Testing the isothermal thermoluminescence dating method to constrain mid-Pleistocene speleothem growth phases in the Bleßberg Cave
Physical Geography
Final Report Abstract
Speleothems provide numerous climate and environmental proxies. Their exceptional suitability for very precise and accurate 230Th/U dating makes them extraordinary terrestrial archives for the reconstruction of past climatic and environmental changes. However, 230Th/U dating is not applicable for samples older than 600,000 years or for samples contaminated by substantial amounts of non-radiogenic thorium. U-Pb dating is applicable for speleothem samples beyond the dating range of the 230Th/U-method. However, U-Pb dating requires samples with high U and radiogenic Pb, and low common Pb, which is not the case for most speleothem samples. As an alternative, the thermoluminescence (TL) signal of calcite can be used to date the growth of speleothems over millions of years. In contrast to 230Th/U and U-Pb dating, TL dating is also applicable for speleothems with detrital Th contamination and does not require high U concentrations. However, until now, two drawbacks have hindered its application on speleothems: 1) the spurious TL signal, which occurs in the high temperature range, and 2) the variation of dose rate with time due to the potential disequilibrium of the U decay series. Isothermal thermoluminescence (ITL) measurements at a relatively lower temperature can avoid the spurious TL signal. However, the reliability of the ITL dating method has not been validated on samples with independent age control. In our project, we applied the ITL dating method to a speleothem, which was accurately dated with the 230Th/U dating method. In addition, we modelled the variation of the dose rate with time, considering the initial activities of 238U, 234U, 230Th and their decay constants. The determined ITL ages agree within uncertainty with the 230Th/U ages. ITL dating thus provides a very promising pathway to construct chronologies for speleothems if the 230Th/U and U-Pb methods are not applicable.
Publications
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Isothermal thermoluminescence (ITL) dating of a speleothem from Bleßberg Cave. German Luminescence and Electron Spin Resonance Meeting 2022 (DLED2022), 06.11.2022, Bonn, Germany.
Junjie Zhang, Jennifer Klose, Melanie Sierralta, Sumiko Tsukamoto, Denis Scholz, Norbert Marwan, Sebastian Breitenbach & Tony Reimann
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Acquisition and analysis of greyscale data from stalagmites using ImageJ software. Cave and Karst Science 50(2), 69–78.
Breitenbach, S. F. M. & Marwan, N.
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Isothermal thermoluminescence (ITL) dating of a speleothem from Bleßberg Cave. 17th International Luminescence and Electron Spin Resonance Dating conference (LED2023), 29.06.2023, Copenhagen, Denmark.
Junjie Zhang, Jennifer Klose, Sumiko Tsukamoto, Denis Scholz, Norbert Marwan, Sebastian Breitenbach, Norbert Mercier, Chantal Tribolo & Sebastian Kreutzer
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MATLAB scripts for acquisition and analysis of grey scale data from stalagmites. Zenodo, May 2023
Norbert Marwan & Sebastian Breitenbach
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Isothermal thermoluminescence dating of speleothem growth – A case study from Bleßberg cave 2, Germany. Quaternary Geochronology, 85, 101628.
Zhang, Junjie; Klose, Jennifer; Scholz, Denis; Marwan, Norbert; Breitenbach, Sebastian F.M.; Katzschmann, Lutz; Kraemer, Dennis & Tsukamoto, Sumiko
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R scripts for 'Isothermal thermoluminescence dating of speleothem growth – A case study from Bleßberg cave 2, Germany'. Zenodo, November 2024
Junjie Zhang
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Using Low-Cost Software to Obtain and Study Stalagmite Greyscale Data. CREG Journal 125, 7–10.
Breitenbach, S. F. M. & Marwan, N.
