晚新生代风尘沉积的稀土元素地球化学特征及其古气候意义

REE GEOCHEMISTRY OF LATE CENOZOIC EOLIAN SEDIMENTS AND THE PALEOCLIMATE SIGNIFICANCE

通过西峰巴家咀剖面晚新生代风尘沉积中的红粘土、黄土、古土壤的稀土元素、分布模式、特征参数的研究 ,并与晚第三纪红色沙漠风成砂、晚第三纪河流相细砂岩、第四纪沙漠风成砂、现代尘暴粉尘、中国黄土以及青藏高原远源西风粉尘进行对比分析 ,结果表明 ,晚新生代风尘沉积物均具有轻稀土适度富集、缓右倾斜型、Eu负异常的 REE分布模式 ;晚第三纪红色沙漠是红粘土的主要物源之一 ;红粘土和典型的风尘物质——现代尘暴粉尘及中国黄土有相似的沙漠物质来源和形成过程 ,与基岩明显不同 ,这为红粘土的“风成说”而非“残积说”提供了新的证据。巴家咀红粘土的堆积过程与第四纪黄土相似 。

Reported in this paper are the REE geochemistry,distribution patterns and character parameters in late Cenozoic eolian sediments of Bajiazui section at Xifeng City.Also we compare the REE characteristics with other eolian samples from the late Tertiary red desert,late Tertiary fluvial sandstone,Quaternary desert,modern dust storm dust,China loess and remote source westerly dust.All these eolian deposits have similar REE distribution patterns,which are moderately rich in Ce family elements,with negative slopes and negative Eu anomaly.The late Tertiary red desert is one of the major sources of red clay.The red clay has similar material sources and formation to typical eolian deposits such as modern dust storm and China loess.And its REE characters have obvious differences from the fluvial sandstone.These results provide clear evidences for eolian origin of the red clay.The red clay in Bajiazui section was from dust transported by east Asia monsoon circulation rather than westerly circulation from North China desert source areas between 6 5 MaBP and 2 5 MaBP.