Aim of this paper is to better investigate the Thermally Transferred Optically Stimulated Luminescence (TT-OSL) signal generated in quartz samples, both mineral quartz and quartz extracted from sediment, when they are heated after an optical bleaching. In recent years, TT-OSL has become an interesting dating technique because it can extend by an order of magnitude the age range over which OSL dating can be applied. We focused in particular on the source traps that generate this signal, studying the changes in TT-OSL due to the preheat temperature that induces the thermal transfer, and analysing the Thermoluminescence (TL) signals caused by OSL and TT-OSL measurements. By varying the preheating temperature, it was possible to identify the presence of a peak at ∼280-300°C, likely related to a trap responsible for the TT-OSL signal. A similar result was obtained by analysing the glow curves after an optical bleaching, which evidenced a peak at ∼270°C, comparable with a peak previously identified. It was also possible to highlight the fact that the OSL and TT-OSL signals are originated by different mechanisms due to the differences between the source traps responsible for them.