A palaeotemperature record for the mid-Wisconsin in Vancouver Island

Calcite speleothems are deposits of calcium carbonate (stalagmites and flowstones) found in limestone caves. They are formed by precipitation from groundwater supersaturated in Ca2+ and HCO−3. Their oxygen isotopic composition is controlled by the isotopic composition of the seepage waters from which they are deposited and by the temperature of formation. We report here the discovery of mid-Wisconsin speleothems from a cave in Vancouver Island which are significantly depleted in 18O relative to modern calcite in the same cave. We interpret the variations in 18O content over this period as an absolute palaeotemperature record for the area.