STUDY OF PARAMETERS INFLUENCING SOIL FORMATION IN THE GANGA PLAIN

Abstract

The geomorphology of the Ganga Plain restricted to the areas bounded by the river Yamuna in the west and Kosi in the east has been studied in this dissertation. The study area has been divided into three interfluves- the Yamuna-Ganga Interfluve, the Ganga-Ghaghara Interfluve and the Ghaghara-Kosi Interfluve. All geomorphic landforms present in each of the interfluves region as described by the authors Bhosle et al. (2008), Singh et al. (2006), Pati et al. (2011a) and Pati et al. (2015) have been divided into four basic geomorphic unit types- plains, fans, terraces and piedmonts. The tectonic history of the Ganga Plain particularly in the Holocene has also been considered. This dissertation is a study of the impact of different parameters, particularly time and climate, on soil formation in the various geomorphic units of the study area restricted to parts of Upper and Middle Ganga Plain. Analysis has been performed on the age data of soil-geomorphic units published in the works of Bhosle et al. (2008), Singh et al. (2006), Pati et al. (2011a) and Pati et al. (2015). Trends obtained from this analysis have yielded insights on the correlation of soil profile development with time and the rate of soil development with age of the soil geomorphic units in the study area. Piedmonts found in the Ganga Plain are concluded to be associated with neo-tectonic activity and are formed only arid periods. The soil profile thickness developed, the rate of soil profile development and correlation of soil thickness of geomorphic unit types with time is lowest in case of piedmonts and highest in case of terraces among all four major geomorphic landform types. Fans and Piedmonts lie in the middle of these two extremities. The primary reason for this discrepancy can be attributed to the differential relative dominance of different soil forming factors in different geomorphic landform types. The Sand: Shale ratio has also been calculated for altered horizons (horizons above the c- horizons) and unaltered horizon (c-horizon) for the geomorphic units in the study area. Sand-Shale Ratio of the different geomorphic units shows a deceasing trend with age indicating increased soil formation in terms of clay mineral development and the unaltered and altered horizons of soil profile developed are tending towards reaching the same ultimate soil composition.