西藏拉萨河现代河漫滩及一级阶地沉积物植硅体组合特征

摘　要　通过测制西藏拉萨桑达乡第四系剖面，系统采集并分析了植硅体样品，根据植硅体的形态分类及组合、温暖指数等特征，划分为５个植硅体组合带:组合带Ⅰ为齿型—平滑棒型、石屑型、网脊块状，反映气温温凉；组合带Ⅱ为长方型—平滑棒型、多面体型，显示气候转暖；组合带Ⅲ为长方型、齿型—平滑棒型组合带，显示气候干旱的特点；组合带Ⅳ为长方型—亚铃型、齿型—平滑棒型、多面体型组合带，反映此时气候温暖潮湿；组合带Ⅴ为齿型、帽—平滑棒型、多面体型、石屑组合带，显示气候寒冷的特点。最后在总结分析该区植硅体特征的基础上，对拉萨桑达地区第四纪古植被、古环境进行了探讨。

Characteristics of Phytolith Assemblages from Sediments of Modern River Floodplain and First Terraces in Lhasa River, Tibet

Through systematic analysis of phytolith characteristics on the Quaternary section at Sangda Village in Lhasa,Tibet,such as morphological classification,combination character,warmth index,five assemblage zones can be distinguished as follows: the first combination of tooth model-smooth bar model,chip model,muri block,reflecting a warm-cool climate;the second,rectangular model-smooth bar model and polyhedron model,reflecting the warmer climate;the third,rectangular model,tooth model-smooth and bar model,reflecting a drought climate;the fourth,rectangular model-dumbbell model,tooth model-smooth bar model and polyhedron model,indicating warm and damp climate;and the fifth,tooth model,cap model-smooth bar model,polyhedron model and chip mode,indicating a colder climate.The study of morphological classification and combination could be applied for probing into palaeoenvironment and paleo-vegetations of Quaternary in the Sangda village,Lhasa area.