<p>Triple isotope (dD, d17O, d18O) study on precipitation, drip water andspeleothem fluid inclusions for a Western Central European cave (NW Switzerland)</p>

Triple isotope (dD, d17O, d18O) study on precipitation, drip water andspeleothem fluid inclusions for a Western Central European cave (NW Switzerland)

Stephane Affolter, Anamaria D. Hauselmann, Dominik Fleitmann, Philipp Hauselmann, Markus Leuenberger

Quaternary Science Reviews 2015, Vol. 127, Pages 73-89


Deuterium (dD) and oxygen (d18O) isotopes are powerful tracers of the hydrological cycle and have beenextensively used for paleoclimate reconstructions as they can provide information on past precipitation,temperature and atmospheric circulation. More recently, the use of 17Oexcess derived from precisemeasurement of d17O and d18O gives new and additional insights in tracing the hydrological cyclewhereas uncertainties surround this proxy. However, 17Oexcess could provide additional information onthe atmospheric conditions at the moisture source as well as about fractionations associated withtransport and site processes. In this paper we trace water stable isotopes (dD, d17O and d18O) along theirpath from precipitation to cave drip water and finally to speleothem fluid inclusions for Milandre cave innorthwestern Switzerland. A two year-long daily resolved precipitation isotope record close to the cavesite is compared to collected cave drip water (3 months average resolution) and fluid inclusions ofmodern and Holocene stalagmites. Amount weighted mean dD, d18O and d17Oare 71.0‰, 9.9‰, 5.2‰ for precipitation, 60.3‰, 8.7‰, 4.6‰ for cave drip waterand 61.3‰, 8.3‰, 4.7‰ for recent fluid inclusions respectively. Second order parameters have alsobeen derived in precipitation and drip water and present similar values with 18 per meg for 17Oexcesswhereas d-excess is 1.5‰ more negative in drip water. Furthermore, the atmospheric signal is shiftedtowards enriched values in the drip water and fluid inclusions (D of ~ þ 10‰ for dD). The isotopiccomposition of cave drip water exhibits a weak seasonal signal which is shifted by around 8e10 months(groundwater residence time) when compared to the precipitation. Moreover, we carried out the firstd17O measurement in speleothem fluid inclusions, as well as the first comparison of the d17O behaviourfrom the meteoric water to the fluid inclusions entrapment in speleothems. This study on precipitation,drip water and fluid inclusions will be used as a speleothem proxy calibration for Milandre cave in orderto reconstruct paleotemperatures and moisture source variations for Western Central Europe.