Abstract:

       Based on the analysis of the spore-pollens in 529 core samples from 600 m deep borehole HS1 drilled in Nanzhangzhuang Village of Hengshui District, Hebei Province and in combination with the chronostratigraphic framework recovered by the palaeomagnetic and optical luminescent dating, the spore-pollen assemblage sequences in Hengshui District of Central Hebei Plain since 3.50 Ma BP have been established. During the period of 3.50-2.58 Ma BP, the sedimentary environment was stable, mainly with extremely-shallow water flood plain and shallow-lake deposit. The spore and pollen were not abundant and their assemblage structures were simple, indicating that there was not much change in precipitation and temperature,and that the climate was warm and humid by the gradual transition to the cold and dry. During the period of 2.58-0.78 Ma BP, the vegetation changed frequently and the ancient monsoon climate prevailed, representing the frequent change of climate, which was characteristic of being mild and slightly-dry in early stage, warm and humid in the middle stage and cool and slightly-dry in the late stage. During the period of 780-15 ka BP, the composition of spore-pollen assemblage was rich and complicated, but it changed greatly within the period, indicating the dramatic magnitude and high frequency of climate change. Since 15 ka BP, the dry climate has occurred in general with quicker change frequency, the vegetation pattern has presented as the forestry-prairie transition.

Key words: spore-pollen assemblage, ancient vegetation, palaeoclimate, environmental evolution, Hengshui District of Hebei Province