This award supports a radiogenic isotope study of a unique continental record of weathering and climate change preserved in a series of playa lakes in the southeastern California section of the Great Basin. This chain of periodically interconnected lakes, referred to as the Owens River System, is the repository for essentially all of the clastic and chemical sediments shed over the past several million years from the eastern Sierra Nevada from just south of Mono Lake to the Garlock Fault. Despite the large amount of work that has been carried out on the Owens Rivers System, there have been relatively few studies examining the sources of cations and clastic sediments in these Great Basin lacustrine basins. Strontium (Sr) and neodymium (Nd) isotopes are potentially sensitive tracers of cation inputs, both in the dissolved form and as suspended sediments. Preliminary data suggest that these isotope tracers can be successfully used in the Owens River System to monitor (1) changes in location of chemical weathering and sediment sources (therefore of precipitation patterns); (2) the relationship of chemical to mechanical weathering in the alpine environment; and (3) hydrologic connectivity between lakes that share a common water supply during wet periods but that become closed, isolated basins during dry periods. Integration of the results from the proposed study with previous and ongoing work in the Owens River System will provide powerful constraints on Quaternary climate shifts in the Basin and Range Province, which have in turn been linked to North Atlantic and global climate fluctuations.
