REFINING THE RECORD OF PLEISTOCENE LAKE LEVEL CHANGE, LAKE BONNEVILLE, UTAH; EVIDENCE OF CLIMATE-DRIVEN OSCILLATIONS FROM THE PROVO SHOREZONE
Topographic profiles of shorelines from select sites in the Bonneville basin provide a detailed record of the magnitude and relative rate of change in lake level during the formation of the Provo shoreline. A series of prograding and aggrading beach ridges with abrupt terminations occur during the early stages of the Provo shoreline suggesting that lake level was being controlled by outlet dynamics during this time. In contrast, shorezone deposits from the late stages of the Provo shoreline terminate in a more gradual manner, indicating the onset of climatically influenced lake oscillations and marking the initiation of the lake's regressive phase to the pre-Holocene lowstand. Tufa may also be a useful indicator of climate influence on lake level during Provo time. At the studied locations, tufa occurs solely on the late stages of the Provo shoreline. This is consistent with probable higher total dissolved solids as the Bonneville basin water balance became increasingly negative during this time.