OSL-thermochronology: introduction, application and limitations

We present here how we have recently developed a new thermochronologic method based on optically stimulated luminescence (OSL)-dating, that we call OSL-thermochronology. This system has a very low closure temperature (30-35 C, assuming a cooling rate of 10 C/Myr). In this particular case, OSL is used to determine the time since quartz grains commenced trapping charge in the appropriate electron traps in response to environmental ionizing radiation, as they cooled through the effective closure temperature. Beside its low closure temperature, OSL has the advantage that the measurement procedure is relatively simple, though comprising a large number of steps in comparison to fission track or (U-Th)/He dating. Recent technical developments, specifically the introduction of the single aliquot regenerative-dose (SAR) protocol for quartz, which has been tested very thoroughly for sediment samples by comparison to independent age estimates, also makes this technique an attractive low temperature thermochronometer. We will describe here the kinetics of the system, present its practical aspects and discuss its limitations. Finally, we will present how we applied this new technique in settings where exhumation rates are high (i.e.; between 1 and 10 mm/yr) and relatively well constrained (New Zealand, Alps and Himalayas). Our findings empirically demonstrate that OSL-dating can be used as a thermochronologic method.