Dose-rate dependence of natural TL signals from feldspars extracted from bedrock samples

The influence of dose rate on feldspar thermoluminescence shape is considered for a variety of natural dose rates. The geologic dose rate experienced by bedrock samples is observed to control the position of the low-temperature edge of the bulk TL signal (the parameter), with higher dose rates producing natural TL signals that begin to emit at lower measurement temperatures. This behavior can be explained in terms of the natural equilibrium between electron trapping and detrapping rates, as the trapping rate depends directly on the dose rate. The role of anomalous fading is more subtle. While a wide range of values is found at low fading rates, only high values are found when the fading rate is greater. This suggests that high fading rates may also influence the natural value by making low-temperature regions of the TL curve unstable. Our results illustrate the need to consider dose-rate and fading-rate variations between bedrock samples before interpreting the minimum stability of each natural TL signal, a consequential result for future low-temperature thermochronology applications.