Chronology and paleoclimate records of the late Pleistocene Wilson Creek Formation at Mono Lake, California

Mono Lake California, located in the eastern rain shadow of the Sierra Nevada, contains multiple shoreline terraces and sets of moraines which testify to fluctuations in lake level and valley glaciers. These large changes in paleoclimatic conditions are recorded at high resolution in geochemical and sedimentary proxies preserved in the sediments of the Wilson Creek Formation, and are the focus of this thesis.; Assignment of an accurate, high-resolution chronology to the Wilson Creek sediments has been hampered by problems with traditional radiometric methods. Correlation of a new relative paleomagnetic intensity record to global stacks of paleointensity demonstrates that the Wilson Creek Formation began to be deposited at ∼67 ka, about 25 kyr earlier than previously thought. On this new age model, lake level is controlled by glacial-interglacial cycles (100 kyr) and local insolation (20 kyr), and shows correlatives to the Greenland Dansgaard-Oeschger events during periods of high insolation.; Comparison to independent geomorphic and stratigraphic evidence shows that the authigenic minerals calcite and Mg-smectite record fluctuations in lake level. Sr-isotopes recorded in ostracodes reflect changes in run-off balance from eastern and western parts of the basin, showing less radiogenic values (Tertiary volcanic-like) during wet periods and more radiogenic values (Sierran-like) during drier periods. Fine-fraction chemistry and magnetic remanence curves record fluctuations in input of glacial rock flour to the basin, and are similar to flour records in the nearby Owens Basin. Ice-rafted debris, as measured in outcrop and sediment samples, appears to be dominated by rafting by shore ice, rather than glacial icebergs.; An important implication of the new chronology is for the age of the paleomagnetic directional excursion in the Wilson Creek sediments ("Mono Lake Excursion"). Originally considered to be 25 ka (14C), the excursion has been correlated to the global geomagnetic field paleointensity low and the ice core 36Cl peak at 32 ka. However, our new age model results in an age of 40 ka for the excursion, indicating that it is a regional record of the global Laschamp excursion.