The plateau glacier in the Sierra de Béjar (Iberian Central System) during its maximum extent. Reconstruction and chronology

Abstract

A detailed study of the glacial morphology in the Sierra de Béjar (Iberian Central System) provided a data set of geomorphic indicators to reconstruct the paleoglaciers developed in this mountain area during the last glacial cycle (Late Pleistocene). Applying a physical-based glacier model and using the geomorphic indicators, a three dimensional reconstruction of the ice mass during the maximum extent of the glaciers has been carried out. We used this reconstruction to project hypsometric curves over the former glaciers and to estimate the ELAs (Equilibrium Line Altitudes) of the paleoglaciers for their stage of maximum extent. At this stage the Sierra de Béjar hosted a plateau glacier, considered as a dome-shaped icecap around 57 km2 in area. According to our estimations, the maximum thickness of the ice was 211 m, the minimum elevation of paleoglaciers 1210 m asl, and the regional ELA was at 2010 m asl. During later stages, reduction in ice mass due to deglaciation caused the icecap to evolve into an icefield, and finally the main glacier was fragmented in valley and cirque glaciers. The geochronological data obtained with 10Be provides an age of ~ 27 ka for the maximum extent of the glaciers (GM), whereas the global Last Glacial Maximum (LGM) represents a younger stage of the Sierra de Béjar glacier evolution. Finally, the new data obtained in the Sierra de Béjar allow evaluating the influence of some factors such as the continentality and latitudinal location, in the development of glacial processes in these areas of the Iberian Central System.