Preprints
https://doi.org/10.5194/gchron-2020-43
https://doi.org/10.5194/gchron-2020-43

  28 Jan 2021

28 Jan 2021

Review status: this preprint is currently under review for the journal GChron.

Spatially Resolved Infrared Radiofluorescence: Single-grain K-feldspar Dating using CCD Imaging

Dirk Mittelstraß1 and Sebastian Kreutzer2,3 Dirk Mittelstraß and Sebastian Kreutzer
  • 1Independent Researcher, Berthelsdorfer Str. 13, 09599 Freiberg, Germany
  • 2Geography & Earth Sciences, Aberystwyth University, Wales, United Kingdom
  • 3IRAMAT-CRP2A, UMR 5060, CNRS-Université Bordeaux Montaigne, Pessac, France

Abstract. The success of luminescence dating as a chronological tool in Quaternary science builds upon innovative methodological approaches, providing new insights into past landscapes. Infrared radiofluorescence (IR-RF) on K-feldspar is such an innovative method already introduced two decades ago. IR-RF promises considerable extended temporal range and a simple measurement protocol, with more dating applications published recently. To date, all applications use multi-grain measurements. Herein, we take the next step by enabling IR-RF measurements on a single grain level. Our contribution introduces spatially resolved infrared radiofluorescence (SR IR-RF) on K-feldspars and intends to make SR IR-RF broadly accessible as a geochronological tool. In the first part of the manuscript, we detail equipment, CCD camera settings and software needed to perform and analyse SR IR-RF measurements. We use a newly developed ImageJ macro to process the image data, identify IR-RF emitting grains and obtain single-grain IR-RF signal curves. For subsequent analysis, we apply the statistical programming environment R and the package Luminescence. In the second part of the manuscript, we test SR IR-RF on two K-feldspar samples. One sample was irradiated artificially; the other sample received a natural dose. The artificially irradiated sample renders results, indistinguishable from conventional IR-RF measurements with the photomultiplier tube. The natural sample seems to overestimate the expected dose by ca 50 % on average. However, it also shows a lower dose component resulting in ages consistent with the same sample's quartz fraction. Our experiments also revealed an unstable signal background due to our cameras' degenerated cooling system. Besides this technical issue specific to the system we used, SR IR-RF is ready for application. Our contribution provides guidance and software tools for methodological and applied luminescence(-dating) studies on single grain feldspars using radiofluorescence.

Dirk Mittelstraß and Sebastian Kreutzer

Status: open (until 22 Mar 2021)

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Dirk Mittelstraß and Sebastian Kreutzer

Data sets

Spatially Resolved Infrared Radiofluorescence (SR IR-RF) Image Data Sebastian Kreutzer and Dirk Mittelstraß https://doi.org/10.5281/zenodo.4395968

Dirk Mittelstraß and Sebastian Kreutzer

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Short summary
Our contribution enhances the infrared-radiofluorescence dating technique, used to determine the last sunlight exposure of potassium feldspars in a range of about 600 to 600.000 years backwards. We recorded radiofluorescence images of fine sands and processed them with tailored open-source software to obtain ages from single grains. Finally, we tested our new method successfully on two natural sediment samples. Studies in Earth science will benefit from improved age accuracy and new insights.