The northwestern edge of Junggar Basin experienced multiphase tectonic movements of different natures

and it appeared as a foreland basin since Cenozoic. Extensive collision

compression and thrusting occurred along with regional tectonic movement

and faulting apparently had the nature of overthrusting

resulting in fold structures to be in parallel with the fracture zone. The overthrust faults were commonly syngenetic and controlled obviously the development of fans. Thrusting occurred continuously

so topographies on the hanging walls were greatly different from those on the footwalls. Clastics denuded from the thrust sheets accumulated on the foot of fault scarps

leading to the formation of various fans (alluvial fan

fan delta and submarine fan

etc.). Step thrust faults led to the formation of multistage fans. Tectonic activities attenuated gradually from Permian to Jurassic and the sizes of fans decreased gradually. Lateral displacement of tectonic activities resulted in the migration of fans. As a whole

the strongest and longest tectonic activities occurred in Baikouquan-Xiazijie area

hence the fans in that area would be relatively large

highly superimposed and largely migrated; while those in Cheguai-Karamay area were relatively weak

so the fans would be small

poorly superimposed and shortly migrated.