Geochronological reconstruction of the glacial evolution in the Ésera valley (Central Pyrenees) during the Late Pleistocene and Holocene

Abstract. Since the MIS (Marine Isotope Stage) 4, glaciers in the Pyrenees were subject to intricate dynamics, encompassing some advances and retreats not always aligned with the fluctuations observed in other European glaciers. The Ésera valley, located in the Central Pyrenees (northern Spain), provides a distinctive opportunity to reconstruct past climate and glacier fluctuations in high-mountain regions since the Pyrenean Last Glacial Maximum (PLGM). Previous studies of glacial evolution in this valley have employed a variety of methods, including the analysis of glacial lake sediments and detailed geomorphological studies of glacial landforms that are integrated here with new. Measurements of cosmogenic 10Be exposure ages, together with calculations of the equilibrium line altitude (ELA), with the objective of reconstructing the evolution of the Ésera glacier and the associated environmental implications. Following the PLGM, at approximately 75 ka in the Ésera valley, the Ésera glacier commenced a period of retreat during part of the Marine Isotopic Stage (MIS) 3, reaching a point of stabilisation at approximately 47 ka at the location of the Pllan d'Están proglacial lake. Subsequently, a new glacial advance resulted forming the Llanos del Hospital moraine (∼ 16 ka), a glacial deposit located a lower altitude in the valley than Pllan d'Están lake. During that time interval, and including the global Last Glacial Maximum (LGM), lacustrine sediments deposited at Pllan d'Están paleolake indicate that sedimentation took place in a subglacial environment. Following the conclusion of the Oldest Dryas period (OD; ∼ 16 ka) and continuing into the Early Holocene, the Ésera glacier underwent a rapid retreat. The Little Ice Age (LIA) represented the last cold period documented in the Ésera valley, after which the glacier has exhibited a persistent retreatment. The ELA analyses indicate that the temperature in the Ésera valley increased by 3.6 ± 0.45 °C over the past 16 ka, which resulted in the retreat of the glacier front from 1750 to 3000 metres above sea level (m a.s.l.).