LATEST PLEISTOCENE THROUGH HOLOCENE LAKE LEVELS FROM TULARE LAKE, CA: TESTING RESULTS USING THE SMEAR SLIDE TECHNIQUE

The core-based, lake-level proxy record of Blunt (2013) for Tulare Lake, CA has extended the trench-based record of Negrini et al. (2006) back to ~20,000 years ago for Tulare Lake. Furthermore, the former has an 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 technique involves smearing chemically and physically unaltered sample onto a glass microscope slide using Norland optical cement as a medium and curing with an ultraviolet light.

The smear slide technique allows for a detailed petrographic microscopic description of the unconsolidated core sediments for every 5cm, including the detection of features diagnostic of both deep, freshwater and shallow, brackish water paleoenvironments. So far, the results are consistent with the predictions of Blunt (2013). For example, at the lower end of the record, the smear slides from within the interval hypothesized to contain sand-sized grains of Tioagan-aged glacial outwash from the Sierra Nevada ice cap, have, as predicted, little to no organic matter or carbonate present and are characterized by sand grains of granitic composition. In the time interval from 2,500 to 1,800 cal. yr. BP, Blunt (2013) suggests shallow, freshwater lake conditions due to a low total inorganic carbon (TIC) value and relatively coarse grains. The predictions are consistent with new observations of pristine sponge spicules and the pollen species Typha (i.e. cattail) in the smear slides from the corresponding depth interval. Further observations of fluctuating levels of clay and silt, and occasional coarse grain deposits within this zone are also present within the smear slides, which are uniform with the Blunt (2013) study.