The last deglaciation in the central Pyrenees: The 47 ka Pllan d’Están paleolake record (Ésera valley)

Abstract

Last deglaciation was a complex period in southern European mountains with several glacier advances associated to rapid climate changes which differ in terms of timing and intensity. The 46.7 ka BP lacustrine sequence of Pllan d’Están paleolake (1840 m a.s.l.) located in the Central Southern Pyrenees (northern Spain) provides new information about that deglaciation period for the first time in the Ésera valley. We present a multiproxy analysis including sedimentological, geochemical and biological (pollen and diatoms) indicators that, together with a chronological frame constrained by 14C and OSL dates, 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 BP. The vegetation succession determined by the palynological analyses is similar to other Pyrenean valleys but dates the onset of mesophytes 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 to the Bølling period. The colder conditions of the Younger Dryas (13–11.7 ka BP) 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.