青藏高原米林地区晚更新世晚期植被演替与环境变迁

Vegetation Succession and Environmental Transition During Late Pleistocene in Milin Area,Tibetan Plateau

位于青藏高原南部的米林地区在晚更新世晚期沉积了一套湖相沉积体系,为了探讨当时米林地区的古植被、古环境信息,在米林机场实测了一条晚更新世晚期剖面。根据样品14C测年结果初步认定该剖面湖积物的底部年龄约40kaBP,顶部年龄约12kaBP。根据孢粉分析研究把该剖面自下而上划分为4个孢粉组合带以及对应的4个植被发展演替阶段:①第一阶段(对应孢粉组合带Ⅰ;36～28kaBP)为森林草甸植被类型;②第二阶段(对应孢粉组合带Ⅱ;28～23kaBP)为高山草原植被类型;③第三阶段(对应孢粉组合带Ⅲ;23～18kaBP)为蒿草草原植被类型;④第四阶段(对应孢粉组合带Ⅳ;16～13kaBP)为荒漠草原植被类型。在此基础上,初步推论青藏高原南部晚更新世晚期气候环境演化为:从40kaBP至全新世高原南部气候类型总体寒冷偏干旱出现小型波动,与全球的冰期和间冰期吻合较好。

In order to probe into the vegetation succession and environmental transition of Milin region during the Late Pleistocene,a measured section nearby the Milin airport,Southern of Tibetan Plateau,was carried out.The sediment of Milin section represents a set of lake sedimentary facies in the late stage of Late Pleistocene.The age of the sediment is between 40-12 kaBP by the test of 14C.According to the pollen analysis from bottom to up,this section is divided into four sporo-pollen assemblage belts and the corresponding four vegetation succession stages of development.（1） the first stage（corresponding with sporo-pollen assemblage belt I;36-28 kaBP）： the forest meadow vegetation type;（2） the second stage（corresponding with sporo-pollen assemblage belt Ⅱ;28-23 kaBP）： the alpine grassland vegetation type;（3） the third stage（corresponding with sporo-pollen assemblage belt Ⅲ;23-18 kaBP）： the Artemisia grassland vegetation type;（4） the fourth stage（corresponding with sporo-pollen assemblage belt Ⅳ;16-13 kaBP）： the desert grassland vegetation type.Based on these analysis,it indicats that from 40 KaBp to Holocene the climate of the southern Tibetan Plateau is in general cold and drought with small fluctuations,and it has good coherence with global glacial stage and interglacial stage.