Environmental change in Bashang Region historical periods

摘要

The Bashang region is a typical vulnerable eco|environmental zone. Our analysis of paleodunes, paleosol profiles, and lake changes taking place during last ten thousands years indicated that:(1) 10-6 9 ka B.P. was a post|glacial temperature|increasing stage, in which lakes had their high water level; (2) 6 9-3 0 ka B. P. was a large warm stage, during which four paleosol layers were developed and climate fluctuation has assumed 4-5 small cold|humid and cold|dry alternations. Since 5 4 ka B.P, the lakes tended to gradually shrink; and by 2 1 ka B.P., water level has fallen by 2 7 m; (3) since 3 0 ka B. P. a general trend of the region was to change into a dry, warm|dry and cold|dry environment.