Emmanuel Garcia, CSU Bakersfield. May 31, 2012 October 3, Dr. Robert Negrini, CSU Bakersfield

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1 Determination of Tulare Lake, CA Late Pleistocene and Holocene Lake Level History through Geochemical Analysis Emmanuel Garcia, CSU Bakersfield May 31, 2012 October 3, 2012 Dr. Robert Negrini, CSU Bakersfield October 3, 2012

2 2 TABLE OF CONTENTS Acknowledgements...3 Abstract..4 Introduction.5 Methods...6 Results Discussion.8-9 Literature Cited..10

3 3 ACKNOWLEDGEMENTS This project was supported by Agriculture and Food Research Initiative Competitive Grant no from the USDA National Institute of Food and Agriculture. Many thanks to Dr. Robert Negrini, Ashleigh Blunt, Kathy Randall, Elizabeth Powers, James Wilson, and Logan Prosser for all their help and patience. I would also like to extend my thanks to Julie Lappin, Chelsea Rammelsberg, and Steve Keough for always making themselves available to answer all of our questions.

4 4 ABSTRACT Prior to diversion of streamflow for the purpose of irrigation, the lake level of Tulare lake was linearly 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 reconstructing the discharge of these rivers through time by locating and dating the past surface elevations of Tulare Lake. Through the use of geochemical and geophysical proxies we can begin to construct a record of lake elevation and build upon previous research, (Negrini et al. 2006) wherein a series of 2 trenches and a preexisting core were used to obtain a low resolution record of lake elevation through time. By increasing our sampling interval, we improved the age control and increased the resolution of the record to decadal scale. Our results indicate that core-based proxies can be vital in creating a precise and relatively uninterrupted record of Tulare Lake levels for the past 18,000 years. Once established, this record will allow us to accurately forecast changes in the future water supply of the San Joaquin Valley.

5 5 INTRODUCTION Previous research has shown that, prior to the diversion of streamflow for irrigation purposes, the lake level of Tulare Lake was directly associated with the discharge of four Sierran streams, the Kern, Tule, Kaweah, and Kings Rivers (Atwater et al., 1986). Our research aims to establish a lake level record for the past 18,000 years by using core-based geochemical analysis to form lake-level proxies. To increase the resolution of the record established by Negrini et al. (2006), we will sample the TL05-A sediment core in one-centimeter increments. Each centimeter in each core is roughly equivalent to 30 years of sediment deposition. Our study will measure TIC (total inorganic carbon) amounts derived from precipitated carbonates. Such carbonates begin to deposit when evaporation exceeds inflow. Drops in lake level result in a higher concentration of minerals in a smaller volume of water. As concentrations of said carbonates increase, deposition ensues (Cohen, 2003, p.77). Through the use of carbon coulometry, we can detect high levels of inorganic carbon, which are an indication of dry periods with respect to the lake. The research conducted during the duration of this internship will prepare me for a career as a geologist for the Forest Service through the USDA by strengthening my critical thinking skills and teaching me to form proxies by using the data at hand.

6 6 METHODS Samples were taken from three separate core drives in one-centimeter intervals. Each one-centimeter interval was then ground to a powder using a mortar and pestle and placed into a crucible. The crucibles were then placed in an oven and dehydrated for twenty-four hours at 100⁰C. Once the samples had dehydrated for twenty-four hours, they were placed inside a desiccator for a minimum of two hours before being weighed. The sample weight used was 100 milligrams. Once weighed, each sample was placed in a reaction vessel that was then placed in our UIC acidification module. As the sample was reacting with the perchloric acid in the acidification module, the CO2 released by the reaction was quantified and recorded by the UIC cm150 coulometer. Each sample reacted with 10 milliliters of 2N (normal) perchloric acid. This process was repeated for each individual one-centimeter sample of our A-core. In order to ensure our coulometer was functioning properly, we ran standards before every first sample of the day, every ten samples after that, and again after the last sample. The standard we chose to use was pure calcite, CaCO 3. After dehydrating the standard in our oven for twenty-four hours at 100⁰C, we stored it in our desiccator and only removed it when we needed to weigh out our standards. Standard weight used for the duration of this research was 20 milligrams. Once weighed, the standard was placed in the acidification module and reacted upon by 10 milliliters of perchloric acid. Results were then quantified and recorded by the cm150 coulometer.

