Cosmogenic Radionuclides

Earth is continuously bombarded by galactic cosmic rays. Nuclear reactions, for example with the oxygen or nitrogen in the atmosphere and in the rocks on the Earth’ surface, produce cosmogenic nuclides. These can be used to study a variety of geological processes. Due to the low production rates (few atoms per year and gram of matter, see Table 1), concentrations of terrestrial cosmogenic nuclides in natural materials are extremely low. With Accelerator Mass Spectrometry (AMS) we can measure concentrations of 10³ - 10⁵ atoms per sample!

Applications

Exposure dating and erosion rates. Long-lived cosmogenic radionuclides such as ¹⁰Be, ²⁶Al and ³⁶Cl are produced in situ in exposed rock. Accumulation of these nuclides can be used to determine the age of certain geological events that bring fresh rock suddenly to the surface, for example, rock fall events, earthquakes, or volcanic eruptions. The exposure dating of moraine boulders and glacially polished bedrock yields insight into the timing and extent of past glacial advances and is used to reconstruct climate oscillations of the last million years. Nuclide concentrations in river sediments reflect denudation in the river catchment area and quantify erosion and sediment transport and deposition. Burial-dating, i.e., dating since when an object is no longer exposed to cosmic rays can constrain, for example, the age of river terraces, but is also used in archaeology.

Meteoric cosmogenic nuclides. Cosmogenic nuclides that are produced in the atmosphere are introduced into the hydrologic cycle and into the soil and adsorb to fine-grained sediments. Glacial ice, which has accumulated over thousands of years, but also sediments in lakes and oceans and deep-sea manganese crusts are therefore archives of meteoric ¹⁰Be and ²⁶Al concentrations over these time scales. Cosmogenic nuclides can be used to date these archives. On the other hand, sediment and ice cores yield insight into temporal variations of nuclide production, e.g., due to variations in solar activity. Cosmogenic nuclides are thus also important for climate reconstructions.

A catchmentwide erosion rate determined from the ¹⁰Be concentration in quartz from a riversand sample is often more meaningful than the erosion rate of an individual rock outcrop. riversand is a python package developed by our group, which calculates catchmentwide erosion rates from a digital elevation model (geotiff) and catchment outlines (polygon shapefile) and the cosmogenic nuclide concentrations measured in quartz samples from the catchment outlets. Unlike previously published catchmentwide erosion rate calculators, riversand obtains nuclide productions from G. Balco's online calculator (hess.ess.washington.edu, stoneage.ice-d.org or stoneage.hzdr.de), which is widely used for point-based exposure age and erosion rate calculations, and the results are therefore fully compatible.

Erosion rate calculation with riversand is fast (few seconds for one catchment) for all production scaling methods implemented in the online calculator (St, Lm, LSDn) and independent of the catchment size or the resolution of the digital elevation model, and there is no need to rely on a time-constant scaling method in order to keep computation times short. The package is available through PyPI or github and comes with a quick tutorial and some test data.

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User Information

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Projects and Collaborations

Topography and landscape evolution Pamir, DFG project STU 525-2 (doi: 10.1016/j.qsa.2023.100135) Florian Adolphi, Alfred-Wegener-Institute Bremerhaven: Solar-induced production rate changes using 10Be in Arctic shelf sediments (Project CLOC — Cosmic Links between Ocean Sediments and Ice Cores) Nele Lehmann, Alfred-Wegener-Institute Potsdam & Helmholtz-Zentrum Hereon Geesthacht: Determination of erosion rates in the Arctic using terrestrial cosmogenic nuclides Roman Garba, Jan Kameník, Czech Academy of Sciences, Prague: Burial dating of the lower Paleolithic horizon at the Korolevo site in Transcarpathia, West Ukraine (doi: 10.1007/s10967-022-08738-8) John Jansen, Shantamoy Guha, Czech Academy of Sciences, Prague: Dating the first major Pleistocene Glaciers in the Western Alps Toshiyuki Fujioka, Cosmogenic Nuclide Dating Laboratory, National Research Centre on Human Evolution (CENIEH), Burgos, Spain: (i) Late Cenozoic incision history of Duero Basin, N Spain (ii) Formation of Galiana multilevel caves in NE Spain (iii) Fluvial terrace chronology in Guadiana River, central Spain (iv) History of Acheulian lithic industries in Iberian Peninsula

Further Reading

Fundamentals

Balco, G., Stone, J.O., Lifton, N.A. and Dunai, T.J. (2008). A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements. Quaternary Geochronology, 3(3), 174-195. https://doi.org/10.1016/j.quageo.2007.12.001 Dunai, T.J. (2010). Cosmogenic Nuclides: Principles, Concepts and Applications in the Earth Surface Sciences. Cambridge University Press. https://doi.org/10.1017/CBO9780511804519 von Blanckenburg, F., Willenbring, J.K. and Dove, P.M. (Eds.) (2014) Cosmogenic Nuclides. Elements, 10(5).

Own Publications (see also here)

Stübner, K., Gadoev, M., Rugel, G., Lachner, J. and Bookhagen, B. (2024). Three Pleistocene glacial advances and a warm episode during MIS-3: Towards a more complete glacial history of the Pamir mountains. Quaternary Science Advances, 13, 100135. https://doi.org/10.1016/j.qsa.2023.100135 Stübner, K., Bookhagen, B., Merchel, S., Lachner, J. and Gadoev, M. (2021). Unravelling the Pleistocene glacial history of the Pamir mountains, Central Asia. Quaternary Science Reviews, 257, 106857. https://doi.org/10.1016/j.quascirev.2021.106857 Gärtner, A., Merchel, S., Niedermann, S., Braucher, R., ASTER-Team, Steier, P., Rugel, G., Scharf, A., Le Bras, L. and Linnemann, U. (2020). Nature does the averaging—in-situ produced 10Be, 21Ne, and 26Al in a very young river terrace. Geosciences, 10(6), 237. https://doi.org/10.3390/geosciences10060237 Stolle, A., Schwanghart, W., Andermann, C., Bernhardt, A., Fort, M., Jansen, J.D., Wittmann, H., Merchel, S., Rugel, G., Adhikari, B.R. and Korup, O. (2019). Protracted river response to medieval earthquakes. Earth Surface Processes and Landforms, 44(1), 331-341. https://doi.org/10.1002/esp.4517