Geological Survey of Denmark and Greenland Bulletin 35, 2016, 103-106


103© 2016 GEUS. Geological Survey of Denmark and Greenland Bulletin 35, 103–106. Open access:  www.geus.dk/publications/bull

During the past 10–15 years, analytical innovations in geo-

chronology have greatly enhanced the application of geo-

chronological data to geological problems. The advances 

are mainly driven by developments in laser ablation in-

ductively coupled plasma mass spectrometry (LA-ICPMS) 

which allows for rapid determination of U-Th-Pb ages of 

mineral grains in large sample sets. LA-ICPMS has now 

become the most common tool in the application of zircon 

geochronology to a host of different geological problems.

 One of the most regularly used approaches to evaluate 

complex U-Th-Pb geochronological data populations is to 

use a diagram that combines a binned frequency histogram 

and a probability density distribution plot (PDP), as de-

scribed by Sircombe (2004) and Ludwig (2003). This type 

of diagram is particularly common in sedimentary prov-

enance studies using large sets of age data (Morton et al. 

1996; Pell et al. 1997; Rainbird et al. 1997; Sircombe 1999; 

Fergusson et al. 2001). It is also useful for the analysis of 

complex age patterns in metamorphic and igneous rocks. 

The Microsoft Excel workbook AgeDisplay (Sircombe 

2004) has often been used to produce these diagrams but 

it is not supported by versions of Excel that are newer than 

2003. Stand-alone software for PC written in Java was 

therefore developed by the Geological Survey of Denmark 

and Greenland (GEUS). It is based on the same formulae as 

described in Sircombe (2004), thus the name jAgeDisplay 

(with j for Java), and has additional features and graphic 

improvements. Here we present the setup, operation and 

capability of the software with examples from single-grain 

U/Pb age data obtained by LA-ICPMS spot analysis.

jAgeDisplay: software for evaluation of data distributions 
in U-Th-Pb geochronology

Tonny B. Thomsen, Tjerk Heijboer and Pierpaolo Guarnieri

Open Data file

Connect to Database

Save Chart

Quit

jAge Display X

File

Fig.1. Combined 400–2400 Ma histogram and PDP chart with calculated maximum probability ages for distinct distribution peaks of zircon popula-

tions from a single sample, using coupled 206Pb/238U and 207Pb/206Pb age pairs. A crossover age of 1100 Ma is used, where 206Pb/238U ages and 207Pb/206Pb 

ages are used below and above this age, respectively. A Fixed bin size of 50 Ma/bin and a Concordia Filter of ±10% were used.



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Setup and operation of jAgeDisplay
The jAgeDisplay package (current version 1.0) for PC in-

cludes an executable Jar file, a Java MS DOS batch file, a 

HTML readme file, a brief manual and a folder with test 

data files. The application is available as shareware from 

the corresponding author, and it is installed by copying the 

files you receive to any PC with Java. 

 jAgeDisplay supports both comma-separated (CSV) 

and tab-delimited (TAB) input text files, with the same 

table headers and data types as in AgeDisplay, Iolite (Pa-

ton et al. 2011), and GEUS’ in-house Zirchron software 

and database. The input file can include age data from one 

or more samples, which are loaded from the File menu in 

the main window (Fig. 1) using the Open Data file option. 

The input file includes four commonly used radiogenic U-

Th-Pb age pairs, viz. 206Pb/238U, 207Pb/235U, 207Pb/206Pb and 
208Pb/232Th, together with the sample identification, the 

name or number of individual analyses, the name of the 

analytical sequence and information about correction for 

common lead content. Output charts can be saved in PDF 

or PNG file format through the Save Chart option in the 

File menu. 

 The main window consists of a chart area to the left and 

the selected sample parameters to the right. When an input 

file has been loaded, the samples available for plotting are 

found in the File Samples field or, if loaded from a database, 

in the Database Samples field. To plot one or more of the 

loaded samples, they are dragged and dropped in their re-

spective Selected File Items or Selected Db Items fields. The 

parameters to be used for the chart are selected, and the 

Create new chart button is pressed. 

 Combined histograms and probability–density plots for 

each radiogenic age pair (206Pb/238U, 207Pb/235U, 207Pb/206Pb,  
208Pb/232Th) can be produced. In addition, charts combin-

ing the 206Pb/238U and 207Pb/206Pb age pairs can be made 

by manually setting a specific age (denoted Cutoff value) 

that controls the change from using 206Pb/238U ages for the 

younger age range to 207Pb/206Pb ages for the older age range 

of the chart (Fig. 1). The frequency in terms of number of 

analyses for each bin in the histogram is shown on the left 

y-axis, and the calculated probability distribution of zircon 

ages for the data set on the right y-axis. Thus, the probabil-

ity–density distribution provides an estimate of the true 

mineral-age distribution for a given rock sample.

