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Spatially and temporally variable catchment denudation rates determined by cosmogenic nuclides - clues from the Alps and the Altiplano

Applicant Kober Florian
Number 135317
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Geology
Start/End 01.02.2012 - 30.11.2015
Approved amount 214'939.00
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All Disciplines (2)

Discipline
Geology
Geochemistry

Keywords (5)

cosmogenic nuclides; denudation rates; Alps; climate; tectonic

Lay Summary (English)

Lead
Lay summary

The evolution of the alpine landscapes is a result of the composite effects of climate, tectonics and erosion. In order to understand the landscape evolution it is necessary to establish erosion or denudation rates. However, it is known that denudation rates are variable over time and space, but it is largely unknown to what extend this variability exists, can be quantitatively constrained and what induced these variations. Specifically, after the last glaciations (e.g., in the European Alps), geomorphic processes and denudation rates must have adjusted to the new interglacial condition. The main questions hereby - amongst others - are: 1.) Did denudation rates first increased and later decreased since the retreat of the glaciers? 2.) What impact has a Holocene climate change on denudation rates? 3.) How does a climate change affects permafrost areas and thus processes in this region? 4.)What is the influence of episodic events (thunderstorms, floods) on short, medium and long term denudation rates, that occur rather infrequent but with high magnitude? 5.) Are their lag times of cause and effect? 6.) Can we quantify climate change (e.g., increasing numbers of heavy rainstorms and floods, landslides and debris flows) and the related change of denudation rates, and thus study natural hazards and try to better perform on predicting natural risks?

The projects tackles these questions by trying to establish time series of denudation rates using terrestrial cosmogenic nuclides, in combination with field work and GIS analysis. We will use multiple cosmogenic nuclides (10Be 14C, 21Ne, 26Al) in sand from modern rivers and from lake archives for resolving Holocene denudation rates in various catchments of the European Alps. These rates are furthermore evaluated in the light of denudation rates obtained by other methods (sediment yield or thermochronology) that will enable us to have an idea about the steadiness or variability of denudation rates over various temporal and spatial scales. Furthermore we will compare the results of the European Alps with data from the Chilean-Bolivian Andes in South America. This region is characterized by a different climatic and tectonic setting and we thus expect different rates over different integrating timescales. Finally, in combination of the data from the Alps and the Andes we hope to get a better understanding of geomorphic processes, their rates and their driving forces.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Tectonic and lithological controls on denudation rates in the central
Kober Florian (2015), Tectonic and lithological controls on denudation rates in the central, in Tectonphysics, 657, 230-244.

Collaboration

Group / person Country
Types of collaboration
Geologische Bundesanstalt Wien Austria (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Depatment of Earth Sciences, ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
AMS Group at Ion Beam Physics ETHZ Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Inst. of Geology, University of Potsdam, Germany Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Geological Sciences, University Milano-Bicocca Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
118038 Glacial chronologies in mid and high latitudes: geological field and cosmogenic multi-nuclide analysis 01.10.2007 Project funding

Abstract

Changing erosion rates are strong evidence of changes in the environmental and tectonic forcings that act upon landscapes. On millennial timescales changes are attributed mostly to varying climate, i.e., changes in e.g., precipitation rates, temperature, in magnitudes and recurrence intervals of floods, debris flows, landslides etc. Catchment wide denudation rate determinations by terrestrial cosmogenic nuclides (TCN) have gained a wide appreciation in the last decade given their ability to quantify long-term mean average erosion rates for entire catchments. A major assumption in these studies is that denudation is steady. This assumption may not hold when climate, and thus boundary conditions for erosion rates, change on timescales shorter than needed to approach steady state conditions for a landscape and its cosmogenic nuclide concentrations. However, very limited knowledge exists on the impact of varying climate on catchment wide denudation rates obtained by TCN. Taking the currently published denudation rates by TCN to find correlations with morphometric landscape parameters or external forcings, such as uplift, can lead to misinterpretations. This project aims to have a detailed look into the temporal and spatial distribution of TCN concentrations in places where it is independently known that climate was not constant and landscapes are likely to be transient. Specifically, data will be collected from 1) paleorecords of boreholes from multiple stratigraphic depths in Swiss perialpine lakes, 2) samples at a single location in Swiss perialpine catchments at various times and 3) by analysing multiple TCNs in one sample by using 10Be, 14C, 21Ne and 26Al in a transient landscape of the Altiplano and Eastern Andes, Bolivia. These approaches will allow us to determine the degree of steadiness or transience of a landscape’s morphology. 10Be is commonly applied in catchment wide denudation rate studies, while 21Ne and 26Al have been used less frequently. We propose to additionally use 14C for the first time in catchment wide denudation rate studies and thus to add a new tool to the method. Due to the short half-life of 14C (5.37ky), its response time to changing boundary conditions is shorter than those of the longer-term radionuclides (10Be, 26Al) or the stable 21Ne. By an improved characterisation of the nature (steady-state or transient) of a landscape (as determined from TCN derived catchment wide denudation rates) we will be able to better understand landscape forms and formation processes. Furthermore, since TCN-derived catchment wide denudation rates bridge the timescales obtained by decadal sediment yield studies and low temperature geochronological methods (e.g., fission track dating) we will be able to look in more detail into the short- to long-term process rates and finally the evolution of landscapes and mountain belts.The knowledge gained in this project will help to better constrain past environmental conditions and processes as well as to set the basis for predictions and modeling. Current national and international projects that target landscape evolution and climate change in the Alps (FloodAlp, TopoAlps, SediMont) will be an excellent environment for discussion, application and progress.
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