"The online exposure age calculator formerly known as the CRONUS-Earth online exposure age calculator:"
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This describes the input format for version 3 of the online exposure age calculator.
Questions about this page: Greg Balco, firstname.lastname@example.org
Production rate calibration
The main thing that is improved between versions 2 and 3 is that in version 3, information about the sample, i.e. the location, thickness, independently determined erosion rate, etc., is separated from information about a cosmogenic-nuclide measurement.
The reason for doing this is that it facilitates entering data for multiple nuclide measurements on the same sample. You only have to enter data about the sample once, and you only enter data about as many nuclide measurements pertaining to that sample as you want, and you don't have to either (i) redundantly enter the sample info for each nuclide measurement, or (ii) enter a lot of zeros for measurements that you didn't make. So this is a big advantage in terms of flexibility and compactness. It looks a little like a relational database, which is not a huge surprise as it's kind of derived from how the ICE-D database is set up.
The disadvantage is that is is a very little bit more complicated than the version 2 input format. However, it is still spreadsheet-friendly and should require only minor changes to input spreadsheets. In addition, the version 3 input page will continue to accept data formatted in version 2 form, at least for the time being, so you may not have to worry about this at all.
What the overall format looks like:
Data to be entered are arranged in blocks, or lines, that are separated by semicolons; so each string of text that ends in a semicolon describes either a sample or a nuclide concentration measurement made on that sample. Here is an example:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD; PH-1 Al-26 quartz 712408 31238 KNSTD;
This has three lines: one that describes properties of the sample (what the properties are is described in more detail below); one that describes a Be-10 measurement; and one that describes an Al-26 measurement.
The order of the lines doesn't matter, and the nuclide concentration lines don't need to appear right after the sample they pertain to -- they are linked to the sample by the fact that the sample name is included in each of the nuclide concentration lines.
So this text block describing two samples with both Be-10 and Al-26 measurements:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD; PH-1 Al-26 quartz 712408 31238 KNSTD; WR-2 41.3937 -70.6991 54 std 2 2.65 1 0.00008 1999; WR-2 Be-10 quartz 122903 3584 KNSTD; WR-2 Al-26 quartz 749102 42198 KNSTD;
Works the same as this block:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999; WR-2 41.3937 -70.6991 54 std 2 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD; PH-1 Al-26 quartz 712408 31238 KNSTD; WR-2 Be-10 quartz 122903 3584 KNSTD; WR-2 Al-26 quartz 749102 42198 KNSTD;
And the same as this block:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999; WR-2 41.3937 -70.6991 54 std 2 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD; WR-2 Be-10 quartz 122903 3584 KNSTD; PH-1 Al-26 quartz 712408 31238 KNSTD; WR-2 Al-26 quartz 749102 42198 KNSTD;
Although I've shown the data lines as separate lines of text, the separator is actually the semicolon, so this:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD;
Is the same as this, which may often be easier to lay out in spreadsheets:
PH-1 41.3567 -70.73483333 91 std 4.5 2.65 1 0.00008 1999; PH-1 Be-10 quartz 123453 3717 KNSTD;
So to summarize, relative to the version 2 input format:
The downside is that this requires separating data into sample-related and nuclide-measurement-related blocks; repeating the sample name in multiple blocks so the nuclide concentration measurements can be correctly linked to the samples, and adding some semicolons and a couple of additional bits of information, which are described below.
The upside is that you don't have to carry around a lot of zeros for nuclide measurements that were never made (as you do in version 2), and you can enter as many nuclide measurements as you want for each sample. The latter is particularly important as version 3 is designed to support He-3-in-quartz, He-3-in-olivine, He-3-in-pyroxene, C-14-in-quartz, and Ne-21-in-quartz in addition to Be-10-in-quartz and Al-26-in-quartz, as described below. That is, all the reasonably commonly used nuclide-mineral pairs where production is primarily by spallation with minor production by muons. Sorry, chlorine-36 fans.
