【摘要】 以苏北盆地里下河地区获取的SG钻孔沉积岩心为研究对象,进行了AMS14C年代、粒度、Rb和Sr含量分析。结果表明,苏北盆地湖沼沉积的粒度分布和Rb/Sr比值能够很好地指示东亚季风区的气候变化。根据粒度和Rb/Sr比值的变化,可将苏北盆地30~17cal ka BP期间的气候变化划分为3个阶段。在30.3~25.9cal ka BP期间,降雨量相对增多,气候相对湿润;25.9~18.3cal ka BP期间,降雨量减少,气候相对干旱;18.3~17.1cal ka BP期间,降雨量又明显增加,气候相对湿润,期间还可能存在变干突变。SG钻孔沉积岩心的环境代用指标与西峰黄土平均粒径、葫芦洞石笋氧同位素有着很好的可比性,并且SG钻孔沉积岩心的黏土含量趋势线与北半球30°N六月的太阳辐射强度曲线极为相似,这表明苏北盆地的气候受太阳辐射驱动下的东亚季风系统影响明显。更多还原

【Abstract】 Sediment cores extracted in Lixiahe area of Subei Basin,eastern China,were analyzed at 2to3 cm intervals for grain size,Rb and Sr content.The results show that grain size distributions and Rb/Sr ratio of the lacustrine deposits can be the index of the past changes in East Asian monsoon precipitation.For instance,greater clay content,smaller mean grain size and higher Rb/Sr ratio reflect increased monsoon precipitation rates.The grain size and Rb/Sr ratio of SG core during 30-17 cal ka BP indicate that the paleoclimate in the region can be divided into three major stages.The first stage is from 30.3to 25.9cal ka BP,in which the climate was humid,and is marked by an higher precipitation rate and expanding water area,as indicated by higher clay content,smaller mean grain size and higher Rb/Sr ratio of SG core sediments.The second stage is from 25.9to 18.3cal ka BP,when the clay content and the mean grain size are relatively low and big,and the Rb/Sr ratio is relatively low,which suggests relatively low precipitation and the shrinkage water area.The third stage is from 18.3to 17.1cal ka BP,in which the climate became humid quickly,and is marked by a higher precipitation rate and expanding water area.The clay content and Rb/Sr ratio curves of SG core sediments are comparable to the mean grain size curve of Xifeng loess and stalagmites oxygen isotope curve of Hulu Cave,and the trend line of clay content curve of SG core sediment is similar to the solar insolation curve in June at 30°N.This indicates that the climate change of Subei Basin should be obviously affected by East Asian monsoon system driven by solar insolation.更多还原