A review of the thermally transferred optically stimulated luminescence signal from quartz for dating sediments

Luminescence dating based on measurement of the fast component of the optically stimulated luminescence (OSL) signal of quartz now plays a key role in providing chronological control for late Quaternary sediments. Although highly successful, the method is commonly limited to the last ∼100 ka due to saturation of the fast component of the OSL signal. In the last few years studies have been undertaken into a new signal from quartz termed the thermally transferred optically stimulated luminescence (TT-OSL) signal. This saturates at far higher radiation doses than does the fast component of the OSL signal, and thus offers the potential to date sediments back to 1 million years (1 Ma) or more. This paper reviews current knowledge of the TT-OSL signal and highlights the complexity of the measurement procedures so far developed, and their related terminology, the lack of knowledge of the thermal stability of the charge, the experimental details of the protocol applied to each group of samples, particularly the temperatures used, the slow rate at which the signal is reset by light, and the continuing need for testing of the method on samples with independent age control beyond the range of radiocarbon.