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At least 883 records · Page 49Linked to original sources
USGS1974

Stratigraphic evidence on the age of the Roberts Mountains thrust, Eureka and White Pine Counties, Nevada

Several stratigraphic discontinuities in Devonian and Mississippian sedimentary sequences in folded thrust plates east of the Roberts Mountains thrust of central Nevada indicate that the thrust was sporadically active during this interval. From estimates for displacement and time involved for the thrust, the average rate of movement was 1 cm/5 yr, which is comparable to current concepts of the rate of orogenic movements. A further extrapolation of this rate to the longer period during which orogenies have been recognized in the Great Basin suggests total horizontal shortening of 400 to 500 mi (640-800 km).

Nevada↗
USGS1974

Folds and overthrusts of late Jurassic or early Cretaceous age in northern Nevada

The partly isoclinal, partly overturned Adobe syncline extends for at least 75 mi northeastward across the northern Cortez Mountains, the northern Pinon Range, and along the entire length of the Adobe Range. The folded rocks range in age from Ordovician through Jurassic and may include some rocks of Cretaceous age. This syncline is flanked by anticlines in the central and southern parts of the Pinon Range and in the southern Independence Mountains. In places the Adobe syncline is discordantly overlain by nearly flat-lying thrust plates composed of Ordovician, Devonian, Mississippian, and Permian rocks. The geometric relations indicate that these thrust plates moved at least 6 mi, but postfold thrust movement was not great, because the Mississippian and Permian rocks of the thrust plates closely resemble correlative autochthonous rocks nearby. The Ordovician and Devonian rocks have been thrust to their present position in at least two stages; the earlier movement or movements took place long before folding of the Adobe syncline and the later movement immediately afterward. The folding and last stage of thrusting were in Late Jurassic or Early Cretaceous time.

Nevada↗
USGS1974

Shallow seismic compressional and shear wave refraction and electrical resistivity investigations at Rocky Flats, Jefferson County, Colorado

Seismic refraction and electrical resistivity investigations at Rocky Flats, Colo., a gravel-capped pediment, indicated an irregular bedrock surface which ranges in depth from 3 to 27 m (10-90 ft). Layers within the gravel that were revealed by interpretation of seismic and electrical data do not correlate, but the combining of results reveals information about water saturation and elastic properties of the overburden. Velocity variations within bedrock affect depth calculations.

Colorado↗
USGS1974

Palynology and stratigraphy of Cretaceous strata in Long Island, New York, and Block Island, Rhode Island

Palynologic analysis of core samples from Fire Island well, S21,091T, in southern Long Island and of surface samples from Garvies Point in northern Long Island and from eastern Block Island indicates that the Cretaceous of this region includes Raritan, Magothy, Matawan, and Monmouth (as previously defined) strata, and ranges in age from Cenomanian to Maestrichtian, in agreement with recent studies in New Jersey. In this study, the oldest Cretaceous, which is equivalent to the Woodbridge day Member of the Raritan Formation of New Jersey, occurs just above sea level at Garvies Point, Glen Cove, and in the Port Washington sand pits in northwestern Long Island, whereas sediments from near the base of the Fire Island well arc correlated with the South Amboy Fire Clay Member. The Magothy and Matawan combined in Long Island are about 1,500 ft (457 m) thick, whereas in New Jersey both units rarely exceed a thickness of 500 ft (152 m). Outcropping Cretaceous sediments in Block Island are equivalent to the South Amboy Fire Clay Member rather than the Magothy, as indicated in prior studies. Palynologic zonation of the Late Cretaceous is tentatively extended to Magothy and younger strata on the basis of the appearance and proliferation of the more advanced, angiosperm pollen forms. This study also provides a basis for extending the zonation and hence the correlation to the sediments of the Continental Shelf.

New York, Rhode Island↗
USGS1974

Energy dispersive spectrometry for quantitative mineralogical analyses: An ancillary system on an electron microphobe

Investigation of the Li-drifted Si-semiconductor X-ray detector for quantitative elemental analysis of some common rock-forming minerals shows that amounts of certain major elements having K spectra in the energy range of about 1.74 (Si) to 8.64 (Zn) kiloelectronvolts may be accurately determined, if spectral interferences are absent. Elements in major concentrations between 0.5 and 1.00 percent may be analyzed quantitatively without corrections of K spectra X-ray intensities when reference standards of similar composition are used and significant K spectra interferences between two adjacent elements are absent. Elemental concentrations less than about 0.5 weight percent cannot be precisely determined from raw X-ray intensity data owing to high and variable spectral background. Data show that spectral background corrections are feasible because spectral background is a linear function for the light-element oxides and silicates. Simultaneous quantitative elemental analysis, with both the energy dispersive spectrometer and the conventional wavelength dispersive spectrometers on the electron microprobe, is feasible.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Activity-product constants of aragonite at 90° and 51°C

