Lithofacies-Paleogeography Of Silurian-Devonian, In Bachu-Maigaiti Region, TarimBasin

The Bachu-Maigaiti aera is in the west of Tarim basin,covering the Bachu Upliftof west central uplift and the Maigaiti Slop in the southwest Tarim sag region. Inrecent years, the discovery of petroleum within the Silurian-Devonian of theBachu-Maigaiti aera in the Tarim basin indicate that,this aera has widely explorativeprospect and is badly in need of fine research, such as the distribution characteristicsand rules of sand body, the types of sedimentary facies and the characters ofLithofacies-Paleogeography. Provide foundation for further exploration activity of theSilurian-Devonian of this aera.In the full collection of forerunners’ data, based on systematic analysis of fieldoutcrops、drilling and logging data, combined with the characteristics of sand bodyand seismic facies, the Silurian-Devonian of the Bachu-Maigaiti aera in the Tarimbasin can be divided into four kind of sedimentary systems such as shoreland, delta,tidal flat, shallow sea. Each of the sedimentary systems can be subdivided into severalsubfacies and microfacies, which were described and generalized in detail. At last, wededuce two sedimentary models: delta-shoreland-shallow sea and delta-tidal flat-shallow sea.According to the sedimentary facies patterns、characteristics and evolve rules,and the distribution characteristics of sedimentary models, combining thecharacteristics of regional tectonic background, we established the Lithofacies-Paleogeography maps of each formation in the Silurian-Devonian of theBachu-Maigaiti aera.On the whole, the character of Lithofacies-Paleogeography is different in eachphase, but it is succession, which performed as follows:the basic tectonic framework of paleo-erosion area and paleo-depression area in each sedimentary period has nogreat changes, and the providing of provenance are main came from southwest andsoutheast. The difference are mainly performed in the Lithofacies-Paleogeography ofeach phase. From Early Silurian to Late, the sea depth、the deposition range、theprovenance supply and the delta scale were gradually shorten. Until Early-MiddleDevonian, because of stronger differential uplift, the provenance supply re-increased,and undergo the regional uplifting and denudation after Middle Devonian. Theregional transgression occurred once more in the early Late Devonian, and developeddelta-shoreland-shallow sea sedimentary model. In the late Late Devonian, thephysiognomy flatten out again, the provenance supply decreased accompanied by thefurther enlarged sea area. Finally，tidal flat facies is mostly developed in the studyarea, and formed delta-tidal flat-shallow sea sedimentary model.