Heidelberg 2006 – scientific programme
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UP: Umweltphysik
UP 9: Poster: Hydrosph
äre
UP 9.3: Poster
Tuesday, March 14, 2006, 14:00–16:00, C
Noble gases in fluid inclusions of speleothems: a new palaeoenvironmental proxy? — •Y. Scheidegger1, M.S. Brennwald1, V.S. Heber2, R. Wieler2, and R. Kipfer1,2 — 1Water Resources & Drinking Water, Eawag, Switzerland — 2Isotope Geochemistry & Mineral Resources, ETH Zürich, Switzerland
The concentrations of dissolved atmospheric noble gases in water reflect temperature and salinity of the water that prevailed during gas exchange between the water and the atmosphere. This principle has been successfully applied to reconstruct palaeoenvironmental conditions from groundwater or from pore water of lake sediments. While both these archives provide long-term palaeoclimatic records, their temporal resolution remains limited due to mixing and diffusion in the water. We therefore propose to apply noble gases as palaeoenvironmental proxies in water inclusions of speleothems, which provide a well-defined and high-resolution timeframe. While experimental difficulties prevented the assessment of the potential of this archive until now, we recently developed a new approach to determine the noble gas abundance in fluid inclusions of speleothems. We found that a large fraction of the noble gases we extracted from bulk speleothem samples originate from air inclusions. In addition to this air component, we observed a small component with the same noble-gas signature as air-equilibrated water, which indicates that this latter fraction originates from water inclusions in the speleothems. This shows that the noble gas signature of the water inclusions is experimentally accessible, which supports the potential of noble gases in water inclusions in speleothems as palaeoenvironmental proxies.