The activity-product constants of aragonite, K A =[Ca 2+ ][CO 3 2- ] (where the brackets denote activities), were determined experimentally at 90°C and at 51°C. Results at 90°C were obtained from four separate dolomite dissolution runs, in which aragonite precipitated and came to equilibrium with the aqueous phase (from the direction of. supersaturation), and from two runs starting with aragonite suspended in dilute MgCl 2 solutions (from the direction of undersaturation). The average values of K A from the six runs were in excellent agreement; for the negative logarithm of K A , P K A , they yield a value of 8.95±0.05. One run was made at 51° C starting with aragonite suspended in dilute MgCl 2 solution; the value of p K A at 51°C is 8.61±0.05. No X-ray detectable calcite was found at the conclusion of any of the runs, including a dolomite dissolution run at 90°C (D-10) that was sampled over a period of 10,268 h and toward the end had a concentration of approximately 0.002 molal total dissolved magnesium.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Regional flow system and ground-water quality in western Ohio

Most relatively deep wells drilled in the carbonate aquifers in western Ohio tap a recognizable regional flow system encompassing all or parts of several major basins. The principal recharge area includes the higher, central part of the region, where much of the terrane is hummocky to hilly glacial moraine. The principal discharge areas are the valleys of the major streams and lowlands along Lake Erie. Ground water moving through this system undergoes a progressive change in chemical quality, from a calcium bicarbonate type in recharge areas to a calcium sulfate type in discharge areas. Changes in selected chemical constituents are orderly and, within the observed parameters, predictable.

Ohio↗
USGS1974

Comparison of bacterial and phytoplankton populations under natural and laboratory conditions

Bacteria and blue-green algae were isolated from Oneida Lake, N.Y., and other sources. The blue-green algae Anabaena flos-aquae , Anabaena spiroides , Gloeotrichia echinulata , and Microcystis aeruginosa were grown under laboratory conditions and were separated into unialgal cultures. The bacterial population living in association with the unialgal blue-green algae differed significantly from the bacterial flora of Oneida Lake. Bacillus , Pseudomonas , Aeromonas , and Zoogloea were the most frequently occurring genera of bacteria from the lake, whereas Flavobacterium , Achromobacter , and Pseudomonas were the most common bacteria isolated from laboratory blue-green cultures. Nutritional and physiological characteristics of bacteria isolated in the laboratory were more uniform than those isolated from the lake.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Distribution of chlorinated hydrocarbons in stream-bottom material

Six stream-bottom samples, contaminated in situ with high levels of chlorinated hydrocarbons, were size graded and the separates were analyzed. The contaminants were found distributed throughout the sample. The complexity of bottom-material samples is such that the distribution of chlorinated hydrocarbons may be controlled to a major extent by the organic matter and associated organisms. All particle-size fractions must be considered if representative samples are to be taken and quantitatively related to a stream.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Calculated volumes of individual shield volcanoes along the Hawaiian-Emperor chain

Volume was calculated for the 107 individual volcanic shields along the Hawaiian Ridge Emperor Seamounts chain to help fulfill the need for volume data essential to determining eruption rates, fraction of mantle melted, and other parameters. Boundaries used were based principally upon location of rift zones related to each shield. Volcanic loci shown are modified from an earlier map to accommodate changes in bathymetry. Total volumes calculated for the Emperor and Hawaiian chains are 336.3 X 10 3 km 3 and 744.9 X 10 3 km 3

Hawaii↗
USGS1974

Stratiform chromitite at Campo Formoso, Bahia, Brazil

Serpentinized ultramafic rocks of pre-Minas age (Precambrian) crop out in an elongate belt 1 km wide and 15 km long on the west side of the Serra de Jacobina near Campo Formoso, Brazil. The original stratiform ultramafic body has been so metamorphosed, faulted, and eroded that only narrow dismembered segments occur along the thrust-faulted west side of the Serra de Jacobina. The most economically important segment is that near Campo Formoso where chromitite layers can be followed for about 8 km near the base of the intrusion. Three to five chromitite layers of minable thicknesses have been mapped, the thickest being 1.4 to 1.8 m. The aggregate thickness of chromitite is about 5 m and the average grade is about 43.5 percent Cr 2 0 3 . The Cr:Fe ratio ranges from 1.6:1 in weathered friable chromite to 3:1 in massive unweathered chromitite; in cleaned chromite concentrates the ratio is as much as 3.3:1. Estimates of indicated chromite ore reserves range from 16 to 20 million metric tons, of which only an estimated 6 million tons can profitably be mined. Factors preventing full exploitation of the chromite include (1) the local presence of as much as 7 m of overlying colluvium, (2) the extremely faulted character of the chromitite layers, (3) the presence of an overlying quartzite thrust plate very near the line of chromitite outcrops, and (4) the steep dips of the chromitite layers, 15° to 40° along the Pedrinhas-Limoeiro trends and 50° to 65° along the Cascabulhos trend.

