"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.

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

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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, the version 3 input page will continue to accept data formatted in version 2 form, 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.


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
	

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.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.


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.

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 exist for developmental purposes at present and are not processed by the existing code. They are needed for nuclide/mineral pairs where the production rate is compositionally dependent.


D.1. Major element composition.

In development


D.2. Trace elements related to neutron transport.

In developent