pool during the late Wisconsin stage of glaciation at the base of a waterfall formed by the retreating glaciers, which is the reason for its extreme depth relative to a small surface area. The outflow for FGL runs underneath the Erie Canal, which is located within 300 m of the north shore of the lake. FGL is currently located in Green Lakes State Park, and since 1933, large quantities of sand have been dumped on the shore of the north end to create a swimming area. Biogeochemistry Fayetteville Green Lake is located in the Oswego River-Lake Ontario drainage system, and receives surface water from Round Lake. The water column is chemically stratified into an oxygenated upper portion (mixolimnion) and a euxinic deeper portion (monimolimnion). The stratification is maintained through the large input of ground water rich in dissolved solids to the deeper portion of the lake. The difference in the dissolved solids (Ca, Mg, SO4) between the water input to the surface and water input to the deep creates the permanent stratification observed. FGL has a sulfate concentration around 13.5 mmol/L (about half that of modern seawater) which is derived from groundwater input to the deep portion of the lake. A well-developed separation in a body of water due to differing chemistries is present between 18 and 20 m depth. The water below the chemocline is anoxic and sulfidic, and at the chemocline is a dense layer of purple sulfur bacteria which makes the water appear pink. The purple sulfur bacteria thrive in the anoxic waters and use the sulfide from the deeper water in their chemosynthesis. The color of the lake is created by the total dissolved solids (from the groundwater input) which disperse the sunlight creating a greenish color. Annual whiting events occur in FGL, due to the large Synechococcus population in the lake. Calcite precipitates in microenvironments surrounding the Synechococcus and this is believed to dominate the whiting events. Calcite precipitation is common year round at FGL, and this leads to the carbonate crust that surrounds most of the lake, and covers branches and other material that falls below the surface. Dead Man's Point is a notable example of this, and is classified as a thrombolitic bioherm. Geologic significance The meromictic character of FGL is believed to represent a possible analog to ancient ocean environments during the Precambrian and during times of environmental stress. (i.e. mass extinction