Different implications of OSL and radiocarbon ages in archaeological sites in the Qaidam Basin, Qinghai-Tibetan Plateau

Both Optically Stimulated Luminescence (OSL) dating and ¹⁴C dating are main dating method for archaeological sites, while their disagreements are quite often. In the Qaidam Basin (QB), human activity remains (HMRs) are frequently found within aeolian sediments, offering opportunities to make comparison between OSL and ¹⁴C ages, and to discuss their potential disagreements in archaeological sites. In this study, we present comparison between 18(10 of them had been published) OSL and 17 AMS ¹⁴C ages for samples from aeolian sediments in the eastern QB, including some samples from archaeological sites. Comparisons show better agreement in natural aeolian section, but more disagreements in sections with many HARs. This should be due to postdepositional anthropogenic disturbance, which can cause different influences to OSL and ¹⁴C ages. The age disagreement might display their different significances, with ¹⁴C chronology represent human activities, while OSL chronology more likely to reveal ages of original stratigraphy. Field hearth experiment was taken to check to what extent can heat from a hearth affect luminescence signals in the surrounding sediments. Results show that both OSL and Thermoluminescence signals in sediments under the hearths are not easy to be reset by the heat due to the poor downward thermal conductivity into the humid soil. This reminds the risk of OSL age overestimation for hearths. This study emphasizes the importance of cross-check between different dating methods for chronology building in archaeological contexts, and the necessity to analyze the dating materials, depositional process, and post-depositional disturbance when age disagreement is discovered.