THE LATEST PLEISTOCENE IN SOUTHWESTERN SIBERIA AND KAZAKSTAN

The fossil pollen record of a lake and a swamp in Kazakhstan have prov ided the first dated evidence of Late Glacial sedimentation in that ar ea. During the Late Glacial, open spruce Picea obovata Ledeb. forests began to spread along river valleys and over the Kazakhstan hills. Sib erian larch, honeysuckle, sea buckthorn, dwarf alder and dwarf birch g rew in the Irtish Valley. At that rime, both the average January and J uly temperatures in the northern part of the Kazakhstan hills were at least 2.5-3 degrees C below the present-day values. The greatest depre ssion of the July temperature is estimated for the Semipalatinsk-Irtys h area, at 4.5-5 degrees C; the corresponding figures for January bein g 2.5-3 degrees C. The amount of rainfall remained approximately at it s present level. Existing records fail to identify significant changes in the vegetation and climate at the time of the Late Glacial/Holocen e transition between 12,000 and 9500 BP. At the end of Preboreal time, the southern limits of spruce, Siberian silver-fir and larch approach ed their present positions. During the first half of the Boreal phase, both steppe and open birch forests formed the vegetation in the south ern part of the West Siberian Lowland. Dry bunchgrass-wormwood steppe and semi-desert were the main types of vegetation in Kazakhstan. By 60 00 BP, pine (Pinus sylvestris L.) reached its present day southern lim it in Kazakhstan. (C) 1997 INQUA/Elsevier Science Ltd.