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At least 379 records · Page 21Linked to original sources
USGS1975

A characteristic pattern of disequilibrium in some uranium ore deposits

A redistribution of radium-226 in uranium ore deposits produces a characteristic pattern of disequilibrium in which uranium is greater than equivalent uranium in high-grade samples and equivalent uranium is greater than uranium in low-grade samples. The redistribution is a continuous process in uranium deposits, and the resulting pattern of disequilibrium is itself a system in equilibrium.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Origin of lunar light plains

Most Cayley-type Imbrian-age plains deposits and adjacent mantled slopes, including those at the Apollo 16 site, may be composed at least near the surface of ejecta from the Orientale basin, the youngest multiringed impact basin on the Moon. The distribution and apparent age of the plains deposits and preliminary data on the highly feldspathic breccias collected by the Apollo 16 crew indicate that these surficial materials are neither locally derived nor part of the Imbrium ejecta. Stratigraphic relations, crater size-frequency distributions, and dating by erosional morphology of superposed craters have established Cayley light-plains deposits as younger than the Imbrium basin and older than mare material. All such crater-dated Cayley-type plains on both the near and far sides of the Moon are contemporaneous within the limits of the technique. Furthermore, comparisons of the crater size-frequency distributions of the Hevelius Formation (Orientale ejecta) and the plains show that the Cayley and Hevelius Formations are indistinguishable in age. The surface and near-surface materials of the Apollo 16 plains, therefore, are contemporaneous with Orientale basin ejecta not with Imbrium ejecta, in which both crater densities and crater degradation are greater than in the light plains. Imbrium ejecta may, however, be present on the surface at the Apollo 16 site where excavated by craters from depth. Limited age data now available on the Apollo 16 samples are consistent with this interpretation. We conclude that rocks of Orientale provenance may be predominant on and near the surface at the Apollo 16 site. This hypothesis implies that the catastrophic Orientale impact struck a highland area underlain by highly feldspathic material and spread it over much of the Moon. Thus, much of the lunar highlands crust need not consist of anorthositic materials to any significant depth. These conclusions apply to the plains at the Apollo 16 site and most of the other Cayley-type plains, but we do not exclude the possibility that, moonwide, the plains may be polygenetic.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Computer-generated shaded-relief images

Digital image-processing techniques have been developed to make shaded-relief images from digitized topographic data. The resulting images have at least two advantages over aerial photographs: (1) The images are true map projections containing no relief-induced distortion, and (2) tonal variation is unambiguously identified with relief, rather than with snow, vegetation, or other albedo variations. Parallax can be introduced into these images in the computer, and stereoscopic pairs can thus be created.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Whitlockite and apatite of surficial phosphate occurrences on Enderbury Island, Phoenix Islands, Pacific Ocean

Whitlockite and apatite are the principal phosphate minerals in the surficial deposits of Enderbury Island; monetite and brushite are present in small amounts. All are derived from the guano of sea birds. The abundance of whitlockite discovered on Enderbury, and reported in samples from Remire Island in the Indian Ocean, indicates that the mineral is probably of common occurrence in young insular phosphate deposits. The composition of whitlockite from Enderbury Island is roughly (Ca, Mg, Sr, Na) 3 (PO 4 , CO 3 ) 2 , similar to the composition indicated for other insular occurrences by the sparse data available. The variety of apatite found on the island is carbonate fluor-hydroxylapatite, low in fluorine content. Whitlockite appears to have formed directly from guano components in surficial aqueous solutions, possibly accompanied by apatite, but changes with time to apatite.

Enderbury Island, Phoenix Islands↗
USGS1975

Andesite sills in the Red Mountain area, Scapegoat Wilderness, Lewis and Clark County, Montana

Sills 2-200 ft (0.6-60 in) thick in the Red Mountain area of the Scapegoat Wilderness in northwest Montana consist of altered andesite, basaltic andesite, and dacite and occur over a stratigraphic range of 8,000 ft (2,400 m) in the Helena and Snowslip Formations. The approximate compositional range of the sills is 50-80 percent plagioclase, 0-25 percent orthoclase, and 5-30 percent amphibole, pyroxene, and biotite; the uppermost sill contains about 15 percent quartz in the groundmass. Accessory minerals include quartz, magnetite, ilmenite, apatite, and pyrite. The petrology and alteration of the sills distinguish them from other sills in the region. Field observations and laboratory studies consisting of chemical, isotopic and X-ray analyses, and petrographic and mineralogic investigations suggest that the sills may have been emplaced in Precambrian Y time at about the same time as the extrusion of the Purcell Lava in the vicinity of Glacier National Park. Alternatively, the sills may represent a Precambrian igneous event not previously recognized in the Belt basin.

