Textural Attributes and Lithofacies Analysis of Quaternary Geomorphic Surfaces in Middle Ganga Plain, India

Abstract

Abstract Geomorphic surfaces of the Ganga plain are depositional surfaces, and the succession of sediment deposited on their top is younger than the time of the formation of the relevant surface. The relative timing of their deposition is recognized based on their morphological interrelationship and order of superposition. In the middle Ganga plain, three geomorphic surfaces are well-developed. The oldest geomorphic surface (T2), formed by sheet flow processes during monsoon season, consists of silt, sandy silt, and silty sand. Sediments are poorly to very poorly sorted, very fine skewed to fine skewed, and kurtosis ranges from leptokurtic to platykurtic. The Ganga River is incised into the T1 surface up to 4–8 m in the study area; T1, also known as the river valley terrace, is incised into the T2 surface exposing cliffs of 8 to 20 m heights. T1 surface representing older sediments of active channels is characterized by rippled and cross-bedded silt, sand, and lensoid units of silty mud. Mean grain size ranges from very fine sand to medium silt; sediments are poorly to moderately sorted, Skewness ranges from very fine skewed to fine skewed, and kurtosis ranges from very leptokurtic, leptokurtic, and mesokurtic. The T0 surface is the youngest geomorphic surface of the Ganga basin representing river channels and their associated flood plains. The Ganga River shows varied channel patterns, from meandering to braided and straight channels. Channels carry medium sand to very fine silt; sorting is very poorly to poorly sorted, Skewness is very fine skewed to fine skewed, and kurtosis ranges from leptokurtic, mesokurtic, and platykurtic.