Differences Analysis Of Uplifting Processes In The Bachu Uplift,Tarim Basin

The complexity and mutiperiodic activity of the Bachu uplift is the most difficult problem of researching Bachu uplift thermal evolution.Based on 2D and 3D seismic data,the key drilling wells and log data,the geological data and amount of previous research results in Bachu Uplift of Tarim Basin and its peripheral areas,combined with regional geological structure,the stratigraphic correlation,structural evolution and thermal history simulation experiments have been carried out.The geological structure and evolution characteristics,the difference of uplifting and thermal history processes in the Bachu uplift are presented.(1)The stratigraphic development of the Bachu uplift has clear differences and the changes of the thickness in diffirent stratigraphic strata have certain regularity.In the Early and Middle Cambrian,the stratum in the north is thicker than the south.In the Late Cambrian,the stratum in the southern part is thicker than the northern parts.It changed in the Late Ordovician,the thicker stratum transformed into the northern part otherwise than the southern part.In Silurian and the Early-Middle Devonian,the stratum is thinning from the northwestern to the southeastern parts.In the Carboniferous,the stratum is thicker the middle part.In the Mesozoic,the stratum on the hanging wall of the southern margin and northern fault belts are thinnest.In the Paleogene and Miocene,the stratum in the southern part is thicker than the northern part.(2)Bachu uplift experienced the effects and tansformations of the multiphase tectonic movements,is a long evolutionary uplift.The different grades of faults played important roles during the process of the evolution in Bachu Uplift.Especially,the southern and northern fault belts,which contained the Tumuxiuke and,Aqia fault on the north,and the Mazhatage and Selibuya fault on the south,controlled the uplifting and subsidence process of Bachu Uplift with different extents.The deformation of Bachu Uplift is the largest in the Late Ordovican and the Cenozoic.Activities of the north and south fault belts in Bachu Uplift were intensely.(3)According to the different direction of long axis of the subsidence area,there are three stages of Paleogeomorphology frameworks and two transitions during the development of the Bachu Uplift.Three stages included from the Cambrian to the Ordovician,from the Devonian to the Permian and from the Paleogene to the Present.And the end of the Silurian as well as the end of the Triassic is important the transition periods.During the Cambrian to the Ordovician,subsidence zone was NW-trending.During the Devonian to the Permian,subsidence zone changed to the NE-trending direction.The subsidence zone converted to the NW-trending from the Paleogene to the Present again.(4)There are at least seven significant uplifting events in the evolution process of uplifting in Bachu Uplift.These events respectively are the late Ordovician(452 Ma),from the early stage of the Late Silurian to the Early Devonian(423?405 Ma),Late Devonian(385?360 Ma),from late stage of the Middle Triassic to middle of the Late Jurassic(236?155 Ma),from late stage of the Early Cretaceous to the late Late Cretaceous(118?80 Ma),from the Paleocene to the Oligocene(57?25 Ma)and from the Early Miocene to the Present(since 15 Ma).(5)The uplifting and subsiding of the Bachu uplift in different periods responed to the tectionisms from the southern and northern periphery orogenic belts of Tarim basin and from the the deep tectonism of the basin in different periods.Otherwise,the adjacent Tangguzibas depression responded to the tectonisms from the southern margin orogenic belts of the Tatim basin and the Tibet Pleateau.Since the Mesozoic,the Bachu Uplift and Tangguzibas depression have reverse evolution stages,except Jurassic(199?155 Ma)in the same state of uplifting.