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Hydrochemical Facies in a Tertiary Basin in the Milligan Canyon Area, Southwest Montana
Author(s) -
Krothe Noel C.,
Bergeron Marcel P.
Publication year - 1981
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1981.tb03486.x
Subject(s) - gypsum , calcite , sulfate , bicarbonate , geology , dolomite , calcium , dilution , dissolution , karst , mineralogy , hydrology (agriculture) , chemistry , paleontology , physics , organic chemistry , thermodynamics , geotechnical engineering
Equilibria studies of ground‐water chemistry in a synclinal basin at Three Forks, Montana indicate that most waters in the Tertiary sediments and Madison Group carbonates are calcium‐bicarbonate, or calcium‐sulfate waters which are supersaturated with respect to calcite. Calcium concentrations range from 13 to 426 mg/l, bicarbonate concentrations range from 112 to 328 mg/l and sulfate concentration varies between 29 to 114 mg/l. Sodium concentration is between 10 and 312 mg/l, producing sodium‐bicarbonate waters in some areas. Water‐level data were used to construct a potentiometric map that shows flow direction to the east. The water evolution along the flow path is from calcium‐bicarbonate in the recharge areas, to calcium‐sulfate in the center of the area, and finally sodium‐bicarbonate in the discharge area. This evolutionary sequence can be explained by calcite, dolomite and gypsum dissolution, ion exchange, sulfate reduction and dilution by recharging waters from the Elkhorn Mountains Volcanics.