10Be - 26Al exposure age calculator

For calculating an exposure age when erosion rate is known independently.

Multiple sample form -- User-supplied calibration data
Version 2.2. March, 2008. Written by Greg Balco, balcs@u.washington.edu

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Be-10 calibration data from:

Heyman, J., 2014. Paleoglaciation of the Tibetan Plateau and surrounding mountains based on exposure ages and ELA depression estimates.

Reference production rates and fit values are computed using this page and this calibration data set excerpted from the supplemental data table in the paper. This differs from the calculations in the paper in that all samples are weighted equally according to their uncertainties, rather than all sites being weighted equally. However, this method ensures that exactly the same code is used for both production rate and exposure age calculations. Note, however, that the results of both methods are indistinguishable.

Heyman did not compile Al-26 concentrations. Thus, reference production rates for Al-26 in the table below are calculated from those for Be-10 using (P26 / P10) = 6.75.

Trace information from calibration code:

Calibration data set name: Heyman 2014
Computation time: 258.17 sec
Calibration wrapper version: 2.2-cal-dev
Objective function version: 2.2-dev
Age calculation version: 2.1
Muon calculation version: 1.1
Constants version: 2.2.1

Scaling scheme Reference Be-10 Percentage Reduced Reference Al-26
for spallation production rate (atoms/g/yr) uncertainty chi-squared production rate (atoms/g/yr)


Scaling scheme fits to calibration data: This plot shows the fit between each scaling scheme and the calibration data. The filled circles are calculated reduced chi-squared values for evenly spaced trial values of the reference Be-10 production rate. The corresponding lines are the polynomial interpolations used to determine the value that minimizes the fit parameter. Colors: black, St; red, De; green, Du; blue, Li; cyan, Lm. If the lines don't go through the corresponding colored data points, or if they don't look more or less parabolic, there is likely a problem with the fit algorithm.

Same thing, different presentation:This plot shows ratios of exposure ages for the calibration calculated using the best-fitting reference production rate (t) to the actual independently determined ages of the sites (truet). Color coding for scaling schemes as above. The gray band represents the 1-std-err uncertainty in the best-fitting reference production rate. There is no particular significance to elevation as the independent variable other than that it usually spreads out the data nicely.

Sample data entry:

Enter data block here.

Note change in Version 2.2:

Production rates and decay constants have been updated in this version to reflect the Be-10 restandardization and half-life revision in Nishiizumi et al., 2007. Thus, you must now specify the standard to which your Be-10 and Al-26 measurements have been normalized. This means that two input fields, the Be-10 and Al-26 standard names, have been added. You'll need to add two columns to your spreadsheets before cutting and pasting data. Refer to the new example spreadsheet here. For a list of currently available standards, see this page.

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