Anyway, now you basically know how to do this. For the exact details of what goes where, see the section below on 'tedious and pedantic formatting details.' Possibly more useful are some additional examples:
A couple of samples with Be-10, Al-26, and Ne-21 data:
05-EG-118-BR -77.6419 160.9399 1721 ant 7 2.06 0.9823 0 2005 ; 05-EG-118-BR Be-10 quartz 22742349 216150 KNSTD ; 05-EG-118-BR Al-26 quartz 101685581 3330990 KNSTD ; 05-EG-119-BR -77.64415 160.9446333 1671 ant 7 2.06 0.9978 0 2005; 05-EG-119-BR Be-10 quartz 14034604 222356 KNSTD ; 05-EG-119-BR Al-26 quartz 66375138 1830399 KNSTD ; 05-EG-118-BR Ne-21 quartz 133775104 3221778 CRONUS-A 3.32E+08 ; 05-EG-119-BR Ne-21 quartz 78325044 2374951 CRONUS-A 3.32E+08 ;
A sample with a lot of different measurements of different nuclides, some replicates:
10-MPS-046-NNS -83.27825 -58.16226 499 ant 10 2.6 0.9958 0 2010 ; 10-MPS-046-NNS Be-10 quartz 2.43E+06 3.29E+04 07KNSTD ; 10-MPS-046-NNS He-3 quartz 2.50E+06 2.73E+05 CRONUS-P 5.20E+09 ; 10-MPS-046-NNS He-3 quartz 2.34E+06 2.59E+05 CRONUS-P 5.20E+09 ; 10-MPS-046-NNS Ne-21 quartz 2.97E+07 2.88E+06 CRONUS-A 3.38E+08 ; 10-MPS-046-NNS C-14 quartz 4.71E+05 1.20E+04 ;
Some samples with just Be-10 data as a single line for each sample:
MV3-07-2 41.3758 -70.7320 54 std 2 2.65 1 0.00008 1999 ; MV3-07-2 Be-10 quartz 246010 6122 LLNL3000 ; MV3-07-3 41.3417 -70.8143 51 std 2.5 2.65 1 0.00008 1999 ; MV3-07-3 Be-10 quartz 97125 3554 LLNL3000 ;
And remember, if you just have Be-10 and/or Al-26 measurements, the version 2 input format will still work.
Some additional information for chlorine-36 data:
Development of a chlorine-36 capability for the version 3 calculators is, now, actually happening. The input format for Cl-36 is basically the same as outlined above for everything else, but, as with anything else to do with Cl-36, it is more complicated. A Cl-36 measurement requires a sample information block and a Cl-36 measurement block like anything else, and in addition requires imformation about the major and trace element geochemistry of the bulk rock sample as well as of the target mineral or combination of minerals used for the Cl-36 measurement, and possibly also information about the crystallization age of the rock. Thus, data entry for computing a Cl-36 exposure age requires a sample line, a Cl-36 line, lines describing the major element composition of the bulk rock and, optionally, a target separate, a line describing the trace element composition of the bulk rock, and, finally and optionally, a line containing the rock formation age. Details on all these different types of data line are in the pedantic part below. Here is an example of a complete set of Cl-36 input data:
Jom2018-Ker-31 -49.27679 70.04468 302 std 2.0 2.40 0.9900 0.000e+00 0; Jom2018-Ker-31 Cl-36 8.054e+04 4.081e+03 12.45 0.64; Jom2018-Ker-31 formation_age_Ma 17.00 0; Jom2018-Ker-31 major_elements target LOI 0.3 O 46.0 Na 2.7 Mg 1.8 Al 8.3 Si 25.0 P 0.0 K 1.2 0.1 Ca 6.0 0.1 Ti 2.0 0.1 Mn 0.1 Fe 6.8 0.1; Jom2018-Ker-31 major_elements WR LOI 2.2 O 46.3 Na 2.6 Mg 2.6 Al 8.5 Si 22.5 P 0.2 K 1.1 Ca 6.2 Ti 1.7 Mn 0.1 Fe 8.2; Jom2018-Ker-31 trace_elements Li 6.3 B 2.0 Cl 54.0 Cr 69.1 Co 32.7 Sm 6.8 Gd 6.3 Th 3.6 U 0.7;
That includes a sample line, a Cl-36 measurement line, major elements lines for both bulk rock ("whole rock" or WR) and target separate, a trace element line for the bulk rock, and a line with the rock formation age. That is a little more than the minimum possible information needed -- the minimum would be something like this:
Jom2018-Ker-31 -49.27679 70.04468 302 std 2.0 2.40 0.9900 0.000e+00 0; Jom2018-Ker-31 Cl-36 8.054e+04 4.081e+03 12.45 0.64; Jom2018-Ker-31 major_elements WR LOI 2.2 O 46.3 Na 2.6 Mg 2.6 Al 8.5 Si 22.5 P 0.2 K 1.1 Ca 6.2 Ti 1.7 Mn 0.1 Fe 8.2; Jom2018-Ker-31 trace_elements Li 6.3 B 2.0 Cl 54.0 Cr 69.1 Co 32.7 Sm 6.8 Gd 6.3 Th 3.6 U 0.7;
Omitting the formation age just implies that the rock is more than a few half-lives of Cl-36 old, so that nucleogenic Cl-36 is at steady state. Omitting the major element composition of the target implies that the Cl-36 measurement was made on the whole rock rather than a mineral separate, i.e. the bulk rock and the target separate are the same thing.
