"The online exposure age calculator formerly known as the CRONUS-Earth online exposure age calculator:"


The same look, feel and performance you've come to rely on...with exciting new features and terrible documentation!

This describes the input format for version 3 of the online exposure age calculator.

This page is getting really long and needs better indexing.

Questions about this page: Greg Balco, balcs@bgc.org

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Exposure ages
v3 documentation

Overall concept:

The main thing that is different here from version 2 is that 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 the nuclide measurements you actually made, and you don't have to 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, at least for the time being the version 3 input page still accepts data formatted in version 2 form, so you may not have to worry about this at all.

There are online calculators for both Cl-36 data and all other kinds of data. The input format is similar for both, but they are never input together -- either you are preparing non-Cl-36 single- or multi-nuclide data, or you are preparing Cl-36 data.

What the overall format looks like for non-Cl-36 data:

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.

For chlorine-36 data, there is an online calculator in development, but it is currently separate online calculator entry form, so you can't put Cl-36 data in the same text input block as other nuclide data (yet). However, the basic concept is the same, except that additional input lines are required for major and trace element data, which are explained below.

The other special case is for production rate calibration data. For a sample to be used for production rate calibration, an additional data line with the independent age information is needed. Again this is explained below.

For lots of examples of correctly formatted data, see the ICE-D databases.

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.

What the overall format looks like for chlorine-36 data:

The exposure age calculator for Cl-36 is separate from the exposure-age and erosion-rate calculators for all other nuclides, so Cl-36 and other data are never entered together in the same data block. The Cl-36 input format is similar, except that a Cl-36 exposure age requires not only a Cl-36 (and total Cl) measurement, but also various other chemistry data on the major and trace element composition of the whole rock and target fraction. A simple example of Cl-36 input data would be:

	05-TAB-02 38.93010 -112.52220 1463 std  5.0 2.10 1.0000 0.00e+00 2005;
	05-TAB-02 Cl-36 4.170e+05 2.200e+04 93.400 2.900;
	05-TAB-02 major_elements WR H 0.03 C 0.00 O 45.14 Na 2.41 Mg 3.24 Al 9.61 Si 23.35 P 0.08 S 0.00 K 0.70 Ca 7.20 Ti 1.02 Mn 0.12 Fe 6.92;
	05-TAB-02 trace_elements Li 1.0 B 1.0 Cl 93.4 Cr 304.5 Sm 3.8 Gd 4.0 Th 1.4 U 0.3;
	05-TAB-02 formation_age_Ma 0.018 0.000;

This has one line with sample information, one line with Cl-36/Cl data, a line for the Cl-36/Cl concentration of the whole rock, one for the trace element concentration of the whole rock, and a line specifying the rock formation age (needed to correct for nucleogenic Cl-36). In this example the target separate would be the same as the whole rock.

Here is a slightly more complicated example in which the target separate has different chemistry from the whole rock. On the other hand, we don't care about the rock age (that is, we are assuming production-decay equilibrium for nucleogenic Cl-36), so that line is not present:

	07-NE-001-BH 44.31430 -71.57400 417 std  3.6 2.63 0.9999 7.19e-05 2007;
	07-NE-001-BH Cl-36 3.168e+05 1.148e+04 21.700 0.800;
	07-NE-001-BH major_elements WR H 0.08 C 0.04 O 48.66 Na 2.83 Mg 0.34 Al 8.41 Si 32.25 P 0.05 S 0.00 K 4.57 Ca 1.32 Ti 0.22 Mn 0.03 Fe 1.92;
	07-NE-001-BH major_elements target K 8.88 0.01 Ca 0.41 0.01 Ti 0.01 Fe 0.04;
	07-NE-001-BH trace_elements Li 10.0 B 30.0 Cl 21.7 Cr 10.0 Sm 8.0 Gd 6.6 Th 15.2 U 2.1;

The difference is that there are two major element composition lines linked to the same sample, one for the whole rock and one for the target separate.

