桑植-石门复向斜的形成与演化

桑植-石门构造带是湘鄂西构造带最东边的一个二级构造单元，紧密接壤雪峰陆内变形系统的北西侧，属于二者之间的盆地过渡带，同时也是一个典型的多旋回叠合的复合沉积区。该地区自前寒武纪以来长期受板块构造运动和陆内造山运动的影响，构造轴迹由NNE-SSW 向逐渐过渡到近E-W 向，构造变形极其复杂。对该构造带进行精细的构造解析有助于揭示雪峰山和川东-湘鄂西构造带之间的过渡关系以及探究中上扬子陆内构造的变形机制，对复杂地形区的油气勘探具有重要的指导意义。在此之前，受限于地震资料的品质和数量，前人对湘鄂西-雪峰山之间过渡带的构造变形特征，构造演化及其动力机制的认识还不完善，尚需进一步深化。本文以最新的二维地震资料为基础，结合浅表地质资料和测井资料，依据断层相关褶皱原理，精细刻画了桑植-石门构造带的构造特征，建立了构造带内南、北段相应的地质结构演化模型：桑植-石门构造带南、北段的变形过程大体相似，都是在反冲断层与低角度逆冲推覆断层共同作用下构成了原地埋藏体，之后受燕山期以来的多幕构造运动影响，逐步形成现今的褶皱形态。但二者之间也存在着一定的差异。导致其差异的主控因素：1）“钉线”与变形带之间的距离；2） 后缘的雪峰推覆体的差异变形。

Formation and evolution of Sangzhi-Shimen complex syncline

Sangzhi-Shimen tectonic belt is a secondary-unit in the east of the western Hubei and Hunan tectonic belt, bordering the northwest side of Xuefeng intracontinental deformation system, belonging to the transition zone between western Hubei and Hunan tectonic belt and Xuefeng intracontinental deformation system. In the mean time, it is also a typical multicycle-superimposed sedimentary zone. Since the Precambrian, the area has been affected by plate tectonic movement and intracontinental orogeny for a long time. Therefore, the structural trace has gradually shifted from NNE-SSW to nearly E-W direction from southwest to northeast, also making structural deformation become very complex. The structural analysis on the tectonic belt helps to reveal the transition relationship between the Xuefeng Mountain and East-Sichuan-western Hubei and Hunan tectonic belt and explore the deformation mechanism of the middle and upper Yangtze region, which means a lot to the oil and gas exploration in the complex terrain area. Prior to this, limited by the quality and quantity of seismic data, the understanding of the deformation characteristics, the evolution, and the dynamic mechanism of the transition zone between western Hubei and Hunan tectonic belt and Xuefeng intracontinental deformation system is quite-incomplete. This paper finely depicts the structural characteristics of the Sangzhi-Shimen tectonic belt, establishing the model of tectonic evolution of south segment and north segment of tectonic belt, based on 2D seismic data, geological data and logging data, according to the principle of fault related folds. The deformation process of south segment and north segment of tectonic belt are similar: folds gradually form after recoil fault and low angle overthrust fault forming autochthonous burial structure together, influenced by multi-stage tectonic movements since Yanshan period. However, there are certain differences. The main controlling factors of the differential evolution are as follows: 1） the distance between the nail line and the deformation belt; 2） the differential deformation of the Xuefeng nappe at the back edge.