Noble gas thermometry on fluid inclusions in speleothems: Optimization and application of a new method for paleoclimate reconstruction

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Dissolved noble gases in groundwater are established as excellent indicators of paleotemperatures. The strength of the so-called noble gas thermometer is its ability to provide reliable absolute temperatures. Its weakness is the confinement to the groundwater archive, which has limitations with regard to absolute dating and temporal resolution. Carbonate sinters are archives that can be dated precisely and with high resolution. However, the reconstruction of paleotemperatures based on (18O-values from carbonates is problematic. An improvement has been achieved recently by analysing the stable isotopes directly on the drip water that is stored in microscopic inclusions. Such fluid inclusions represent a climate archive that potentially can be accessed also by the noble gas thermometer. If noble gas concentrations in fluid inclusions of carbonates could be measured and converted into temperatures, this would constitute a very powerful method of paleoclimate reconstruction. It would combine the advantages of the noble gas thermometer and the speleothem archive. The noble gases would yield absolute temperature reconstructions, which would significantly facilitate the interpretation of stable isotope data. The current project combines experience in noble gas analytics and interpretation with the broad knowledge on speleothems present in the researcher group. The project plans to adapt recently developed methods of water extraction from fluid inclusions for noble gas analysis and to assess the potential of the noble gas paleothermometer in this archive.