Information for expage.m calculating 10Be and 26Al exposure ages.
The calculator is fixed by Jakob Heyman (jakob.heyman@gu.se) 2015-2019 mainly based on the CRONUS
calculator (Balco et al. 2008) and the LSD production rate scaling (Lifton et al. 2014).


TO USE THE CALCULATOR:
1. Fix the input.txt file (see below).
2. Run expage.m in Octave or Matlab.
3. 10Be and/or 26Al exposure ages (yr) are saved in out-expages.txt.


The calculator is based on the CRONUS calculator (Balco et al. 2008) with some modifications:
* Nuclide-specific LSD spallation and muon production rate scaling based on simulated cosmic ray
  fluxes (Lifton et al. 2014).
* Time-dependent spallation production rate with reference production rates based on global average
  from calibration studies published 2009-2019 calibrated using prodrate.m.
* Time-constant muon production rate parameterization (modified to reduce near-surface artifacts),
  including depth dependence for samples with an assumed erosion rate, based on Antarctica depth
  profile data (Borchers et al. 2016; Marrero et al. 2016; Phillips et al. 2016; Balco 2017) with
  fstar and sigma0 calibrated using muclib.m.
* Adjustment of the time-dependent production rate to the year of sampling (assuming a constant
  production since 2010).
* Atmospheric pressure based on sample elevation and ERA-40 re-analysis dataset ('std'), Antarctica
  best-fit interpolation ('ant') (Balco et al. 2008), or given directly ('pre') in hPa.
* Attenuation length for calculating the spallation production rate adjustments for sample thickness
  and erosion rate interpolated from atmospheric pressure and cutoff rigidity (Marrero et al. 2016).


INPUT INSTRUCTIONS:
The input is similar to the input for the CRONUS calcuator version 2 (Balco et al. 2008), with
changed unit for erosion rate and the addition of sampling year. Each row in input.txt is one sample
(rows can be commented out with '%') and should contain 16 columns with the following information:
1. Sample name - (strange characters may cause problems).
2. Latitude [DD (WGS84)] - North latitudes are positive. South latitudes are negative.
3. Longitude [DD (WGS84)] - East longitudes are positive. West longitudes are negative.
4. Elevation/pressure [m a.s.l. / hPa].
5. Elevation/pressure flag - std/ant/pre (ERA40 elev interpol/Antarctica elev/atmospheric pressure).
6. Sample thickness [cm].
7. Sample density [g/cm3].
8. Correction factor - Unitless factor used for topo/geom shielding correction (no shielding -> 1).
9. Erosion rate [mm/ka]. NOTE: different unit than in the CRONUS calculator.
10. 10Be concentration [atoms/g] - (if no 10Be measurement: use 0).
11. 10Be concentration uncertainty [atoms/g] - (if no 10Be measurement: use 0).
12. 10Be standardization - See make_consts_expage.m lines 34-38 for acceptable names and values.
13. 26Al concentration [atoms/g] - (if no 26Al measurement: use 0).
14. 26Al concentration uncertainty [atoms/g] - (if no 26Al measurement: use 0).
15. 26Al standardization - See make_consts_expage.m lines 41-42 for acceptable names and values.
16. Sampling year [CE].


OUTPUT INFORMATION:
The calculator saves 10Be and/or 26Al exposure ages in the file out-expage.txt.
Exposure ages (yr) are saved with external and internal uncertainties (Balco et al. 2008).
Fully saturated samples yield exposure age 10000000 (10Be) and 6000000 (26Al).
Samples with 0/0 concentration/uncertainty yield '-' in the output.
If all input 10Be concentration/uncertainty are 0/0 no 10Be exposure ages are saved.
If all input 26Al concentration/uncertainty are 0/0 no 26Al exposure ages are saved.


PLOTTING:
Plotting of point ages and/or probability density curves can be set in lines 20-21.
Setting plotpointages = 1 plots point ages with external uncertainty (separate plots for 10Be/26Al).
Setting plotprobdens = 1 plots individual sample probability density curves (using internal
uncertainty) plus a summed probability density curve and a weighted mean age with propagated
reference production rate uncertainty if more than one sample.
