Abstract: The Lower Silurian rocks are fully developed in Shun-IWell with classification of Llandoverian Kalpintag formation, Tataaiertag formation and Wenlokian Yimugantawu formation. The Kalpintag formation is subdivided into three members as upper and lower sand-stone members and middle mudstone member with grey and grey-greenish colors. Tataaiertag formation is subdivided into upper member with red-brownish and red mudstone intercalated with siltstone and lower member with purple-red mudstone. The Yimugantawu formation is composed of brown and dark brown mudstones intercalated with siltstone and fine grained sandstone. The Charchag formation of Upper Ordovician with lithology of grey and dark grey mudstone is only penetrated by 1 10m in thickness. The lithological and electrical properties of these formations are distinct. Prolifie Chitinozoan fossils were discovered from lower member of Kalpintag formation and Charchag formation, and five species of three genera and numerous others were identified. Furthermore, their ages and geographic distributions are discussed in detail. Based on the characteristics of the fossil assemblages, they are assigned to the Conochitina elaca and Conochitina sp.2 zones, respectively. According to the spatial distribution of Chitinozoans in global scope, the age of the Chitinozoan-bearing zones in Shun-1 Well is determined and the reclassification of its Lower Silurian is made by the litho stratigraphy, bio-stratigraphy and logging stratigraphy. It is the first time to provide important fossil evidences for the classification and the correlation of Lower Silurian in this area.

Key words: Tarim basin, Chitinozoan, stratigraphic classification