Montana↗
USGS1975

Age provinces in the basement rocks of Liberia

Fourteen new Rb-Sr ages and 17 new K-Ar ages, when combined with published ages, confirm the previous subdivision of the basement rocks of Liberia into 3 age provinces. The Liberian age province was metamorphosed and intruded 2,700 m.y. ago, but the data suggest that many of the rocks of this province are probably considerably older. The Eburnean age province was metamorphosed approximately 2,150 m.y. ago. Rocks of the Pan-African age province were originally part of the Liberian province, but underwent a relatively intense metamorphism 500 m.y. ago. The K-Ar age patterns suggest that the Pan-African province was uplifted relative to the Liberian province sometime after 500 m.y. ago, but fission-track ages of apatites indicate that any such relative vertical displacements must have occurred prior to 120 m.y. ago.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Ordovician and middle Silurian rocks of the Wildhorse window, northeastern Pioneer Mountains, central Idaho

Along Wildhorse Creek in the northeastern Pioneer Mountains, autochthonous Ordovician and Silurian rocks of an eastern carbonate assemblage are exposed in a structural window through allochthonous flysch deposits of the Mississippian Copper Basin Group. Graptolite-bearing Middle and Upper Ordovician dolomite and cherty dolomite 210 ft (64 m) thick are lithologically and faunally similar to the Hanson Creek Formation of central Nevada and the Saturday Mountain Formation of central Idaho. Monograptus -bearing Middle Silurian platy limestone at least 130 ft (40 m) thick resembles the Roberts Mountains Formation of central Nevada and rocks improperly designated Trail Creek Formation in the Bayhorse region of central Idaho. Allochthonous age-equivalent units of a more western transitional assemblage (the type Phi Kappa and Trail Creek Formations) occur 5 mi (8 km) west of the Wildhorse window, along the crest of the Pioneer Mountains.

Idaho↗
USGS1975

Palynological evidence for late Cretaceous, Paleocene, and early and middle Eocene ages for strata in the kaolin belt, central Georgia

Falynomorphs of Late Cretaceous (Maestrichtian), Paleocene, Paleocene or early Eocene (Wilcox), and middle Eocene (Claiborne) ages have been found in lignitic and carbonaceous clays and silts in the Tuscaloosa Formation, as used in central and east-central Georgia. The occurrence of palynomorphs of Maestrichtian (Navarro) age above thick kaolin deposits at one locality and a suite of Claiborne age fossils below a thick deposit at another locality establish that kaolins of both Late Cretaceous and middle Eocene or younger ages are present. However, the recognition of the Paleocene and middle Eocene beds in the Tuscaloosa Formation of several authors indicates that part of it is much younger than previously thought. The palynomorphs and other characteristics of the carbonaceous materials of Cretaceous and middle Eocene ages indicate freshwater accumulation. The beds of Paleocene age contain both terrestrial and marine forms indicating deposition in marine swamps or estuaries. These findings and the range in ages support the conclusion that the deptositional history of the Late Cretaceous and early Tertiary formations in Georgia is complex.

Georgia↗
USGS1975

Radiochemical determination of very low concentrations of nickel in rocks and minerals

A radiochemical procedure has been developed for the determination of very low concentrations of nickel in rocks and minerals. Sensitivity is 0.01 μ g Ni. Accuracy and precision is estimated to be ±5 percent to levels as low as 0.1 μ g Ni a marked improvement over other analytical techniques. Samples are irradiated, combined with nickel carrier, and treated by a series of chemical procedures: (1) collection of nickel in a lead bead using a fire-assay technique, (2) refusion of the lead bead and precipitation of basic element hydroxides, (3) anion-exchange chromatography, and (4) precipitation of nickel dimethylglyoxime. The nickel precipitate is weighed to determine chemical yield and counted for β activity of Ni 65 along with a precipitate from irradiated nickel standard solution.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Effects of sediment control on sediment transport in the northwest branch Anacostia River basin, Montgomery County, Maryland

Streamflow and sediment were monitored in an urbanizing drainage basin in southeastern Montgomery County, Md., from 1962 to 1972. During this period, urban construction areas averaged about 3 percent of the 21.1 mi 2 (54.6 km 2 ) basin. Urban land increased from 3.5 percent in 1959 to 20 percent in 1971. Virtually all the suspended sediment was transported during storms; three-fourths of it, during large storms. High sediment yields were observed in February, March, June, and August; and low yields, generally from September through January. The decrease in sediment discharge in the latter half of the study period is attributed to a sediment-control program. Sediment discharge decreased 35 percent between 1967 and 1972, when effective control measures were installed on about half the construction sites.

Maryland↗
USGS1975

Ore grade, metal production, and energy

Recent resource estimates have been stimulated by national concern over present and pending shortages of energy and mineral resources. Although some believe that the resource base of a commodity is the total amount in the crust, the energy consumption for mining and milling under present technology suggests that grades of the metallic ores have a lower limit when production is assumed to be for common usages. The tonnage required to mine and mill ores to obtain one unit of metal is a hyperbolic function of the grade, and as the tonnage increases hyperbolically, so does the energy consumed. For copper, the hyperbolic relation suggests that deposits with grades below about 0.20-0.25 percent Cu will not be mined to produce metal for common electrical and construction uses. Although the energy used to mine and mill a unit of metal differs from one metal to another, all show the hyperbolic increase in energy consumption as grade decreases.

