Periodic Reporting for period 3 - ICED (Impact of climate on mountain denudation)
Periodo di rendicontazione: 2022-10-01 al 2024-03-31
The ICED project addresses a number of outstanding questions in the Earth sciences, and specifically with regard to how changes in climate might affect changes in rates of erosion. Within the European Alps, during the ice-age, large glaciers formed and advanced, calving the landscape that we see today e.g. overdeepened valleys. However it remains unclear how effective glaciers are at erosion, and so exactly which processes led to Alpine valley formation and when the valleys were formed. By allowing the timing of valley formation to be measured more precisely, the ICED project will address this question. Understanding the processes of glacial erosion and Alpine valley formation are criticil for the appropriate storage of nuclear waste materials so that they are not disturbed by future glacial advances.
To date the project has been exploring the properties of different samples collected from calibration sites as well as from field-sites in the western European Alps. We are developing a technique called Electron Spin Resonance thermochronometry, which measures how the trapped electron population in quartz minerals responds to temperature. If we can explain the processes of electron trapping and detrapping precisely, we can use this method to determine when the Alpine valleys were formed, as rocks cool when they get closer to the surface following erosion. Because the method is relatively new, we need to measure samples with known thermal history, to ensure that we get the correct age. We took samples from the KTB borehole in Germany, and also from the MIZ1 core in Japan for this purpose. Whereas the KTB samples have very challenging properties, the MIZ1 samples have good ESR properties and the measurements are continuing. Our initial measurements are promising and show that the signals are sensitive to temperature, the next step is to determine if we can quantitatively recover the temperature that the rocks have been exposed to. Once we have done this we will be able to finalise our numerical models, allowing us to apply the technique to our samples from the western European Alps.
The methods that we are developing in this project have not been systematically investigated on this scale (number of experiments, range of samples) previously. We plan to fully establish the technique as a robust method that can be applied in other regions globally to understand changes in erosion rates and their link to climate.