7 7 RESULTS Total inorganic content percentages indicate three major low lake periods. One at ~9900 cal. years BP, another at ~7800 cal. years BP, and the most recent at ~3000 cal. years BP. The peaks shown in Figure 1 indicate high total inorganic carbon percentages for the samples corresponding to those years. These high amounts of TIC were deposited at times when lake elevation was reduced drastically due to evaporation and mineral concentrations caused evaporites to precipitate. Our findings were consistent with results for carbon/nitrogen ratios, which agree with the wet and dry periods presented by Figure 1. That is, C/N ratios were high when TIC% values were low consistent with the hypothesis that the high lake levels inferred from low TIC% values were fed by high stream flows which transported high C/N ratio terrigenous plant matter into the lake. Figure 1. Total Inorganic Carbon content plotted against age. Peaks show periods when lake level was low and evaporites were allowed to precipitate.

8 8 DISCUSSION This research supplied us with enough data to build an improved lake-level record, but gaps in our TL05-4A sediment core require a supplemental study of our TL05-4B core. The TL05-4B sediment core is a separate core of equal depth that was taken near the 4A core-site. Due to the nature of the coring process, sections of core may be lost during retrieval and these sections can be recovered by taking two cores side by side with staggered core depth breaks. In order to fill the gaps in our findings from sediment core 4A, studies of sediment core 4B must be conducted. A supplemental study such as this will allow us to complete our lake-level record and form proxies that will aid in determining the future water needs of the San Joaquin Valley. There are many other studies that need to be conducted in order to form an accurate climate model. Lake level is directly affected by a number of variables, e.g., rainfall, influx, and temperature. Supplemental studies including, but not limited to, analysis of carbon/nitrogen ratios, magnetic susceptibility analysis, and grain-size analysis must be conducted in order to form a proper climate model. For example, a low, or zero, inorganic carbon percentage indicates a period of higher lake level, but does not provide a reason for such an elevated lakelevel. By pairing low inorganic carbon percentages with a proxy that analyzes grain size and carbon/nitrogen ratios we can determine whether this was a flood period or a period of regular influx. Low total inorganic content paired with poorly sorted grain size and a high carbon/nitrogen ratio would indicate a higher energy influx of water that brought with it a large amount of terrestrial plant tissue, e.g., a flood. This experiential learning internship has showed me how interesting and rewarding participating in research can be by allowing me to become involved in research that will benefit the San Joaquin Valley. The improved lake-level record

9 9 that resulted from my research was my reward for the time and effort I invested during this internship. My internship has also allowed me to further develop my problem solving skills, which will prove useful in my career as a geologist. The research I conducted during my internship has also taught me how to approach certain problems and form useful proxies with the data at hand. I am now convinced that I want to get my Ph.D. in the near future. I look forward to renewing my internship and continuing my research as well as building a lasting relationship with the USDA. I am confident that a career as a geologist for the U.S. Forest Service would be equally rewarding and I look forward to exploring the opportunities that the USDA has to offer.

10 10 LITERATURE CITED Atwater, B.F., D.P. Adam, J.P. Bradbury, R.M. Forester, R.K. Mark, W.L. Lettis, G.R. Fisher, K.W. Gobalet, S.W. Robinson (1986). Fan dam for Tulare Lake, California and implications for the Wisconsin glacial of the Sierra Nevada, Bulletin of the Geological Society of America, 97, Cohen, A.S. (2003). Paleolimnology: The history and evolution of lake systems. Oxford: Oxford Univ. Press. Negrini, R.M., P.E. Wigand, S. Draucker, K. Gobalet, J.K. Gardner, M.Q. Sutton, R.M. Yohe, II., (2006). The Rambla highstand shoreline and the Holocene lake-level history of Tulare Lake, California, USA, Quaternary Science Reviews, v. 25, p