长江三角洲东部岛屿风尘堆积赤铁矿和针铁矿含量及古气候意义

Hematite and Goethite Content in the Dust Deposition from the Eastern Islands of the Yangtze River Delta and Its Paleoclimatic Significance

长江三角洲东延海域嵊山岛屿风尘堆积地层是记录晚更新世晚期东亚季风演变的重要载体。采用漫反射光谱(DRS)法、柠檬酸钠—重碳酸钠—连二亚硫酸钠(CBD)浸提法结合标准赤铁矿、针铁矿建立标准铁氧化物含量与反射率之间的校准方程,定量重建了东部岛屿风尘堆积的赤铁矿、针铁矿含量的变化特征。结果显示,东海嵊山岛风尘堆积中赤铁矿的含量为0.18%~0.40%,平均值为0.31%,针铁矿的含量为0.7%~1.19%,平均值为1.11%。根据赤铁矿、针铁矿含量特征结合地球化学和环境磁学参数,分析其记录的古环境信息:54~46 ka B.P.时期内气候相对干燥,季风降水减弱,46~39 ka B.P.时期内气候相对潮湿,季风降水增强;46±4 ka B.P.时期的高值可能指示了一个冷事件。

The dust deposition in Shengshan Island,East China Sea is an important aeolian archive,which can pro-vide information on the East China monsoon during the Late Quaternary.In this paper,the sodium citrate-sodium bi-carbonate-sodium dithionite(CBD)method was used to remove free iron,different proportions of hematite and goe-thite were added to the matrix,and the standard was established by the multiple linear regression method.The results show that the hematite content in Shengshan Island is 0.18%-0.40%with an average value of 0.31%,and the content of goethite is 0.77%-1.19%with an average value of 1.11%.According to the content characteristics of hematite and goethite combined with geochemical and environmental magnetic parameters,we conclude that the monsoon precipi-tation decreased from 54 ka to 46 ka,and the monsoon precipitation increased from 46 ka to 39 ka.High values at 46±4 ka may indicate a cold event.