Stability of TL signal in fine grains from Loess

The TL signals of fine grain loess samples observed using Corning 5-58 and Schott UG-11 filters were compared. The UG-11 filter had already been shown to increase the luminescence from the feldspar grains which bleach most easily and are therefore the most suitable for dating. However, this filter produces greater enhancement of the lower temperature component of the natural TL, around 230 C. A summary of kinetic studies in this temperature region demonstrates that it is not stable enough for geological dating applications. In samples over 20 kyr this signal interferes with the stable high temperature TL around 300 C resulting in poor plateaux. Pre-heating disc samples for 1 min at 230 C to remove the unstable component is proposed. Good agreement was shown between this method and the original method using the 5-58 filter and no pre-heat for young samples. Applying both methods to samples thought to be at least 200 kyr on geological evidence gave rise to severe underestimation of the EDs. (author)