Glacial oscillations during the Bølling–Allerød Interstadial–Younger Dryas transition in the Ruda Valley, Central Pyrenees

International audience; The Upper Garonne Basin included the largest glacial system in the Pyrenees during the last glacial cycle. Within the long-term glacial retreat during Termination-1 (T-1), glacier fluctuations left geomorphic evidence in the area. However, the chronology of T-1 glacial oscillations on the northern slope of the Central Pyrenees is still poorly constrained. Here, we introduce new geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages from the Ruda Valley. This U-shaped valley, surrounded by peaks exceeding 2800 m a.s.l., includes a sequence of moraines and polished surfaces that enabled to reconstruct the chronology of the last deglaciation. Following the maximum ice extent, warmer conditions prevailing at ~15-14 ka, during the Bølling-Allerød (B-A) Interstadial, favoured glacial retreat in the Ruda Valley. Within the B-A, glaciers experienced two phases of advance/stillstand with moraine formation at 13.5 and 13.0 ka. During the early YD, glacial retreat exposed the highest surfaces of the Saboredo Cirque (~2300-2350 m) at 12.7 ka. Small glaciers persisted only inside the highest cirques (~2470 m), such as in Sendrosa Cirque, with moraines stabilizing at 12.6 ka. The results of this work present the most complete chronology for Pyrenean glacial oscillations from the B-A to the YD.