Surface resetting of thermoluminescence in milled quartz grains

Thermoluminescence (TL) dating of fault movements assumes TL resetting in gouges during faulting due to frictional heating. However, this assumption is often doubted. Here, we quantitatively examine the TL resetting in milled grains of quartz previously 1 kGy dosed. The TL intensity as a function of the grain diameter indicated the TL reduction only in surface layers of unetched grains. The layer thickness was estimated to be about 500 nm based on the comparison with a model. This TL reduction layer is equivalent to the surface disordered layer that has been found to be generally amorphous and/or highly disturbed due to thermal and mechanical damage during milling and faulting. For detailed modeling of TL resetting during milling and faulting, both frictional heating and mechanical deformation of the surface structure need to be considered. Fine or finest gouges are potentially the best type of sample for TL dating of fault movements.