Articles

A metasomatic origin seems established for large parts of the granite phacoliths in the northwest Adirondack Mountains, New York. This conclusion is based upon the discovery and detailed mapping of a blurred but widespread stratigraphic sequence in the phacoliths. Highly complicated patterns of relict beds are defined by alternations of granitic gneiss, amphibolite, oligoclase-quartz gneiss, and a

Natural gamma-radioactivity patterns in Washington County, Maryland, reflect the principal variations in lithology. The highest radioactivity is associated with the more argillaceous parts of the geologic section and with soils derived from high-potassium carbonate rocks. Surface radiation intensity ranges from about 5 to 30 microroentgens per hour, of which the rocks contribute 30 to 90 percent.

No abstract available. 

he Reef Creek fault is in northwestern Wyoming, a few miles east of the northeast border of Yellowstone National Park. It lies within the area covered by the more extensive Heart Mountain fault. Like that fault, it is a décollement or detachment fault in which strata became detached along a basal shearing plane and moved laterally on a slightly inclined fault surface. At the most northwesterly exp

When high pressure (250 to 300 kilobars) was applied suddenly (shock-loading) to gabbro, the plagioclase was transformed to a noncrystalline phase (maskelynite) by a solid-state reaction at a low temperature, while the proxene remained crystalline. The shock-loaded gabbro resembles meteorites of the shergottite class; this suggests that the latter formed as a result of shock. The shock-loading of

There is a vital need for hydrologic data representing various environments that are free from the effects of man's activities. Without such data hydrologists will be stymied in distinguishing hydrologic changes caused by man from those caused by climate. To provide this background information, the U. S. Geological Survey is planning a nationwide hydrologic bench‐mark program in which runoff, tran

Vast quantities of saline ground water await new commercial uses and economical demineralization processes for recognition as a valuable resource. Saline ground water is more widely distributed than any other natural resource, occurring throughout the United States and in geologic formations ranging from the oldest to the youngest. The Coastal Plain has the greatest reserve of fresh water in the c

Gibson Peak pluton is the most discordant of several dominantly granitic intrusions in the Trinity Alps of northern California. It formed during Nevadan (Late Jurassic) deformation by emplacement of at least five discrete rock units that define a successively more silicic series, ranging from hypersthene gabbro to trondhjemitic tonalite. Contact features suggest that several units were incompletel

A composite dike of probable Tertiary age intrudes Precambrian granodiorite 6 miles north of Klondyke, Arizona. The dike is exposed discontinuously for about 1500 feet along the strike and has a core of porphyritic rhyolite 15-20 feet thick flanked by coarsely porphyritic andesite 1-2 feet thick. Field evidence indicates that the rhyolite is later than the andesite but that the core of the origina

The influence of individual factors such as geologic and hydrologic characteristics of environment, biologic activity in soil, and pollutants on ground‐water composition is discussed. Aspects of chemical equilibria in ground water, sorption reactions, carbonate equilibria, chemistry of iron, and factors altering equilibria are presented.

No abstract available.

The old surface that extends over a long north-striking belt in northern Chile probably reached the mature stage of erosion by middle Tertiary time. Low areas are mantled by the piedmont deposits of the pampa, and the higher parts exhibit rock decay, oxidation, leaching, and super-gene enrichment of sulfide mineral deposits as a result of deep weathering. The surface and its deposits are deeply er