Cuiot, J . and Couteaux, M. 1992. Quantitative climate reconstruction from pollen data in the Grand Duchy of Luxembourg since 15 000 yr BP. /ourna/ of ABSTRACT: Monthly temperature and precipitation estimates for the period 15 000-2000 yr BP are statistically derived from pollen analytical data obtained from a site near Echternach, Luxembourg. A continuous warming trend of over 10°C is recorded for the period 10 500-8000 yr BP, along with a rise in precipitation of 500 mm. A fairly constant temperature characterised the period between 8000 and 2000 yr BP, though an episode of slight temperature decrease (-2°C) occurred at about 4500 yr BP. The most humid intervals seem to have been at around 9000-7000 and 5000-3000 yr BP (principally during the warm season: more continental influence). In contrast with results obtained from more southerly sites, the 'Older Dryas' climatic reversal is clearly recorded at Echternach slightly before 12000 yr BP. It is marked by a cooling in July temperature of about 4°C and a decrease in monthly precipitation of about 30 mm (40%). Journal of Quaternary Science

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An attempt is made to reconstruct the palaeoenvironmental Holocene history at the timberline on the basis of the analysis of various palaeoecological proxy indicators available on a marshy area and its surroundings in the Taillefer Massif (Isère. France). The multidisciplinary approach involves analyses of pollen assemblages. plant macrofossils, coleoptera remains. subfossil trunks extracted from lakes or peat‐bogs. and charcoals derived from the surrounding soils. This enables definition of the respective roles of five forest taxa (Pinus uncinata Mill., Pinus cembra L., Larix decidua Mill., Abies alba Mill, and Picea abies L. Karsten) in the evolution of high altitude forests during the Holocene. Pinus uncinata was present on the plateau throughout the Holocene. Larix and Pinus cembra were present only during two periods: 7500‐5000 BP and 3500‐2000 BP. All trees disappeared from the plateau at about 2000 BP, while, at lower altitude. Abies was replaced by Picea. The action of both climate and early human impact can explain these changes.

Alors que la majorité des auteurs rattachent la précipitation du tuf calcaire aux périodes chaudes, le contraire avait été affirmé récemment pour les tufs de Gaume. L'analyse pollinique prouve que l'optimum de formation se situe dans les périodes d'optimum climatique. Seul un tuf lacustre à Characées à Echternach est déposé en période froide en conditions particulières. Deux affirmations se trouvent pratiquement dans toutes les publications sur les tufs : les eaux de source seraient sursaturées en carbonates et la photosynthèse favoriserait la formation des dépôts. Les mesures effectuées prouvent que les eaux des sources incrustantes sont encore agressives et que la photosynthèse ne joue aucun rôle.