Study of Depositional Model of Silurian System in Tazhong Area, Tarim Basin

Key words: 
• epicontinental sea clastic /
• tidal flat facies model /
• Silurian System /
• Tazhong area

Abstract: Studies showed that the Silurian sytem in the Tazhong area was deposited in an epicontinental sea tidal flat environment. Combined its depositional feature and setting with the hydrodynamic feature ofepicontinental sea area, an epicontinental sea facies model of clastic deposits of the Silurian system in theTazhong area is established. Furthermore,it can be subdivided into three microfacies: mud flat and mixedflat, and sand flat. Its facies is broad and stable, but there exist no barrier island deposits. Compared withthe flat depositional facies nowadays,it is deposited in deeper water. part of the mud flat and most of themixed flat develop under the water, the hydrodynamics of the sand flat is relatively weak. Tidal currentand hurricane current mainly control the transportation and reconstruction of the clastics, so their de-posits are popular, especially in the sand flat and mixed flat. A vertical coarsing-upward sequence is pre-sent in the transgressive period and cross- bedding is common in the sandstone. In the retrogressive pe-riod, sandstones with good continuity and a stable mud flat are formed in a broad area. Near some of the underwater high land in the sand flat environment, there may exist purer quartz sandstones, which maybe a good reservoir. As an example, the analysis of the Tazhong-11 well shows that it is suitable for the study on the Silurian system in the Tazhong area with this model.