Pacific Section AAPG, SPE and SEPM Joint Technical Conference

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Changes In Tulare Lake Levels For The Past 35,000 Years From The Upper Eight Meters Of The TL05-4 Cores.


Physical and chemical changes in the lithology of deposited sediment can act as proxies for past lake levels and, hence, climate change, particularly when terminal lake basins are studied. Here we report on a relative paleolake-level record of one such terminal lake, Tulare Lake, CA, which now represents the past ∼35ka. Tulare Lake is the terminus of four of the largest rivers from the southern Sierra Nevada Mountains and hydrologic modeling has shown that its surface elevation is a good gauge of Sierran stream discharge. This study reconstructs relative lake level using geochemical and geophysical proxy data from overlapping lake sediment cores, TL05-4A and -4B, taken from near Kettleman City, CA. Proxy data from these cores include magnetic susceptibility, grain size, total inorganic and organic carbon, and carbon-nitrogen ratios. These data co-vary to some extent and, based on comparisons with earlier lake-level records based on trench samples, reflect relative lake level. The associated shifts in lake conditions appear to correlate with expected regional climate change, like the high discharge conditions corresponding to the Tioga Glaciation. Further work including additional radiocarbon dating will be necessary to test these initial conclusions. This study will ultimately help forecast the effect on the water supply of the San Joaquin Valley due to century to millennial-scale changes in climate.