GRANULOMETRIC STUDIES TO INTERPRET THE ORIGIN OF THE SEDIMENT TRAPPED WITHIN A POCKET ALONG THE PRAVARA RIVER BASIN, MAHARASHTRA, INDIA

Abstract

Sediment populations may have characteristics associated with multiple sources. Grain size parameters will therefore reflect spatial as well as temporal variations in transport mechanism and flow direction along with the nature and energy flux of the transporting agents. Herein, the author has investigated a small watershed area along Mahalungi River in Maharashtra, India. Samples were collected from the surface and from litho-facies at various depths and were subjected to granulometric analysis. The sediment sizes were separated principally on the basis of their intermediate axial diameter and shape using microscope, sedigraph and pipette method appropriately. Bivariate relationships from textural parameters were obtained and Visher’s log-probability plots were constructed. Incorporation of all results of the analyses and a careful inspection of the geomorphic settings of the area lead us to the conclusion that the present deposits are part of the alluvial deposits of Pravara and haven’t descended from the footslope to form colluvial deposits. The fact that the silt population is found right at the footslope indicates that during the floods, flood waters must have entered and hit the amphitheater. As the flood water receded, the narrow outlet did not allow free retraction of the flow but created an eddy effect every time and gave a temporary ponding effect within the amphitheater.