山东东营盆地早第三纪介形虫壳体微量元素的特征及意义

CHARACTERISTICS OF TRACE ELEMENTS IN PALEOGENE OSTRACOD SHELLS FROM THE DONGYING BASIN AND THEIR SIGNIFICANCE

通过对山东东营盆地早第三纪生油层中介形虫化石壳体进行微量元素分析 ,得出在沙河街组一段中、下亚段沉积时期 ,湖水较浅、盐度高 ,气候干燥 ,古湖泊营养水平低 ;上亚段沉积时期 ,湖水变深、变淡 ,气候凉湿 ,湖水营养化程度增高。这些结论与沉积学、古生物学和稳定同位素研究的结果是一致的 ,表明介形虫壳体微量元素化学分析对于早第三纪生油层沉积环境的再造能发挥重要的作用。

Trace element analysis has been carried out on ostracod shells from the first member of the Shahejie Formation (Oligocene)(SHA 1) in the Dongying Basin, East China. These elements involve Ca, Sr, Mg, K, Na, Cl, P, Fe, Mn, Al, and Si. According to the changes of these elements and the ratios of Sr/Ca, Mg/Ca, Na/Ca, Fe/Mn, we concluded that the paleosalinity is higher, the water depth is lower, the paleoclimate is dry, and the trophic level of the paleolake is lower during the early—middle SHA 1 depositional periods; and in the late SHA 1 depositional period, the water becomes deeper, paleosalinity becomes lower, the temperature is lower, but the trophic level of the paleolake becomes higher. These conclusions are compatible with the results of the sedimentological, paleontological and stable isotopic studies on the Dongying Basin. This also proved that the trace element chemistry could provide an important tool to reconstruct the paleoenvironments of Paleogene oil source rocks.