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At least 649 records · Page 36Linked to original sources
USGS1977

Relation of surflcial erosion on hillslopes to profile geometry

Differences in erosion rates in relation to the geometry of hillslope profiles were hypothesized by R. E. Horton in 1945. Experimental testing of this hypothesis is described for natural hillslopes in western Colorado using a rainfall simulator to apply five "storms" each having an intensity of 1.85 inches per hour (47 millimeters per hour). Erosion from straight hillslope segments was about twice the amount from convex and concave segments along nine hillslope transects. Standard deviations of erosion measurements for each segment show that the greatest variation occurs in concave slope segments. This is probably because the concave segment is the only place on the profile where deposition occurs. Analysis of variance indicates that the amount of erosion is significant at the 1-percent level of confidence between convex and straight slope segments and at the 5-percent level of confidence between straight and convex slope segments.

Colorado↗
USGS1977

A Galerkin, finite-element analysis of steady-state flow and heat transport in the shallow hydrothermal system in the East Mesa area, Imperial Valley, California

A steady-state simulation model was applied to the shallow hydrothermal system in the East Mesa area of Imperial Valley, Calif. The steady-state equations of flow and heat transport were solved by use of a Galerkin, finite-element method. A solution was obtained by iterating between the temperature and pressure equations, using updated densities and viscosities. Temperature and pressure were obtained for each node, and corresponding head values were calculated. The simulated temperature and pressure patterns correlated well with the observed patterns. Additional data, mainly from test drilling, would be required for construction of a similar model of the deep hydrothermal system.

California↗
USGS1977

Solubility of natural fluorite at 25°C

The solubility products of two samples of natural fluorite from Rosiclare, Ill., and from Madoc, Ontario, were determined at 25°C by analyses of calcium and fluoride in sodium perchlorate solutions of varying ionic strength over a period of 3 years. Calcium concentrations were analyzed by atomic absorption spectrophotometry, fluoride concentrations were measured colorimetrically, and fluoride activities were measured using a specific ion electrode. The solubility products at the end of 3 years were determined by extrapolation to zero ionic strength. The final solubility product was found to be 10 -10.58±0.17 .

Journal of Research of the U.S. Geological Survey↗
USGS1977

Benthic invertebrates in an arctic mountain stream, Brooks Range, Alaska

A 1-day, late-summer reconnaissance of the Dietrich River, Alaska, determined species composition and diversity of benthic invertebrates and examined the correlation between stream order and invertebrate distribution. Benthic invertebrates were collected by dip net, drift net, and 10-rock collections, and results were combined for each station. Forty-nine taxa were identified from 5 stations representing stream orders 1 through 5. Aquatic insects comprised 88 percent of all taxa and 97 percent of all individuals from the Dietrich River. Diptera, especially Chironomidae, was the most abundant, followed by Plecoptera. Diamesinae was abundant at the headwaters, decreasing downstream; Orthocladiinae exhibited the reverse distribution pattern. Diversity of collections generally increased downstream. The station collections were compared using coefficients of similarity, cluster analysis, and taxonomy. Collections from adjacent stations were most similar and similarity decreased with increasing distance. The fauna was tentatively divided into zones with characteristic communities: a Diamesinae-Simuliidae fauna in zone I (stream order 1), zone II, a region of transition (orders 2-4), and an Orthocladiinae-Plecoptera-Ephemeroptera fauna in zone III (order 5). The fauna compares closely with that of other arctic streams. Although not conclusive, the benthic invertebrate results are consistent with the hypothesis that stream order is related to lotic biological communities.

Alaska↗
USGS1974

Major chemical characteristics of Mesozoic Coast Range ophiolite in California

Sixty-four major element analyses of rocks representative of the Coast Range ophiolite in California were compared with analyses of other onland ophiolite sequences and those of rocks from oceanic ridges. The rocks can be classed in five groups harzburgite-dunite, clinopyroxenite-wehrlite, gabbro, basalt-spilite, and keratophyre-quartz keratophyre which on various diagrams occupy nonoverlapping fields. The harzburgite-dunite from onland ophiolite and ocean ridges are comparable and very low in alkalies. Possible differentiation trends defined on AFM diagrams by other rocks from onland ophiolites and ocean ridges suggest two lines of descent: (1) A trend much like the calc-alkalic trend, though shifted somewhat toward higher iron, and (2) an iron-enrichment trend defined chiefly by the more iron-rich gabbros and amphibolite. MgO-variation diagrams for rocks from the Coast Range ophiolite further distinguish the iron-rich gabbros and amphibolite from the other rock groups and indicate that the iron enrichment, unlike that of the Skaergaard trend, is related to the formation of amphibole. Ophiolite sequences that include the most silicic rock types, such as quartz keratophyre, also exhibit the most pronounced dual lines of descent, suggesting that the silicic rocks and the amphibole-rich gabbros are somehow related. Although the major element chemistry of the Coast Range ophiolite is clearly like that of rocks dredged from oceanic ridges, it is not sufficiently diagnostic to discriminate among the choices of a spreading ridge, an interarc basin, or perhaps even the root zone of an island arc as the site of ophiolite formation.

