Geomorphic History and Lithostratigraphy of a part of Eastern Gangetic Plain, Uttar Pradesh

The Quaternary deposits of the area are classified into three lithounits, viz., Varanasi Older Alluvium, Chhoti Sarju Older Flood Plain Deposits and Chhoti Sarju Recent Flood Plain Deposits. The facies organisation of the Varanasi Older Alluvium (+300 m thick), indicates a braided to meandering river environment for the lower sandy facies and meandering river to local lacustrine conditions for the upper silt clay facies. Presence of a regionally persistent shell-bearing silty-clay horizon (at a depth of about 1 m to 2 m below ground level) indicates commencement of lacustrine conditions towards the waning phase of sedimentation of Varanasi Older Alluvium. The Chhoti Sarju Older Flood Plain Deposits rest over the eroded surface of Varanasi Older Alluvium. This deposit is about 10 m thick with fining upwards sandy facies deposited in a meandering river regime. The Chhoti Sarju Recent Flood Plain Deposits are confined within a very narrow zone (approx. 250 m wide) in the bed portion and flood plain of the river. In this regime, the sedimentation is still going on in the form of point bars, channel bars and side bars. At places, lacustrine conditions (oxbow lakes) are also present.

The Quaternary history of the area indicates at least two prominent episodes of base-level (sea-level) rise during the Late Pleistocene-Holocene period.