Geology topics
Publications and source records attributed to J. S. Downey.
The geochemistry of water in five aquifers and two confining units in the Williston Basin of the Northern Great Plains is similar and is controlled by halite dissolution. In areas outside the Williston Basin ground-water is fresh and controlled by the solution chemistry of carbonate and sulfate minerals.
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The Fairbanks-North Star Borough, Alaska, landfill is located on silt, sand, and gravel deposits of the Tanana River flood plain, about 3 miles south of the city of Fairbanks water supply wells. The landfill has been in operation for about 25 years in this sub-arctic region of discontinuous permafrost. The cold climate limits biological activity within the landfill with corresponding low gas and leachate production. Chloride concentrations, specific conductance, water temperature, and earth conductivity measurements indicate a small plume of leachate flowing to the northwest from the landfill. The leachate remains near the water table as it flows northwestward toward a drainage ditch. Results of computer modeling of this local hydrologic system indicate that some of the leachate may be discharging to the ditch. Chemical data show that higher-than-background concentrations of several ions are present in the plume. However, the concentrations appear to be reduced to background levels within a short distance along the path of groundwater flow from the landfill, and thus the leachate is not expected to affect the water supply wells. (USGS)
As part of the paleohydrology study of the Yucca Mountain Project, strontium-isotope analyses of carbonate deposits, ground water, and major rock reservoirs of strontium are in progress. This paper presents a summary of the strontium-isotope data obtained through 1989. Calcium carbonate is ubiquitous in the vicinity of Yucca Mountain, where it occurs as pedogenic horizons and rhizoliths, small veins and fracture fillings in Tertiary volcanic rocks, large veins and masses along faults, and freshwater and marine limestones. With the exception of marine limestones, which are Paleozoic, the calcium carbonate has been precipitated directly from water during the past 107 years. This paper reports strontium-isotope compositions of the following carbonate groups: 1) limestones of the Paleozoic basement, 2) calcite-silica veins, 3) small calcite veins, 4) pedogenic carbonate deposits, and 5) spring deposits (i.e., tufa). The authors have also analyzed the strontium from samples of Tertiary volcanic rocks and from ground water.
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Rocks of Paleozoic and Mesozoic age underlie the entire northern Great Plains of the United States. These rocks form 5 artesian aquifer systems that are recharged in the mountainous areas of Montana, South Dakota, and Wyoming and extend more than 600 miles to discharge areas in the northeastern part of North Dakota and in the Canadian Province of Manitoba. Generally, the principal direction of flow in each aquifer is deflected to the north and south around the Williston basin. Flow through the Williston basin is restricted because of geologic structure, and decreased permeability of rocks in the deeper parts of the basin. Major fracture systems or lineaments traverse the geologic section and are either vertical or horizontal conduits, or barriers to, groundwater flow. Vertical leakage from the aquifers is restricted by shale of minimal permeability, halite beds, and stratigraphic traps or minimal-permeability zones associated with petroleum accumulations. Interaquifer leakage appears to occur through and along some of the major lineaments. During the Pleistocene Epoch, thick ice sheets completely covered the discharge areas of the bedrock aquifers. This effectively blocked flow northeastward from the system and, at some locations, it may have caused a reversal of flow. The existing flow, system therefore, may not have reached hydrologic equilibrium with the stress of the last glacial period. (USGS)
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Lists of machine-readable data files were developed for the Madison Limestone and Northern Great Plains Regional Aquifer System Analysis (RASA) projects. They are stored on magnetic tape and available from the U.S. Geological Survey. Record format, file content, and size are given for: (1) Drill-stem-test data for Paleozoic and Mesozoic formations, (2) geologic data from the Madison Limestone project, (3) data sets used in the regional simulation model, (4) head data for the Lower and Upper Cretaceous aquifers, and (5) geologic data for Mesozoic formations of the Northern Great Plains. (USGS)
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No abstract available.