Sedimentology of Quaternary Alluvial Deposits of the Gandak-Kosi Interfan, North Bihar Plains

An account of sedimentolpgical characteristics such as grain size distribution, clay mineralogy, sand mineralogy and magnetic susceptibility of the alluvial sediments from the Gandak Kosi interfan area in the Indo-Gangetic plains of north Bihar is presented. Fine-grained sediments consisting of significant percentage of detrital clays and variable carbonate content are present in the plains and are distinctly derived from the Himalaya. Sedimentation in the interfan is episodic through overbank flooding forming thick muddy sequences. Changes in depositional regime occurred because of shifting of channels which, in turn, affected channel proximity of floodplain sites.