Using cosmogenic radionuclide concentrations to determine glacial erosion across alpine valleys.

s 49 rate of stopped negative muons I_(z), the chemical compound factor fc, the probability of nuclear capture fD and the probability f* of the reaction channel after nuclear μ' capture to the investigated nuclide. The production due to fast muons is given by Pμ,fast(z) _ fast a with the flux of fast muons μ,fast The energy-dependent cross section a is given by a = a° Fe07 according to the Wolfendale rule with the mean muon energy Emean in GeV at the considered depth. With the PSI irradiations, the following probabilities f* of particle emission channels after u capture have been measured: f* _ (5.2 ± 0.6) 10'3 for O(μ',vμapxn)10Be [x =1-3], and f* _ (1.4 ± 0.4) 10'3 for S(μ',vaxn)26A1 [x = 2-4,6]. From the result of the oxygen irradiation and the earlier result obtained for 26A1 from the irradiation of quartz (Strack et al. 1994), the production ratio of 26A1 to 10Be after,u' capture in quartz has been deduced to be P(26Al)fP(i°Be) = 7.3 ± 1.5 (Heisinger et al. in preparation). In another experiment, the channel probability from Ca to 36C1 was measured. For the determination of the fast muon cross section a° of 10Be (from 0),14C (from 0), 26A1(from Si, S and Al), 36C1 (from Ca), 53Mn (from Fe) and 250Pb (from Tl), several targets have been irradiated at CERN. This work is still in progress. Depth profiles of 10Be and 26A1 in natural quartz samples were measured in northern Bavaria up to depths of 260 m and were compared with calculated profiles taking into account erosion. From this comparison, the erosion rate in the last million years was determined to be ca. 51um yr-1(Heisinger et al. in preparation).