New techniques to investigate erosion patterns
The question of whether erosion rates increase under colder climates is the subject of intense debate in the geomorphology field. The team behind the ICED project are developing novel techniques that could shed new light on the topic, as Georgina King , Melanie Kranz-Bartz , Aditi Dave, Xiaoxia Wen and Maxime Bernard explain.
The importance of glaciers as erosion agents is the subject of intense debate, and while a 2013 study suggested that erosion rates accelerated during the Quaternary period, there is also evidence to support other viewpoints. Thermochronology techniques provide evidence of how the temperature of rocks have evolved over time, yet established methods are associated with large uncertainties, an issue the ICED project team are working to address. “We’re developing methods that provide more precise measurements of rock cooling over a time window of between one thousand and one million years, so we can see if there has been an acceleration in erosion rates during cold periods, or glaciations,” explains Georgina King, Associate Professor in the Institute of Earth Surface Dynamics at the University of Lausanne. These thermochronometers are based on using luminescence and electron spin resonance (ESR) to detect unpaired electrons in minerals such as quartz. “We use specific centres or defects in quartz minerals to get an idea of their thermal sensitivity,” says Professor Melanie Kranz-Bartz, a former post-doctoral researcher on the ICED project.
Thermochronometry
Thermochronometry is based on the idea that once a mineral has passed a specific temperature in the earth’s crust – its closure temperature – a signal accumulates. This allows researchers to calculate an age corresponding to the time of closure and to learn more about the thermal history of a mineral. “We can convert [the cooling age] into a cooling rate, and transfer it into an erosion rate. We are looking to develop this method further – using ESR we are able to cover the entire Quarternary period, and potentially beyond,” outlines Professor Kranz-Bartz. Alongside developing the new thermochronometry method, researchers in the team are also applying it on rock samples from different regions, including PhD student Xiaoxia Wen’s work in the Western Alps. “I’ve been working mainly in the upper Rhone valley, in Switzerland, where there is a really high documented relief change. We collect rock samples at different elevations along a vertical transect, from the top to the valley bottom, and
see how the ESR signal evolves,” she explains. “The data is consistent with that from existing, classical thermochronometry methods.”
The next stage in the project will be to implement the ESR method in a thermokinematic model, which will enable researchers to create thermal – or exhumation – histories, and build a fuller picture of past erosion patterns, with the ultimate goal of reconstructing past topography evolution. As part of his post-doctoral research in the ICED project, Dr Maxime Bernard has been working with data from around the Mont Blanc tunnel.
“We used 3-d software to invert the data and constrain the evolution of the area’s topography. Evidence seems to show that the most recent glaciations cooled the Massif quite significantly,” he says. Researchers aim to understand the influence of these glaciations on the cooling history of the Massif, while at the same time taking into account other factors which affect erosion patterns. “There are feedbacks between erosion and the climate on longer timescales, in the millions of years,” continues Dr Bernard. “By modelling and constraining erosion and the total volumes of sediment exporting carbon to sedimentary basins, we want to constrain how this ice erosion may have contributed to the further cooling of the planet that has been observed, on timescales of millions of years.”
Researchers are also able to investigate processes occurring over shorter timescales with luminescence thermochronology, and look at more spatially localised erosion patterns. Much remains to be learned about how ice reshapes topography close to mountain summits for example, and Dr Bernard says the project’s work could help shed new light. “We can try to constrain these processes on different spatial and topographical scales,” he outlines. The project team are also exploring whether this method could be applied to other minerals aside from quartz, which could allow researchers to investigate previously neglected regions. “Thermochronometric techniques have previously been applied to silicate-rich lithologies, which are really clustered in particular parts of the Alps,” explains Professor Kranz-Bartz. “I’m
investigating whether we can apply ESR thermochronometry to carbonate minerals as well, and if we can use it to constrain rates of rock cooling and exhumation rates. It looks pretty positive so far, and we hope to gain new insights into valley formation and other geomorphological processes.”
Verifying the method
The method itself still needs to be fully verified, and while there are still some challenges to overcome, Professor King is confident that it will be shown to be robust and reliable. The data gathered so far is consistent with other thermochronometric records, and the methods could open up new investigative possibilities. “We’re starting to show some
A further potential application of the method is in geothermal exploration, identifying locations where geothermal fluids are relatively close to the earth’s surface. Water can circulate at depths of
“We’re developing a method that provides more precise measurements over a time window of between one thousand and one million years, so we can see if there has been an acceleration in erosion rates during cold periods, or glaciations.”
case studies where we’ve been able to resolve things that can’t be measured otherwise,” says Professor King. The next step will be to heighten awareness of the technique’s potential, with plans to attend the International Conference on Thermochronology in September 2025, while further research is planned beyond the conclusion of the project. “I’m interested in dating earthquakes. The general consensus in the research community is that signals from earthquakes do not completely reset. So with the traditional way of applying luminescence or ESR for dating, we usually overestimate the time since the last earthquake activity,” explains Dr Aditi Dave, a post-doctoral researcher working on the project.
“Thermal signals may provide a better way of looking at unanswered questions like the timing of past earthquakes.”
20 kms below the earth’s surface where temperatures are always very hot, and these fluids can then come up to the surface, thanks to faults and fracture zones. “The challenge is to find out where this can happen – the faults and fracture zones have to be sufficiently permeable for these fluids to circulate,” outlines Dr Bernard. Thermochronometry techniques could be used to detect geothermal reservoirs at depth, and to generate a kind of probability map, providing a more cost-effective way of investigating potential sites for the development of geothermal energy.
“Conventional geothermal exploration techniques are quite expensive. We can use thermochronology to conduct investigations from the surface,” continues Dr Bernard.
ICED
Impact of climate on mountain denudation
Project Objectives
The ICED project seeks to explore the timing of alpine valley development through the application of a novel set of thermochronometric methods that can resolve changes in rock exhumation at the timescale of glacial and interglacial cycles. By using methods based on trapped-charge dating (optically stimulated luminescence and electron spin resonance dating) this project will offer a more precise insight into the timing of alpine valley development and thus processes of glacial and fluvial erosion.
Project Funding
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 85164.
Contact Details
Project Coordinator, Georgina King
University of Lausanne Institute of Earth Surface Dynamics (IDyST) Quartier UNIL-Mouline Géopolis building CH-1015 Lausanne
T: +021 692 35 33
E: georgina.king@unil.ch
W: https://wp.unil.ch/ice/
King is Associate Professor at the University of Lausanne. She develops trappedcharge dating thermochronological methods.
Aditi Dave is a postdoctoral researcher, working on methodological development of Quartz ESR thermochronology.
Maxime Bernard is a Post-doctoral researcher dedicated to investigating how glaciations reshaped mountain topographies.
Melanie Kranz-Bartz is a geomorphologist. She is an expert in electron spin resonance and luminescence dating.
Xiaoxia Wen is pursuing a PhD in geomorphology, studying landscape evolution in the Rhône valley.
