When measuring samples from southern Peru, we discovered an age offset between
feldspar infrared-stimulated luminescence (IRSL) and quartz optically stimulated
luminescence (OSL) ages. This age offset was not only found in these particular samples but
was also observed in samples from a range of geographical localities. Extensive analysis
revealed that it is actually the quartz age that underestimates the true depositional age, and
this is due to a very weak fast component combined with other thermally unstable OSL …