Paper No. 16
Presentation Time: 1:30 PM-5:30 PM
MULTIPROXY STUDY OF LATE PLEISTOCENE/HOLOCENE CLIMATE VARIABILITY AT LOUGH GALLAUN, WESTERN IRELAND FROM STABLE ISOTOPES OF LACUSTRINE MARL AND ORGANIC SEDIMENT
We present preliminary geochemical results obtained from a 6.3 m Livingston piston core from western Ireland. We determined δ13C and δ18O values from lacustrine marl, δ13C and δ15N from bulk organic sediment, loss on ignition, C-14 dating, and standard lithological characteristics. Stable isotope analyses were conducted at a 2.5 cm resolution to provide a record of paleoenvironmental variability. Periods of rapid climate change were identified and at adjacent levels the core was sampled at a higher resolution. Marl content in the core ranges from a few percent in the upper peat layers and basal gray clay layers to more than 90% in the marl layers. Based on cross correlation with lithological characteristics from an ongoing study at nearby Loch Inse Uí Chuínn, the base of the profile dates to ~16ka. Lough Gallaun is located in the Burren region of western Ireland approximately 7 km north of Corofin. Ireland has a temperate climate with annual temperature variation moderated by proximity to the North Atlantic Ocean resulting in low seasonality. The Burren region of County Clare is of special interest due to its ecological, archaeological and climatological uniqueness. Significant vegetation has not returned to this region since the last glacial maximum due to the lack of soil formation in higher areas and little soil formation in low lands resulting in exposure of the Carboniferous limestone bedrock. The δ18O values of the calcite range from 6.5 to -4.6 VPDB which is likely too large to reflect changes in lake temperature. We interpret these large shifts in δ18O to reflect changes in precipitation δ18O altering the δ18O of the lake water. The δ13C values record a shift of greater than 11, which is not likely attributed to lake productivity alone. We are interested in identifying the effect of DIC derived from the limestone bedrock (δ13C=+3.2VPDB) on the δ13C of the calcite and the bulk organic sediment. Isotope values will be compared to a study at Loch Inse Uí Chuínn and to a previously dated pollen record at Lough Gortlecka 200m to the north to generate a more comprehensive regional climate record.