Grain Size Analysis of Dune and Bar Sediments of the Shyok River between Khalsar and Hunder Village, Karakoram Range, Ladakh, India

The Nubra and Shyok valleys are located between the central Karakoram and Ladakh range of northwest India and have preserved excellent sand dune and bar sediments between Khalsar and Hunder village. The present study aims to understand the evolution of these landforms using grain size characteristics. The sand dunes are formed by the aeolian processes and the bars are produced by the fluvial processes. The actions of fluvial and aeolian processes are different and landforms formed by these processes have completely different sedimentological and grain size characteristics. The mean grain size of dune sediments is dominated by fine sand while in bar sediments, it varies from medium to fine sand. The sand-silt-clay ternary plot shows that all samples are concentrated in sand corner. The histograms of sand dune sediments are unimodal while the histograms of bar sediments vary from unimodal to bimodal. The grain size parameters reveal that the bar and sand dune sediments are different but deposited in the same moderate to low energy riverine environments. The dune sediments are well sorted and are transported and deposited in uniform energy environment. Due to energy variations in the hydrodynamic system, the bar sediments are moderate to well-sorted at Diskit and Hunder villages. Overall 45.5% of sediments samples are platykurtic in nature, indicating the maturity of the deposited sand. The high and low values of kurtosis imply that some fractions of sediments were sorted in a high energy environment. The present study of grain size parameters reflects different sediment character for bars and sand dunes that are deposited in modrate to low energy environments. The results of the study may be used as an analougue for understanding depositional environment in high altitude region.