沉积地球化学在层序地层分析中的应用

对于层序地层学研究来说最基本的、也是最关键的问题是层序的识别,而层序的识别包括两个方面的内容,一是层序界面的识别,二是层序内体系域构成的识别.层序界面和层序内体系域的识别除宏观的沉积记录分析方法外,还可通过微观的沉积地球化学分析资料来识别.研究表明,在层序界面的形成过程中,伴随着风化作用的进行,在层序界面上的Fe元素以高价Fe的氧化物形式出现;Al含量高,主要为Al的氧化物;K的含量大于Na元素的含量;Th/U比值很大.体系域与REE和微量元素、常量元素含量密切相关,LST(或SMST)期REE含量最低,TST期REE含量逐渐增高至最大,海泛期达到最高, HST期又逐渐下降.LST期,微量元素含量最低,TST期微量元素含量逐渐增高直至最高,HST期微量元素含量又逐渐下降.

Application of sedimentary geochemistry in the analysis of sequence stratigraphy

The most basic and critical question of the sequence stratigraphy study is sequence identification. The sequence identification contains the identification of sequence boundaries and the constitut on identification of inter systems tract. Besides the macroscopic sedimentary records analytical methods, the sequence boundary and inter systems tract can also be identified by microcosmic analysis information of sedimentary geochemistry. The results show that during the forming process of the sequence boundaries, accompanied by physical, chemical and biological weathering, on the sequence boundaries, the element Fe exists in high valence oxide; the content of AI is high, and major AI exists in oxide; the content of K is higher than that of Na; the ratio of Th/ U is large. The contents of REE, trace elements, major elements are closely related with the systems tract. The content of REE during the period of LST or SMST is minimum, and it gradually rises during TST until it gets the maximum during the maximum flooding period, then gradually decreases during HST period. The trace elements also have the minimum contents during LST period, and their contents gradually increase during TST period until the maximum, then gradually decrease during the HST period.