Tedious and pedantic formatting details for each data line:
There is a lot of information here, but it is really not that complicated.
A. Sample data line. These have 10 fields, as follows. Here is an example:
PH-1 41.3567 -70.7348 91 std 4.5 2.65 1 0.00008 1999;
B. Nuclide concentration lines.
In general, all the lines describing nuclide concentration measurements have information in the following order: the name of the corresponding sample; the nuclide measured; the mineral in which it is measured; the nuclide concentration and uncertainty; and then standardization information, which varies by nuclide, at the end. The currently available set of nuclide-mineral pairs is as follows:
He-3 quartz He-3 olivine He-3 pyroxene Be-10 quartz C-14 quartz Al-26 quartz Ne-21 quartz
Exotica such as Ne-21 in sanidine or Be-10 in olivine are not, at present, supported. Also, no chlorine-36 at present. The following sections detail the format of the data entry lines for all the nuclide-mineral pairs listed above.
B.1. Be-10-in-quartz and Al-26-in-quartz measurement lines. These have 6 fields, as follows. Here are examples of both:
PH-1 Be-10 quartz 123453 3717 KNSTD; PH-1 Al-26 quartz 712408 31238 KNSTD;
B.2. C-14-in-quartz measurement lines. This has 5 fields, as follows. Here is an example:
10-MPS-046-NNS C-14 quartz 4.71E+05 1.20E+04;
B.3. He-3-in-quartz, He-3-in-pyroxene, and He-3-in-olivine measurement lines. These have seven fields, as follows. Here is an example:
10-MPS-046-NNS He-3 quartz 2.50E+06 2.73E+05 CRONUS-P 5.20E+09;
The overall concept for standardization information for noble gas measurements is that different noble gas labs obtain slightly different apparent He-3 concentrations for the same standard material. At present, the only such standard is the CRONUS-P pyroxene standard, which is described in the following reference:
Blard, P-H., G. Balco, P. G. Burnard, K. A. Farley, C. R. Fenton, R. Friedrich, A. J. T. Jull et al. "An inter-laboratory comparison of cosmogenic He-3 and radiogenic He-4 in the CRONUS-P pyroxene standard." Quaternary Geochronology (2014).
It can be argued that if lab 1 finds that CRONUS-P has a concentration that is 5% lower than the concentration found by lab 2, then He-3 concentrations in other samples measured by lab 1 should be adjusted upward by 5% prior to being compared with He-3 concentrations in other samples measured by lab 2. Or, the concentrations measured by lab 2 could be adjusted downward for comparison with lab 1.
So what happens in the online calculator is that if you measure He-3 in an unknown sample, and your lab has also measured He-3 in the CRONUS-P standard, you enter both pieces of information and the online calculator will normalize the He-3 measurement in the unknown sample by the amount needed to make your measurement of CRONUS-P agree with a consensus value (which in this case is 5.02e9 atoms/g; see the Blard paper). Furthermore, the idea is that the production rate used to compute exposure ages will also be based on measurements normalized to the same value for CRONUS-P (note, however, that it is unclear if this is the case at present).
This whole approach is not, at present, common practice for cosmogenic noble gas measurements. So if you think this is stupid, or you don't want to worry about it, you can enter "NONE" in position 6 and zero in position 7, for example:
10-MPS-046-NNS He-3 quartz 2.50E+06 2.73E+05 NONE 0;
In this case no restandardization happens and your He-3 concentration gets processed as is.
