莱州湾E孔中更新世末期以来的地球化学特征

Geochemistry of Core E in the Laizhou Bay since late stage of Middle Pleistocene

对 1 994年在莱州湾沿岸所取的E孔 (37°0 7′N ,1 1 8°5 5′E ,孔深为 82 1m)岩心进行了地球化学研究 .用等离子光谱法测量了 9个常量元素、1 5个微量元素和碳酸钙的含量 .结果表明 ,(1 )E孔大部分常量元素、微量元素含量、尤其元素特征比值(Mn/Fe ,Sr/Ba,Sr/Ca ,Ti/Al)在地层分界处都有明显变化 ,可作为该区第四纪地层划分的重要指标 ;(2 )常量元素含量变化主要受宿主矿物控制 ,主要反映物质来源 ,同时也反映沉积作用和沉积环境 ,Fe,Al,Ca ,Mg ,Mn ,Ti对物源和环境反映较为敏感 ;(3)微量元素在中更新世末期、最后间冰期、最后冰期和全新世四个不同沉积时期分布特征不同 ,尤其在气候“冷期”和“暖期”有不同分布规律 ;大多数微量元素含量变化旋回曲线之“波谷”对应着沙层沉积 ,有 6个沙层代表“暖期”沉积 ,1个沙层代表“冷期”沉积 ;(4)E孔在冰期低海面时期风成粉砂沉积中碳酸钙含量偏高 ,间冰期时海侵沙层中碳酸钙的含量偏低 ,碳酸钙含量变化与粒度和沉积物类型有关 ,对气候。

Geochemistry analysis has been done on Core E taken from (37°07′N,118°55′E, depth: 82.1 m) the Laizhou Bay in 1994. Contents of 9 kinds of invariable elements, 15 kinds of microelements and lime carbonate are measured by means of ICP. The results indicate that most of the invariable elements and microelements in Core E and the ratios of Mn/Fe, Sr/Ba, Sr/Ca, Ti/Al in especial show significant changes in the boundary strata type. So they can be used as characteristic indicator to distinguish Quaternary strata. The changes of the invariable elements are primarily controlled by the host minerals, and they mainly indicate the provenance as well as the sedimentation and depositional environment. Several elements, such as Fe, Al, Ca, Mg, Mn and Ti, are very sensitive to the provenance and environment. The distributions of microelements differ in four depositional periods: late stage of Middle Pleistocene, last interglacial period, last glacial period and Holocene, and especially in the “cold period” and “warm period”. The valleys in the cycle curves of most of microelements correspond with the sand bed sediments, among which there are six sand units representing “warm period” sediments, and one representing “cold period” sediments. The carbonate is on the high side in the aeolian silt sediments formed in the glacial lowering of sea level in Core E, but on the low side in the transgressive sand beds formed in interglacial period. The content variation of carbonate has a direct bearing on the grain size and the styles of sediments, and is a good indicator to the climate, environment and stratigraphic division.