36Cl exposure age calculator

Version 0.1. July 2002.

Written by Greg Balco,, and John Stone,

Current status:

Includes production due to spallation on Ca, K, Fe, Ti, secondary spallogenic neutron capture on 35Cl, and supported radioactive-decay-produced neutrons on 35Cl. Does not yet include production from fast muons or negative muon capture. Does not include paleomagnetic corrections. Some question as to how we're gonna deal with erosion rates in light of our numerical model for neutron capture. No error propagation yet. Many other problems currently.

1. Calibrated production rates.

1.A. Spallation on various targets. Units are atoms 36Cl/g target element/yr.
+/- +/- +/- +/-

1.B. Production rate of epithermal neutrons from fast neutrons in the atmosphere at the land/atmosphere interface, at sea level and high latitude. Units neutrons/g/yr (?).

Pf(0): +/-

2. Sample data. Enter data for a single sample only.

2.A. Sample location and geometry. Units

Sample name: Any string not exceeding 24 characters. Example: 01-MBL-007-VVB

Latitude: Decimal degrees.
S latitude and W longitude are negative.
Example: 45.9846 or -103.5467

Elevation/pressure: Meters or hPa, depending on selection below.
Elevation values in m, use standard atmosphere
Elevation values in m, use Antarctic atmosphere
Site pressure values in hPa
Why are there three atmosphere options?

Sample thickness: Centimeters.

Sample density: g/cm3.

Shielding correction: Samples with no topographic shielding, enter 1.
For shielded sites, enter a fraction less than 1.
Calculate shielding here.

Erosion rate: cm/yr.

2.B. Sample chemistry.

2.B.1. Whole-rock XRF data. Units of oxide weight percent. Enter a space-delimited string containing 15 numbers corresponding to oxide percents in the following order:

SiO2  TiO2  Al2O3  Fe2O3  FeO  MnO  MgO  CaO  Na2O  K2O  P2O5  SO4  S  H2O  CO2

and a second similar string containing RELATIVE measurement uncertainties (i.e., for 1% uncertainty, enter 0.01) in the same order.

Oxide percents:

2.B.2. Whole-rock trace element data. Units of ppm. Enter a space-delimited string containing 8 numbers corresponding to the following elements:

Li B Cl Cr Sm Gd U Th

and a second similar string containing absolute measurement uncertainties in the same order.


2.B.3. Target mineral XRF data. Units and order same as above. If the target mineral chemistry is the same as the whole-rock chemistry (for whole-rock analyses) leave these fields blank. If only some of the elements are different, you're out of luck and have to enter all the strings in their entirety.

Oxide percents:

2.B.4. Target mineral trace element data. Units and order same as above.


2.C. 36Cl analytical data Units

[36Cl]: Atoms/gram. Standard or scientific notation.
Example: 415000 or 4.15e5.