西藏扎布耶盐湖晚第四纪孢粉植物群的初步研究

A PRELIMINARY STUDY ON LATE QUATERNARY FLORA IN CHABYER CAKA SALT LAKE,XIZANG(TIBET)

扎布耶盐湖位于西藏青藏高原腹地。通过该湖ＺＫ２钻孔的孢粉分析，揭示了约３６０００ａＢ．Ｐ．以来扎布耶地区的气候和湖盆演变。约在３６０００－３３０００ａＢ．Ｐ．，扎布耶地区为森林草原，气候冷、湿；约３３０００－３００００ａＢ．Ｐ．，为灌丛草原，气候温、干；约３００００－２７５００ａＢ，Ｐ．为干旱草原，气候偏暖、湿；约１８０００－１２０００ａＢ．Ｐ．，为干旱草原，环境寒冷，干燥；约１２０００－４０００ａＢ．Ｐ．，扎布耶地区各类草本植物繁茂，气候偏温、干。另外，根据水生藻类化石群的分析，自３６０００ａＢ．Ｐ以来，扎布耶盐湖有三次湖进、淡水湖期，同时也有三次湖退事件。

The Chabyer Caka Salt lake is located in the hinterland of Tibetan Plateau.Sediments of Borehole ZK2 in the lake have been studied with pollen analysis methods.The pollen data reveal several stages of evolution in flora,environment and the lake basin since 36KaB.P .The Chabyer Caka area was a forest steppe with a cold and wet climate from 36 to 33KaB.P.It was a shrub steppe of a slightly temperate and dry climate during the period of 33 to 30KaB.P.and developed into a drought steppe of a cold and dry climate in the period of 30-27.5KaB.P.,then it became a shrub steppe again and tended to be under a temperate and wet environment from 27.5 to 18Ka B.P.The area changed to a desert steppe with a cold and dry climate during the period of 18-12Ka B.P.and to a steppe plant cover with a cool and dry climate in the Period of 12-4Ka B.P.This salt lake was almost freshwater before Holocene.There were three cycles of transgressions and regressions in the lake from 36 to 12KaB.P.,which were controlled hy both climatic and tectonic changes.