A multi-radionuclide approach for in situ produced terrestrial cosmogenic nuclides: 10Be, 26Al, 36Cl and 41Ca from carbonate rocks

In contrary to siliceous environments, there is a severe lack of cosmogenic nuclides, that can be used for in situ dating of calcareous environments. Thus, we have investigated other nuclides than 36Cl as possible dating tools by cross-calibration. Cosmogenic 10Be is highly contaminated with atmospheric 10Be and cannot be removed quantitatively, even by a very sophisticated chemical cleaning procedure. Only working on clay-free calcite provides correct 10Be data, giving a 2.7 times higher production rate of 10Be from CaCO3 than from SiO2. Though, the production rate of 26Al is only ∼4.6% (CaCO3 relative to SiO2), 26Al can be easily determined in calcite, as the low intrinsic 27Al concentration yields to nearly as high 26Al/27Al as within corresponding quartz. The measurement of 41Ca, mainly produced via thermal-neutron-capture, is hindered by very low 41Ca/Ca:<5 x 10-15.