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UP: Fachverband Umweltphysik

UP 2: Bodenphysik und Ozeanographie

UP 2.3: Talk

Tuesday, March 11, 2008, 12:15–12:30, 3B

Noble gas measurements on fluid inclusions in speleothems — Tobias Kluge, •Thomas Marx, and Werner Aeschbach-Hertig — Institut für Umweltphysik, Universität Heidelberg

Measurements of dissolved atmospheric noble gases in groundwater enable paleotemperature reconstruction using their temperature dependent solubility. In contrast to groundwater, speleothems allow a more precise dating and offer high resolution records of stable oxygen and carbon isotopes. Unfortunately these data cannot be translated into paleotemperatures easily. By adopting the noble gas temperature (NGT) method to microscopic water-filled inclusions in speleothems it may be feasible to derive paleotemperatures.

Techniques for water and noble gas extraction from inclusions based on crushing and heating have been developed and are still improved continuously. In order to calculate NGTs by inverse modelling, NG concentrations are needed. Thus water amounts of about 0.1 to 1 µ l have to be measured precisely, which can be achieved manometrically with a typical uncertainty of ≤ 2 %. The small gas amounts are measured using a sector field mass spectrometer and compared to a diluted standard. Additionally an extensive background control was performed. Most of the examined stalagmites contain too much air inclusions which mask the temperature signal. Methods to separate air from water filled inclusions are currently under development. However, calculation of NGTs was successful for a set of samples from one stalagmite and a soda straw.