Structural Geometrics And Kinematics And Formation Mechanism In West Hubei And Hunan Andeast Chongqing Province

The thin- skinned tectonic belt of West Hunan and Hubei and East Chongqing is located on the east of Sichuan Basin, the southeast of Qinling orogen and the west- north of Xuefeng tectonic belt. The western border is Huayingshan fault, the east is Dayong fault and the south border is located on the line Fuling – Pengshui- Cili. From the Proterozoic to the Cenozoic, sedimentary and tectonic evolution of study area is controlled by the tectonic evolution of North China plate, South China plate and the complex multi- role of orogeny in intra-continental orogen. While the Qinghai- Tibet Plateau has a strong influence on it since Cenozoic. The current structures reveal the phenomena clearly and strongly. With the interaction of plate collision, intra- continental orogen, plateau uplift and the basement structure, a series of folds with the shape of trough, barrier and trough-barrier have formed, which reflects the complex and regular tectonic changes in the process of tectonic movement and uplift. Otherwise, with the field observations, the stratigraphic composition are Precambiran to the Zhengyang group of Early Cretaceous from the west to the east of study area, the denudation of the Cretaceous and the Cenozoic shows the process that the rapid changes of tectonic environment and tectonic uplift have a strong influence and reform on the study area. While the uplift time, formation mechanism and the process of multi- detachment tectonic evolution have not been revealed or have a perfect explanation and achievement, which are important problems to solve the South China tectonic and petroleum exploration.On the basis of the theory of fault-related folds, tectonic geology, constructed chronology, this article aim to have a detailed characterization and analysis of geom- etry and kinematics, including the geological structure, the location and deformation styles of detachment with the help of previous results, new geological data, 2D/3D seismic, well logging and drilling and field data. After more research, we want to have an analysis of formation mechanisms and make a prediction of favorable hydrocarbon preservation unit, which will be geological recommendations and evidence to oil and gas exploration and the tectonic formation and evolution of fold belts in the East Si- chuan and Xuefengshan. With the study, we achieve the following results:(1) The structural features show that it is layered decollement deformation in West Hubei and Hunan and East Chongqing province. There are four detachments in the study area: the base detachment, the Middle-Early detachment, the Early Silurian detachment and the Early Triassic gypsum.(2) The base detachment controls the basement structure layer and plays a vital role in tectonic uplift process, and the amplitude decreases from the West Hunan and Hubei to East Chongqing. The Early Cambrian decollement is gypsum in Longwangmiao group in East Chongqing,While it is mud stone in Qiongzhusi group in most of the West Hunan and Hubei area. The Early Silurian decollement is mud stone and shale of Longmaxi Group. It doesn’t play an important role in East Sichuan, while it is a regional detachment in West Hunan and Hubei. The uppermost is Jialingjiang group detachment which is located in East Sichuan and disappeared in Most of West Hunan and Hubei area.(3) Study area mainly developed dual structure, constructed wedge, fault propagation fold and fault-bend fold.(4) It develops barrier folds, the detachment layer is shallow with high viscosity in the East Chongqing province, while it develops trough folds in West Hubei and Hunan, the detachment layer is deep with low viscosity.(5) The ejective folds develop after the trough-like folds and the structural deformation begins from the East to the West. During the process of thrusting, a double structure first develops, and we can see that the detachment folds form in front of it. Another, the reverse faults in the East Sichuan may be related to rigid substrates.(6) Deformation is divided into two phases in the study area. The first is in the Late Jurassic(165 Ma-145 Ma) in West Hunan and Hubei, and it is deformation development stage. The second stage is the late Paleogene(45 Ma-32 Ma) for the rapid uplift stage and the critical deformation period. While in the East Chongqing: the first is in the Late Cretaceous(135 Ma-100 Ma), the structure began to uplift and develop with detachment folds, the total shortening is 2.62km-3.5km and shortening rate 4.89%-5.6%; the second is the Himalayan advanced(25 Ma-15 Ma) for the rapid uplift deformation stage.