Sedimentary record of environmental evolution since ca 2000 cal yr B P ago in Qehan Lake, Inner Mongolia

A 97cm long lacustrine section from Qehan Lake, situated in eastern Inner Mongolia, was used to reestablish the environ-ment and climate changes since the last 2070cal a BP. The chronological framework was built on seven AMS¹⁴C ages. On the basis of pollen-spore characteristics and grain size distribution, three environmental stages can be recognized. From 2070~1150cal a BP, this interval was featured by high total pollen concentration, with the dominance of Artemisia and Chenopodiaceae; lacustrine sediments were mainly composed of silt and each fraction presented quite low amplitudes of increases, indicating the weak hydrological condi-tions and high lake level; this period was characterized by a warm, cool and slightly humid climate. During the period of 1150~825cal a BP, the total pollen concentration significantly decreased and the pollen percentages of xerophyte, especially Ephedra, reached the maximum; the coarse particle content showed obviously increase, sugge sting strong hydrodynamic conditions and low lake level; so in this period, the climate was cold and dry, especially from 940cal a BP to 870cal a BP. Since 825cal a BP, the climate mainly tend-ed to become warm and slightly humid with the occurrence of cold and dry oscillations. Solar activities might have been the domi-nant force that drove the climate changes in Qehan Lake area since 2000 years ago.