CRONUS-EARTH (COSMIC-RAY PRODUCED NUCLIDE SYSTEMATICS ON EARTH) PROJECT: THE START-UP

Cosmogenic nuclides are now widely applied to problems in the earth sciences. However, their application has been significantly hindered by inadequate understanding of the factors controlling their production. The objective of the CRONUS-Earth Project is to rigorously and systematically investigate the sources of uncertainty in cosmogenic-nuclide production so as to improve the accuracy and reliability of cosmogenic surface-exposure applications. The Project will focus on the following issues: (i) standard materials and laboratory intercomparisons, (ii) measurement of energy-dependent production cross-sections using laboratory-generated neutron beams, (iii) measurement of actual effective production cross-sections using artificial targets placed in the natural environment, (iv) refinement of neutron-monitor data interpretation so as to better understand the interaction of the earth’s magnetic field with the cosmic-ray flux, (v) measurement of multiple nuclides at sites that have geologically well-constrained exposure histories to obtain production rates averaged over geologically-significant periods, and (vi) modeling to synthesize the results. The modeling will include fundamental physics-based models, statistically-based parameter-estimation models, and “user models”. The project is intended to lead to benchmark parameters and models that will provide the earth-science community with consistent, accurate, and precise estimates of exposure history based on measurements of cosmogenic nuclides. (Note: The current CRONUS-Earth Steering Committee consists of M. Caffee, T. Dunai [CRONUS-EU liaison], R. Finkel, T. Jull, M. Kurz, N. Lifton, F. Phillips, J. Schaefer, and J. Stone).