Vertical Successions of Channel Bar, Point Bar and Natural Levee Deposits, Ganga and Yamuna River, Allahabad, U.P.

The modern sediments of Ganga and Yamuna rivers at Allahabad, Uttar Pradesh are studied in 17 vertical sections of channel bar, point bar and natural levee deposits. Based on this study nine lithofacies, i.e. St, Sp₂, Sp₁, Sr₁, Sr₂, SI, Sh, FI and Fm (8-Sand and 1-Mud sub-lithofacies) have been identified. An attempt has been made to evolve a generalised lithofacies succession for channel bar, point bar and natural levee deposits. The channel bar exhibits the lithofacies succession of Sp₂, Sp₁, Sr₂, Sr₁, Sh and FI; Sp₂, Sp₁, Sr₁ Sh and FI succession in point bar-and Sp₂, Sp₁, Sr₁, Sh, FI and Fm lithofacies succession in natural levee deposits. No major difference in channel bar and point bar lithofacies succession have been found. The point bars are characterised by trough cross-bedded lithofacies - St, which are formed by the migration of 3-D dunes. The Fm lithofacies is characteristics of natural levee, the muddy deposits often show desiccation cracks. Deposition of mud takes place in low energy conditions mostly during receding floods.