Glacial and fluvial deposits in the aragón valley, central‐western pyrenees: chronology of the pyrenean late pleistocene glaciers

33 páginas, 9 figuras.- Versión pre-print
[EN] The Aragón Valley glacier (Central Western Pyrenees) has been studied since the late nineteenth century and has become one of the best areas in the Pyrenees to study the occurrence of Pleistocene glaciations and the relationships between moraines and fluvial terraces. New morphological studies and absolute ages for moraines and fluvial terraces in the Aragón Valley allow a correlation with other Pyrenean glaciers and provide solid chronologies about the asynchroneity between global last glacial maximum (LGM) and the maximum ice extent (MIE). Six frontal arcs and three lateral morainic ridges were identified in the Villanúa basin terminal glacial complex. The main moraines (M1 and M2) correspond to two glacial stages (oxygen isotopic stages MIS 6 and MIS 4), dated at 171±22ka and 68±7ka, respectively. From a topographical point of view, moraine M1 appears to be linked to the 60m fluvioglacial terrace, dated in a tributary of the Aragón River at 263±21ka. The difference in age between M1 moraine and the 60m fluvioglacial terrace suggests that the latter belongs to an earlier glacial stage (MIS 8). Moraine M2 was clearly linked to the fluvioglacial 20m terrace. Other minor internal moraines were related to the 7-8m terrace. The dates obtained for the last glacial cycle (20-18ka) are similar to other chronologies for Mediterranean mountains, and confirm the occurrence of an early MIE in the Central Pyrenees that does not coincide with the global LGM. © 2012 Swedish Society for Anthropology and Geography.
Support for this research was provided by the projects CALIBRE-LIMNOCAL (CGL2006-13327-C04-01) and GRACCIE-CONSOLIDER (CSD2007-00067), financed by the Spanish Inter-Ministry Commission of Science and Technology; and PIRINEOS ABRUPT (PM073/2007), financed by the Diputación General de Aragón. Additional funding was provided by the Spanish National Parks Agency through the project “Evolución climática y ambiental del Parque Nacional Picos de Europa desde el ultimo máximo glaciar” (ref. 53/2006), provided by the Spanish Ministry of Environment. The authors gratefully acknowledge Dr P.D. Hughes and an anonymous reviewer for their comments and suggestions, which significantly improve this paper.