| Based on integrated analysis of data of seismic data, core and well logging of Tarim Basin, one second-order sequence and five third-order sequences are identified in Silurian of Tarim Basin. The second-order sequence is bounded in both sides by widely spread regional unconformities and the third-order sequences, which can be described as type 1 sequences, consist of complete lowstand, transgressive and highstand systems tracts. Based on comprehensive investigation data of seismic, core and well-logging, five kinds of depositional systems are identified in Silurian of Tarim Basin, namely, clastic coastal depositional system with no barriers, clastic tidal depositional system with no barriers, offshore and slightly deep-water basin depositional system, delta depositional system and braided delta depositional system. Each depositional system exhibits varied distribution pattern and evolution history, with north Tarim Basin and Kelping area dominated by clastic coastal depositional system with no barrier, Manjiaer by offshore and relatively deep-water basin depositional system and east Tarim Basin by braided delta. Seawater inpoured the Silurian Tarim Basin in two directions around the north Tarim uplift, which took a look of an isolated island, but the main direction changes. During the early period of Silurian, seawater inpoured Tarim Basin mainly from northeast, and during the late period of Silurian, seawater inpoured Tarim Basin chiefly from northwest. The change reflects the tectonically evolution of Tarim Basin. In Silurian Tarim Basin, five main sediment sources developed, namely, the North Tarim uplift, the East Tarim uplift, the Bachu uplift, the Central Tarim uplift and Kelping area. The Silurian Tarim Basin is enriched with ichnofossils, which can be classified into ichnofossils with clear morphology and bioturbation. The ichnofossils with clear morphology, which is predominantly fodinichnia, domichnia and pascinichnia, consist of at least 14 ichnogenera and 15 ichnospecies and can be classified into five ichnoassemblages, namely, Cochlichnus-Planolites ichnoassemblage, Palaeophycus-Planolites ichnoassemblage, Skolithos ichnoassemblage, Planolites-Taenidium ichnoassemblage and Helminthopsis ichnoassemblage. Bioturbation can be classified into 4 types, namely, bioturbation in surface layer, bioturbation in thinly silty mudstone or mudstone, bioturbation in fine sandstone and bioturbation in thinly interbedded sandstone and mudstone. Different ichnoassemblages and bioturbations represent different sedimentary environments. The trace fossils not only provide important evidence for recognizing of sedimentary environment but also identifying sequence boundaries, maximum flooding surface, and facies association of parasequence. According to the causes of formation, Silurian sequence boundaries can be grouped into three unconformity types, namely, uplifted erosional unconformity, tectonically pressed unconformity and subaerial exposures unconformity. The boundaries of second-order sequence belong to tectonically uplifted erosional unconformities that originate from the uplift of basin base. The bottom boundary of sequence 2 belongs to tectonically pressed unconformity that originates from the pressure of plates. The bottom boundary of sequence 3, sequence 4 and sequence 5 belong to subaerial exposure unconformities that results from integrated effect of change of climate, sediment source and tectonic activity under falling global eustasy. The Silurian are formed under the background of subsidence of the base that underwent previously sharp erosion because of late Caledonian Movement. During the early period of Silurian, the Tarim Basin subsided rapidly because of the pressure of the surrounding plates, while during the late period, the tectonic pressure weakened gradually, and the eustasy began to decline. In the end, the sedimentation of Silurian terminates because of the last stage of Caledonian Movement, and then sedimentation of Devonian began.
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