Optically stimulated luminescence and radiocarbon dating of sediments from Lop Nur (Lop Nor), China

Lop Nur is a playa lake occupying the lowest part of the Tarim Basin, northwestern China, and is now a desolate and barren region. In the past decades, the ages of the lacustrine sediments from the lake were determined mainly by radiocarbon dating on bulk sediment. In this study, both optically stimulated luminescence (OSL) and radiocarbon methods were used to date the sediments from a pit in the central part of the lake. The OSL ages obtained for ten samples range from 0.5 to 9.4 ka, and are in stratigraphic order except for one sample. The 14C ages obtained for twenty-two bulk sediment samples range from 5.8 to 30.2 cal ka BP with erratic distribution. Based on the comparison of 14C with OSL ages and their age-depth models, we argue that the OSL ages are relatively reliable. The disequilibria in the U decay chain for some samples are deduced from the comparison of the NAA and TSAC results. We suggest that the OSL dating technique should preferably be applied to the playa sediments from Lop Nur, but the disequilibria in the U decay chain should be considered in evaluating dose rates. Additionally, radiocarbon reservoir effects in lakes in western China are reviewed.

► Lop Nur is a playa lake occupying the lowest part of the Tarim Basin, northwestern China.
► Radiocarbon reservoir effect in lakes in western China is reviewed.
► Radiocarbon dating of bulk sediment is considered problematic.
► The playa sediments are suitable for luminescence dating.
► The disequilibrium in the U decay chain for some samples is deduced from the comparison of the NAA and TSAC results.