子长地区延长组长6段基准面旋回层序识别

The recognition of base-level cyclic sequences in member 6 of Yanchang Formation,Upper Triassic in Zichang Area,Ordos Basin

目的探讨鄂尔多斯盆地子长地区上三叠统延长组长6段基准面旋回层序的识别方法、结构特征、变化规律及成因机理。方法根据岩心、露头、测井资料识别界面,应用旋回层序测井响应模式划分层序,采用等时对比方法横向追踪对比旋回层序。结果研究区长6段可划分为1个长期、7个中期、31个短期旋回层序,建立了研究区以长期旋回层序为框架、以中期旋回层序为对比单元的等时地层格架。结论晚三叠世鄂尔多斯盆地超长期基准面下降之初的三角洲建设时期,研究区沉积了以长6段为主体的C1型长期基准面旋回层序,其长、中期旋回层序等时地层格架的建立为进一步开展短期、超短期旋回层序划分与对比、小层砂体追踪及流动单元识别奠定了基础。

Aim To discuss the characteristic of high-resolution sequence stratigraphy of member 6 of Yanchang Formation,Upper Triassic in Yujiawan area,Zichang,Ordos Basin.Methods Cyclic sequence boundaries were recognized based on cores,outcrops,logging data.Results The formation may be divided into one long-term,7 middle-term,31 short-term cyclic sequences according to boundaries.The isochronous stratigraphic framework was set up by stratigraphic correlation and classification in the studied area with long-term cyclic sequences as frame and middle ones as contrasting units.Conclusion The results indicated that the formation deposited during the basin slowly rising and quickly subsiding.The long cyclic sequences and middle ones are the foundation of stratigraphic correlation and classification of short cyclic sequences and super-short ones as well as the base of tracking correlation of sandy bodies and flow units.