Geologic Records Inferred Form Cosmic Ray Produced Neon at the Surface of the Earth

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In the last few years, several cosmic-ray-produced radionuclides (10Be, 14C, 26Al, 36Cl), as well as stable, 3He, Ne and 22Ne have been discovered in terrestrial surface materials. Some of these nuclides are already employed as tracers in studies of geophysical and geological phenomena and open up a new field of study and are expected to provide essential data on rates of change in global change research. Such studies require an accurate knowledge of the production rates, present and past, which are not currently available. The relevant excitation functions for different nuclides are not known. A simulation of the cosmic ray flux is a rather complex endeavor. We propose a direct method for the determination of some of present production rates, by exposing relevant targets at mountain altitudes. Production rates averaged over the last solar cycles can be obtained by comparing production rates with neutron monitor data. We propose to determine the relevant production ratio P21/P26 of the cosmic-ray- produced nuclides 21Ne and 26Al by isotopic measurements of Ne in quartz samples. Average production rates over 104-105 years can be obtained from measurements of samples of known age. Measurements of the 3He/21Ne ratio show and that 3He is often incompletely retained in quartzites. Therefore, 21Ne production rates and 21Ne/10Be and 21Ne/Al ratios provide essential information, which is required to evaluate erosion rates and to define geological processes (uplift, variations in ice cover etc).