Geomorphological Inventory of glacial, periglacial and paraglacial landforms of the Northern Patagonian Andes
The cold climate events of the Upper Cenozoic greatly modified the landscape of the Northern Patagonian Andes (NPA), where a large number of glacial, periglacial and paraglacial landforms are preserved. A detailed geomorphological inventory of glacial, periglacial and paraglacial landforms described from seven mountain range of the NPA is here presented. The analysis of satellite images and digital elevation model, fieldwork research and its integration in a Geographical Information System were used to recognize erosive landforms (glacial cirques, glacial valleys, nivation hollows), depositional landforms (moraines, rock glacial, solifluction lobes, nivation crests) and mass wasting landforms (debris slopes, debris cones, debris flow, and others). More than 550 active and relict morphosedimentary units were identified inside glacial valleys. The geomorphological analysis and the corresponding cartographic elaboration carried on in a large number of mountain valleys, were allowed to define for each studied valley, a local temporal-spatial sequence. Four cold climate stabilization were interpreted from the regional analisys, being the event "A" the oldest, and "D" the last cold climate event before the present climate conditions.
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Geomorphological mapping was performed complementing mapping and fieldwork, which allowed the elaboration of detailed geomorphological maps with the further preparation of morphostratigraphic schemes. The mapping process employed high-resolution satellite images from Google Earth TM, World Imagery Map and Bing Maps TM displayed by the QGIS Open Layers (~5 m or less spatial resolutions). Also, SRTM (https://earthexplorer.usgs.gov/), ALOS Palsar (https://asf.alaska.edu/) digital elevation models (DEMs, 30 m spatial resolution) and ALOS Palsar (https://asf.alaska.edu/) DEMs (12.5 m resolution) were useful as a topographic base. High-resolution photographic images were acquired with an Unmanned Aerial Vehicle (UAV, Phantom 3), in some areas of La Hoya, at south of Cordón Esquel Mountain, and in the north oriental valley of the Nahuel Pan Mountain (Fig. 1: 3 and 4). These flights allowed the creation of high spatial resolution DEMs (6-7 cm) and images, for a better identification of landforms. The frontal slope and other morphometric features of rock glaciers of the La Hoya and the Nahuel Pan ranges were well measured by these DEMs, which improve the geomorphological classification of rock glaciers, active or inactive, in the mentioned places (explained later). All cartographic information was placed in a Geographic Information System (QGIS 3.10.14) and the elaborated maps were projected in UTM Zone 19S using a WGS 84 datum. Mountain valleys (glacial or fluvial) were classified as individual systems to analyze the landform assemblage and their temporal distribution. Superficial analysis of landforms, such as drainage network development and soil-vegetation system, among others, were used to establish the degree of conservation and their relative age in the system. The GIS developed contemplates, for each landform, its geographical coordinates, genesis and associated morphoclimatic system, orientation/aspect, surface, length and altitude (Inventory and morphostratigraphy.xlsx). The landform characterization was made according to their shape, size, superficial morphology and spatial distribution and location in each mountain valley. Equilibrium Line Altitude of paleoglaciers (paleoELAs) was obtained from the glacial cirques and lateral moraines. From rock glaciers, the minimum altitude of rock glacier allowed the extraction of the Lower Boundary of Mountain Permafrost, (LBMP in Haeberli, 1985; Barsch, 1996) and the Rock Glacier Initiation Line Altitude (RILA in Humlum, 1988). Both indicates the upper and lower limits of mountain permafrost.