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Latest Pleistocene Through Holocene Lake Levels From Tulare Lake, CA: Testing Results Using The Smear Slide Technique


Lake sediments from deep lake settings are often associated with high deposition rates, offering a detailed repository of measurable quantities providing information on lake level, climate, and the terrestrial environment surrounding the lake. Prior to diversion of stream flow for the purpose of irrigation, Tulare Lake was the largest fresh water lake west of the Great Lakes (Preston, 1981). At that time, its lake level was predictably related to the discharge of four Sierran streams, the Kern, Tule, Kaweah, and Kings Rivers (Atwater et al., 1986). This relationship is the basis for temporal river discharge reconstruction by locating and dating the past surface elevations of Tulare Lake. This, in turn, will ultimately lead to improved forecasting for Sierran discharge over the next several decades after this record is compared to improving coeval records of sea-surface temperatures of the Pacific Ocean. The core-based record of Blunt (2013) has extended the trench-based record of Negrini et al. (2006) back to ∼20,000 years ago. Furthermore, the former has a much improved resolution corresponding to one sample every ∼50 years, making it more useful towards decadal-scale forecasts of recharge. This study uses the smear slide technique of Schnurrenberger et al. (2003) to test the findings of Blunt (2013). The smear slide technique allows for a detailed petrographic microscopic description of the core every 5cm, including the detection of features diagnostic of both deep, freshwater and shallow, brackish water paleoenvironments. In the time interval from 2,500 to 1,800 cal yr BP, Blunt (2013) suggests lake conditions as a shallow, fresh water marsh due to a low total inorganic carbon (TIC) value, which is not inconsistent with our initial observations of pristine sponge spicules and the pollen species Typha (i.e., cattail) in the smear slides from the corresponding depth interval. Using these initially observed relationships between smear slide content and previously collected geochemical and geophysical data, we may expect to have little to no organic matter present in the smear slides during the Tioga glaciation at ∼18000 cal yr BP, which is characterized by a high silt content, low carbon to nitrogen ratio (C/N), and low TIC predicting a cold climate.