利用露头、井震及地球化学综合厘定层序界面

侏罗系为鄂尔多斯盆地主要的含煤和含铀岩系，目前对侏罗系层序界面的识别主要依靠野外露头、录井岩性等进行宏观厘定，但在宏观特征无明显差别的地层中，层序界面厘定往往存在人为经验识别的随意性。为此，通过东北缘露头剖面和近千口钻孔电测曲线等常规识别工作，综合二维地震剖面和化学蚀变指数（CIA）垂向上的变化，在鄂尔多斯盆地东北缘侏罗系中识别出3个长期旋回层序界面（TSB1—TSB3）和7个中期旋回层序界面（SB1—SB7）。由于CIA垂向上的变化反映了延安组和直罗组沉积期古气候环境的变化，可将其用于层序界面厘定。综合识别层序界面不仅可以提高识别的准确性，而且可以赋予关键层序界面古沉积环境属性，减弱人为经验识别的影响，从而为整个盆地侏罗系层序地层的划分对比提供可靠依据。 

Integrated identification of sequence boundary through outcrop,seismic with logging and geochemistry: A case of Jurassic in northeastern margin of Ordos basin

Jurassic strata is mainly rock series containing coal and uranium in Ordos basin. The recognition of Jurassic sequence interfaces were mainly relied on the field outcrop, logging lithology of unconformity surface or the sedimentary discontinuity. However, it is tend to experience human recognition of randomness in the sequence interfaces recognition without macroscopic characteristics. Therefore, based on routine identification work such as outcrop profile and electrical curve of nearly 1 000 boreholes, combined with vertical changes of two-dimensional seismic profile and chemical index of alteration(CIA), three long-term cycle sequence interfaces(TSB1-TSB3) and seven medium-term cycle sequence interfaces(SB1-SB7) were finally identified in Jurassic period. The vertical change of CIA generally reflects that the paleoclimate experienced a transition process from warm-humid(dry-wet) alternation to drought-semi-drought from Yan'an to Zhiluo period, which can be used to identify the interfaces. Comprehensive identification of sequence interfaces can not only improve the accuracy,but also endow key sequence interfaces with paleo sedimentary environment attributes, and reduces the impact of human experience influence. Thus provide reliable basis for the division and correlation of Jurassic sequence strata in the whole basin.