Research On The Fault Features And Structural Evolution Of Hami Depression

The exploration of Tulufan depression has been investigated deeply in recentyears, while exploration degree of Hami depression, which is eastern part of Tuhabasin, is generally low. Guided by the principle of structural geology and balancedcross section, using2D seismic data and drilling data, this thesis carries out theresearch of two key points-fault system and tectonic evolution, expecting to having acompletely understanding of the tectonic framework and evolution of Hamidepression.In this thesis, basic factors of the main faults in Hami depression have been listedand the distribution of the fault system is clear. In order to get a better understandingof the tectonism during the Indosinian-Himalayan movement,3reversed fault models（single-force thrust model, double-force slip model and basement uplift model） hasbeen proposed and the slip value of every fault during every period has beencomputed. Based on the research of fault system, balanced cross sections have beendrawn and the structural evolution （from Late Carboniferous to Quaternary） of Hamidepression is clear.The results show that:（1） there are mainly4directions of fault strike: EW, NNE,NWW and NEE. In Huoshizhen Sag, several faults of NNE strike cross on NanhuFault （EW strike）, structural deformation is mainly intense thrusting. While inSanbao Sag, faults of NNE strike and NWW strike cross together, structuraldeformation is mainly strata fold.（2） Fault activity analysis indicates that, energyconverge strong at the south while weak at the north during Indo-Chinese period.But fault activity has been remarkably weakened during Yanshanian period, withfaults in the north area changing more seriously than in the south. During Himalayanperiod, fault activity often presents with inherited activities.（3）The evolution ofHami depression from Late Carboniferous to Quaternary can be divided into5periods: back-arc ocean basin and remnant sea basin period （D-C）, back-arc rift basin period （P₁）, foreland basin period （P₂-T₃）, regenerative foreland basin period（J-K）, inland intermont basin period （E-Q）.（4）The evolution of Hami depression has4characters: different evolution process in different areas, different distribution ofdifferent strata, complex tectonic framework and independent evolution comparedwith Tulufan depression. In Huoshizhen Sag, Permian and Triassic is the main strata,tectonic framework was determined after the Late Indosinian movement. While inSanbao Sag, Triassic and Jurassic is the main strata, tectonic framework was formedduring the Late Indosinian movement but was completely fixed after Yanshanmovement.