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An uneven erosion surface separates calcareous sedimentary rocks above and vesicular andesite porphyry below at the Guayacan mine of central Chile. Channel-like depressions filled with sedimentary rock flank elongate, stratiform bodies of disseminated copper ore which impregnate the vesicular crests of andesite lava flows. The "channels" lie parallel to and mark the margins of tongues of lava. Erosional features...

The iron ores of Minas Gerais, Brazil, fall into two categories: (1) hypogene hematite ore averaging 66 percent or more Fe, and (2) lower-grade supergene ores. Most ore now extracted is high-grade hypogene ore; lower-grade supergene ores will be of much future value. All supergene ores formed by weathering of itabirite, a metamorphosed oxide-facies iron formation averaging about 38 percent Fe and 44 percent Si02. The Caue Itabirite crops out for...

The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper...

The apical parts of large volcanoes along the East Pacific Rise (islands and seamounts) are encrusted with rocks of the alkali volcanic suite (alkali basalt, andesine- and oligoclase-andesite, and trachyte). In contrast, the more submerged parts of the Rise are largely composed of a tholeiitic basalt which has low concentrations...

Rigid plastic collars of one to three colors proved useful for recognition of individual Canada geese (Branta canadensis). The collars did not seem to affect the behavior of the geese, and there was little mortality caused by their use. In good light, bright colors are visible through a 20-power spotting...

Isotopic composition of lead and strontium has been determined in a series of rock samples from two islands on the Mid-Atlantic Ridge. Both interand intra-island variations exist in the abundance of radiogenic isotopes of both elements. Lead from basalt of Ascension Island has a Pb206-Pb204 ratio of 19.5, while the corresponding...

Larger Foraminifera from the middle Eocene of Florida and southern Georgia are discussed, including 2 new species, and their geographic and stratigraphic distribution, not only in the U. S., but also at selected localities in the Caribbean region, is analyzed. Several species not previously reported from the U. S. are...

Work toward establishing a program of international cooperative studies in scientific hydrology began about 4 years ago, and the IHD (International Hydrological Decade) will begin under international auspices in January 1965. This program will be highly important for hydrology and hydrologists, and it should contribute greatly to human welfare in the future. Fortuitously, the opening year...

The biblical Jordan River Valley, which extends from Lake Tiberias (the Sea of Galilee) to the Dead Sea, is decidedly similar to the Jordan River Valley of Utah, which joins Lake Utah and Great Salt Lake. Both Jordan Rivers drain relatively large fresh-water lakes and also are major sources of discharge into large salty lakes that have no outlets to the ocean.The...

Most of the granitic rocks in the Bokan Mountain area, southeastern Alaska, are early Paleozoic (probably Ordovician) judged by potassium-argon and lead-alpha age measurements. The Bokan Mountain Granite, the youngest intrusive unit in the area, belongs to a Mesozoic plutonic episode. These age measurements are the first direct evidence for...

No abstract available....

The fugacity of sulfur along the curve representing the univariant equilibrium assemblage, chalcopyrite + bornite + pyrite + vapor, has been determined by the electrum tarnish method (1). The conditions of the equilibrium may be expressed by the equation (TP) - /°s 2 (T, 1 atm) = -50,730 + 56.95T (cal.) (350 - 500° C) (T in °K). With gentle curvature, the line...

Officer's Cave is the uppermost of four rapidly eroding cave levels constituting a cavern complex about 700 feet long developed chiefly in clay and silt. Its outer room is 35 feet by 43.5 feet by 100 feet and slopes about 45° east into the western end of a narrow linear hill called Officer's Cave Ridge. Dry valleys, blind valleys, hanging valleys, sinkholes, pipes,...

Pre-Tertiary rocks of the Blue Mountain region of central and northeastern Oregon comprise three major sedimentary and volcanic sequences and two distinct intrusive magma series. The ages of the sedimentary-volcanic sequences are Paleozoic, Late Triassic-Late Jurassic, and middle Cretaceous (Albian to Cenomanian), respectively. The earlier intrusive magma series ranges in composition from peridotite to albite granite and was emplaced during the major...

Profiles of the basement surface in western Kansas and Nebraska were constructed by drawing smooth curves through the shallowest depths estimated from aeromagnetic anomalies along six widely spaced traverses. Ratios of inferred-depth-to-basement to true depth along the traverses ranges from 0.7 to 1.0. Clusters of shallow depth estimates commonly yield an average estimate within 15 percent of the true depth....

Granite gneiss, with an age of approximately 2.5 billion years, in the Black Hills, South Dakota , provides a link betweeen ancient rocks in western Wyoming and Montana and in eastern North and South Dakota and Minnesota. The discovery suggests that early Precambrian rocks covered an extensive area in northcentral...

THIS note reports measurements made in an attempt to determine: (1) the possible effect of xenoliths on whole-rock basalt age determinations; (2) whether or not potassium-argon age determinations on xenoliths in basalt might approximate the age of the basalt flow. The field location is in the...

THROUGH a fortunate circumstance, a recording magnetometer was operating in the city of Kodiak, 30 km north-west of the surface trace of a fault zone along which movement occurred at the time when the earthquake occurred in Alaska on March 27, 1964. Fortunately, too, the instrument...

Characteristic minerals are psilomelane, hollandite, cryptomelane, and coronadite, more rarely ramsdellite and pyrolusite. Host rocks are Mn-deficient; 80 percent of examples are middle to late Tertiary layered volcanics. Though deposits are shallow, mostly mined to only 100-200 feet (maximum 500 feet), a hypogene origin is...

The ratio of cation to hydrogen-ion concentration is used as a basis for coordinating many observed varieties of silicate rock alteration. Low ratios drive alteration from feldspar through sericite, montmorillonite, or paragonite, toward kaolinite or pyrophyllite. Principal controls of ratio are reactions with wall rock,...

Deposits of ferruginous nickeliferous lateritic soils formed by weathering in place of ultramafic rocks occur at several places in northwestern California and southwestern Oregon, mostly in the Klamath Mountains province. Most of the deposits have been derived from relatively fresh peridotite, although at least one...

A well drilled for geothermal power near Salton Sea in Imperial Valley, Calif., is 5,232 feet deep; it is the deepest well in the world (1962) in a high-temperature hot spring area. In the lower half of the hole temperatures are too high to measure with available equipment, but are...

Right-lateral separation of about 120 miles along Chatham Strait Fault is suggested by apparent displacement of major geologic features on opposite sides of the fault....