California↗
USGS1974

Ultramafic rocks of the Eagle quadrangle, east-central Alaska

More than 97 separate occurrences of ultramafic rocks, some of which are included in a north west-trending zone of alpine-type ultramafic rocks, have been mapped in the Eagle quadrangle, east-central Alaska. They are divided into three groups primarily on the basis of degree of serpentinization. Group I consists of lens-shaped bodies of serpentinite 1 m 2 (10 ft 2 ) to several 100 m 2 (1,000 ft 2 ) in area. Relict textures and presence of bastite indicate that the original rock was harzburgite and dunite. Group II consists of bodies composed of partially serpentinized harzburgite and dunite and includes the large Mount Sorenson and American Creek bodies. Group III is dominantly hornblendite and pyroxenite, probably intrusive and not genetically related to groups I and II. The authors believe that the ultramafic bodies of groups I and II are alpine-type peridotites and may include dismembered ophiolitc. The Tintina fault system could have provided a zone of weakness along which mantle material was tectonically emplaced or it may have been a plate boundary in late Paleozoic time. If it represents a plate boundary, the metamorphic terrane which lies between the Tintina and Denali fault systems would have to be allochthonous, perhaps originating as a northward-moving slice of continental crustal material. During the course of the movement as the two continental masses approached and perhaps collided, mantle peridotite and oceanic crustal material were squeezed up along the continental margin onto the continental slice.

Alaska↗
USGS1974

Barium in hybrid granitoid rocks of the southern Snake Range, Nevada

In a magmatic environment, barium usually substitutes for potassium in the crystallizing silicates, and the two increase together in rocks late in the differentiation sequence. Results of this study show the opposite trend in an equivalent of a large part (63-76 percent SiO 2 ) of the classic differentiation sequence that resulted mainly from assimilation of chemically distinct host rocks. The barium content of the hybrid granitoid rock appears to be controlled mainly by the barium contents of the various sedimentary rock types assimilated.

Nevada↗
USGS1974

Distribution and occurrence of rare earths in the thorium veins on Hall Mountain, Idaho

Rare earths, although equal to or more abundant than thorium in many thorium veins, are much less abundant than thorium in the veins on Hall Mountain, Idaho. Total rare-earth content of these veins ranges from 0.00111 to 0.197 percent in 12 samples from 10 veins; the thoria (ThO 2 ) content, from 0.011 to 5.84 percent. The rare-earth oxide to thoria ratios range from 0.0019 to 3.22. Only two samples contained more rare earths than thorium, and these two samples came from veins related to a fault near the base of a thick sill; the others came from veins near the top of the same sill. The relative amounts of the individual lanthanides are remarkably similar in the Hall Mountain veins, although cerium, gadolinium, or dysprosium are the most abundant in different samples. These veins differ in lanthanide distribution both from the Earth's crust and from the thorium veins of the Lemhi Pass district, Idaho and Montana, in that they contain chiefly yttrium-group rare earths. Most of the rare earths occur in thorite, whose atomic structure will accommodate wide-ranging proportions of the rare earths. Cenosite, one of the few minerals with a high content of the yttrium group of rare earths, was found in one vein.

Idaho↗
USGS1974

Origin of spongy cherts

The spongy-textured surface in some cherts, visible on electron micrographs, is inherited from authigenic cristobalite. Spongy bedded cherts were originally bedded porcelanites similar to the porcelanite in the Miocene Monterey Formation of California.

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

Optical and X-ray crystallographic investigations of strontioginorites

Compositional, optical, and unit-cell data are presented for a suite of strontioginorites. These crystals show that Sr:Ca ≈ 1 is preferred. Lack of variation in the Sr:Ca resulted in no meaningful correlation between composition and physical properties.

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

Buddingtonite, ammonium feldspar, in the Phosphoria Formation, southeastern Idaho

Buddingtonite is distributed widely in the rocks of the Meade Peak Member of the Phosphoria Formation in southeastern Idaho and occurs in amounts up to about 50 percent. Most of the buddingtonite is in the middle mudstone interval of the member between two phosphate-rich intervals. The composition of the buddingtonite, in terms of a buddingtonite K-feldspar series, shows an apparent range of Bd 82 KF 18 to Bd 13 KF 87 , and compositions of Bd 72 KF 28 to Bd 50 KF 50 may be the most common. The predominant silicate mineral suite consists of buddingtonite-albite-illite. Albite is present in amounts up to about 20 percent. Buddingtonite may have developed directly from volcanic glass in the presence of abundant ammonium, derived from the decomposition of organic matter, in interstitial waters, or it may have formed at some later diagenetic stage from other products of volcanic glass alteration, such as montmorillonite or zeolites.

