Production of cosmogenic radionuclides at great depth: a multi element approach

For the last two decades, in situ produced cosmogenic nuclides are increasingly applied in Earth sciences to quantify surface processes. In parallel, significant reduction of the analytical uncertainties linked to advances in accelerator mass spectrometry (AMS) allows more precise measurements. However, among all the published works on cosmogenic nuclides, only few studies are dedicated to a better understanding of their production systematic or to a better constrain of the physical parameters involved in their production. Thus, an approach to investigate in situ produced cosmogenic nuclides ¹⁰Be, ²⁶Al and ³⁶Cl along a single 11-meter long core drilled from the surface and composed of carbonates and quartzose conglomerates has been launched. These measurements have been used to quantify muon-induced productions based on natural samples for each studied nuclide. Contrary to the currently most often used calculation of muon-induced production parameters which are based on irradiation experiments at discrete energies, productions based on natural samples are considering the entire energy range of particles reaching the ground surface. The evolution of ³⁶Cl concentrations with depth needs to agree with those parameters deduced from ¹⁰Be and ²⁶Al data. This is optimized when considering a fast muon-induced ³⁶Cl production contribution and a spallation production rate at Sea Level High Latitude (SLHL) of (42.0 ± 2.0) atoms ³⁶Cl g_Ca ^-1 a^-1 (1sigma uncertainty).