湖相富有机质泥页岩地球化学元素高频变化及其地质意义：以泌阳凹陷 BY1井取心段为例

摘要

In this paper,based on the variation of major and trace elements of samples from the core-taking seg-ment of the well BY1 in Biyang Depression by the method of portable fluorescence analyzer,all the tested ele-ments above are sorted into four types of proxies for paleoclimate,paleoproductivity,paleoredox and paleosalini-ty.The results show that there is a good correspondence between the vertical change of geochemical elements and parasequence cycle changes,and the change of the geochemical element cycles can be also used for classifi-cation of more high-frequency sequences.During the process of lake-water depth changes from deep to shallow in a high-frequency sequence unit,varies of elements in shales show apparently regular change,especially on the high-frequency cycle interface,such as the gypsum and dolomite occur near the interface of saltwater and brackish environment respectively,in which the paleoproductivity decreases and the depositional environment transform gradually to oxidation.Those facts result in the organic matter content markedly decreasing near the top interface of high-frequency cycles.The change of geochemical element cycles provides a new effective method for dividing high-frequency stratigraphic unit and forecasting the heterogeneity of organic matter distribution.%利用便携式 X 衍射荧光仪对泌阳凹陷 BY1井2415～2451 m 取心段进行分析，获得多种常量元素和微量元素，并将其中与古气候、古盐度、古生产力和古氧化还原替代指标相关联的部分元素进行归类。结果显示这些相关联的部分元素垂向上的变化和准层序旋回变化两者之间有着较好的对应关系，且利用这些相关联的部分元素旋回变化可进行更高频层序划分。在一个高频层序划分单元内，随着水深由深向浅变化，页岩中部分元素呈现明显规律性的变化，特别是高频旋回界面变化最为明显，如咸水环境高频层序界面附近出现石膏、半咸水环境界面附近出现白云石，相对应的古生产力降低以及向氧化环境逐渐转变，进而导致高频旋回顶部界面附近有机质含量明显减小。利用这些相关化学元素的旋回变化可以进行高频地层单元划分和有机质非均质性分布预测。