Using the new R package for TL dating

Abstract

Since the development of the SAR protocol (Murray and Wintle, 2000), most luminescence dating applica-tions use OSL rather than TL. When it comes to dating sediments, as often in Geoscience, using OSL is clearly the best choice. However, for burnt material, e.g., in archaeological context, using TL is still relevant. Moreover, the SAR protocol was shown to be easily adaptable to TL dating (Schmidt, 2013).

R is a programming language and environment for statistical computing and graphics. It provides a wide va-riety of statistical and graphical techniques and is highly extensible (R core team, 2015). A package specifically designed for luminescence dating is available (Kreutzer et al., 2012). However, it mainly includes functions for the analysis of OSL data.

We developed a new R package specifically designed for TL dating. The structure of this package is based on the existing Luminescence package. However, it treats the uncertainties completely differently. Analysis of TL data needs pre-treatment before any estimation of the equivalent dose. The background signal has to be subtracted and, very often, the peaks have to be aligned. These operations affect the uncertainties. Therefore, an uncertainty matrix, which contains an estimation of the random uncertainty for each data point, was added to the existing signal matrix, which contains the signal intensity/time information. Rather than estimating the uncertainties at posteriori, the new package functions update the uncertainty matrix each time the signal ma-trix is modified.

The TLdating package is designed to be as easy to use as possible. It includes two functions called script_TL.MAAD and script_TL.SAR, depending on the protocol applied. These functions only need the name of the .binx file, the uncertainty, and the temperature boundary for the integration, in order to provide De estima-tions. Complementary parameters, like the dose interval used for the growth curve, the fitting method (linear, exponential; weighted or unweighted) or the rejection criteria, help to improve the De estimation. However, if these are not specified, default values are provided. After using the readBIN2R function, from the luminescence package, these script_* functions successively call a series of other functions from the TLdating package, in-cluding: (i) Risoe.BINfileData2TLum.FileData, which convert the data in the proper format and create the un-certainty matrix; (ii) mod_extract.TL and mod_remove.preheat which only keep the TL curves and removing those identified as preheat curves; (iii) mod_substract.background which subtracts the background signal from the luminescence signal; (iv) mod_align.peaks which aligns the peaks; and (v) analyse_TL.MAAD or ana-lyse_TL.SAR which provides the equivalent dose estimation using the MAAD or the SAR protocol, respectively. For the SAR protocol, the final result can easily be plotted using plot_AbanicoPlot from the Luminescence pack-age. On the other hand, TLum.fileData2Risoe.BINfileData converts your data backwards, allowing to use all the functions from the luminescence package including writeR2BIN. It is therefore possible to analyse the modified data with, e.g, Risø Analyst. Finally, it has to be noted that the analyse_* functions provide not only a De esti-mation for the growth curve approach but also for the De plateau approach, allowing a better estimation of the temperature boundary that are used for the integration.

This project was realized in the context of the CRC 806 “Our way to Europe” funded by the German Re-search Foundation (DFG).


Kreutzer, S., Schmidt, C., Fuchs, M.C., Dietze, M., Fischer, M., and Fuchs, M. (2012). Introducing an R package for luminescence dating analysis. Ancient TL, 30, 1-8.
Murray & Wintle (2000). Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol. Radiation Measurements, Vol.32, No.1, 57-73
R Core Team (2015). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.r-project.org/.
Schmidt, C. (2013) Luminescence dating of heated silex - Potential to improve accuracy and precision and application to Paleolithic sites. PhD thesis, Universität zu Köln.

Resources

• Paris poster David Strebler FINAL.pdf

Bibliography

Strebler, D., Brill, D., Burow, C., Brückner, H. (2015): Using the new R package for TL dating. Luminescence in Archaeology International Symposium 2015, Paris, France