Paper No. 80-6
Presentation Time: 2:30 PM
PROSPECTS FOR A MILLION-YEAR HISTORY OF THE MONO LAKE BASIN FROM A LONG DRILL CORE
ZIMMERMAN, Susan Herrgesell, Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, P.O. Box 808, L-397, Livermore, CA 94550, HEMMING, Sidney R., Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, DEINO, Alan L., Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, JAYKO, Angela S., Earth Surface Processes Team, U.S. Geological Survey, 3000 East Line St, Bishop, CA 93514, COLMAN, Steven M., University of Minnesota Duluth, Large Lakes Observatory and Dept. Geol. Sci, Duluth, MN 55812 and STARRATT, Scott W., U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025-3591
The Mono Lake basin is an extensional basin on the eastern flank of the Sierra Nevada, and has long been occupied by a lake of variable size, depth, chemistry, and hydrology. It has provided a catchment for pyroclastic products of Pliocene and Pleistocene volcanic activity from surrounding volcanic centers of Long Valley, Inyo-Mono Craters and the Bodie Hills. Dramatic glacial canyons, many containing multiple sets of moraines, terminate in the lake basin, making the lake a proximal archive of glacial sediment and run-off from the Sierra Nevada. The combination of large fluctuations in lake level with volcanic and hydrothermal activity makes Mono Lake a geochemically intriguing water body in which to explore biological and mineralogical interactions.
The last glacial period at Mono Lake is preserved in one of the classic Quaternary lake sequences in the western US, the Wilson Creek Formation (WCF). The rock flour- and tephra-rich sediments of the WCF are exposed in multiple creek beds around the basin, and preserve rich, high-quality records of paleoclimatic and paleomagnetic change, as well as an exceptional record of regional volcanism. The post-glacial record remains elusive, in deep water buried beneath disrupted deposits resulting from the uplift of Paoha Island ~300 years ago, and in shallower water interrupted by dramatic lowstands during intervals of arid climate. The great potential for a record of older glacial-interglacial climate variability and volcanic activity is indicated by deformed and incomplete exposures on Paoha Island, which contain interbedded glacial sediment, diatomites, and multiple tephras.
We propose that a long drill core in Mono Lake could connect these disparate archives and produce a unique record of past changes in the magnetic field, the climate system, regional volcanic and tectonic activity, and extreme biogeochemistry. Seismic data and the stratigraphy of multiple gravity and piston cores, along with other geophysical data, provide a framework for selecting coring sites that optimize the paleoclimatic, paleomagnetic, volcanologic, and biogeochemical records that can be recovered from the Mono Lake basin.
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