AN EARLY-MID HOLOCENE PALEOTEMPERATURE RECORD FROM FLUID INCLUSION STUDY ON A STALAGMITE FROM JACKLAH JILL CAVE, VANCOUVER ISLAND, BRITISH COLUMBIA, CANADA

We report a new carbonate speleothem fluid inclusion extraction method in which continuous helium flow during crushing allows the transfer of the liberated inclusion waters without isotopic fractionation. The new technique can analyze <0.2μl water, which may further reduce sample size and accordingly increase temporal resolution. Replication error of δD on identical aliquots is better than ±2‰, which is equivalent to an uncertainty of ±1^oC in paleotemperature if there is no error in deuterium excess—an assumption usually considered to be valid for the Holocene. A 5000-year paleotemperature record was obtained on a 30cm tall calcite stalagmite that grew between 10.8-5.2 ka ago in Jacklah Jill Cave, Vancouver Island, BC, Canada. The validity of the paleotemperature record has been verified by excellent agreement between the reconstructed long-term T-δD correlation and the modern dδD/dT value derived from the GNIP database. Overall, the early Holocene was about 3-5 ^oC warmer than today, but there was a longer-lived cooling trend from ca. 9.0 to 7.5 ka ago, which was interrupted by a short-lived alpine glacier advance around 7.7 ka ago. The mid Holocene, characterized by gentle temperature fluctuations, had an average value of 7.1±1.2 ^oC, which is almost the same as today's value of 6.9 ^oC, suggesting regional climate had stabilized by then.