Origin of loess deposits in the North Tian Shan piedmont, Central Asia

Abstract

Loess deposits are widely distributed along the mountain piedmonts of Central Asia. The transport processes and origins of Central Asian loess sediments remain poorly understood. Here we investigate the origin and formation of loess along the northern piedmont of the Tian Shan based on trace element (including rare earth element) ratios and multidimensional scaling analysis. Our results indicate that the loess has undergone weak chemical weathering. Using a selection of geochemical fingerprinting techniques based on Pearson correlation and Kruskal–Wallis H tests, we establish a genetic link between alluvial-proluvial fans/plains, deserts, and loess along the Tian Shan piedmont in northern Kyrgyzstan and southern Kazakhstan. The unsorted sediments on the piedmont slopes and alluvial-proluvial plains are common sources for both deserts and loess to the north of the Tian Shan. Dune sediments are not the main source of the fine-grained loess. Origin and formation of Central Asian loess is strongly dependent on local topographic context and wind dynamics. Only once loess provenance and formation has been understood across both space and time can reliable interpretations of palaeoclimatic proxies in these deposits be made.