Potential of ikaite to record the evolution of oceanic [[delta].sup.18]O

A challenge in the quest to understand the sensitivity of the climate system is the separation of the competing effects of ice volume or sea level, salinity, and temperature on foraminiferal [[delta].sup.18]O. We present precipitation experiments on the mineral ikaite, a hydrated form of calcium carbonate found in organic carbon-rich deep-marine sediments, that show that the hydration waters within the ikaite crystal capture the [[delta].sup.18]O of seawater [[delta].sup.18][O.sub.sw]) with a fractionation factor of 1.0029 ([+ or -] 0.0002). The [[delta].sup.18][O.sub.sw] measures the volume of continental ice, with an overprint of local salinity. Isolation of [[delta].sup.18][O.sub.sw] by analysis of the hydration waters of sedimentary ikaite preserved at temperatures Keywords: Pleistocene, ikaite, sea level, ice volume, oxygen isotopes, climate.