Journal of Research of the U.S. Geological Survey↗
USGS1975

The megaspore genus Henrisporites from the Cretaceous of Massachusetts

A new megaspore species belonging to the genus Henrisporites was found in Cretaceous (probably Cenomanian) rocks from Massachusetts. Megaspores of Paxillitriletcs dakotaensis (Hall) Hall and Nicolson were found in the same rocks. This paper discusses the occurrence of these two megaspores in North America and describes Henrisporites angustus n. sp. from Massachusetts.

Massachusetts↗
USGS1975

Quantitative determination of dawsonite in Green River Shale by powder-sample X-ray diffraction; effect of grinding

In an effort to evaluate the method of quantitative analysis by X-ray diffraction as a means of determining dawsonite abundances in Green River" oil shale, we performed a series of grinding experiments. Weighed mixtures of dawsonite + quartz and dawsonite + quartz + shale were ground for preset lengths of time, and the following X-ray diffraction peaks were measured for intensity: dawsonite (110) at 15.6 2 θ and (211) (002) at 32.1° 2 θ , and quartz (100) at 20.9° 2 θ and (101) at 26.6° 2 θ . Heights and areas were measured. Intensity ratios were plotted as functions of grinding time with a calculated probable error. Intensity ratios generally decrease as grinding time increases. The intensity of the 15.6° peak, D 15.6° , is most affected, and the most drastic reduction occurs during the first 20 min of grinding. The D 32.1° peak is least sensitive to grinding but is subject to interference by other minerals in the shale. We conclude that the X-ray diffraction method is not well adapted to the routine quantitative determination of dawsonite in oil shale of the Green River Formation.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Notes on the origin of Colluma Crater, Bolivia

Colluma Crater, on the semiarid Altiplano (high plain) of western Bolivia, is an oval structure having overall dimensions of 6.7 km by 6.0 km. The structure has two almost concentric cuestaform rims (the inner rim is 3.6 km by 3.1 km) composed of poorly consolidated clastic sediments that dip outward. The center of the crater is about 80 m below the maximum height of the rims and about at the altitude of the surrounding plain. Because of the double rim, the centripetal drainage, and the absence of volcanic rocks, this structure is considered a collapsed dome. We believe it was probably formed by the doming of lower Quaternary (?) sediments by a subjacent igneous intrusion, partial retreat of the magma, collapse of the central part of the dome, erosional etching of the two rims, and partial filling of the center by detritus from the walls. Evidence for origin by impact (nickel-iron materials, shock structures, ejecta, and so forth) is lacking or was unrecognized, but this mode of origin is not rejected at this time. Geophysical surveys are recommended to determine whether the structure continues in depth and if an igneous, plug is below the crater.

Colluma Crater↗
USGS1976

Factors affecting declining water levels in a sewered area of Nassau County, New York

Double-mass-curve analysis of ground-water levels in Nassau County, Long Island, N.Y., shows that the average-weighted ground-water levels in a 32-mi 2 (83-km 2 ) segment of a sewered area declined 11.8 ft (3.6 m) relative to an adjacent unsewered area to the east during 1953-72. Electric-analog-model analysis indicates that 4.9 ft (1.5 m) of the decline is due to pumping in nearby Queens County, west of the sewered area. Most of the remaining 6.9 ft (2.1 m) of the decline is due to sewering. Streamflow within the sewered area has also declined because of the lowered ground-water levels.

New York↗
USGS1975

K-Ar age of the Similkameen Batholith and Kruger Alkalic Complex, Washington and British Columbia

Twelve K-Ar age determinations from the Similkameen batholith and the contiguous Kruger Alkalic Complex, including seven newly reported here, range from 69.9 m.y. to 177.2 m.y. Ages of coexisting hornblende and biotite show discordancies ranging from about 72 m.y. to 106 m.y., with hornblende consistently showing the greater analytical age. The hornblendes, with one exception, show increasing analytical age with increasing potassium content and approximately fit a 191.0-m.y. 40 Ar (radiogenic )/K isochron. The isochron shows a negative intersection with the 40 Ar (radiogenic) axis, indicating partial argon loss. The large negative deviation from the isochron of one low-potassium sample suggests that the isochron is biased to older ages. If so, the Similkameen and Kruger rocks probably crystallized between roughly 177 m.y. and 191 m.y. ago. The discordancies between hornblende and coexisting biotite are attributed to argon loss during one or possibly more episodes of thermal metamorphism, the most recent of which was probably between about 50 and 70 m.y. ago. This bracket is based on the age of apparently unmetamorphosed sedimentary deposits containing detritus from the Similkameen and Kruger bodies and the analytical age of the youngest biotite.

British Columbia, Washington↗