A much more complicated example arises when multiple aliquots have been measured on the same sample, in which case there is only one sample line but each aliquot needs its own complete set of chemistry data. All the chemistry data are now indexed both to sample (the first position) and aliquot (the second position). This is rarely necessary and mosly used only for calibration data. Here is an example with one sample that has three separate aliquots that were measured at different labs (named 'PLAG-NXHN', 'Dal-bag-14', and 'PRIME01'):

	05-TAB-04 38.93050 -112.52210 1457.00000 std 5.0 1.90 1.0000 0 2005;
	05-TAB-04 PLAG-NXHN Cl-36 299000.000 12000.000 10.90 1.20;
	05-TAB-04 PLAG-NXHN major_elements WR H 0.06 C 0.00 O 45.46 Na 2.34 Mg 4.76 Al 8.72 Si 22.96 P 0.10 S 0.00 K 0.57 Ca 6.59 Ti 0.94 Mn 0.14 Fe 8.39;
	05-TAB-04 PLAG-NXHN major_elements target K 0.20 0.00 Ca 9.36 0.09 Ti 0.05 0.00 Fe 0.43 0.01;
	05-TAB-04 PLAG-NXHN trace_elements Li 5.0 B 5.0 Cl 90.0 Cr 200.0 Sm 3.0 Gd 3.0 Th 1.5 U 0.5;
	05-TAB-04 PLAG-NXHN formation_age_Ma 0.018 0.000;
	05-TAB-04 DAL-bag-14 Cl-36 360000.000 15000.000 74.50 1.40;
	05-TAB-04 DAL-bag-14 major_elements WR H 0.11 C 0.00 O 45.36 Na 2.14 Mg 4.35 Al 8.99 Si 22.75 P 0.10 S 0.00 K 0.57 Ca 6.50 Ti 0.90 Mn 0.13 Fe 8.01;
	05-TAB-04 DAL-bag-14 trace_elements Li 1.0 B 10.0 Cl 74.5 Cr 302.5 Sm 3.6 Gd 3.6 Th 1.5 U 0.4;
	05-TAB-04 DAL-bag-14 formation_age_Ma 0.018 0.000;
	05-TAB-04 PRIME01 Cl-36 374000.000 12000.000 75.59 1.20;
	05-TAB-04 PRIME01 major_elements WR H 0.04 C 0.00 O 45.13 Na 2.27 Mg 4.62 Al 8.81 Si 22.89 P 0.10 S 0.00 K 0.57 Ca 6.56 Ti 0.93 Mn 0.14 Fe 8.27;
	05-TAB-04 PRIME01 trace_elements Li 1.0 B 5.0 Cl 75.6 Cr 303.0 Sm 3.3 Gd 3.3 Th 1.5 U 0.4;
	05-TAB-04 PRIME01 formation_age_Ma 0.018 0.000;
	

Obviously, this can get kind of complicated. Again, the details of the format of each type of line are enumerated below, and lots of correctly formatted data can be found at the ICE-D websites.


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;
	

A.1. Sample name. Same as version 2 - a text string not exceeding 24 characters. Can include letters, numbers, and dashes (hyphens). May not contain white space or anything that even vaguely resembles an escape character, e.g., slashes of either direction, commas, quotes, colons, or semicolons.

A.2. Latitude. Same as version 2. Decimal degrees: north positive, south negative.

A.3. Longitude. Same as version 2. Decimal degrees: east positive, west negative.

A.4. Elevation/pressure. Same as version 2: meters or hPa, depending on selection below.

A.5. Elevation/pressure handling flag. Same as version 2; this is a three-letter text string. If you have supplied elevations in meters and the default elevation/pressure relationship (currently a spatially variable scheme based on the ERA-40 reanalysis, courtesy of Nat Lifton) is applicable at your site, enter "std" here. If you have supplied elevations in meters, your site is in Antarctica, and you want to use an Antarctic-specific elevation/pressure relationship, enter "ant" here. If you have entered pressure in hPa, enter "pre" here. Any text other than these three options will cause an error.

A.6. Sample thickness. Same as version 2. Centimeters.

A.7. Sample density. Same as version 2. Grams per cubic centimeter.

A.8. Shielding correction. Same as version 2; a shielding factor between 0 and 1.

A.9. Erosion rate inferred from independent evidence. Same as version 2. Centimeters per year.

A.10. Date of sample collection. This is not in version 2. The idea here is so that paleomagnetic reconstructions for the last couple of hundred years are correctly aligned with the date the sample was collected. Of course, this issue is totally irrelevant for samples that are more than a few hundred years old, and it's probably irrelevant for young samples too. In any case, you only need to worry about this at all if you have really young samples. Thus, you can also enter zero and a default date of 2010 will be assumed.

