THE HOLOCENE DIATOM FLORA OF BIG SODA LAKE, CHURCHILL COUNTY, NEVADA

Although the physical characteristics of Big Soda Lake (BSL; 39.53^oN, 118.87^oW; 1,251 masl) in the Great Basin were described in the late 19^th Century (Russell, 1885), the potential for generating a record of climate variability there has been ignored in favor of larger lakes in the region. In conjunction with a multi-proxy study of a 9.30-m-long sediment core collected from the lake in 2010, 61 samples were analyzed for siliceous microfossils.

Two distinct diatom assemblages are present in the core. Between 9.30 m and 4.35 m the flora is dominated by poorly preserved planktonic taxa (Stephanodiscus spp. and Cyclotella spp.). These species are found in the Holocene records of other fresh to subsaline lakes in the Great Basin (Walker Lake, Ruby Lake), and adjacent middle and high elevation lakes. Tychoplanktonic and benthic species are absent. The upper 4.30 m of the core is dominated by species that prefer subsaline to brackish conditions. Many of the species in this assemblage are presently found in Mono Lake and several other shallow lakes and marshes in the Great Basin. The observed change in the diatom assemblages occurred about 5,000 cal yr B.P., and because BSL has a small watershed and groundwater contributes significantly to lake volume, it is likely that the abrupt shift in diatom assemblages is due to changes in regional climate.

Russell, I.C., 1885, Soda lakes, near Ragtown, Nevada: In: Geological History of Lake Lahonton, a Quaternary lake of northwestern Nevada: USGS Monograph 11, p. 73-80.