The rise and fall of latest Pleistocene pluvial lakes in the northern Great Basin
March 18th (Wednesday), 12 p.m. / noon, JH Senior Center – Open to Public. Presentation: “The rise and fall of latest Pleistocene pluvial lakes in the northern Great Basin”, Presented by Daniel Enrique Ibarra, UC Berkeley
G.K. Gilbert’s 1890 monograph on Lake Bonneville for the United States Geological Survey started over a century of research on Quaternary lakes in the American west that continues today with an increased need to forecast future water resources in the regions. Early geologists documented extensive lacustrine shoreline deposits in many terminal basins of the Great Basin, and in doing so formally documented evidence for many classic Earth science concepts including uniformitarianism, isostasy and diastrophism, and glacial-interglacial cycles. Now the application of stable isotope techniques and radiometric age determination provide the constraints necessary to disentangle the timing and magnitude of hydrologic change from shoreline deposits and lacustrine sediments. In this talk I will: 1) document the rapid rise to highstand conditions in Surprise Valley, California after, rather than during, the Last Glacial Maximum; 2) demonstrate that as the Laurentide icesheet retreated the Great Basin lakes (Bonneville, Franklin, Lahontan, Surprise, Chewaucan and others) are not synchronous in their highstand timing due to sinuosity and steering of the westerly storm track; and 3) model the increases in precipitation necessary to drive post-LGM highstand areas. In doing so the results presented here provide quantitative targets for assessing the performance of climate model simulations of the terrestrial water cycle during the LGM and subsequent deglaciation.