TOWARD THE RECONSTRUCTION OF THE PALEOHYDROLOGY OF THE GREAT SALT LAKE, UTAH, USING STABLE ISOTOPE RATIOS OF BRINE SHRIMP CHITIN

Climate model predictions suggest the Great Basin will likely become more arid under expected warmer conditions. Past response of local hydrology to warmer conditions is thus of great interest to the burgeoning population of this region. The Great Salt Lake (GSL) hosts populations of brine shrimp (Artemia franciscana)--crustaceans that produce dormant chitinous cysts that are preserved in sediments for thousands of years. We plan to reconstruct the hydrologic balance of the GSL, a lake located in Northern Utah, using the δ²H and δ¹⁸O of brine shrimp chitin combined with radiocarbon dating of the Holocene portion of a GSL core. In order to confidently interpret the isotope record from the cysts, a calibration experiment designed to establish the relationship between the δ²H and δ¹⁸O of water, food, and chitin, is necessary. A relationship between the δ¹⁸O of Chironomid fly larvae head capsules and growth water was established for a series of freshwater arctic lakes by Wooller, et. al (2004) and has been proposed as a proxy for the oxygen isotopic composition of those lakes. We establish relationships between the δ²H and δ¹⁸O composition of brine shrimp chitin and that of their growth water and food with a set of culture experiments. The contribution of food to chitin is determined by varying the δ²H and δ¹⁸O of food while keeping water constant, and the contribution of water inferred by varying the δ²H and δ¹⁸O of growth water while keeping food constant. Natural samples, collected monthly from the GSL, are compared to the calibration samples for validation. Future work will involve the application of these relationships to reconstruct changes in lake water δ²H, δ¹⁸O and water balance through the Holocene.