The deglaciation of the Pyrenees through the 47 ka record of Pllan d'Están paleolake (Ésera valley)

The last deglaciation in the Pyrenees was a complex period with several glacier advances associated with rapid climate changes which differ in terms of timing and intensity. The 46.7 ka lacustrine sequence of Pllan d’Están paleolake (1,840 m a.s.l.) provides new information about that deglaciation period for the first time in the Ésera valley. The multiproxy analysis (sedimentological, geochemical and biological indicators) constrained with a robust chronological model, enabled the longest reconstruction of the glacier evolution, climate and environmental change made in the Pyrenees to date. This lacustrine sedimentary sequence (4.9 m) is composed of banded to finely laminated silts with few intercalations of massive sections where carbonatic, siliciclastic and organic facies appear from the bottom to the top characterizing environmental changes from a subglacial/proglacial lake to the current peatbog. A cold and glacier-dominated period from 46.7 to 15.9 ka BP was interrupted by a warmer period spanning from 38.2 to 34.8 ka. The vegetation succession determined by the palynological analyses is similar to other Pyrenean valleys but dates the onset of mesophyte expansion at 13.8 ka BP during the Allerød, pointing to a difference with other European sequences where temperate forest development took place earlier, associated with the Bølling period. The colder conditions of the Younger Dryas (13-34 11.7 ka) have been detected from cold tolerant diatom taxa that preceded a peatbog development during the Holocene (11.7 ka BP – present-day). These results, together with previously studied Pyrenean sequences, allow characterizing past environmental changes during last deglaciation phases in southern Europe.