Last Glacial Maximum and deglaciation of Sierra de Gredos, central Iberian Peninsula

The study area is located in the Sierra de Gredos, a portion of the Sistema Central range of central Spain, specifically in the Gredos Gorge, on the north side of Pico Almanzor (2596 masl), where glacial forms are present down to an altitude of 1410 m, 10 km from the headwall. This paper presents cosmogenic 36Cl surface exposure dates of four closely spaced lateral moraine ridges within the area of maximum advance of the ancient glacier, 8 km from the headwall; and two glacially polished bedrock thresholds 3 and 5 km from the headwall. The dates are overall coherent and indicate a maximum advance at 26–24 ka. Subsequently the glacier front stabilized around its maximum position for ∼3 ka, with small scale fluctuations resulting in small, closely spaced moraines ridges. Glacier recession began after 21 ka, accelerating sharply by ∼16 ka. The glacier had probably disappeared from the Gredos Gorge by 15 ka. There are no traces of older or more recent moraines than those dated in this study. These results are in agreement with the well known late Pleistocene climatic evolution of the Northern Atlantic and with the glacial chronology of the Alps and other Mediterranean mountains. However, the Gredos Gorge has no geomorphic evidence of the Younger Dryas cold event, probably because of the low altitude and southern character of these mountains.