The hydrogeology and chemical quality of ground waters from the lower Paleozoic aquifers in the Tri-State region of Kansas, Missouri, and Oklahoma
By P. Allen Macfarlane and Lawrence R. Hathaway
Originally published in 1987 as Kansas Geological Survey Ground Water Series 9. This is, in general, the original text as published. The information has not been updated. This publication is also available as an Acrobat PDF file (3 MB).
The lower Paleozoic aquifer system is an important natural resource in southeast Kansas, southwest Missouri, and northeast Oklahoma (the Tri-State region). This system consists of aquifers in the limestones and dolomites of Mississippian and Cambrian-Ordovician age. Three ground-water regions can be broadly defined in the Cambrian-Ordovician aquifer reflecting the mixing of low total-solids recharge waters from the Ozark region and high total-solids sodium chloride brines in Kansas and Oklahoma. To the west of the freshwater portion of the aquifer is a reservoir containing scattered accumulations of oil. This study was undertaken to define the regional hydrogeology and variations in ground-water chemical quality of this aquifer system in the Tri-State region.
Abundant supplies of freshwater suitable for most uses can be obtained from aquifers in the Cambrian-Ordovician rocks in Crawford and Cherokee counties in Kansas, in southwest Missouri, and in northeast Oklahoma. This is the major aquifer system in the study area. Aquifers in Mississippian rocks supply most domestic needs in parts of the study area but are not widely used.
Ground waters in the lower Paleozoic aquifer system generally move westward across the study area from recharge areas in the Ozarks of Missouri. Static water-level declines since wells began pumping have been generally less than 50 ft (15 m) over most of the area except where large cones of depression have been created. Static water-level declines in excess of 450 ft (135 m) have occurred in the Miami, Oklahoma, area and in excess of 150 ft (45 m) in northwestern Jasper County, Missouri. Both the Mississippian and Cambrian-Ordovician aquifers seem to be interconnected in portions of the Tri-State region. The spatial variations in ground-water chemistry in the Cambrian-Ordovician aquifer are largely consistent with this mixing phenomenon. A similar zonation probably occurs in the Mississippian aquifer, but not enough data were collected during the study to fully describe the mixing of fresh and saline waters in this aquifer.
The lower Paleozoic aquifers (principally the Cambrian-Ordovician) are an important resource producing freshwater for municipal water supplies, industry, and agriculture in southeast Kansas, southwest Missouri, and northeast Oklahoma (the Tri-State region). These aquifers produce oil in Labette and Montgomery counties in Kansas. Aquifers in undifferentiated Mississippian and Cambrian-Ordovician carbonate rocks comprise the lower Paleozoic aquifer system. The Mississippian and Cambrian-Ordovician aquifers are generally separated by confining layers of shale and dense dolomite except in areas of southern Cherokee County, Kansas; northern Ottawa County, Oklahoma; and Jasper and Newton counties, Missouri. Both aquifer systems seem to be interconnected in these areas on the basis of the hydrogeochemistry and the hydraulic-head differences between the aquifers. The undifferentiated Mississippian is unconfined where the unit is at the surface in the southeastern part of the study area. Along the Kansas-Missouri state line, ground-water flow in both aquifers is generally westward except in the vicinity of municipal and industrial well fields where large-scale withdrawals of ground water may have changed the prevailing direction of ground-water flow. Very little hydrologic data are available for the Mississippian aquifer. Three ground-water regions can be broadly defined in the Cambrian-Ordovician aquifer reflecting the mixing of fresh and saline waters. From east to west, one encounters: 1) a freshwater portion containing Ca-HCO3-type ground waters; 2) a transition zone where the total dissolved solids and the contribution from NaCl-type waters increase rapidly in a westerly direction; and 3) a saline portion containing sodium chloride brines. The Mississippian outcrop is the approximate boundary of the freshwater transition zone. The 2,500 mg/L isochlor is taken as the boundary of the saline transition zone. Sulfide concentrations >0.2 mg/L are associated with ground waters west of the Mississippian outcrop. These three zones in the Cambrian-Ordovician aquifer evolved over geologic time as freshwater recharge entering the aquifer in the Ozark region of Missouri flushed saline waters from large portions of the study area. The distribution of radium-226, uranium, and uranium-234/uranium-238 activity ratios in waters from the Cambrian-Ordovician aquifer is consistent with a freshwater transition zone and saline hydrogeochemical partitioning of the aquifer. The manner in which these parameters change from the freshwater to transitional environments suggests that the source of radium-226 in the eastern part of the transition zone is largely from the radioactive decay of uranium precipitated on surfaces in the carbonate aquifer in the comparatively recent geologic past. The relative enrichment of radium-226 in waters from the saline portion of the aquifer system is problematic.
The authors would like to acknowledge the help and support of the following people and organizations. We would like to particularly thank H. Dean Bolick for sharing his knowledge of the Tri-State region with us, for giving guidance, and for letting us use his back office as a field laboratory. We would also like to thank Bill Roberts, now deceased, and Layne-Western for their assistance. Credit also should be given to Wes Karnes of Earth Scientists, Ltd., for providing well logs and for locating oil wells for water sampling. John Bashor also provided assistance by locating recently drilled oil-field water-supply wells and supplying much needed well logs. We also would like to thank D. O. Whittemore, O. K. Galle, and T. C. Waugh at the Kansas Geological Survey and their student assistants for ground-water chemical -quality analytical services. Radium-isotope analyses were performed by the Central Laboratory, U.S. Geological Survey, Denver, Colorado. Uranium analyses were performed by J. B. Cowart, Florida State University. Support for this study was provided by the Kansas Geological Survey and the Kansas Department of Health and Environment. We would also like to thank those who critically reviewed this manuscript: Don Jorgensen and Bob Leonard, U.S. Geological Survey; E. E. Angino, Department of Geology, University of Kansas; and Don Miller, Missouri Geological Survey.
Kansas Geological Survey, Geohydrology
Placed on web Sept. 1, 2010; originally published 1987.
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