基于内蒙古东南缘西拉木伦河上游刘家店河湖相剖面的粒度、磁化率、微量元素地球化学指标,重建该区35 ka BP以来的气候演化过程。结果表明,在MIS 3晚期(35.23 ~ 25.15 ka BP)研究区气候条件总体温暖湿润,并伴有区域变干的趋势; MIS 2阶段(25.15 ~ 11.13 ka BP)气候整体寒冷干燥,但叠加有短暂回暖气候事件。剖面记录的末次盛冰期(LGM)出现于22.25 ~ 18.47 ka BP,此时气候极度干冷; MIS 2阶段叠加了两个短暂气候适宜期,分别出现于18.47 ~ 16.24 ka BP和14.72 ~ 11.13 ka BP。在11.13 ka BP前后研究区进入全新世,气候变得暖湿。刘家店剖面的气候记录与周边气候记录具有可对比性,揭示了区域上东亚夏季风进退具有一致性,并认为自MIS 3晚期以来东亚夏季风受北半球太阳辐射及冰量的共同驱动。此外,刘家店剖面记录揭示的千年尺度气候变化对典型气候事件具有一定的响应,推测这些千年尺度的季风强度变化可能与北大西洋经向翻转环流(AMOC)相关。
英文摘要:
A multi-proxy record including grain size,magnetic susceptibility and trace element from the fluviallacustrine Linjiadian section in the upper reaches of Xilamulun River,situated in the southeastern margin of Inner Mongolia,has been proposed to reconstruct the environmental and climatic changes since the last 36 ka BP. The results show that,during 35.23 to 25.15 ka BP,the late stage of Marine Isotope Stage 3 (MIS 3),warm and wet climate conditions dominated this region accompanied by the trend of regional drought climate. The following period,approximately 25.25 ~ 11.35 ka BP,corresponding to MIS 2,was characterized by frequent fluctuations in climate change. The driest and coldest interval was recognized as the last glacial maximum (LGM),ranging from 22.25 to 18.47 ka BP,and two minor climate optimums occurred in 18.47 ~ 16.24 ka BP and 14.72 ~ 11.13 ka BP. The Holocene commenced at about 11.13 ka BP with the transition to a relatively humid and warm climate. Regional comparisons suggest a roughly synchronous pattern of climate change and variation in the East Asian summer monsoon (EASM),attributing to the force of the northern hemisphere summer insolation and ice volume. In addition,the millennial-scale EASM fluctuation had some influence on the Heinrich (H),and the Younger Dryas (YD),indicating the relevance to the rapid Atlantic meridional overturning circulation (AMOC) oscillations.