Cosmogenic Dating of Old, High Pluvial Shorelines in the Western Great Basin

New Mexico Institute Of Mining And Technology, Socorro NM

Investigators

Abstract

0001063 Phillips The late Pleistocene history of Lake Lahontan has been intensively studied for over 100 years. It is well known that the late Pleistocene Labontan lake cycle is only the most recent of several lake cycles since the mid Pleistocene, but very little is known about the timing of extent of these lakes, in large part because these cycles have been evidenced only by poorly exposed lacustrine sediments that yielded limited information on lacustrine extent. A new avenue of research as recently been opened by the discovery of sequences of shorelines above the Lahontan maximum level and above the shore elevations of other late Pleistocene pluvial lakes in Nevada. Chronological constraints on these shorelines are presently minimal. We propose to date these shoreline features using the accumulation of cosmogenic 36C1 and 10Be. Establishing a chronology of these lake cycles will enable a long-term comparison of paleoclimate in the Great Basin with that of global glacial-interglacial cycles, will aid in understanding the origin of the apparent long-term decrease in maximum lake extent, will help to reconstruct the geomorphic integration of the Humboldt River system, and will contribute to explaining the geographical distribution of aquatic biota in the (presently) closed drainages of the western and central Great Basin.