The Silurian is composed of Kepingtage Formation, Tataaiertage Formation and Yimugantawu Formation.With the well samples and field investigation,there are green-grey mudstone,silty mudstone,mudy siltstone,siltstone,fine sandstone and middle sandstone in the Silurian in Tazhong area.The sedimentary structures include horizontal bedding,parallel bedding,lower angle cross bedding,wedge-shaped cross bedding and trough cross bedding.The author presents the shore-neritic depositional system was developed in the lower bitumen-bearing sandstone member during Silurian in Tazhong area of Tarim basin ,which were made up of foreshore-nearshore facies, neritic shelf facies, neritic sand bar, tidal ridge facies which have more storm deposits. There are mainly tidal flat depositional system in the upper bitumen-bearing sandstone member,which have some foreshore and nearshore facies. The width of the shore-neritic depositional sysytem is n×10 KM. The shore-neritic depositional sandstones are good reservoir.
