Modern Sedimentation Patterns in Lake Issyk Kul (Kyrgyzstan), Derived From Surface Sediment and Inlet Stream Samples

Abstract

This study provides a descriptive characterization of the modern sedimentary processes in Lake Issyk Kul, Kyrgyzstan, important for the selection of a suitable coring or deep‐drilling site, interpretation of future core data and applicability of proxies. The quasi‐equidistant sampling grid of 66 sediment surface samples covers the entirety of the lake basin and is complemented by 10 samples from the major inflows. The methodological approach includes geochemical, granulometric, lipid biomarker, diatom, and statistical analyses. The quantitative and qualitative changes in sediment composition yield information on its generic origin and prevailing transport and depositional environments. The composition of the surface sediments in Issyk Kul is highly heterogenous. Nearshore deposition is mainly controlled by wave action and by fluvial sediment supply with highest quantities of detrital input coming from the high‐energetic, eastern tributaries. Sediments in the deep central basin are mainly produced in situ and dominated by authigenic calcite. Biogenic accumulation is overall low, except for the western extremity of the lake, where the nearshore, shallow‐water, and low‐energetic environment favors aquatic productivity and subsequent preservation of organic material and diatoms. Redeposition of sediments is a dominant process along the slopes across the southern and western basin floor, where run‐out distances of mass movement deposits are up to 5 km. Directional sediment transport by lake currents appears to be less important, except for the transport of very fine‐grained organic matter. Biomarker‐inferred temperature reconstructions suggest lake surface temperatures of ∼15°C in the western littoral zone and in Tyup Bay and a decrease to ∼13°C basinward.