Timing of deglaciation and rock glacier origin in the southeastern Pyrenees: a review and new data

Abstract

The aim of this research is to improve our current understanding of the deglaciation stages in the southeastern Pyrenees and integrate it into reconstructions of the long-term deglaciation in the Iberian mountains since the Last Glaciation. First, we examine the existing chronological data for deglaciation in Iberian mountain ranges, mainly focusing on the Pyrenees and the results derived from cosmic ray exposure dating methods. Then, we recalculate the age of 17 samples from four different areas in the SE Pyrenees (Arànser, La Llosa and Duran valleys and Malniu-Guils complex) based on the 36Cl isotope and applying a new age calculator. In addition, we date eight new samples from the Malniu-Guils complex to provide a more accurate chronology for this site. The results do not clarify the timing of the maximum glacier extent, but support an extensive glacial advance followed by multiple small advances and retreats during the Last Glacial Maximum (LGM). Geomorphological and chronological data show evidence of massive deglaciation at the end of the LGM around 18 ka, and deglaciation was practically complete during the Bølling-Allerød interstadial. There is no geomorphological evidence of glacial advances in the cirques during the Younger Dryas. Instead, cirque walls were covered with rock glaciers during the Bølling-Allerød interstadial. The fronts of these rock glaciers stabilized at the end of this period, while their roots remained active until well into the Holocene.