A reevaluation of in situ cosmogenic 3He production rates |
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| Authors: | Brent M Goehring Mark D Kurz Greg Balco Joerg M Schaefer Joseph Licciardi Nathaniel Lifton |
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| Institution: | 1. Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, USA;2. Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA;3. Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA;4. Department of Earth Sciences, University of New Hampshire, Durham, NH 03824, USA;5. Department of Geosciences and Arizona AMS Facility, University of Arizona, Tucson, AZ 85721, USA |
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| Abstract: | 3He is among the most commonly measured terrestrial cosmogenic nuclides, but an incomplete understanding of the 3He production rate has limited robust interpretation of cosmogenic 3He concentrations. We use new measurements of cosmogenic 3He in olivine from a well-dated lava flow at Tabernacle Hill, Utah, USA, to calibrate the local 3He production rate. The new 3He measurements (n = 8) show excellent internal consistency and yield a sea level high latitude (SLHL) production rate of 123 ± 4 at g?1 yr?1 following the Lal (1991)/Stone (2000) scaling model Lal, D., 1991. Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models. Earth and Planetary Science Letters, 104, 424–439.; Stone, J.O., 2000. Air pressure and cosmogenic isotope production. Journal of Geophysical Research, 105, 23753–23759.]. We incorporate the new measurements from Tabernacle Hill in a compilation of all published production rate determinations, characterizing the mean global SLHL production rates (e.g. 120 ± 9.4 at g?1 yr?1 with Lal (1991)/Stone (2000)). The internal consistency of the global 3He production rate dataset is as good as the other commonly used cosmogenic nuclides. Additionally, 3He production rates in olivine and pyroxene agree within experimental error. The 3He production rates are implemented in an age and erosion rate calculator, forming a new module of the CRONUS-Earth web-based calculator, a simple platform for cosmogenic nuclide data interpretation Balco, G., Stone, J., Lifton, N.A., and Dunai, T.J., 2008. A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements. Quaternary Geochronology, 3, 174–195.]. The 3He calculator is available online at http://www.cronuscalculators.nmt.edu/. |
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