Deglaciation and postglacial evolution of the Cere Valley (Cantal, French Massif Central) based on geomorphological mapping, Cl-36 surface exposure dating and glacier modelling

The landform assemblage in the Cere Valley (Cantal, France) provides one of the most complete sequences for Late Pleistocene glacial fluctuations in the French Massif Central. However, the associated glacial chronology has been debated since the 1980s. This paper aims to improve the glacial chronology of the Cere Valley using Cl-36 surface exposure ages. Geomorphological results define two glacier stadials with reconstructed equilibrium line altitudes of 1078 +/- 43 and 1152 +/- 34 m above sea level. These results are comparable to those obtained in the Alps or the Pyrenees during the Last Glacial Maximum (26-19.5 ka). However, Cl-36 surface exposure ages are centred around the Younger Dryas (YD), between 13 and 11 ka (n = 4). We suggest that these Cl-36 ages are not related to a standstill during the YD but rather to the effects of the postglacial evolution of the Cere Valley. We investigate two geomorphological end-member scenarios to explain the postponed exposure of sampled boulders: the Aurillac Lake scenario and the later fluvial incision scenario. While the nature of the geomorphological events leading to the boulder exhumation is not fully resolved, we highlight a long phase of postglacial evolution in the Cere Valley.