黄陵背斜的构造几何形态及其成因探讨

Structural geometry and the origin of the Huangling anticline

黄陵背斜位于扬子克拉通的东缘,其核部出露的崆岭群被认为是扬予克拉通的基底岩石,并成为华南地质学研究的热点地区。从区域上看,黄陵背斜紧邻江汉盆地,东西两侧分别是荆当盆地与秭归盆地,黄陵背斜和周缘盆地构成明显的隆起—坳陷相互对应的构造。详细的野外观察和构造几何学的剖析表明,黄陵背斜的两翼西陡东缓,构成不对称背形的穹隆构造。在穹隆形成过程中,相应的岩石变形以顺层滑脱及相关的褶皱和小规模的逆冲断层为主,在早三叠世薄层灰岩、志留纪龙马溪组页岩、奥陶纪灰岩、寒武纪炭质灰岩以及震旦纪陡山沱组薄层灰岩广泛发育,并具有垂向缩短的重力滑脱特点,构造叠加关系指示了其形成于晚侏罗—早白垩纪之间。在构造变形分析的基础上,并深入探讨了黄陵背斜成因的3种可能的动力学背景。

Huangling anticline,located in the east of the Yangtze Craton,is becoming a hotspot of the geology research in south China, because the Kongling Group exposed in its core region is thought to be the basement of the Yangtze Craton. On regional scale, Huangling anticline is adjacent to the Jianghan Basin and between the Jingdang Basin to the east and the Zigui Basin to the west respectively, which form a significant uplift-depression structure. With detailed fieldwork and structural study, Huangling anticline is an asymmetrical antiform of which the western limb is more steep and the eastern limb is more gentle. During the formation of the dome ,layer-slip with related folds and small-scale thrust faults, as the dominant deformation style, are well developed in the Early Triassic limestone, Silurian shale of the Longmaxi Formation, Ordovician limestone, the Cambrian limestone and the Sinian limestone of the Doushantuo Formation. Those deformations are characterized by vertical shortening and gravity collapse, and according to structural superposition relations, the timing of the doming is between Late Jurassic and Early Cretaceous. Based on the structure deformation, we discuss three possible dynamics setting of the Huangling anticline.