Exceptionally fast growth rate of <100-yr-old tufa, Big Soda Lake, Nevada; implications for using tufa as a paleoclimate proxy
- Cenozoic
- chemically precipitated rocks
- Churchill County Nevada
- crater lakes
- geochemistry
- ground water
- growth rates
- Holocene
- hydrochemistry
- lacustrine environment
- lake-level changes
- lakes
- limnology
- mixing
- modern
- mounds
- Nevada
- paleoclimatology
- precipitation
- Quaternary
- sedimentary rocks
- surface water
- tufa
- United States
- upper Holocene
- Fallon Nevada
- Big Soda Lake
Large tufa mounds (>3 m tall, with a basal circumference of 5 m) have been discovered on the margin of Big Soda Lake, Nevada, USA. These tufa mounds are rooted at a maximum of 4 m below the current lake surface and are actively forming from groundwater seepage, which can be seen emanating from the top of the tufa mounds. Big Soda Lake is a volcanic crater lake whose water level is maintained exclusively by groundwater. The age of the tufa mounds is well constrained because prior to the development of the Newlands Irrigation Project in 1907, the water level was approximately 18 m lower than the current lake level. The vertical columnar nature of the tufa mounds indicates that they formed under the lake and not subaerially. Thus, the tufa mounds are <100 yr old and have grown at a rate > or =30 mm/yr. Stable oxygen and carbon isotope analyses of tufa carbonate compared to isotopic analyses of groundwater and lake water and hydrochemical data indicate that the fluids responsible for their precipitation are a simple mixture of modern groundwater and lake water and do not reflect a recent climate signature. The exceptionally fast growth of the tufa mounds indicates that large tufa deposits may form almost instantaneously in geologic time. Given this potential for rapid growth and the fact that variations in isotopic compositions of tufa deposits have been interpreted in terms of changes in paleoclimate and changes in the composition of recharge water over thousands of years, care should be taken when trying to determine the significance of variations in isotopic or chemical compositions of tufas that may have been caused by mixing with groundwater.