Developments and applications of luminescence dating in earth sciences

Abstract

This thesis aims to address fundamental questions about developments and applications in luminescence dating in the past, present, and future, including the age range, accuracy, and thermochronological studies. To estimate the equivalent dose (De) of calcite, a single-aliquot regenerative-dose (SAR) protocol with low-temperature measurements is employed. It uses the isothermal thermoluminescence (ITL) signals measured at ~225-240 °C, where a De vs. ITL temperature (De-T) plateau is observed. These ITL signals correspond to the TL signals of the 280 °C TL peak. Notably, ITL signals at 230-235 °C saturate at ~4000-5000 Gy, which has the potential to date geological and archaeological samples spanning the entire Quaternary period. The absence of detectable anomalous fading of ITL signals suggests that the signal is free of fading. Dose recovery tests further confirm the suitability of the SAR-ITL protocol for De estimation. The SAR-ITL protocol was then employed to study the thermochronological applications of limestone rocks in the middle of the Nujiang River, southeastern Tibetan Plateau. The results show that apparent De values of ITL230 signals increase with increasing heights, while apparent ages increase before approximately 400 ka (the apparent age) and then reach dynamic equilibrium stages. From the isochron plot of apparent De values against dose rates, the effect lifetimes of ITL signals were obtained, which constrains the applicable ranges of ITL signals from calcite. It is proposed that calcite can be used in thermochronology within the applicable ranges from 530±25 ka to the present. The accurate luminescence dating of volcanic-related materials remains challenging. This study focuses on quartz minerals extracted from lava-baked sediments in the Tengchong volcanic field, southeastern the Tibetan Plateau, using the optically stimulated luminescence (OSL) technique. The results show that samples with initial OSL signals dominated by the fast component yield reliable ages. Conversely, samples dominated by unstable medium and slow components broadly underestimate their OSL ages, requiring corrections. By using the plot of De against recuperation for each aliquot, the underestimated OSL ages can be corrected. The final single-aliquot quartz OSL ages are consistent with single-grain quartz OSL and 14C ages recording the same eruption event, thus validating the reliability of the dating ages. The comprehensive research on photoluminescence (PL) emission spectra of various feldspar types remains poorly understood and the limited availability of instruments has hindered its research. This study investigated the PL properties of six feldspar types using a commercial Raman instrument. The results indicate that the number and medium positions of emission peaks depend on the specific feldspar types and samples analyzed. Additionally, the sensitivity of PL signals to irradiation dose varies across feldspar types and peak positions. Notably, PL emissions from ~865 and ~910 nm of K-feldspar are sensitive and show potential applicability for dating applications. The dose-response curves obtained using 860-870 nm PL signals of potassium feldspar conform to a relationship of a single saturating exponential function between the signal and irradiation dose. This study demonstrates that a commonly available Raman system can be utilized for PL measurements of single grains.