Regional beryllium-10 production rate calibration for late-glacial northeastern North America |
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| Authors: | Greg Balco Jason Briner Robert C Finkel John A Rayburn John C Ridge Joerg M Schaefer |
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| Institution: | 1. Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA;2. Geology Department, University at Buffalo, Buffalo, NY, USA;3. University of California, Berkeley, CA, USA;4. Geology Department, State University of New York at New Paltz, New Paltz, NY, USA;5. Department of Geology, Tufts University, Medford, MA, USA;6. Lamont-Doherty Earth Observatory, Palisades, NY, USA |
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| Abstract: | The major uncertainty in relating cosmogenic-nuclide exposure ages to ages measured by other dating methods comes from extrapolating nuclide production rates measured at globally scattered calibration sites to the sites of unknown age that are to be dated. This uncertainty can be reduced by locating production rate calibration sites that are similar in location and age to the sites to be dated. We use this strategy to reconcile exposure age and radiocarbon deglaciation chronologies for northeastern North America by compiling 10Be production rate calibration measurements from independently dated late-glacial and early Holocene ice-marginal landforms in this region. 10Be production rates measured at these sites are 6–12% lower than predicted by the commonly accepted global 10Be calibration data set used with any published production rate scaling scheme. In addition, the regional calibration data set shows significantly less internal scatter than the global calibration data set. Thus, this calibration data set can be used to improve both the precision and accuracy of exposure dating of regional late-glacial events. For example, if the global calibration data set is used to calculate exposure ages, the exposure-age deglaciation chronology for central New England is inconsistent with the deglaciation chronology inferred from radiocarbon dating and varve stratigraphy. We show that using the regional data set instead makes the exposure age and radiocarbon chronologies consistent. This increases confidence in correlating exposure ages of ice-marginal landforms in northeastern North America with glacial and climate events dated by other means. |
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