Characteristics of thermally transferred optically stimulated luminescence (TT-OSL) in quartz and its potential for dating sediments

The temperature dependence, dose response and bleaching characteristics of the thermally transferred optically stimulated luminescence (TT-OSL) of sedimentary quartz were studied, in order to assess the potential of the TT-OSL signal for dating. The TT-OSL was separated into two components; recuperated OSL (ReOSL) and basic transfer (BT-OSL) by annealing samples at 300 degrees C for 10s as suggested in an earlier study. Four quartz extracts were studied, two from loess from China and two from coastal sands from South Africa. The equivalent doses of the two recent samples (one sand and one loess) were similar to 15 Gy and this suggests that the signal can be bleached by sunlight but may not be totally zeroed. The sensitivity-corrected ReOSL from the older samples did not reach zero and gave doses of 14 and 52 Gy, respectively, after 7 days bleaching with a solar simulator. A single aliquot regenerative dose (SAR) protocol using ReOSL was proposed and tested. In this protocol, a blue light stimulation at 280 degrees C for 100s at the end of each cycle resulted in the recovery of identical sensitivity-corrected ReOSL values, in spite of similar to 20-30% loss in sensitivity for the four samples that were tested. Two dose response curves were constructed using the sensitivity-corrected ReOSL, one for the initial 2 s signal and the other for the fast component obtained by curve fitting. Using the additional high temperature bleach and the separated fast component of the ReOSL, it was possible to recover given doses within 10%, up to similar to 1000 Gy for the loess and similar to 2000 Gy for the coarse grained quartz. However, the natural dose obtained for the older sand was twice that obtained using the conventional SAR OSL method. (C) 2008 Elsevier Ltd. All rights reserved.