Textural analysis and statistical synthesis to interpret depositional environments in the palaeochannel of the Assi River in the Central Ganga Plain, India

Abstract

The current study is aimed to characterize the facies based on grain-size composition and textural parameters along the palaeo-course of the Assi River in Central Ganga Plain, India. Grain size fractions are expressed in terms of ratios of sand, silt and clay and plotted in ternary diagrams, while grain-size variations are used to explain the sediment transport mechanism, depositional history and energy levels during sedimentation. The palaeochannel deposits of the river in study largely consist of silty sandy mud with sand silt clay in various proportions. The occurrence of minor proportions of fine sands and silts in clay suggests successive stream episodes/floods in the recent past. The palaeochannel sediments show mean size ranges from 3.83 to 7.02 phi (average = 5.38 phi), indicating coarse to very fine silt, and sorting ranges from 0.81 to 2.49 phi (average = 1.87 phi), indicating moderately to very poor sorted sediments. Skewness varies from − 0.01 to 0.81(average = 0.28), indicating near-symmetrical to very fine-skewed sediment distributions and kurtosis ranges from 0.85 to 1.89 (average = 1.21) suggest that the majority of the sediments are mesokurtic to very leptokurtic in nature. The bivariate plot of mean grain size versus sorting shows that the bulk of the sediments were deposited in quiet-water environment under episodic fluvial regimes. The C–M pattern of the sediments in the palaeochannel suggests that sediments were transported in graded to uniform suspension before they are deposited. © Indian National Science Academy 2025.