HR: 0800h
AN: PP11A-0243    [Abstracts]
TI: Leachable Li and Mg Evidence for Hydrological Changes in the Mono Basin, CA, USA
AU: * Sahajpal, R
EM: rahulsahajpal@yahoo.com
AF: Queens College School of Earth and Environmental Sciences, 65-30 Kissena Blvd, Flushing, NY 11367, United States
AU: Hemming, N
EM: hemming@ldeo.columbia.edu
AF: Queens College School of Earth and Environmental Sciences, 65-30 Kissena Blvd, Flushing, NY 11367, United States
AU: Hemming, N
EM: hemming@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964, United States
AU: Zimmerman, S R
EM: zimmerman17@llnl.gov
AF: Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA 94550, United States
AU: Hemming, S R
EM: sidney@ldeo.columbia.edu
AF: Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory of Columbia University, 61 Rt. 9W, Palisades, NY 10964, United States
AB: Hydrology in closed basin lakes, such as Mono Lake of the US western Great Basin, is sensitive to regional climate changes. Lake level history of the Mono Basin has been put into a precise age framework using the paleomagnetic intensity of the Wilson Creek Formation sediments to North Atlantic records, and accordingly Greenland's GISP2 oxygen isotope record (Zimmerman et al., 2006, EPSL, v. 252, pp. 94- 106). This allows correlation of the lake level indicators and Greenland climate at high resolution. The physical evidence for lake level, based on the association of strata in near shore terraces, can be confidently correlated to proxies of lake chemistry preserved in the strata. We have tested the application of leachable Li, following the procedure developed by Bischoff et al. (1997, Quaternary Research, v. 48, pp. 313-325) for Owens Lake. At Owens Lake there is a positive correlation between salinity based on diatoms with leachable Li concentrations. In contrast, at Mono Lake the leachable Li concentration follows the bulk carbonate concentration, generally correlating low lake levels (high salinity) with low leachable Li concentrations. Our preferred explanation for both the carbonate and leachable Li concentrations is based on the fact that the Mono Basin rarely overflows, and therefore precipitation of minerals during evaporation leads to chemical divides (Garrels and Mackenzie., 1967, in "Equilibrium Concepts in Natural Water Systems", W. Stumm, Ed., pp. 222-242). As Li behaves conservatively compared to elements like Ca2+ and Mg2+, it might be expected that the leachable Li would be higher when lake level is lower. However, the host for the Li appears to be Mg-smectite. Therefore, the concentration of leachable Li in the sediment is controlled by the concentration of Mg-smectite, as well as the Li/Mg of the water from which the Mg- smectite precipitated and the Kd of the Li into the Mg-smectite. We are studying the Li and Mg systematics of these samples in order to deconvolve these factors and contribute to paleo-hydrological studies of this and other closed basin lakes.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4914 Continental climate records
DE: 4924 Geochemical tracers
DE: 4926 Glacial
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting