F u n d a d a e n 1 9 6 2 S O C I E D A D G E O L O G I C A D E C H I L E la serena octubre 2015 628 Factors controlling alpine glaciations in the Sierra Baguales Mountain Range (50º - 51º S) as inferred from morphometric analysis of glacial cirques José Araos* **, Jacobus Le Roux* *** and Mike Kaplan**** * Departamento de Geología. Universidad de Chile. Plaza Ercilla 803, Santiago, Chile. ** Departamento de Geografía. Universidad Alberto Hurtado. Cienfuegos 41, Santiago, Chile. *** Andean Geothermal Centre of Excellence, Plaza Ercilla 803, Santiago, Chile. **** LDEO of Columbia University, Palisades, NY 10964. *Mail:josearaos@ug.uchile.cl Abstract. We mapped the spatial and elevation distribution of 143 cirques in southern Patagonia, between 50 º and 51º S, and analyzed their morphometry using simple and multivariate statistical methods. The cirque basins are located east of the Southern Patagonian Ice Field and around the Sierra Baguales Mountain Range, about 200 km from the Pacific coast. The geomorphologic evidence indicates that alpine glaciations have been the predominant style in the study area. The distribution and activity on glacial cirques are influenced by both tectonic factors (Andean uplift) and climate (Westerly Winds). Morphometric characteristics indicates a persistent climate contrasts between the western (maritime, temperate) and eastern (dry and cold) sides of southern Patagonia since the Last Glacial Maximum (LGM). Based on our analyses, we infer that glaciers located at the higher elevations were not affected by post LGM high- frequency climatic variations that would have led to only small glaciers of limited influence on cirque form evolution; on the other hand most glacial cirques analyzed shows an isometric developing trend, which could indicate that the deglaciation process in Sierra Baguales occurred quickly and continuously, and equilibrium line altitudes (ELAs) experienced a relatively rapid rise of about 400 m after the last major occupation. Keywords: Southern Patagonian Ice Sheet, alpine glaciations, ELA, Last Glacial Maximum. 1 Introduction Patagonian past glacier variations have shaped the landscape, generating geomorphological, sedimentological and stratigraphic evidence, that according to Rabassa et al. (2011), represent the action of continental and alpine glaciations of varying ages and extensions. Glacial chronologies developed for the last glacial cycle in outlet glaciers located at the Torres del Paine massif and surroundings of the Patagonian Ice Cap, indicate that the ice retreat after the last glacial term T1 (~ 18-10 ka, 103 cal. Years) did not happen quickly, and in addition was interrupted by a glacial readvance or stabilization at about 11.8 Ka. The Sierra Baguales Mountain Range in the eastern foothills of the Andes (Figure 1), located 50 km northeast of the Torres del Paine massif presents active alpine glaciers and geomorphological evidence that indicates the existence of an former system of glacial cirques located in the Westerly Winds area and topographically isolated from the SPI. The accumulation zone of these glacial cirques is located above1000 m a.s.l and more than 200 km from the Pacific coast. Therefore, it represents a suitable site for the description and estimation of the factors that controlled the variations of isolated alpine glaciers located toward the interior of the continent and that possibly responded independently to climatic changes that operated since the LGM. The research will help to clarify the current knowledge gap identified by various authors (Rabassa et al., 2011), related to the duration and structure of the LGM in an area neighboring Torres del Paine (Marden, 1997; Garcia et al., 2012; Sagredo et al., 2011). 2 Method, Samples, Results 2.1 Cirques morphological types Cirques mapping was carried out using topographic maps at a scale of 1:50,000, aerial photographs at a scale of 1:70,000, Landsat imagery and digital elevation models. Three field campaigns were carried out during 2013 and 2014 to map cirques and observe, describe and interpret the general geomorphology of the Sierra Baguales Mountain Range. Each cirque was digitized as a closed polygon with a unique ID number, upon which a table containing morphometric information associated with each digitized polygon was generated. Calculations of planimetric and hypsometric indices (Křížek et al., 2012) were conducted using the open source software QuantumGIS 2.2 and GRASS 6.0. Following Delmas et al. (2013), morphometric variables