Depth-dependence of the production rate of in situ 14C in quartz from the Leymon High core, Spain

To constrain the depth-dependence of in situ 14C production we measured the cosmogenic 14C concentration of quartz separates along a quartzite core from the Leymon High site in northwest Spain. A total of 16 quartz samples were measured over a depth range of 1-1545 cm (3-4017 g cm−2). The obtained 14C profile was modeled using a neutron production rate, exponentially decreasing with depth, and a fast and negative muon production parameterized as a function of the local muon flux as derived by (Heisinger et al., 2002a, 2002b). This model yields a total negative muon capture probability of 1.72 (+0.22/−0.56) × 10−2 and a fast muon reaction cross section of 0 (+11.8/−0.00) μb. Rescaled to sea level high latitude using a Lal/Stone scaling scheme, these estimates yield a surface muon production rate of 3.31 (+0.43/−1.07) and 0 (+0.42/−0.00) at·g−1 yr−1 for negative muon capture and fast muons, respectively. This is the first muon production estimate for in situ 14C from a natural setting and is within uncertainty of the previous experimental estimates. The present contribution also provides new long-term blank and standard (PP-4, CRONUS-A & CRONUS-N) in situ 14C data from the ETH Zürich 14C extraction line.