Environment evolution since the Holocene revealed by lacustrine sediments of Meiyan borehole in Taihu Lake,eastern China
In this study,we investigate the Meiyan borehole located on the southeastern shore of Taihu Lake.Based on a reliable chronological sequence established by AMS14C dating,we use elemental geochemistry,including Rb and Sr concentrations and the Rb/Sr ratio,to reconstruct Holocene climate changes.Additionally,foraminifera analysis is employed to explore whether the Taihu Lake region was af-fected by transgressions.The results show that from 11.0-9.1 cal.ka BP,the climate of Taihu Lake Basin gradually changed from humid to dry;from 9.1-6.1 cal.ka BP,the general climate was generally hu-mid,with the wettest period occurring during 8.8-7.1 cal.ka BP;from 6.1～2.0 cal.ka BP,the cli-mate was generally dry with the lowest precipitation;from 2.0-0 cal.ka BP,the precipitation gradually increased and the climate was humid.During the whole Holocene period,the eastern area of Taihu Lake was unlikely to have been influenced by transgressions.Regional comparisons show that the Rb/Sr record in Taihu Lake are consistent with environmental proxies record in neighboring regions during the middle and late Holocene,which is characterized by gradually drying climate in the Middle Holocene and wet cli-mate since 2.0 cal.ka BP.To further explore the climate dynamics,we compared the environmental proxy index with the 30° solar radiation in the northern hemisphere,ENSO frequency records and Holocene mean sea level records.We found that the climate of Taihu Lake Basin was controlled by the solar radiation and ENSO changes,with distinct phases of dominance and coupling between the two factors.Solar radia-tion affected the early and middle Holocene climate of Taihu Lake Basin through direct and indirect effects.Since 2.0 cal.ka BP,the climate has exhibited an El Nino-like state,with an intensified ENSO frequency balancing the effects of weakened solar radiation on precipitation in the monsoon region.As a result,ENSO frequency became the main controlling factor of the climate in the Taihu Lake Basin.The results will provide a reliable basis for understanding the relationship between monsoon and climate change in the lower reaches of the Yangtze River since the Holocene.
万方数据
维普
