Geological calibration of spallation production rates in the CRONUS-Earth project

Brian Borchers, Shasta Marrero, Greg Balco, Marc Caffee, Brent Goehring, Nathaniel Lifton, Kunihiko Nishiizumi, Fred Phillips, Joerg Schaefer, John Stone

Research output: Contribution to journalArticlepeer-review

Abstract

Models of the production of cosmogenic nuclides typically incorporate an adjustable production rate parameter that is scaled for variations in production with latitude and altitude. In practice, this production rate parameter is set by calibration of the model using cosmogenic nuclide data from sites with independent age constraints. In this paper, we describe a calibration procedure developed during the Cosmic-Ray Produced Nuclide Systematics on Earth (CRONUS-Earth) project and its application to an extensive data set that included both new CRONUS-Earth samples and samples from previously published studies. We considered seven frameworks for elevation and latitude scaling and five commonly used cosmogenic nuclides, 3He, 10Be, 14C, 26Al, and 36Cl. In general, the results show that the calibrated production rates fail statistical tests of goodness-of-fit. One conclusion from the calibration results is that two newly developed scaling frameworks and the widely used Lal scaling framework provide qualitatively similar fits to the data, while neutron-monitor based scaling frameworks have much poorer fit to the data. To further test the fitted models, we computed site ages for a number of secondary sites not included in the primary calibration data set. The root-mean-square percent differences between the median computed ages for these secondary sites and independent ages range from 7.1% to 27.1%, differences that are much larger than the typical uncertainties in the site ages. The results indicate that there are substantial unresolved difficulties in modeling cosmogenic nuclide production and the calibration of production rates.
Original languageEnglish
Pages (from-to)188-198
JournalQuaternary Geochronology
Volume31
Early online date30 Jan 2015
DOIs
Publication statusPublished - 1 Feb 2016

Keywords

  • cosmogenic nuclide
  • production rate
  • calibration
  • beryllium-10
  • aluminum-26
  • carbon-14
  • helium-3
  • chlorine-36

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