Aeolian sand dunes alongside the Yarlung River in southern Tibet: A provenance perspective

The potential interactions between aeolian and fluvial systems are critical in understanding environmental change. Whether aeolian products originated from the river depends on the river characteristics and wind regimes. In southern Tibet, aeolian sand dunes are widespread along the Yarlung River, and thus provide an ideal example to explore the relationships between large fluvial systems and aeolian products. Although previous studies postulated that those aeolian products were originated from the Yarlung River, few empirical data actually exist to support this idea. We analysed the spatial pattern, sand transportation directions, and granulometric characteristics of the sand dunes to evaluate the potential influence of the Yarlung River on the aeolian processes. Comparison of the dune field distribution against channel width and longitudinal profile of the Yarlung River shows that sand dunes are clustered at the wide and flat segments of the river. Analyses of >4,600 sand dune orientations using Google Earth imagery show that the dunes located at the southern and northern sides of the Yarlung River demonstrate opposite sand transportation directions that generally point against the river. This suggests that the sand grains probably originated from the river. Grain size distributions from dune samples show unimodal or unimodal‐like patterns. This means that each sand dune field was dominantly fed by a simple transportation process rather than by compound processes from smaller‐level fluvial systems, which in turn implies that the Yarlung River was the most possible candidate for the provenance of these aeolian deposits. This study provides new constraints to demonstrate that the Yarlung River provides both accommodation space and sorted fluvial sand for the aeolian sand dunes along the river.