Fluid inclusion water isotopes in speleothems using CRDS - understanding carbonate d18O responses to climate variability

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Fluid inclusions refer to small aliquots of water and/or gases contained inside minerals. They are relicts of the original fluid environment and in suitable archives can provide insights into the solution d18O and dD values and their evolution through time. Especially promising is an application to fluid inclusions in speleothems as this archive provides a good age control and is ubiquitous in most continental regions. Speleothems from Sauerland (Germany) grew during the Holocene and with their carbonate d18O values largely follow the global climatic patterns during this time period. d18O values, however, show discrepant responses to climatic events, in particular, during the 8.2 ka event and the Little Ice Age (LIA). Fluid inclusions can constrain the water d18O values and therefore help to disentangle the causes for the discrepant carbonate d18O values during 8.2 ka event and LIA. Furthermore, fluid inclusions in the Sauerland speleothems can be used to reconstruct the isotopic evolution of the precipitation in Germany during the Holocene and give clues for natural variability and its influence on the Central European climate. We intend to combine an apparatus for quantitative water and gas extraction from fluid inclusion with an absorption-spectroscopic (CRDS) system for isotopic analysis of the released water amount. We apply for funding for the CRDS system and a PhD student to setup and calibrate the system and for the analysis of samples from the Sauerland stalagmites. Beyond the planned study, the fluid inclusion system has a vast range of potential applications in hydrology and paleoclimate.