Last glacial fluctuations in the southwestern Massif Central, Aubrac (France): First direct chronology from cosmogenic 10Be and 26Al exposure dating. (1st June 2022) - Ancrenaz, Arthur
Abstract: The chronology of the late Pleistocene glaciation in the Massif Central, France, is not well documented and there are divergent hypotheses regarding the timing of glacial events in this area. This study aims at reconstructing the chronology of late Pleistocene glacial fluctuations in the Aubrac Mountains. We present a new set of Be-10 and Al-26 exposure ages from twenty erratic boulders embedded in six glacial landforms. Glacial landforms were sampled to determine the timing of three glacial stades and the deglaciation of the Aubrac Mountains. These new data allowed us to constrain the timing of: (i) the Local Last Glacial Maximum, which is coeval with the early Marine Isotopic Stage 2 (MIS 2) (28–24 ka), and (ii) the Grandvals and Bouquincan stades, which are both coeval with the late MIS 2 (24–16 ka). Deglaciation occurred during Heinrich Stadial 1 (18–15.6 ka). This new direct glacial chronology is supported by regional paleoenvironmental proxies and it updates the chronostratigraphic framework available for the southwestern Massif Central. Western European atmospheric circulation changes (i.e., a southward shift in North Atlantic storm tracks and Mediterranean influences) during MIS 2 were identified as significant factors controlling glacier growth in the Aubrac Mountains as well as other glaciated mountains within the southwestern Massif Central, such as the Cantal, Margeride and Lozère mountains. Highlights: The Aubrac icefield fluctuations (Marine Isotopic Stage 2) were used as significant climatic proxies in the Massif Central. Timing of three distinct glacial stades were inferred from cosmogenic exposure dating (n = 20). The Local Last Glacial Maximum was coeval withthe early Marine Isotopic Stage 2 (28–24 ka). Minor glacier advances were recorded during the late Marine Isotopic Stage 2 (24–16 ka). The Heinrich Stadial 1 (18–15.6 ka), characterized by an arid climate, was coeval with the Aubrac Mountains deglaciation.