Lake levels for the past 19,000 years from the TL05-4 cores, Tulare Lake, California, USA: Geophysical and geochemical proxies

Abstract

Geochemical and geophysical proxy data from the TL05-4 lake-plain cores of Tulare Lake, California, are reported on here representing most of the past 19,000 years. The new record consists of carbon/nitrogen ratios, total organic carbon (TOC), nitrogen (N), total inorganic carbon (TIC), grain size, and magnetic susceptibility analyses from samples taken at 1-cm intervals (∼45 yr/sample). Age control is provided by 22 radiocarbon dates. The first part of the record (∼19.0–14.5 cal ka BP) consists of elevated sand and silt percentages and higher sedimentation rates interpreted as elevated runoff associated with melting of the Tioga-age Sierra Nevada ice cap. The TIC was undetectable and TOC and N were low suggesting low productivity in a relatively sterile, freshwater lake. From 14.5 to 10.3 cal ka BP, the deposits consisted of 50% clay and 50% silt with TIC and TOC extremely low, which is consistent with a stable, low productivity lake. From 10.3 to 7.5 cal ka BP, an initial pulse of fining upward sand gave way to increased clay deposition that suggests a lake transgression to a stable highstand, coeval with the deep water event found in previously published records of Tulare Lake and other lakes from central and southern California, including Owens Lake and Lake Elsinore. A few-hundred-year duration spikes in TIC centered at 8.0 cal ka BP is suggestive of evaporating lake conditions toward the end of this early Holocene highstand. Tulare Lake dropped quickly to a relative low at 7.5 cal ka BP, but then lake level increased steadily until 3.0 cal ka BP. High amplitude fluctuation in almost all proxies occurs from 2.5 to 1.8 cal ka BP at the end of the record, suggesting that this time interval was characterized by rapid fluctuations in lake level. Tulare Lake levels during the Holocene vary in conjunction with sea surface temperature (SST) records from the Ocean Drilling Program (ODP) Site 1017 located off the coast of central California, which suggests that variations in SSTs throughout the Holocene drove changes in precipitation in the Sierra Nevada and hence, Tulare Lake level. Since historic lake-level histories have been shown to be directly related to stream discharge from the Sierra Nevada, this observation will be integral in forecasting future decadal-scale changes in southern San Joaquin Valley water supply due to anticipated climate change.