 

The plots can be adjusted by the following parameters:

• Concordia Filter is the maximum allowed discordance 

(in per cent) for analyses to be considered as concordant, 

and is determined as 100 ± Set#Value. This separates 

the age data used for the plot into two different fields 

representing ‘concordant’ and ‘discordant’ data. In de-

trital zircon provenance studies a value of ±10% is often 

used, where this threshold is used as a measure of the 

quality of the calculated ages. In contrast to AgeDisplay, 

the complete data set including the ‘discordant’ data is 

not shown behind the ‘concordant’ data, but separately 

using the same axis as for the concordant data.

• Use Fixed bin size (Ma/bin) allows a histogram of fil-

tered ages to be plotted (based on the concordant data 

obtained via the Concordia Filter), where the bin size in 

million years (Ma) is manually chosen. If this checkbox 

is deselected, a calculated value for the bin size is used, 

based on the formulae in Doane (1985).

• Display Max Probability (checkbox) shows the ages of 

the calculated probability peaks for the ‘concordant’ 

data set.

• Min/Max age controls the age range to be shown in the 

chart.

Additional parameters can be set through right-clicking on 

the produced chart, where the title, chart title, axis range, 

appearance and colours can be modified.

 jAgeDisplay can display a single chart for one data set or 

stacked charts of several data sets (Fig. 2). Stacked charts 

are useful for comparison of data sets sampled, e.g. at dif-

ferent geographical, stratigraphical or lithological locations 

in order to identify trends or differences in the age distribu-

tions. The stacking follows the order chosen in the Selected 

File Items (or Selected DB Items) window at the right, and 

can be rearranged as appropriate. As the purpose of stack-

ing is to compare, the stacked data sets are displayed for the 

same age range as set by the Min/Max age control. 

Use of jAgeDisplay in sedimentary 
provenance and petrological studies
Detrital studies typically aim to characterise the age 

population(s) from a sample by means of a large number 

of single grain analyses, e.g. obtained by LA-ICPMS. In 

statistical terms the goal of such studies is to estimate the 

so-called probability density function that gives the rela-

tive likelihood of the different ages in the population (Ver-

meesch 2012). Zircon is the most common mineral used 

for detrital studies, but other mineral phases like rutile and 

titanite are increasingly being employed in order to obtain 

supplementary information (e.g. Zack et al. 2004; Stendal 

et al. 2006; Meinhold et al. 2008; Thomsen et al. 2015; 



105

Bruand et al. 2016). Signatures of sediment sources not 

represented in the zircon data set may be present in detri-

tal titanite, rutile or apatite populations. In addition, age 

data on these minerals may provide further chronological 

and petrogenetic insight into the tectono-thermal history 

of their source regions (e.g. McAteer et al. 2010, 2014; 

Knudsen et al. 2015; Thomsen et al. 2015). Similarily, in 

metamorphic and magmatic petrology, complex zoning 

patterns that correspond to distinct geological events can 

be recorded in zircon, baddeleyite, titanite, rutile, apatite, 

monazite, xenotime, allanite or any other accessory min-

eral phase for which the age can be determined by U-Th/

Pb methods and can be assessed in probability density plots 

diagrams through the jAgeDisplay software. 

Future options in jAgeDisplay
Although PDPs constitute the most widespread method 

used today for displaying detrital age distributions, they 

lack a firm theoretical basis as probability density estima-

tors, and this may produce counter-intuitive results when 

the number of analyses and/or their quality (precision) is 

high (Vermeesch 2012). Accordingly, an alternative and ro-

bust standard statistical technique, the Kernel Density Es-

timation (KDE) as described in Vermeesch (2012), will be 

included in jAgeDisplay, so that users can compare the two 

methods. We also expect to include a more versatile option 

for age distribution plots, where any two isotopic pairs can 

be used in a PDP or KDE diagram, in a similar way as the 

built-in option for combined 206Pb/238U and 207Pb/206Pb age 

distributions.

Fig. 2. Stacked chart of combined histograms and PDP charts from 1100 to 4000 Ma of zircons from seven samples using 207Pb/206Pb ages, a Fixed bin 

size of 50 Ma/bin and a Concordia Filter of ±10%.



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 Detailed statistics reporting information on the cal-

culated maximum probability peaks can be useful for 

improved age differentiation of, e.g. magmatic or meta-

morphic episodes. At present, this information is only indi-

rectly reported through the plot axis. We expect to include 

this information in pop-up windows for single peaks and 

as a print-out option including the statistics of all peaks or 

a chosen age section of the plot.

 Finally, the jAgeDisplay software offers an option to load 

input files from a database through a local server connec-

tion (File => Connect to Database). At present, this option 

only allows reading of certain data types from GEUS’ Ora-

cle server. It is our intention to expand this and thus provide 

users with access to data from a local server repository.

Additional remark
In this presentation only U/Pb geochronological data ob-

tained by LA-ICPMS analysis on zircon are used. jAge-

Display can of course also evaluate U-Th-Pb data acquired 

by other instrumentation and complex age distribution 

patterns measured from other accessory phases such as ti-

tanite, rutile, apatite, monazite, allanite, perovskite, xeno-

time or other minerals that can incorporate U or Th into 

their crystal structure.

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Authors’ address
Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: tbt@geus.dk