Lead


Lay summary
Project SummaryLow-temperature thermochronology is the study and measurement of the time-temperature history of rocks during exhumation. Given that the thermal field of the uppermost crust is sensitive to details of the topography, low temperature systems can provide information on the history of mountain topographic development as well as timing of tectonic processes. As a consequence, systems of low closure temperature (e.g. apatite (U-Th)/He dating, which has a closure temperature of about 700C) have received widespread development and application. Recently, a new thermochronologic method, based on OSL-dating has been introduced. OSL-thermochronology appears to have a closure temperature of about 25-400C, opening a new window on the latest stage of exhumation of rocks towards the surface. Given its remarkably low closure temperature, this system has the potential to enable quantification of geologic-geomorphic processes at a timescale comparable to that of Quaternary climate cycles. Besides its particularly low closure temperature, OSL-thermochronology also has the advantage of the relative ease of making measurements and the ubiquity of the minerals used: quartz and feldspar. The technique already shows great promise, with an initial study in the Southern Alps of New Zealand and encouraging results from 3 new sample suites (New Zealand, European Alps and Himalayas). However, in order to make the method more rigorous and suitable for routine applications in a wide range of contexts, some of the fundamental principles of OSL need to be established more robustly.In this project we propose to (1) establish a better calibration of the kinetic parameters that define the closure temperature of OSL-thermochronology through a suite of well-defined laboratory experiments, (2) perform in-situ calibration on sites where temperature is well known and erosion is negligible (Australian mine) or demonstrably important (tunnel in the European Alps), (3) demonstrate the usefulness of the method, in particular by showing the information it can provide on the effects of Pleistocene glaciations (with a particular focus here on the European Alps).Research Plan1. Step 1: sample collection in a Non-Eroding terrain: CSA Mine, Australia.2. Step 2: sample collection in an Eroding Terrain: Lötschberg tunnel, Aar Massif, Switzerland.3. Step 3: OSL measurements (Pulse/Linear Modulation) - Pulse annealing and isothermal holding experiments. 4. Step 4: Thermal and landscape evolution models