B.4. Ne-21-in-quartz measurement lines. These are very similar to the He-3 measurement lines; they have seven fields, as follows. Here is an example:
05-WO-140-BR Ne-21 quartz 299185727 4884352 CRONUS-A 3.32E+08;
B.5. Cl-36 measurement lines. A Cl-36 measurement doesn't generally have to associated with any particular mineral (and the chemical composition of the sample is entered separately), so there is no information about what mineral was analyzed in this line. It just contains the sample name, the Cl-36 concentration and uncertainty, and the chloride concentration and uncertainty (because Cl-36 and total Cl concentrations are nearly always both measured by AMS, and often measured simultaneously). Here is an example:
Jom2018-Ker-34 Cl-36 2.173e+05 7.829e+03 17.68 0.90;
C. Independent age control data line. This line is required when entering production rate calibration data for the production rate calibration interface to the v3 online calculators here. Otherwise, of course, the code would never know what the true age of a calibration sample was.
For v3 calibration data input, independent ages are assumed to have units of "years BP" defined as in the radiocarbon calibration literature and meaning years before 1950.
Note that this differs from the output of the exposure age calculator, which is the calculated exposure duration of the sample, that is, the number of years the sample has been exposed prior to collection, rather than a specific calendar year. Suppose you enter a single calibration sample that was collected in 2014 and whose independent age is 11,000 yr BP, and use a production rate calibrated from that sample to compute the exposure age of the same sample. In this case the calculated exposure age will not be 11,000 years, but 11064 years (11000 + (2014-1950)). Confusing at first glance, but the point to remember is that the independent calibration ages have to be in years before 1950.
This type of line has either 5 or 7 fields, as follows.
A line with five fields applies if the independent age is the exact age of the sample. Here is an example with five fields:
06-SKY-03 true_t FEAR 11700 300;
A line with seven fields indicates that there are minumum and maximum independent age constraints, rather than an exact age. Here is an example with seven fields:
CI2-01-2 true_t CLYDE 7950 45 8435 50;
In this case, positions 4 and 5 contain the minumum limiting age and uncertainty (years), and positions 6 and 7 contain the maximum limiting age and uncertainty. For example, the line above indicates a minimum limiting age of 7950 +/- 45 years BP, and a maximum limiting age of 8435 +/- 50 years BP.
In the case where there is only a minimum age constraint, one would enter Inf for the maximum age; likewise, if there is only a maximum age constraint, the minimum age would be zero.
CI2-01-2 true_t CLYDE 7950 45 Inf 0; CI2-01-2 true_t CLYDE 0 0 8435 50;
D. Chemical composition lines.
These describe the chemical composition of the bulk rock sampled, as well as the chemical composition of a target fraction, usually a single mineral, that was extracted for the nuclide concentration measurement. At present, these are only used in Cl-36 calculations, but potentially they could be used for other nuclides in compositionally variable targets (He-3 and Ne-21 in pyroxene or olivine, Ne-21 in feldspars...you get the idea). Basically they consist of an identifier for whether the measurements pertain to the whole rock (WR) or a target fraction, and then a list of elemental symbols and concentrations.
D.1. Major element composition. For Cl-36 calculations, one could have either (i) a single one of these lines describing a case where the Cl-36 measurement is made on the whole rock, or (ii) two lines describing the bulk rock and a target mineral fraction separately. Here's an example of the two-line case:
Jom2018-Ker-34 major_elements target LOI 1.0 O 46.6 Na 2.7 Mg 1.9 Al 8.2 Si 24.7 P 0.1 K 1.2 0.1 Ca 6.0 0.1 Ti 2.0 0.1 Mn 0.1 Fe 6.6 0.1; Jom2018-Ker-34 major_elements WR LOI 2.1 O 46.2 Na 2.6 Mg 2.5 Al 8.7 Si 22.5 P 0.2 K 1.1 Ca 6.3 Ti 1.6 Mn 0.1 Fe 8.2;
D.2. Trace elements related to neutron transport. Again, at least one of these lines describing the trace element concentration in the whole rock is required for a Cl-36 calculation. Example:
Jom2018-Ker-34 trace_elements Li 4.9 B 2.0 Cl 56.0 Cr 76.2 Co 34.8 Sm 7.6 Gd 7.2 Th 3.6 U 0.8;
E. Rock formation age line.
This is sometimes needed for Cl-36 measurements when the formation age of the rock is not old enough that you can just assume that the nucleogenic Cl-36 concentration has reached steady state. Note: if you don't know the formation age but you know it's old enough to assume steady state, that is the default assumption, so this line can be omitted. In any case, here is an example:
Jom2018-Ker-34 formation_age_Ma 17.00 0;