in the development of permafrost. Next to altitudinalimpact, topo-climatic and subsurface conditions furtherinfluence the occurrence of permafrost. As a result, mountainregions show extremely irregular periglacial distributionpatterns which cannot be simply estimated by lapse rates ofair temperature (Schrott, 1994). The Central Andes(30–35°S) are characterized by a high degree of mountainpermafrost occurrence, manifested mainly through thepresence of rock glaciers (Villarroel et al., 2021). However,other periglacial landforms such as block and talus slopes areusually not considered as periglacial landforms with potentialcapacity as a solid-state water reserve and seasonally runoffcontributors. It is hypothesized that, in the Central Andes,specific climatic, topographic, and lithological conditionsfavor the abundance of block slopes and taluses, having asignificant importance as valuable water reserves. The AguaNegra basin is located in the Western part of the San JuanProvince, Argentina at ca. 30ºS and 69ºW. This area is part2 of the Cordillera Principal, and it comprises an area of 57 kmwith maximum elevations around 5.855 m a.s.l. (Schrott,1994). In the upper part of this basin, both periglacial landformsaccount for more than 70% of the areal surface and is asite where field studies in high mountain permafrost remainscarce. Here, as in a large majority of Andean and sub-Andean societies, there is a strong dependence on meltwaterprovided by the cryosphere, which is basically the product ofsnow and ice melt (incl. thawing of active layer of periglaciallandforms) (Crocce and Milana, 2002; Schrott, 1994), thus,setting up a special regional importance. As a result, in-depthknowledge of permafrost distribution of these landforms,which have not yet been properly investigated, is necessaryfor an efficient management of this water resource. Thisstudy focuses on the identification and characterization ofAndean Mountain permafrost in taluses and block slopes inthe Upper Agua Negra Catchment applying a multi-methodapproach. This allows to determine with greater precision thegeomorphic and hydrological significance of permafrost inthe Dry Andes region, as well as the influence of climatic,topographic and lithological conditions on their spatial distribution.