ENVIRONMENTAL MAGNETISM AND PALEOMAGNETIC SECULAR VARIATION OF LATE HOLOCENE-AGED SEDIMENTS OF TULARE LAKE, CA

The Tulare lake level history over the past 10,000 years is consistent with other paleoclimate records of south-central California. The record from this particular lake, if improved with respect to resolution especially in the latest Holocene, will potentially provide valuable constraints on forecasting runoff from the Sierra Nevada over the next several generations into one of the most important agricultural regions in the world. This project focuses on the magnetic properties of Tulare lake sediments in an attempt to better date the sediments and to determine the relative lake level at the time they were deposited.

Toward this end, two new trenches were dug in the southern Tulare lake bed, totaling approximately three meters in depth. These were sampled at centimeter spacing, with three samples collected per horizon. The magnetization of a preliminary set of samples was measured at the UC Davis Paleomagnetics Laboratory to determine their environmental magnetic and paleomagnetic properties. The environmental magnetic data shows lower ARM/IRM values corresponding to lower S-ratio values, which are indicative of larger grain size and a higher percentage of hematite, respectively. This may represent lower lake levels leading to oxidation. Analysis of the remaining samples at UC Davis and IRM laboratories in Minneapolis will further refine these results.