Date of Award

1972

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology

First Advisor

L. Clayton

Abstract

The Spiritwood Lake study area is in a generally undulating to rolling glacial plain 17 miles north and east of Jamestown, North Dakota. Spiritwood Lake is about 50 feet below the surface of the bedrock plain in a former melt-water channel. In the study area, glacial drift unconformably overlies the Pierre Shale, the youngest pre-Pleistocene sediment. The boundary between the two units is marked by a zone of shattered Pierre Shale. The top of this shattered zone forms a plain of moderate relief which probably was the preglacial surface of the study area.

Two large valleys can be distinguished in the bedrock surface of the study area. One valley is 70 feet below the general bedrock surface and was part of a glacial drainage. The second is a channel 200 feet below the bedrock surface and is part of the preglacial drainage.

The Pleistocene sediment of the study area was deposited by glacial, fluvial, lacustrine, and eolian processes. The Pleistocene sediment includes sediment of three facies: till, sand-gravel, and clay-silt.

The potential approach to groundwater was applied to the Spiritwood Lake study. Potential is an expression of the energy of a system. All forms of energy involved in groundwater-flow systems can be expressed in terms of potential. Gravitational, hydrostatic-pressure, velocity, thermal, chemical, and “other” potentials exist for every point in a groundwater-flow system. In the potential approach to groundwater each potential is expressed in terms of head (energy is expressed by the unit weight of water). This allows the comparison of the various types of energy in a groundwater-flow system. Potentiometric surfaces of the various potentials can be contoured either singularly or collectively. Mathematical models can be applied to the various potentials.

Saturation indices and chemical ratios are useful in groundwater studies, especially where they are used in conjunction with the potential approach.

There are two types of groundwater-flow systems in the Spiritwood Lake area, local and intermediate. The local groundwater-flow systems are between adjacent topographic highs and lows. The local flow systems are mostly in till and do not affect the level of Spiritwood Lake appreciably. The intermediate groundwater-flow system occurs along the zone of shattered Pierre Shale between the undisturbed Pierre Shale and the overlying glacial drift. Water in the intermediate flow system moves from northeast to southwest. The level of Spiritwood Lake is controlled by discharge from the intermediate groundwater-flow system. The time required to transfer a change in hydrodynamic-potential gradient from the recharge to the discharge area of the intermediate groundwater-flow system is indicated by the time lag between the fluctuations in the water level of Spiritwood Lake and changes in precipitation.

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