Potential influence of Bond eventson mid-Holocene climate and vegetationin southern Pyrenees as assessed fromBurg lake LOI and pollen records

International audience ; Superimposed on the long-term climate variability attributed to orbital forcing, there are other modes of variability covering timescales from interannualto millennial throughout the Holocene. Their signatures in climate proxy archives can differ substantially because of their lower magnitude and regionaldiversity. However, if identified they can yield better understanding of the physical mechanisms regionally linking causes and effects. Here we describe ahigh-resolution record of organic matter accumulation in the sediments of Burg lake (Pyrenees, NE Iberian Peninsula), as assessed using loss on ignition(LOI), and compare it with the ice rafted debris (IRD) indexes from the North Atlantic. The LOI record indicates two main phases in the water body, alacustrine phase as a shallow lake and a palustrine phase as a fen. The latter covers the period 2600–7200 cal. yr BP and within it there is a high coherencebetween LOI and IRD, which indicates submillennial climate fluctuations in the Pyrenees that can be related to the North Atlantic influence. The Burg’s LOIrecord suggests wetter (and occasionally colder) situations in the Pyrenees during high IRD in the Atlantic (Bond oscillations). These fluctuations wouldlikely affect the snow covered period in the mountains (winter and spring seasons) the most, the period in which Atlantic westerlies currently have higherinfluence on precipitation over the Pyrenees. These climatic oscillations could have favoured Abies penetration during the mid Holocene, as evidencedby increased pollen percentages of this taxon during low IRD values (drier conditions). The pollen record also suggests potential relationships betweenclimate and human activity as early as at mid Holocene, as human-related cereals increase during all the low IRD periods. The human signature (charcoal,cereals) becomes particularly evident at around 2800 cal. yr BP; in this oscillation Pinus overtake Abies in the conifer response to low IRD.