Glacial and Fluvial Deposits in the Aragon Valley, Central-Western Pyrenees: Chronology of the Pyrenean Late Pleistocene Glaciers

The Aragon 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 Aragon 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 Villanua 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 Aragon 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 78m terrace. The dates obtained for the last glacial cycle (2018ka) 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.