Goal.The goal of this first version of the CRONUS-Earth online exposure age calculator is to codify standard practices for calculating exposure ages and erosion rates from cosmogenic nuclide concentrations.

Motivation. First, the number of applications of cosmogenic-nuclide exposure dating, as well as the number of papers published on the subject, has been rapidly growing. Second, these studies are no longer being carried out exclusively by cosmogenic-nuclide specialists, but by geologists and paleoclimatologists who wish to use exposure-age or erosion-rate measurements as part of a broader study. Third, as these techniques are still under development, a variety of data-reduction methods, reference nuclide production rates, and production rate scaling schemes exist in the literature. Many of these schemes are at least in part inconsistent with each other, and yield different results for the same measurements of nuclide concentrations. The overall effect has been that published exposure-age and erosion-rate data sets lack a common basis for comparison. In the case of exposure ages, even without worrying about the accuracy relative to the true calendar year time scale of any of the calculation methods, the variety of inconsistent calculation methods makes it difficult even to compare the results of any two exposure-dating studies. This, in turn, is a serious disadvantage for paleoclimate research or any other broader research goal which relies on synthesizing the results of many studies. Thus, our goal is to provide a standard method of exposure-age and erosion-rate calculation that will allow anyone to easily calculate an exposure age or compare previously published cosmogenic-nuclide measurements on a common basis.

Need for comprehensive data reporting. One critically important part of this effort, that of providing a self-consistent means of comparing exposure ages from different studies, is that it cannot succeed unless everyone who publishes cosmogenic-nuclide exposure ages also reports all the information needed to calculate the ages. In most cases this means the location and elevation of the sample site, the density, thickness, and shielding geometry of the sample, any independent information about the erosion rate, and the measured nuclide concentrations, corresponding analytical uncertainties, and the AMS standard used to make the measurements. If these data don't appear in full in a paper, then the exposure ages cannot be recalculated, either for comparison with other data sets, or to reflect future improvements in the accuracy of production rates or scaling factors, and the study will be effectively useless to future researchers.