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SYER: Symposium Trace species in environmental research

SYER 2: Session II

SYER 2.3: Invited Talk

Wednesday, March 12, 2008, 15:00–15:30, 3C

Geochemistry of rare cosmogenic nuclides — •Friedhelm von Blanckenburg — Institut für Mineralogie, Universität Hannover, Callinstrasse 3, 30167 Hannover

Cosmogenic nuclides (mostly ³He,¹⁰Be, ¹⁴C, ²¹Ne, ²⁶Al, ³⁶Cl) currently fuel a fascinating scientific development boosted by Accelerator Mass Spectrometry (AMS). Cosmogenic nuclides are produced by interaction of galactic cosmic rays (mainly protons of GeV energy) with the surface of meteorites (Cosmochemistry); with molecules in the atmosphere (Environmental and Climate sciences); and with interaction of secondary cosmic rays (mainly MeV neutrons) with the uppermost meter of the Earths surface (Geosciences). The so-called "in-situ produced" cosmogenic nuclides can be used to determine, for example, exposure ages of prominent features of the Earths landscapes, such as glacial moraines or lithospheric faults. However most surfaces of the Earth are always slowly eroding, in which case erosion rates can be calculated. For nuclides produced in the atmosphere from where they are introduced into terrestrial or oceanic material their radioactive decay from an initial isotope ratio (e.g. ¹⁴C/¹²C, ¹⁰Be/⁹Be) can be used to determine ages (such as that of organic matter or of ground water). In ocean water and sediment, they mark paleo-ocean circulation and sedimentation. When measured in well-dated environmental archives, such as tree-rings (¹⁴C) or ice cores (¹⁴Be), the changes of production rates of atmospheric cosmogenic nuclides provide information about the past solar modulation, and its impact on climate change. These developments will be reviewed in this talk.