对青藏高原北缘共和盆地沙珠玉河的尾闾湖达连海钻孔沉积柱(40.92 m)进行了^(14)C年代测定(10个控制点)和粘土矿物分析(按20cm/70 a间隔的分辨率)。沉积柱底部年龄为14.5 cal ka BP。根据沉积柱粘土矿物的类型、组合、比率指标综合分析,重建了共和盆地14.5 cal ka BP以来气候环境的演化历史。冰消期(14.5~10.0 cal ka BP)盆地气候总体特征表现为干冷,盆地物理风化强:早中全新世(10.0~5.0 cal ka BP)气候表现为温湿,盆地化学风化为主,气候最宜期发生在中全新世的6.0 cal ka BP前后;晚全新世(5.0~0.0 cal ka BP)气候表现为干冷,盆地物理风化盛行。末次冰消期以来,共和盆地粘土矿物记录的气候环境变化阶段与高原其它湖泊指标记录的阶段基本一致。共和盆地粘土矿物记录的气候环境兼有西风、季风模式的特征。
With the analysis of the sources and formation mechanism of the clay minerals in the sediment core from the Dalianhai lake in the Gonghe Basin,northeastern Tibet-Qinghai Plateau,clay mineral composition proxies,grain-size and carbonate contents have been employed for high-resolution study in order to reconstruct East Asian Summer Monsoon （EASM） over the northeastern Tibet-Qinghai Plateau during the lastdeglacial.The study also extended to establish a relationship between vegetation cover changes and erosion during the last 14.5 ka with pollen record and clay mineral proxies.Smectite/kaolinite and smectite/（illite＋chlorite） ratios allow us to assess hydrolysis conditions in lowlands and/or physical erosion process in highlands of the Gonghe Basin.Before 12.9 Cal ka BP,both mineralogical ratios show low values indicative of strong physical erosion in the basin with a dominant cold and dry phase.After 12.9 Cal ka BP,an increase in both mineralogical ratios indicates enhanced chemical weathering in the basin associated with a warm and humid climate.The beginning of Holocene is characterized by high smectite/（illite＋chlorite） and smectite/kaolinite ratios that is synchronous as with deposition of many peat laminae,implying the best warm and humid conditions specifically between 8.0 to 5.5 Cal ka BP.The time interval after 5.0 Cai ka BP is characterized by a return to high physical erosion and low chemical weathering with dry climate conditions in the basin.Comparing variations of clay mineral assemblages with previous pollen results,we observe a rapid response in terms of chemical weathering and physical erosion intensity to a modification of the vegetation cover in the basin.
