A 140,000-YEAR CONTINENTAL CLIMATE RECONSTRUCTION FROM 2 EUROPEAN POLLEN RECORDS

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Reconstruction and paleoclimatic interpretation of Holocene lake-level changes in Lac de Saint-Leger, Haute-Provence, southeast France

International audienceLac de Saint-Leger is located in the transitional region between Central Europe and the Mediterranean. The reconstruction of the past lake-level changes was based on plant macrofossil and mollusc analyses of two stratigraphic transects correlated by pollen analysis. Past changes in lake level were quantitatively reconstructed from changes in the recorded level of overgrowth. In the beginning of the Holocene the lake level was high; however, a progressive lowering occurred from about 7500 B.P. Between about 4500 B.P. and 4000 B.P. there was a moderate rise in lake level. Subsequently the lowering was continued and culminated between about 3300 B.P. and 2500 B.P. From the reconstruction there then occurred a progressive rise in lake level until the present. The lake-level changes recorded in Lac de Saint-Leger are compared with a compilation of lake-level data from southern France. The major long-term changes can be supposed to be regionally significant and related to climatic changes. To obtain a basis for paleoclimatic interpretation of the changes in lake level, the reference pollen diagram from Lac de Saint-Leger was used for a quantitative reconstruction of paleoclimate. During the middle and later part of the Holocene there is a reasonable consistency between the recorded pattern of lake-level changes and the paleoclimatic reconstruction. During the earlier part of the Holocene there are some disagreements, which may be explained by the shortage in adequate modern pollen analogues. The paleoclimatic reconstruction indicates that the major changes in lake level were mostly related to changes in precipitation. (C) 1997 Elsevier Science B.V

POLLEN TURNS BACK CLIMATES CLOCK

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RECENT CONTRIBUTIONS TO THE CLIMATOLOGY OF THE LAST GLACIAL INTERGLACIAL CYCLE BASED ON FRENCH POLLEN SEQUENCES

International audienceNew pollen data derived from three long French sequences and methodological improvements in the methods used to reconstruct past climates are summarized here, after a short presentation of the study sites and pollen diagrams. Estimated climate parameters during the major episodes of the last 140,000 years are shown to be coherent between sites. Analysis of the seasonality variations provides much additional information. In particular it is shown that the advection from the ocean has governed the last climatic cycle on the European continent

Tentative Paleoclimatic Reconstruction Linking Pollen and Sedimentology in La-grande Pile (vosges, France)

Quantitative values of palaeotemperature and palaeoprecipitation were reconstructed from pollen record in La Grande Pile (Guiot et al., 1989). Some weaknesses appear in the reconstruction, particularly for the cold periods and for the periods of deglaciation. From sedimentological data, i.e. organic carbon content, periglacial loess content and smectite content, it is attempted to refine the palaeoclimate reconstruction. More accurate values are calculated between the upper and the lower limits of the pollen data. During the deltaO-18 Stages 4 and 2 of the last glacial cycle, the climate was the coldest and the driest. It was less cold and more humid during the Stage 3

THE CLIMATE IN WESTERN-EUROPE DURING THE LAST GLACIAL INTERGLACIAL CYCLE DERIVED FROM POLLEN AND INSECT REMAINS

International audienceUsing the pollen sequence of La Grande Pile XX (France), we review problems with the application of transfer functions in paleoclimatic reconstructions. One of them is to find modem analogues for the herbaceous vegetation of the cold periods. We propose a method to distinguish between steppes and tundra vegetations for which the modems are only partial analogues of the glacial periods. Another method to solve these problems is based on constraining by insect remains. The two methods provide coherent reconstructions. The results are also compared with other paleodata. There is a good correlation with the six cold Heinrich events between 70 and 15 ka B.P. A cooling event during the Eemian period (marked by high percentages of Taxus) at about 125 ka B.P. needs still to be correlated with high resolution ocean and ice cores

Middle Pleistocene temperate deposits at Dinge, Ille-et-Vilaine, northwest France: pollen, plant and insect macrofossil analysis

International audienceNine cores were taken from a damp depression at Dinge, Ille-et-Vilaine, northwest France. Analyses of the pollen, plant macrofossil and Coleoptera remains preserved in the same organic samples of two profiles suggest a temperate vegetation characterised by a mixed deciduous forest with mesophilous taxa (Carpinus, Fagus, Quercus) followed by a coniferous forest with Pinus and Picea. The determination of plant taxa to species was made either directly through the identification of plant macrofossil remains and pollen or indirectly through the identification of phytophagous Coleoptera specifically related to certain plants. Stratigraphical information derived from pollen, plant macrofossil and insect data indicates that this sequence may be correlated with a temperate episode older than the Eemian and younger than the Holsteinian, possibly the Bouchet 2 (Oxygen Isotope Stage 7c) or Bouchet 3 (Oxygen Isotope Stage 7a) temperate periods or the Landos Interglacial (Oxygen Isotope Stage 9 pro parte). (C) 1997 by John Wiley & Sons, Ltd

CLIMATE VARIATIONS IN EUROPE OVER THE PAST 140-KYR DEDUCED FROM ROCK MAGNETISM

International audienceRAPID shifts in climate during the last glacial are now well documented, particularly from the oxygen isotope records of the two Greenland ice cores GRIP(1,2) and GISP2(3). In the GRIP record(1,2) these climate events are also seen during the preceding (Eemian) interglacial which may be an analogue for the future climate, warmed by the greenhouse effect. But these shifts are not found in the Eemian section of the GISP2 core(3) casting doubt on whether the rapid shifts in the GRIP oxygen isotope record really do represent a climate signal. Here we present magnetic susceptibility, pollen and organic carbon records from maar lake deposits in the Massif Central, France. These data provide an independent record of past climate and we find that they correlate well with the ice-core records during the last glacial. During the Eemian, two rapid cooling events seen in our record also correlate with those seen in the GRIP ice core, supporting the idea that rapid climate change did occur in the Eemian interglacial and demonstrating that it extended to continental Europe