Hydrogeologic Significance of Ogallala Fluvial Environments, the Gangplank
Russell G. Shepherd, Willard G. Owens, 1981. "Hydrogeologic Significance of Ogallala Fluvial Environments, the Gangplank", Recent and Ancient Nonmarine Depositional Environments: Models for Exploration, Frank G. Ethridge, Romeo M. Flores
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A “spring line” separates areas of flowing and non-flowing artesian wells completed in alluvial fan deposits of the Pliocene-Miocene Ogallala Formation southwest of Cheyenne, Wyoming. Electric and lithologic logs from water well test holes in the area permit the distinction of depositional subenvironments within and near the ancient fan.
West of the “spring line”, the Ogallala Formation coarsens upward through an aquifer unit of interbedded sand and gravel approximately 35 meters thick, representing low sinuosity fluvial channel deposits. East of the “spring line”, the same unit becomes markedly finer and is characterized by fining-upward subunits 10 to 15 meters thick, representing deposits of fluvial channels with higher sinuosities. Water wells completed in the proximal fan deposits to the west commonly produce a few hundred gallons per minute; in contrast, wells in the distal fan and in interbedded fan and lacustrine deposits to the east produce only several tens of gallons per minute or less.
Identifying the location of the distal margin of the low sinuosity deposits, and thus the “spring line”, through interpretations of depositional environments from outcrops and logs helped locate one industrial water supply in the area.
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This volume is a collection of papers that resulted from a symposium on Recent and Ancient Nonmarine Depositional Environments which was held in Casper, Wyoming on June 3 to 7, 1979. The nineteen papers may be divided into: (1) a review of recent and ancient nonmarine modes, (2) alluvial fan and fluvial deposits, (3) lacustrine deposits, (4) eolian deposits. Knowledge of the physical, biological and chemical characteristics and depostional environments on nonmarine sedimentary deposits has increased significantly over the last decade. Correspondingly, there has also been an increase in our ability to apply this knowledge to the exploration and exploitation of contained energy resources and minerals.