Depositional Sequence and Filling Response Characteristics of Silurian in Tarim Basin

Silurian in Tarim Basin,bounded at the top and base by widely spread regional unconformities,can be divided into 1 second-order sequence and 5 third-order sequences.Three kinds of depositional system assemblages,which represent lowstand systems tract,transgressive systems tract,and highstand systems of the second-order sequence,are identified in Silurian of Tarim Basin,namely,assemblage of meandering river delta and braided river delta depositional systems,assemblage of offshore and slightly deep-water basin depositional systems,and assemblage of clastic coastal depositional system with no barriers and clastic tidal depositional system with no barriers.Based on the integrated analysis of data of tectonics,sedimentology,palaeontology and palaeoclimatology,the base boundary of sequence 1 and top boundary of sequence 5 are thought to be originated from the pressure of peripheral plates and uplift of basin base.The bottom boundary of sequence 2 belongs to tectonically compressed unconformity that originates from the pressure of plates and decline of basin base.The bottom boundary of sequence 3,sequence 4 and sequence 5 results from integrated effect of change of climate,sediment source and tectonic activity under falling global eustacy.