Comparison of OSL and ITL Measurements on Quartz Grains Extracted from Sediments of the Chad Basin, N.E. Nigeria

Optically Stimulated Luminescence (OSL) dating using quartz has now been confirmed to be limited to sediment ages <150 Ka due to the saturation levels of the dose-response curve. Thermoluminescence (TL) of unheated quartz has been used in the past to date sedimentary sequences beyond 200 Ka but became very unpopular among users because of the poor reproducibility observed in the measurement procedure (multiple aliquot) and inadequate resetting of the TL signal at 325°C. The possibility of using Isothermal Thermoluminescence (ITL) on quartz to extend the dating range has been suggested by many workers. Using the Single Aliquot Regenerative dose protocol (SAR), the OSL and ITL (at 270°C for 600 sec) signals have been compared using quartz grains extracted from sediments collected from the Nigeria sector of the Chad basin. The preliminary finding of this research shows that the equivalent doses obtained using ITL signals from the younger samples (<30 Ka) agrees with OSL doses. On the other hand, ITL underestimates the OSL counterpart in the older samples (>100 Ka).