Controls of a Triassic fan‐delta system, Junggar Basin, NW China

Both sedimentology and sequence stratigraphy variability in the deltaic area are distinguished in the fan‐delta system of the Northwestern Junggar Basin. Sediment supply plays a significant role in controlling the fan‐delta petrology, evolution, and depositional processes and the delivery of sediment into deeper parts of the basin. The results of this study show that variations in the lithology of the sediment supply control the fan‐delta petrology and spatial and temporal variations in sediment supply influence the location and shifting of depocentres. A fining‐upward fan‐delta succession developed as accommodation rates outpaced the sediment supply rate. Frequent flood events were mostly recorded by sediment gravity flow deposits, which in turn influenced the geometry of the sandstone bodies and their reservoir quality. Hyperpycnal flow was a significant delta front process and an important mechanism for sediment delivery into deeper waters, favoured by the combination of denudation of coastal ranges and the fresh waters of the receiving basin. This study highlights that a detailed understanding of variations in sediment supply is essential to accurately predict sediment partitions in a delta system and the delivery of coarse‐grained sediments into deeper parts of lacustrine basins.