Glacial and periglacial dynamics during the last deglaciation in the Bonabé Valley (Marimanha Massif), central southern Pyrenees

Abstract

In this study we reconstruct the deglaciation of the Bonabé valley in the Marimanha massif (upper Noguera Pallaresa valley, central southern Pyrenees) by combining geomorphological mapping and cosmic-ray exposure dating methods applied to a set of 17 samples from moraines, rock glacier boulders and glacially-polished surfaces. This valley includes eight moraine systems and two rock glaciers, and the geochronological results reveal one of the most complete sequences of glacial and periglacial phases documented in the Pyrenees, from the Heinrich Stadial 1, Bølling-Allerød and Younger Dryas events to the onset of the Holocene. The cooling recorded during the Heinrich Stadial 1 generated three phases of glacier advance/still stands between 17.3 and 15.3 ka, with the development of 2-4 km long alpine glaciers. The Bølling-Allerød interstadial entailed a rapid process of valley and cirque deglaciation around 15-13 ka, and the replacement of glacial processes by periglacial dynamics characterised by the formation of polygenetic rock glaciers. The Younger Dryas favoured both the development of the upper ridges of a rock glacier that stabilised around 12.3 ka, and the formation of new small cirque glaciers that built moraines which stabilised around 11 ka.