F. A. Swenson
1968
<p><span>The </span>artesian<span> </span>basin<span> of the </span>Dakotas<span> has been studied for many years. The widely held concept has been that </span>recharge<span> enters the equivalents of the </span>Dakota<span> Sandstone, where they are exposed on the flanks of the Black Hills, and moves through this formation to the area of maximum development of the aquifer in eastern North </span>Dakota<span> and South </span>Dakota<span>. Some anomalies, difficult to explain by this concept, have remained unresolved. According to the </span>theory<span> here proposed, </span>recharge<span> enters the Lower Mississippian Pahasapa Limestone and the underlying Englewood Formation where they are exposed on the flanks of the Black Hills. The Pahasapa is in part the equivalent of the Lower and Upper Mississippian Madison Group. The limestones are very cavernous where exposed on the flanks of the Black Hills, and seemingly in the subsurface as well. Streams flowing east from the Precambrian core of the Hills lose virtually all their flow in crossing the cavernous limestones. Widespread karst topography was developed on the Madison during the erosion period which preceded deposition of the Pennsylvanian and Permian Minnelusa Formation. Water moves freely through the cavernous limestone with little head loss for more than 100 miles east of the Black Hills. Pre-</span>Dakota<span> erosion beveled all older rock units and removed many of the intervening beds younger than the Madison. Oil tests indicate that less than 200 feet of strata separate the Madison and </span>Dakota<span> in northern South </span>Dakota<span> east of the Missouri River; this is in marked contrast to the 1800 feet of intervening beds near Rapid City. It is believed that in a zone east of the Missouri River in northern South </span>Dakota<span> and adjacent North </span>Dakota<span>, water which has moved through the limestone more than 150 miles from the Black Hills moves upward into the basal part of the </span>Dakota<span> Sandstone. Much of the water developed in the area of major water use from the </span>Dakota<span> Sandstone has moved a relatively short distance through this formation. The chemical character and </span>artesian<span> pressure of water in the </span>Dakota<span> are influenced significantly by </span>recharge<span> from the Madison Group. West of the zone of </span>recharge<span> the water is highly mineralized and largely of a sodium chloride type. Along the zone of </span>recharge<span> and toward the southeast corner of South </span>Dakota<span>, an area of natural discharge, the water generally is of the calcium sulfate type. North of the Precambrian Sioux Quartzite and east of the calcium sulfate water is an area which has sodium sulfate water. It is inferred that this change results from natural base-exchange softening of the calcium sulfate water as it moves eastward through the </span>Dakota<span> Sandstone.</span></p>
application/pdf
10.1130/0016-7606(1968)79[163:NTORTT]2.0.CO;2
en
Geological Society of America
New theory of recharge to the artesian basin of the Dakotas
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