Bahia↗
USGS1974

Detailed near-bottom geophysical profile across the continental slope off northern California

A geophysical profile was run across the continental slope off the California-Oregon border by use of a deeply submerged instrument package, approximately 50 m above the sea floor, containing a proton magnetometer and a 3.5-kHz transducer for shallow seismic penetration. Surface-towed seismic reflection equipment was operated concurrently. The deep-tow data show that the slope is relatively smooth; this agrees with interpretation of surface seismic profiles. Features smaller than 1 km in length can be resolved with the deep profiles but not with the surface profiles. The deep profiles show smallscale undulations less than 0.5 km long that are especially well formed on the steeper parts of the slope. These undulations may be caused by minor downslope movement of surface sediment or by depositional processes. The deep-tow and surface seismic profiles can be combined to give a more accurate structural picture of the continental slope than can be obtained with surface data alone.

California↗
USGS1974

Mineralogical studies of the nitrate deposits of Chile IV. Brüggenite, Ca(IO3)2-H2O, a new saline mineral

Br ü ggenite, Ca(I0 3 )2 - H2 0, is found in veins of high-purity soda niter in rhyolite tuff at Pampa Pique III, Oficina Lautaro, Chile, as long columnar anhedral crystals, as prismatic crystals, and as irregular anhedral crystals or encrusting masses. The mineral is colorless to bright yellow, and transparent to translucent, has vitreous luster and a hardness of about 3 1 / 2 , is brittle, and has conchoidal fracture. It is biaxial and has variable optic angle and refractive indices, which were determined by the spindle-stage method. Refractive indices are as follows: n α =1.772-1.779, n β =1.795-1.802, and n γ =1.817-1.824 (all ± 0.003); optic angle shows a range of 2 V Z = 86°-96°; Z = b and X ∧ c = -47°; dispersion (Z) is r < v , moderate. Brüggenite is monoclinic, space group P 2 1 / c , with a=8.509±0.001 A, b = 10.027±0.002 A, c = 7.512±0.001 A, β = 95°16.00'±0.55', volume 638.2 A 3 , Z = 4, G (calc) = 4.244, G (meas) =4.24±0.01. The X-ray diffraction powder pattern of brüggenite has the following strong lines ( hkl , d hkl 1 ): 031, 3.051 A (100); 220, 3.238 A (90); 200, 4.235 A (80); 002, 3.739 A (60); 012, 3.503 A (60); 231, 2.522 A (60). The composition was confirmed by chemical analyses.

Antofagasta Province↗
USGS1974

The association of geochemical anomalies with a negative gravity anomaly in the Chief Mountain-Soda Creek area, Clear Creek County, Colorado

Geochemical studies in the Chief Mountain Soda Creek area, Clear Creek County, Colo., show that anomalously high amounts of Au, Ag, Pb, Zn, Cd, and Bi in mull ash, and Cu and Hg in soil, correspond to a negative gravity anomaly in the Front Range mineral belt. The correspondence of the geochemical anomalies to the negative gravity anomaly suggests the presence of altered and mineralized rock and a Tertiary intrusive body at depth. This gravity anomaly and other similar gravity anomalies in the Front Range mineral belt merit further investigation for possible ore deposits.

Colorado↗
USGS1974

Generalization of stream travel rates and dispersion characteristics from time-of-travel measurements

Prediction of travel rates of water in streams is important for pollution control and for warning systems where contaminant spillage is possible. A method of estimating traveltime and dispersion of solutes in streams where such data are not available is provided in this report. Generalized relations for travel rates and dispersion indices as functions of stream-channel and discharge characteristics are developed using available time-of-travel data and the multiple-regression technique.

Journal of Research of the U.S. Geological Survey↗
USGS1974

The Sargent-Berrocal Fault Zone and its relation to the San Andreas Fault system in the southern San Francisco Bay region and Santa Clara Valley, California

The Sargent-Berrocal fault zone is a belt of thrust faults extending for about 58 mi (94 km) southeastward from the vicinity of Los Altos to San Juan Bautista, Calif. The fault zone generally dips southwestward toward the adjacent San Andreas fault at low to steep angles, and the southwest block has moved upward and northeastward. Thrusting across the fault zone has produced large-scale offset, which may increase to the southeast. If strike-slip movement has occurred, it has probably been minor. Offset Quaternary strata, physiographic features, and recent seismic activity all indicate that the Sargent-Berrocal fault zone has been active in the last one million years and that some clastic strain is currently being released along the northwest and southeast parts of the fault zone.

California↗
USGS1974

Investigation of diffusion in open-channel flows

This investigation examines the interrelation between turbulent diffusion, dispersion, and the statistical properties of turbulence in an open-channel flow. The results of the study substantiate Philip's concept relating the ratio of Eulerian to estimated Lagrangian time scales and the reciprocal of the longitudinal intensity of turbulence. The relation may be used to predict coefficients of longitudinal turbulent diffusion at the water surface and in the flow field, A similar concept using an integral scale based on the longitudinal intensity of turbulence may be used to predict coefficients of both surface and depth-averaged turbulent diffusion in three coordinate directions. Longitudinal space-time velocity correlation measurements can be used to predict the Lagrangian time scale only under limited conditions. Within the range of conditions studied, longitudinal diffusion accounted for 4 to 13 percent of the one-dimensional dispersion process.

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