Seminar

Calcite is a crystalline form of calcium carbonate (CaCO₃), which occurs in various geological and archaeological contexts, showing potential to date geological and archaeological events back several million years. However, several issues, such as spurious thermoluminescence (TL) signals due to crystal surface defects appearing at temperatures above 350 °C, have hindered its application to a wide range of samples. A single-aliquot regenerative-dose (SAR) protocol for calcite with low-temperature measurements is proposed to measure the equivalent dose (D_e). It uses the isothermal TL (ITL) signals measured at 230-235 °C, where an equivalent dose vs. measuring temperature (D_e-T) plateau can be observed. Several tests (e.g., fading rate and dose recovery) were conducted, confirming the suitability of the SAR-ITL protocol for D_e estimation. The SAR-ITL protocol measured with temperatures below 300 °C suppresses the effects of spurious luminescence signals induced by high-temperature heating. The ITL signals at 230-235 °C can date geological and archaeological samples with ages spanning the entire Quaternary period. The new protocol for dating calcite can be widely applied to terrestrial and marine sediments, such as biogenic shells and travertines.