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Geochronology Advances in geochronological science
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Discussion papers
https://doi.org/10.5194/gchron-2019-8
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/gchron-2019-8
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 16 Jul 2019

Submitted as: research article | 16 Jul 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geochronology (GChron).

Exploring the advantages and limitations of in situ U-Pb carbonate geochronology using speleothems

Jon Woodhead1 and Joseph Petrus2 Jon Woodhead and Joseph Petrus
  • 1School of Earth Sciences, University of Melbourne, Melbourne, VIC 3010, Australia
  • 2Harquail School of Earth Sciences, Laurentian University, Sudbury, Canada

Abstract. The recent development of methods for in situ U-Pb age determination in carbonates has found widespread application but the benefits and limitations of the method over bulk analysis (isotope dilution – ID) approaches have yet to be fully explored. Here we use speleothems – cave carbonates such as stalagmites and flowstones – to investigate the utility of in situ dating methodologies for challenging matrices with typically low U and Pb contents, and predominantly late Cenozoic ages. Using samples for which ID data have already been published, we show that accurate ages can be obtained for many speleothem types by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA- ICPMS). Consideration of our own and literature data suggests that most carbonates with > 1 ppm Uranium and a few hundred ppb of Pb should be good targets for in situ methodologies, regardless of age. In situ analysis often provides a larger spread in U/Pb ratios which can be advantageous for isochron construction but isochron ages rarely achieve the ultimate precision of ID analyses conducted on the same samples. LA analysis is faster than ID and thus will play a significant role in reconnaissance studies. The major advantage of the in situ methodology appears to be the potential for successful dating outcomes in sample types requiring high spatial resolution analysis.

Jon Woodhead and Joseph Petrus
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Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Jon Woodhead and Joseph Petrus
Jon Woodhead and Joseph Petrus
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Short summary
Recently development methods for in situ U-Pb age determination in carbonates have found widespread application but the benefits and limitations of the method over bulk analysis approaches have yet to be fully explored. Here we use speleothems – cave carbonates such as stalagmites and flowstones – to investigate the utility of in situ dating methodologies for challenging matrices with typically low U and Pb contents, and predominantly late Cenozoic ages.
Recently development methods for in situ U-Pb age determination in carbonates have found...
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