SEASONALITY OF CAVE DRIP HYDROLOGY AND CHEMISTRY IN RELATION TO MID-LATITUDE NORTH AMERICAN HOLOCENE PALEOCLIMATE RECORD FROM SPELEOTHEMS

We are developing a trans-North American record of Holocene climate change based on actively growing stalagmites from 3 caves on the Pacific coast of Vancouver Island, one each in the Bow Valley of the Rocky Mountains, the mid-west (southern Indiana) and the north-eastern U.S. (upstate New York). These sites form a west-east transect across the middle of the continent close to the modern mean position of the Polar Front, with the Pacific coast sites close to the intersection of the north and south Pacific gyres. An important aspect of this project is the assessment of the extent to which d18O of the drip water, and thus the d18O of the calcite, is seasonally biased at a given site and within each cave. Custom drip monitoring stations were deployed in 2004 to provide high frequency records of drip rate, temperature and total dissolved solids from 3 drips in the 6 caves, while monthly bulk water samples are captured for isotopic and chemical analysis. Preliminary analysis shows that temporal variations in all parameters are sometimes concurrent between drip sources located 10's of metres apart in the same cave, while at other times each drip may have independent hydrological characteristics. Furthermore, the range in values between drip sources in one cave may be as great as the total range within the trans-continental dataset. These observations indicate that individual drip sources are fed by varying proportions of fast flow (young) or slow flow (old) waters, such that each drip source may result in distinct speleothem paleoclimate records. These findings are consistent with Serefiddin & Schwarcz (2004) who report significant differences in the stable isotope records of coeval and adjacent speleothems sampled within a single cave. The integration of these drip hydro-chemical data with the study of the modern calcite will enable a more profound understanding of the Holocene paleoclimate records from the sampled speleothems. The results will also help establish the relationship between modern drip waters and the fluid inclusions trapped in speleothems, such that analysis of these inclusions may provide calibrated paleotemperature records in the future.