Depositional Systems, Sediment Dispersal and Controlling Factors of Intracratonic Basin Fills, Early Silurian, Tarim Basin, Northwest China

The development and distribution of depositional and dispersal systems and their controlling factors have long been key topics in basin analysis. The Early Silurian Kalpintag Formation in the Tarim Basin, a nearly 1000 m thick marine siliciclastic succession with important hydrocarbon‐bearing intervals, is characterised by a complex sequence architecture and diverse depositional systems. Based on the integrated analysis of cores, outcrops, well logs, and seismic data, the sequence architecture, sediment provenance, dispersal patterns and their key controls are systematically documented. Five major depositional systems are identified, including tide‐influenced delta, estuary, tidal flat, braided‐river delta, and shallow marine. Their distribution can be classified into three facies tracts: eastern braided‐river delta, northern tide‐influenced delta and estuary, and southern tidal flat and estuary. Strong uplift of the Altyn Mountains along the eastern basin margin produced steep slopes and abundant sediment supply, leading to extensive development of the braided‐river delta system. Sediment input from the Tabei Uplift on a relatively gentle paleoslope controlled the tide‐influenced delta and estuarine deposits in the north. In the south, the limited sediment supply from the Tanan Uplift and low‐relief paleogeomorphology led to widespread tidal flat deposits. Two depositional sequences are identified in the Kalpintag Formation, each comprising transgressive (TST) and highstand (HST) systems tracts. The sequence architecture and shifts in sedimentary environments were clearly controlled by relative sea‐level changes and correlated with the global eustatic curve.