贝加尔湖-钻孔(BDP 96-1)的孢粉分析

贝加尔钻探计划（BDP）中的96－1井位于贝加尔湖中央的科学湖脊，1996年冬从位于332m水深以下的钻井采样，钻孔从湖底向下深2000m，根据古地磁资料，钻孔年代推测为5．1Ma，Tsuga,Lepidobalanus,Ulmaceae,Tilia和Corylus发现于钻孔的下部约60m，因为这些化石花粉目前在贝加尔湖地区已经消失，说明该钻孔上部的气候比下部的冷，因此，第四纪的气候比晚第三纪的更为干冷。在亚北极的西伯利亚，冰期时期以草本植物花粉占统治地位，花粉浓度较低，而在间冰期时期以木本花粉为主，花粉浓度较高，在间冰期时期硅藻及有机物总量增加，潮湿度（wet density)及氧同位素比率都降低，相反，在冰期时期硅藻含量及有机物总量降低，而潮湿度（wet dendity)和氧同位素比率都增加。

POLLEN ANALYSIS OF A SEDIMENT CORE (BDP96-1) FROM LAKE BAIKAL

In winter of 1996 a Baikal Drilling Project (BDP) 96-1 was carried out. Sediment core sample were taken at a water depth of 332 m from Academician Ridge in the central area of Lake Baikal in Siberia. The depth of sediment core was 200 m measured from the lake bottom, and the core was estimated by palaeomagnetism to be about 5.1 million years old. Fossil pollen of Tsuga, Lepidobalanus, Ulmaceae, Tillia and Corylus which are not found in the present vegetation in the Baikal area, were recognized in lower layers from about 60 m depth, indicating that the climate of upper parts was colder than the lower parts. Therefore, the Quaternary was colder and drier than the Late Neogene. In subarctic Siberia, it appears that there was fewer total pollen grains dominated by herb pollen in the glacial samples and more total pollen dominated by arboreal pollen in the interglacial samples. It seems that during interglacial the diatom and the total organic matter content increased, and the wet density and the oxygen isotope ratio decreased. In contrast, during the glacial the abundance of diatom and the total organic matter decreased, the wet density and the oxygen isotope ratio increased.