A HOLOCENE LENGTH OXYGEN ISOTOPE RECORD OF ROCKY MOUNTAIN HYDROCLIMATE VARIABILITY FROM SOUTH HOGARTH LAKE, ALBERTA, CANADA

Oxygen isotope ratios in authigenic carbonate sediment from South Hogarth Lake (Alberta) provide a ~10,000 year record of variations in precipitation-evaporation balance in the southern Canadian Rocky Mountains. Synthesis of this geologic archive with other paleoclimate records in the region provides insight on spatial variability of ocean-atmosphere dynamics and their controls on climate over time. SEM and XRD analyses of the carbonate sediment from South Hogarth Lake indicate authigenic calcite (CaCO₃) throughout. The age model is based on a series of 25 radiocarbon and tephra dates and indicates that sediment has been continuously deposited since deglaciation. The sequence was sampled at 1mm to 1cm intervals, and the isotopic composition (δ¹⁸O) of the fine-grained, authigenic CaCO₃ was measured. Water isotope values are isotopically enriched relative to local meteoric water, indicating that evaporation is a substantial component of the water budget. In closed-basin lakes, low δ¹⁸O values in both water and sediment generally indicate wetter conditions, and high δ¹⁸O values indicate drier conditions. The South Hogarth and Cleland (British Columbia) lake records exhibit higher δ¹⁸O values during the late Holocene, suggesting a decline in lake levels and a reduction in cold season precipitation. Previous work on Shark Lake (Alberta), Cleland Lake, Paradise Lake (British Columbia), Lime Lake (Washington), and Jellybean Lake (Yukon) suggests that mid-Holocene climate was drier than present overall, but wetter conditions persisted during the cold season. Oxygen isotope measurements from South Hogarth Lake provide insight on climate change in an underrepresented region of western North America and thus provide a new spatial perspective for testing hypotheses on ocean-atmosphere control of precipitation-evaporation balance variability during the middle through late Holocene. The development of such paleoclimate proxy records provides a more thorough understanding of the full range of potential hydroclimate variability.