New approaches investigating production rates of in-situ produced terrestrial cosmogenic nuclides

In-situ produced cosmogenic nuclides have proved to be valuable tools for environmental and Earth sciences. However, accurate application of this method is only possible, if terrestrial production rates in a certain environment over a certain time period and their depth-dependence within the exposed material are exactly known. Unfortunately, the existing data and models differ up to several tens of percent.
Thus, one of the European project CRONUS-EU goals is the high quality calibration of the ³⁶Cl production rate by spallation at independently dated surfaces. As part of fulfilling this task we have investigated calcite-rich samples from four medieval landslide areas in the Alps: Mont Granier, Le Claps, Dobratsch, and Veliki Vrh (330-1620 m, 1248-1442 AD).
For investigating the depth-dependence of the different nuclear reactions, especially, the muon- and thermal neutron-induced contributions, we have analysed mixtures of carbonates and siliceous conglomerate samples - for ¹⁰Be, ²⁶Al, and ³⁶Cl - exposed at different shielding depths and taken from a core drilled in 2005 at La Ciotat, France (from surface to 11 m shielding).
AMS of ³⁶Cl was performed at LLNL and ETH, ¹⁰Be and ²⁶Al at ASTER.

Acknowledgments: Thanks to V. Alfimov, M. Arnold, G. Aumaître, J. Borgomano, R. Finkel, I. Mrak, and J.M. Reitner.