The De underestimation caused by the unstable medium component in the initial OSL signal from lava-baked quartz and correction strategies

Abstract

Accurately dating of eruptive events is crucial for understanding the eruptive history of a volcano. The optically stimulated luminescence (OSL) dating technique has been widely used in the geochronological studies of volcanic eruption events. However, its application is challenging due to the complex components of OSL signals in which the unstable medium component often results in age underestimation for quartz related to volcanic activity. In this study, we investigated the quartz OSL properties from a lava-baked sediment layer from the Tengchong volcanic field, southwest China. The results indicated that the initial OSL signal of the lava-baked quartz was primarily dominated by the medium component, which exhibited small Fast Ratio values (<10). The equivalent dose (D_e) values showed a negative correlation with recuperation, and the D_e-t plot concurrently showed a decreasing trend. Pulse-annealing tests confirmed the medium component in the initial OSL signal to be thermally unstable, hence resulting in age underestimation. Consequently, the early background subtraction method and another two correction strategies were employed to derive D_e values from the more stable fast component: Ⅰ) fitting the D_e-t plot, and Ⅱ) fitting the D_e-recuperation plot. The study found that D_e values could only be partially corrected using the early background subtraction method. In contrast, the latter two methods allowed for successful correction. The corrected quartz OSL ages agree well with independent MET-pIRIR ages of potassium feldspar and ¹⁴C ages. The reliable chronological results suggest that the Dayingshan volcano erupted approximately 41–45 thousand years ago.