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At least 325 records · Page 18Linked to original sources
USGS1974

The soil creep-curved tree fallacy

No evidence has been found in eastern deciduous forests to substantiate statements that curved tree trunks, downslope tilted tree trunks, and upslope trailing tree root systems are the result of soil creep. Curvature and tilting of trunks are described as geotropic and phototropic responses to physical and physiological conditions unrelated to soil creep. The occurrence of upslope trailing of roots has not been demonstrated.

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

Some aspects of aquatic insect populations of pools and riffles in gravel bed streams in western United States

Relationships were studied between aquatic-insect populations on rocks of different sizes and variations of populations between different stream localities. All aquatic insects were counted and identified on streambed gravels and cobbles chosen at random from four rivers on three to four types of locations ranging from riffles to pools. The measurements used span 3 to 4 months in 1 year. Insect density (number of insects per unit of rock area) was determined to be a function of rock size. Highest insect densities occurred on rocks between 45 and 90 mm mean diameter, with larger and smaller rocks having lower insect densities. The insect population differed significantly with location within a stream; that is, from pool to riffle, as well as by stream and season.

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

Yachats Basalt: An upper Eocene differentiated volcanic sequence in the Oregon Coast Range

The name Yadials Basalt is proposed for a sequence of largely subacrial basalt flows and breccias and associated dikes of late Eocene age that arc exposed along the central Oregon coast. These volcanic rocks, which have a maximum thickness of 750 m, are underlain by marine siltstonc of late Eocene age and overlain by marine siltstone and basaltic sandstone, also of late Eocene age. The siltstone contains a foraminiferal fauna indicative of a moderately deepwatcr marine environment, indicating that local uplift preceded the extrusion of the flows and local subsidence followed. The Yachats Basalt varies widely in composition. Although the bulk of the extrusive rocks and dikes arc basalt, some grade in composition to basaltic andcsite and andcsite; a few dikes are rhyodacitic. Most of the rocks arc porphyritic with phcnocrysts of labradorite and less commonly augite and olivine. Typical flow rock contains 50 percent SiO 2 and are characterized by high alumina, alkali, titania, and phosphate content. The wide range in composition and porphyritic character of the Yachats Basalt and the abundance of multiple dikes suggest that the magma that produced these rocks was differentiated in the upper crust before extrusion. The Yachats Basalt, and correlative upper Eocene volcanic rocks in western Oregon and Washington, lie along a generally north-trending belt. The predominance of normal faulting in western Oregon and Washington and on the adjacent continental shelf during post mid-late Eocene time suggests that the volcanics were extruded along a zone of tensional rifting. They do not appear to be related to conventional plate models for continental margins that arc characterized by deep trenches flanked by island arcs.

Oregon↗
USGS1974

Relation of mineralization to calderas in the San Juan volcanic field, southwestern Colorado

A review of the calderas in the San Juan volcanic field, southwestern Colorado, indicates that lead, zinc, copper, gold, and silver mineralization took place in and near calderas which had complex histories of postsubsidence intrusive and extrusive igneous activity. Most known ore occurs in veins that follow fractures formed during the different caldera cycles, but some intrusive bodies were extensively mineralized and possibly may host disseminated, porphyry-type deposits. The mineral deposits seem to be related most commonly to the youngest and most highly differentiated late intrusives of a caldera cycle.

Colorado↗
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↗