Idaho↗
USGS1974

Spectrophotometric determination of vanadium in rutile and in mafic igneous rocks

Minor and major levels of vanadium in rutile are separated from titanium and iron by sample fusion with sodium carbonate followed by water leach and filtration. The filtrate is then acidified with hydrochloric acid. Silicates are decomposed with a mixture of hydrofluoric and hydrochloric acids, and iron is separated by extraction of its chloride with diethyl ether. Sample vanadium in hydrochloric acid is then quantitatively reduced to vanadium(IV) with sulfurous acid. The remaining sulfur dioxide is expelled by heating. Vanadium (IV) then is reacted with excess of iron(III) at reduced acidity (pH 5) in the presence of 1,10-phenanthroline to yield the orange-red iron(II) 1,10-phenanthroline complex. Iron(II) generated by vanadium(IV) is a measure of total vanadium in the sample. The proposed method is free from elemental interferences because the color development cannot take place without the two redox reactions described above, and these are, under the outlined experimental conditions, quantitative only for vanadium.

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

Rubidium-strontium dating of the trondhjemite of Rio Brazos, New Mexico and of the Kroenke Granodiorite, Colorado

The quartz-eye trondhjemite and associated hornblendite near Rio Brazos, Brazos Peak quadrangle, New Mexico, and the Kroenke Granodiorite of the Mount Harvard quadrangle and Sawatch Range, Colo., lie on an approximate 1,700-m.y. Rb-Sr isochron. Their initial 8 7 Sr/ 8 6 Sr ratio is about 0.7026. Six samples of the trondhjemite of Rio Brazos contain 8-43 ppm Rb and 57-194 ppm Sr, and six of the Kroenke intrusive, 53-99 ppm Rb and 314-595 ppm Sr. The Rio Brazos intrusive contains more SiO 2 but less Al 2 O 3 and K 2 O than does the Kroenke intrusive. The hornblendite contains much MgO and CaO but is low in alkalies; two samples show 2.5-3.2 ppm Rb and 288-431 ppm Sr. These rocks are of the same general age as the much more abundant, typically calc-alkaline Boulder Creek Granodiorite and associated intrusives of Colorado and northern New Mexico.

New Mexico, Colorado↗
USGS1974

Continental depositon of Antarctic tillite indicated by carbon and oxygen isotopes

Freshwater deposition of the upper Paleozoic, Gondwana tillite in the Pensacola Mountains is indicated by low δ values of +4.9 to +6.1 permil δ0 1 8 (SMOW) and -1.8 to -15.9 permil δC 1 3 (PDB) in primary sedimentary calcite within the tillite. In contrast, Cambrian marine limestone from the Pensacola Mountains contains heavy isotopic abundances that are entirely characteristic of marine deposition.

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

Evidence for the presence of a heart in Paleozoic ostracodes inconclusive

The presence of a heart in some Paleozoic ostracodes has been inferred by analogy with some living myodocopids that have this organ, and an ordinal classification of the leperditiids has been proposed because of this inference. A review of the present knowledge of the internal shell structure of living myodocopids indicates that there is no basis for interpreting certain markings preserved on fossil molds and steinkerns as indicating the presence of a heart.

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

Palynological applications of principal component and cluster analyses

Two multivariate statistical methods are suggested to help describe patterns in pollen data that result from changes in the relative frequencies of pollen types produced by past climatic and environmental variations. These methods, based on a geometric model, compare samples by use of the product-moment correlation coefficient computed from data subjected to a centering transformation. If there are m samples and n pollen types, then the data can be regarded as a set of m points in an n -dimensional space. The first method, cluster analysis, produces a dendrograph or clustering tree in which samples are grouped with other samples on the basis of their similarity to each other. The second method, principal component analysis, produces a set of variates that arc linear combinations of the pollen samples, are uncorrelated with each other, and best describe the data using a minimum number of dimensions. This method is useful in reducing the dimensionality of data sets. A further transformation known as varimax rotation acts on a subset of the principal components to make them easier to interpret. Both methods offer the advantages of reproducibility of results and speed in pattern description. Once the patterns in the data have been described, however, they must be interpreted by the palynologist. An application of the methods in palynology is shown by using data from Osgood Swamp, Calif.

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

The effects of the Hurricane Agnes flood on channel geometry and sediment discharge of selected streams in the Susquehanna River basin, Pennsylvania

The Hurricane Agnes flood seems to have hardly changed the channel geometry of the Pennsylvania streams studied in this report. The 10 sites studied generally showed that the width of the stream channels had been changed little by the flood and that streambed altitudes had been lowered less than a foot (0.3 m). The velocity of the streams at a given discharge had decreased. In comparison, the sediment deposited by the December 1964 flood in northwestern California commonly raised the streambed altitudes several feet. The differences in the effects of the two floods may have been produced by the availability of sediment for transport, by the relative size of sediment carried in suspension or bedload, or by the relative magnitudes of the floods.

Pennsylvania↗