ESR and Luminescence Thermochronometry of the Rhône Valley, Switzerland

The impact of Quaternary glaciation on rates of erosion remains disputed. This is mainly due to a lack of geochronological data that cover the timespan of 103–106 years. To fill this temporal gap, we develop electron spin resonance (ESR) thermochronometry using both the Al and Ti centres in quartz. The combination of ESR thermochronometry with numerical modelling allows rock cooling histories to be determined, enabling changes in erosion rates to be related to glacial advance. In this study, we conducted a series of laboratory experiments using samples from the Rhône valley (Switzerland) which is thought to have substantially deepened around 1 million years ago. Ten quartz samples, from a transect collected near Sion, were used to (i) optimize the measurement protocol (i.e., preheat conditions), (ii) constrain ESR signal growth and thermal stability of the Al and Ti signals to estimate trap kinetic parameters; and (iii) invert the ESR data to constrain rock cooling histories. A preheat plateau experiment showed that 170 °C is the appropriate preheat temperature whilst sensitivity changes are not significant. For most samples the Ti-centre has higher thermal stability than the Al-centre, although the thermal stability of the different samples investigated is highly variable (e.g., s ranges from 7.5 × 109–4.5 × 1012 s−1 and Et from 1.2 to 2 eV for the Ti-centre). Preliminary inversion results yield consistent cooling histories of around 30–60 °C during the Late Quaternary period, except for two valley bottom samples that suggest more rapid rock cooling.