THE ORIGIN OF SALT CITY (SYRACUSE) BRINES: HALITE, FORMATON FLUIDS, AND INDUSTRIAL CONTAMINATION

Onondaga Lake, northwest of Syracuse, New York occupies the head of the eastern-most through valley of the Finger Lakes. The valley extends from Onondaga Lake to the Tully Moraine, 35 kilometers to the south. Groundwater below the lake and valley consists of at least two brines, a halite derived Na-Cl type brine formed from dissolution of Salina Formation salt, and a calcium-chloride type brine migrating from soda-ash waste beds on the western and southern margins of the Lake. These brines may be interacting with a third type of brine associated with hydrocarbons in the Appalachian Basin. The distribution of these brines below Onondaga Lake, and Onondaga Valley, and how they are mixing, is poorly known. The brine derived from dissolving halite consists mostly of sodium and chloride, with minor sulfate and hardness and almost non-detectable bromide. In contrast, the industrial brine mostly consists of calcium and chloride. Finally, Appalachian Basin brines are sodium-chloride type waters with measurable bromide and hardness. This paper presents the results of characterizing these three brines from scatterplots and other fingerprinting methods of solutes analyzed in pore water squeezed from 12 cores drilled through the floor of Onondaga Lake and Onondaga Valley. Pore water was analyzed for specific conductance, Ca, Mg, Na, K, SO4, Cl, and Br. The three kinds of brines could be clearly fingerprinted from bivariate and semi-logarithmic Schoeller Diagrams. For example, a plot of Br versus Cl shows that Salina Formation Brine and Appalachian Basin Brines mix at the periphery of Onondaga Lake. Plots of Ca/Na versus depth indicate that a plume of industrial brine may be migrating underneath Onondaga Lake proper.