Geological Structure And Its Formation And Evolution Of The Foreland Thrust Belt In Southern Margin Of Junggar Basin

The foreland thrust belt of southern margin of Junggar Basin was influenced by several periods of tectonic movements, the especially strong tectonic alteration of Himalayan movement makes the area complex for hydrocarbon exploration. Based on previous studies and the theory of Fault-related Fold, as well as disciplines like structural geology and petroleum geology, combining well data,2d and 3d seismic data, surface geology and DEM data to give a fine interpretation and study the kinematics of the Xihu Anticline and the whole research area,so as to identify the geometry and kinematics of Xihu Anticline, along with geological structure and evolution feature, the following conclusions have been reached:1. Xihu Anticline is composed of two vertically superimposed shear fault bend folds. Its evolution could be divided into three stages:(1) stage of uplifting of north margin and based fault related fold from Late Triassic to Early Jurassic; (2) stage of basin uplifting and erosion of the Jurassic from Late Jurassic to Early Cretaceous; (3) stage of faulting and formation of anticline during Quaternary as well the continued growth of Xihu Anticline.2. The structural scale of the West Segment is comparatively small. Tuositai Anticline is formed by several structural wedges of different times. Since the beginning of Himalayan movement during Quaternary, stresses were transmitted forward from Tuositai Anticline, leading to the successive formation of Dushanzi Anticline and Xihu Anticline. A fault propagating from the Cretaceous detachment formed the Dushanzi Anticline, while two different shear fault bend fold led to formation of Xihu Anticline.3. The structural scale of the Central Segment is comparatively large, with three rows of well-formed structural belts. It is characteristic with thin skinned structures of the sediments. Huomatu Anticline can be divided vertically into two structures:the upper one was formed by thrust structure that is rooted from the detachment in Anjihaihe Formation of Paleogene; the lower one was formed by the superimposition of fault bend fold and thrust wedge, with the former structure rooted from Jurassic detachment and the latter structure rooted from Cretaceous detachment. Qigu Anticline, Changji Anticline and Kazhala Anticline can also be divided vertically into two structures:the upper one is fold formed by the south moving back-thrust fault; the lower one is formed by deep thrust wedge.4. Quite different from the Central Segment and West Segment, strata of the East Segment were shallowly buried and the scale of thrust structure formed by basement fault is comparatively small. The profile in this area is characteristic with thrust imbrication structures, manifested as thick skinned structure that involved the basement.5. Traps in the study area are mainly structural traps. Because of the differences between the three segments and the different formation time and characteristics of the three rows of belts, we should pay attention to the structural characteristics of the area during hydrocarbon exploration. Besides, as structural wedge is an important structure in the study area, we should also pay attention to its influence to hydrocarbons.