Jo

Figure 2.7

continued

On the basis of this information we can present a reasonably detailed reconstruction of climatic and ecological fluctuations over this time range, covering a wide area of western and central Europe (see for example Behre 1990; Zagwijn 1990; LIGA 1991a; Sejrup & Larsen 1991; Behre & Plicht 1992).

Figure 2.7

continued

There is now no doubt that the two major cold periods, i.e. isotope stages 5d and 5b, were glacial in character, in the sense of involving a major expansion of the continental ice sheets from their previous inter-glacial limits (Shackleton 1977, 1987) (Fig. 2.1). The oxygen-isotope records leave no

LES ECHETS GRANDE PILE

Precipitation Temperature Precipitation Temperature

Lars Zagwijn

-600 -400 -200 0 -12-8—4 0 -«X) -600 -400 -200 0 -12 -8 -4 0

Figure 2.8 Estimates of mean annual temperatures and precipitation over the past 140,000 years derived from climatic analyses of the vegetational patterns in the Ees Echets and Ea Grande Pile pollen cores in eastern France (see Figs 2.6, 2.7). The main climatic phases defined in the Grande Pile sequence are shown in the central column; correlations with isotope stages in deep-sea cores are shown on the right. The horizontal bars indicate the confidence limits of the temperature and precipitation estimates. After Guiot et al. 1989, 1993.

-600 -400 -200 0 -12-8—4 0 -«X) -600 -400 -200 0 -12 -8 -4 0

Figure 2.8 Estimates of mean annual temperatures and precipitation over the past 140,000 years derived from climatic analyses of the vegetational patterns in the Ees Echets and Ea Grande Pile pollen cores in eastern France (see Figs 2.6, 2.7). The main climatic phases defined in the Grande Pile sequence are shown in the central column; correlations with isotope stages in deep-sea cores are shown on the right. The horizontal bars indicate the confidence limits of the temperature and precipitation estimates. After Guiot et al. 1989, 1993.

doubt that in global terms the extent of the ice sheets formed during these periods must have attained almost half of the volume of those attained during the period of the last glacial maximum, though of course the growth of these ice sheets could have taken place at rather different rates in different areas of the world - with the growth of the North American ice sheets perhaps preceding by several thousand years those in northern Europe. In northern Europe there is still no clear evidence for the total extent of gla-

ciation during either of these periods, since the direct geological evidence for these ice advances has been obscured by later glaciations in the same areas. The pattern of sharp climatic gradients recorded from north to south and to some extent from east to west across the continent, however, (see below) leaves little doubt that some very substantial glaciation must have built up in the northern parts of Europe during both stages 5d and 5b (Zagwijn 1990; Behre 1990: Sejrup & Larsen 1991).

Estimated timescale (Ka) 70

Was this article helpful?

0 0

Post a comment