A high spatial resolution δ18O profile of a speleothem using an ion-microprobe

The oxygen isotopic composition of a stalactite from the Soreq Cave, Israel has been investigated by in situ high spatial resolution ion microprobe analysis. The δ18O record obtained on portions of the stalactite, which were deposited during the time interval of 18–14.3, 10.8–8.5 and 1.5–0.2 ka, has a temporal resolution ranging from ∼1 to 25 years (depending on the deposition rate during the period investigated). Comparison to results obtained by micro-drilling and phosphoric acid reaction gas-phase mass spectrometry indicates that the ion microprobe analyses are precise and accurate at the 0.4–0.5‰ level. The high resolution of the ion microprobe profile enables the detection of short duration excursions toward low δ18O values during deglaciation (from 18 to 14.3 ka), providing further evidence indicating the instability of the glacial climate.