Second report on a cooperative investigation of the composition of two silicate rocks
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Bulletin↗
Geology topics
Rollin Elbert Stevens
Publications and source records attributed to Rollin Elbert Stevens.
Field method for the determination of zinc in soils
A method is described for the field estimation of total zinc in soils. A small sample of soil is fused with potassium bisulfate, the fused mass dissolved in water, buffered at pH 4 to 5.5 with acetate buffer, and sodium thiosulfate added to form complex ions with metals that might cause interference. Measured increments of the sample solution are added to a carbon-tetrachloride-dithizone solution, with vigorous shaking after each addition, until a standard color is obtained in the organic phase. Under favorable conditions up to 60 determinations per day can be made by one man. Comparisons of data obtained by the field method with accurate laboratory analyses of the same samples indicate that the method is sufficiently reliable for reconnaissance surveys.
Economic Geology↗
The chromograph, a new analytical tool for laboratory and field use
Water supplies in the Greater Atlanta Region, Georgia, are obtained mainly from surface-water sources, but there is concern that these sources may be unable to meet rising demands. This study indicates that large quantities of good-quality ground water are obtainable from selected sites in the crystalline rocks of the area. Hydrogeologic investigations of 1,051 wells that produce 20 to nearly 500 gallons per minute revealed that large supplies can be developed where favorable structural, stratigraphic, and topographic features result in localized increases in bedrock permeability. These features are described in detail and methods are presented for using them in selecting sites for locating high-producing wells. Most of the site-selection methods are applicable to the north half of the report area, which has rectangular and trellis drainage systems, but their use is restricted in the south half where a dendritic drainage system predominates. Borehole geophysical logs and core drilling revealed that some of the highest production wells derive water from 1- to 8-inch wide horizontal fractures. These fractures occur in a variety of topographic settings and are believed to be stress-relief fractures. (USGS)
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