Rapid deglaciation during the Bølling-Allerød Interstadial in the Central Pyrenees and associated glacial and periglacial landforms

• Published in: Geomorphology
• Main Authors: Oliva, Marc, Fernandes, M., Palacios, D., Fernández-Fernández, J.-M., Schimmelpfennig, I., Antoniades, D.
• Other Authors: Universitat de Barcelona (UB), Universidade de Lisboa = University of Lisbon (ULISBOA), Universidad Complutense de Madrid = Complutense University of Madrid Madrid (UCM), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Research Group ANTALP (Antarctic, Arctic, Alpine Environments) - Government of Catalonia2017-SGR-1102Research Group ZEPHYRUS (Climate Change and Environmental Systems) of the Universidade de LisboaSpanish Ministry of Economy and CompetitivenessCTM201787976-PPortuguese Foundation for Science and Technology02/SAICT/2017 -32002Spanish GovernmentRYC-2015-17597Centre National de la Recherche Scientifique (CNRS)French National Research Agency (ANR)College on Polar and Extreme Environments (Polar2E) of the University of Lisbonpostdoctoral grant within the NUNANTAR project, Fundacao para a Ciencia e Tecnologia of PortugalFCT - UIDB/00295/2020
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU]Sciences of the Universe [physics]; Ice cap
• Online Access: https://insu.hal.science/insu-03207633; https://insu.hal.science/insu-03207633/document; https://insu.hal.science/insu-03207633/file/1-s2.0-S0169555X21001434-main.pdf; https://doi.org/10.1016/j.geomorph.2021.107735

International audience The Central Pyrenees hosted a large ice cap during the Late Pleistocene. The cirques under relatively low-altitude peaks (2200–2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. Here, we focus on the headwaters of the Garonne River, namely on the low-altitude Bacivèr Cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. We reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. Ice thickness in the Bacivèr Cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the Garonne paleoglacier. However, by ~15 ka, during the Bølling-Allerød (B-A) Interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the Garonne paleoglacier. Glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debris-covered and rock glaciers in their final stages. Climate conditions prevailing at the transition between the B-A and the Younger Dryas (YD) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the B-A or the YD. The melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. These remained active throughout the Early Holocene until at least ~7 ka. Since then, the landscape of the Bacivèr Cirque has seen a period of relative stability. A similar chronological sequence of deglaciation has been also detected in other cirques of the Pyrenees below 3000 m. As in ...