Sequence stratigraphy of the second member of the Upper Triassic Xujiahe Formation in the middle part of western Sichuan depression
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摘要: 须家河组二段是川西坳陷中的区域气层。长期以来,地质分层采用岩石地层单位界面。这一界面的穿时性,造成了构造演化分析中的误差。笔者以钻井、测井和地震资料为主要研究对象,在引入地震反射"等时"约束条件的前提下,通过对须家河组长期基准面旋回层序及须二段中期基准面旋回层序的划分和对比,在建立高分辨率时间-地层格架的基础上,经过地震微相特征的仔细分析,确认须二段顶面属Ⅲ级整合界面。Abstract: The second member of the Upper Triassic Xujiahe Formation is the regional gas horizons in the middle part of western Sichuan depression. The stratigraphic horizons have long been divided according to a lithostratigraphic boundary. The diachronism of this boundary may give rise to the differences in the examination of tectonic evolution. The findings based on sequence stratigraphy in this study have disclosed that the second member of the Upper Triassic Xujiahe Formation should be the delta deposits consisting of a complete medium-term cyclic succession, including the delta plain-delta front symmetrical cyclic sequence and deepening-upward delta plain asymmetrical cyclic sequence. The top boundary of the second member of the Upper Triassic Xujiahe Formation is interpreted as a third-order conformity.
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