A.11. Then the line ends with a semicolon.


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
	

The chlorine-36 online calculator is separate, so Cl-36 concentration lines are supported but can't be used in the same input block as these nuclide-mineral pairs. Either you are preparing input for (anything that is not Cl-36), or you are preparing input for Cl-36. Cl-36, of course, requires not only a Cl-36 concentration line but also additional lines for major and trace element compositions. The format of all these types of line is documented below; a description of the overall picture for Cl-36 data is in the introductory material above.

Exotica such as Ne-21 in sanidine or Be-10 in olivine are not, at present, supported. 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.1.1 Sample name. This must exactly match the sample name of the corresponding sample as entered in the sample data line, or else, obviously, the code will not be able to match samples to nuclide concentration measurements.

B.1.2. and B.1.3. Nuclide-mineral pair. For Be-10 in quartz, enter "Be-10" and "quartz"; for Al-26 in quartz, this is "Al-26" and "quartz."

B.1.4. and B.1.5. Nuclide concentration and uncertainty. Atoms per gram. Standard or scientific notation.

B.1.6. Name of Be-10 or Al-26 standardization. This is familiar from version 2. Acceptable values for this parameter are given on this page.

B.1.7. Then the line ends with a semicolon.


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.2.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

B.2.2 and B.2.3. Nuclide-mineral pair. Here "C-14" and "quartz".

B.2.4. and B.2.5. Nuclide concentration and uncertainty. Atoms per gram. Standard or scientific notation.

No standardization information is required for C-14 measurements. We assume that carbon isotope ratios have been standardized according to the well-developed and longstanding internationally accepted procedures.

B.2.6. Then the line ends with a semicolon.


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;
	

B.3.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

B.3.2 and B.3.3. Nuclide-mineral pair. Here the nuclide is "He-3" and acceptable mineral options are "quartz," "olivine," and "pyroxene."

B.3.4. and B.3.5. Nuclide concentration and uncertainty. Atoms per gram. Standard or scientific notation. Note that this should be the concentration of actual cosmic-ray-produced He-3; any corrections for magmatic or otherwise non-cosmogenic helium should already have been done.

B.3.6. Name of standard material. For noble gas measurements, the option is available to carry out interlaboratory standardization by entering the apparent concentration of a widely distributed mineral standard as measured at your laboratory. See further discussion below.

B.3.7. He-3 concentration in standard material as measured at the lab where the sample was analysed. Atoms per gram. Standard or scientific notation.

B.3.8. Then the line ends with a semicolon.

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.4.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

B.4.2 and B.4.3. Nuclide-mineral pair. Here the nuclide is "Ne-21" and the mineral is "quartz."

B.4.4. and B.4.5. Nuclide concentration and uncertainty. Atoms per gram. Standard or scientific notation. Note that this should be the concentration of what you believe to be actual cosmic-ray-produced Ne-21; any corrections for trapped, magmatic, atmospheric, nucleogenic, 'crustal,' or otherwise non-cosmogenic neon should already have been done.

B.4.6. Name of standard material. As for the He-3 measurements, the option is available to carry out interlaboratory standardization by entering the apparent concentration of a widely distributed mineral standard as measured at your laboratory. See discussion above in He-3 section. For Ne-21, two options are supported: "CREU-1" (348e6 atoms/g) and "CRONUS-A" (320e6 atoms/g). Both are discussed at length in the following reference. If no restandardization desired, enter "NONE."

Vermeesch, Pieter, Greg Balco, Pierre-Henri Blard, Tibor J. Dunai, Florian Kober, Samuel Niedermann, David L. Shuster et al. "Interlaboratory comparison of cosmogenic Ne-21 in quartz." Quaternary Geochronology (2012).

B.4.7. Ne-21 concentration in standard material as measured at the lab where the sample was analysed. Atoms per gram. Standard or scientific notation. If no restandardization desired, enter zero.

B.4.8. Then the line ends with a semicolon.


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; 
	

Note that the format changes slightly if you intend to associate multiple Cl-36 measurements on different aliquots with a single sample. If you are doing this, then all the measurement lines (Cl-36, major elements, trace elements, formation age) should have an aliquot identifier (alphanumeric plus dashes) as the second element. In this case the above line would look like this:

	Jom2018-Ker-34 Plag-A Cl-36 2.173e+05 7.829e+03 17.68 0.90; 
	

indicating a specific aliquot called 'Plag-A'. Note that if you are indicating specific aliquots for the Cl-36 measurement, you must also have major element, trace element, and formation age (if present) lines indexed to the same aliquot. Any aliquot mentioned must have a complete set of chemistry data.

B.5.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

B.4.2.Nuclide. Here the nuclide is "Cl-36."

B.4.3. and B.4.4. Cl-36 concentration and uncertainty. Atoms per gram. Standard or scientific notation. Note that this should be the total Cl-36 concentration: corrections for nucleogenic Cl-36 happen later in the process.

B.4.5 and B.4.6. Cl concentration and uncertainty. Units of ppm weight (ug/g).

B.4.7. Then the line ends with a semicolon.


C. Independent age control data line. There also exists a third type of data line that enables entering production rate calibration data. This is needed for data entry for the production rate calibration interface to the v3 online calculators here.

Lots of correctly formatted calibration data can be found at ICED: PRODUCTION RATE CALIBRATION.

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;
	

C.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

C.2. Designation as independent age data. The string 'true_t' signals that this line contains independent age information. No other values are allowed.

C.3. Name of the calibration site. This aids downstream code in grouping samples by site. Same rules as sample name -- numbers, letters, no spaces.

C.4. Independent age. Years.

C.5. Uncertainty in independent age. Years.

C.6. Then the line ends with a semicolon.

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; 
	

If you were assigning these to a specific aliquot the form would be:

	Jom2018-Ker-34 Plag-A 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 Plag-A 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.1.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

D.1.2. and D.1.3. Identifiers. The second element is always "major_elements" exactly, and the third can be "WR" (for the whole rock) or "target" (for the target fraction)

D.1.4...D.1.x Element names and concentrations.. The rest of the line consists of (element name, concentration) pairs or (element name, concentration, uncertainty) triplets. The element name must be a recognized chemical symbol or "LOI" to indicate loss on ignition as commonly reported in an XRF analysis. The concentrations are in units of weight percent (100 * g element / g sample); note that this does require conversion from an XRF result. The order of the elements should not matter, and it shoudl be possible to mix pairs (i.e., a measurement with no uncertainty) and triples (including the uncertainty). Normally the elements would include everything typically reported in an XRF or similar measurement, plus O. Sometimes one might enter only the concentrations of important target elements (e.g., Ca, K for Cl-36) in the target line; this should be OK. Note that even though you can enter an uncertainty, lots of uncertainties in this section will never be used...most calculation schemes will only care about the uncertainties in the major target element concentrations (Ca and K in the Cl-36 case).


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;
	

If you were assigning this to a specific aliquot the form would be:

	Jom2018-Ker-34 Plag-A 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;
	

D.2.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

D.2.2.Identifier. The second element is always "trace_elements" exactly. There is no 'WR' or 'target' identifier, because for most neutron transport calculations this is only relevant for the bulk rock. This might have to be changed in future for some applications.

D.2.3...D.2.x Element names and concentrations.. The rest of the line consists of (element name, concentration) pairs or (element name, concentration, uncertainty) triplets. The element name must be a recognized chemical symbol. The concentrations are in units of ppm by weight (ug/g). The order of the elements should not matter, and it shoudl be possible to mix pairs (i.e., a measurement with no uncertainty) and triples (including the uncertainty). This line would normally include Li, B, Cl, Sm, Gd, U, and Th; Co and Cr are sometimes reported in the Cl-36 literature as well. Note that although you can enter uncertainties, there is no guarantee that the calculation will actually use all the uncertainties -- although some of them are sometimes important (e.g., U and Th for Cl-36), most of these uncertainties will generally be ignored by calculation methods.


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; 
	

If you are indexing this line to a specific aliquot, it would look like:

	Jom2018-Ker-34 Plag-A formation_age_Ma 17.00 0; 
	

E.1. Sample name. As above, must exactly match sample name entered in corresponding sample data line.

E.2.Identifier. "formation_age_Ma", exactly.

E.3. and E.4. Formation age and uncertainty.. Millions of years (Ma). At the moment, if you want to signal to the code that the formation age of the rock is unknown, but is the same as the exposure age (this happens when you are exposure-dating lava flows), enter zeros in both positions. It is necessary to use this line to signal this condition -- as noted above, if this line is not present, steady state is assumed.

E.5. Then the line ends with a semicolon.