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At least 253 records · Page 14Linked to original sources
USGS1978

Significance of age relations above and below upper jurassic ophiolite in the Geysers-Clear Lake region, California

In The Geysers-Clear Lake area of northern California, a fragmented Upper Jurassic ophiolite overlain depositionally by the Great Valley sequence is juxtaposed over deformed and metomorphosed rocks of the Franciscan assemblage along the Coast Range thrust. The basal strata of the Great Valley sequence consist of thick breccias of mafic clasts, identical in composition to the upper part of the ophiolite. These breccias and their contact relations suggest that more than 1 km of the upper part of the ophiolite was locally eroded in early Tithonian time. On the basis of their radiolarian faunas, cherts in the Franciscan assemblage below the ophiolite range in age from Late Jurassic (early Tithonian) to Late Cretaceous (early Cenomanian). Of particular significance is an individual chert body (= The Geysers chert) of this age range. The early Cenomanian radiolarians, except for two occurrences associated with pelagic limestone, are significantly younger than those previously reported from the Franciscan assemblage. The existence of a sequence of Late Jurassic to Late Cretaceous radiolarian chert places critical constraints on subduction models for emplacement of the Franciscan assemblage beneath the Coast Range ophiolite and Great Valley sequence in The Geysers-Clear Lake area. From early Tithonian to post-early Cenomanian time, the Franciscan assemblage received pelagic sedimentation far from any site of subduction. By other data, blueschist metamorphism of subducted Franciscan strata also occurred during this time. The radiolarian data from The Geysers area permit a correlation with Upper Cretaceous pelagic limestones in the Laytonville area northwest of The Geysers and also imply that the Great Valley sequence was never depositionally in contact with the Franciscan assemblage.

California↗
USGS1978

Age and composition of igneous rocks, Edna Mountain quadrangle, Humboldt County, Nevada

Six pulses of igneous activity ranging in age from Jurassic to Pliocene have been identified in the Edna Mountain quadrangle, Humboldt County, Nev. Porphyritic syenite am! quartz monzonite of Jurassic age (146-164 million years) at Buffalo Mountain are highly potassic through a wide range in SiO 2 content from olivine-bearing syenite to quartz-rich monzonite, and their composition contrasts sharply with plutons elsewhere in north-central Nevada. Granodiorite and quartz monzonite plutons of Cretaceous age (88- 106 m.y.) are chemically and mineralogically similar to other calc-alkaline plutons in north-central Nevada. Four episodes of Tertiary volcanism include rhyolite ashflow tuffs and slightly younger andesitic basalt flows and tuffs of Oligocene age, rhyolite vitrophyre of late Miocene age, and olivine basalt flows of Pliocene age. Their age and mineralogical and chemical compositions are similar to other Tertiary volcanic rocks in north-central Nevada.

Nevada↗
USGS1978

Pressure gradients and boiling as mechanisms for localizing ore in porphyry systems

Fluid inclusions in ore zones of porphyry systems indicate that extensive boiling of hydrothermal fluids accompanies deposition of ore and gangue minerals. The boiling commonly accompanied a change from a lithostatic to a hydrostatic environment during evolution of an epizonal stock. Pressure gradients near the margin of the stock can determine whether ore or only a diffuse zone of mineralization is formed. A sharp drop in pressure in an epizonal environment is more likely to cause extensive boiling than a comparable change in a deeper environment, as the slope of the boiling curve steepens with an increase 'in pressure. The drop in pressure causes the hydrothermal fluids to boil and creates a crackle (stockwork) breccia, which hosts the veinlets of gangue quartz and ore minerals. The boiling selectively partitions CO 2 , H 2 S, and HCl into the vapor phase, changing the pH, composition, ionic strength, and thus the solubility product of metal complexes in the remaining liquid and causing the ore and gangue to come out of solution. Fluid inclusions trapped from boiling solutions can exhibit several forms, depending on the physical and chemical conditions of the hydrothermal fluid from which they were trapped. In one case, inclusions when heated can homogenize to either liquid or vapor at the same temperature, which is the true boiling temperature. In another case, homogenization of various inclusions can occur through a range of temperatures. The latter case results from the trapping of mixture of liquid and vapor. Variations in salinity can result from boiling of the hydrothermal fluid, or intermittent incorporation of high-salinity fluids from the magma, or trapping of fluids of varying densities at pressure-temperature conditions above the critical point of the fluid. In places, paleopressure-temperature transition zones can be recognized by fluid-inclusion homogenization temperatures and phase relationships and by the presence of anhydrite daughter minerals. Boiling of a hydrothermal fluid in the porphyry environment affects light stable isotopes. Hydrogen is preferentially fractionated into the vapor phase from water boiling below 223°C; above this temperature deuterium is selectively enriched in the vapor phase. In certain environments boiling creates a vapor-dominated system in which the condensate is swept away by meteoric waters and the H/D in the residual fluids is progressively increased through time.

Utah↗
USGS1978

Phosphorus in hydrothermal waters of Yellowstone National Park, Wyoming

Ninety-seven hot-spring and geyser samples (field acidified to pH<1.4 with HCl or HNO 3 ) from Yellowstone National Park, Wyo., were analyzed for PO 4 -P using reduced molybdenum-blue and the selective arsenate reducing agent, metabisulfite-thiosulfate. The PO 4 -P concentrations ranged from below detection limit (~1-73 micrograms per liter). Twenty-five springs had PO 4 -P concentrations exceeding 6.8 &mu; g/L; seven spring samples exceeded 20 &mu;g/L. Elevated PO 4 -P contents were invariably associated with mixed springs, as evidenced by diluted chloride concentrations and, commonly, subboiling temperatures, low pH's, and elevated calcium concentrations. Alkaline high-chloride (>400 milligrams per liter) hydrothermal waters from Upper and Norris Geyser Basins had PO 4 -P concentrations below 2 &mu;g/L and represent the low end of the range of PO 4 -P contents in natural waters.

Wyoming↗
USGS1978

Conductive heat flows in research drill holes in thermal areas of Yellowstone National Park, Wyoming

In convection systems with boiling springs, geysers, fumaroles, and other thermal features, the modes of heat flow become increasingly complex as a single liquid phase at depth rises into the near-surface environment where heat flows by convection of liquid and vapor and by conduction in high thermal gradients. This paper is mainly concerned with the changing patterns of conductive heat flow as related to channels of subsurface convective flow and to horizontal distance from spring vents. The primary data consist of temperatures measured in 13 cored drill holes as drilling progressed. Some temperatures plot convincingly on straight-line segments that suggest conductive gradients in rocks of nearly constant thermal conductivity. Temperature gradients and the conductive component of total heat flow nearly always decrease drastically downward; the gradient and heat flow of the lowest depth interval recognized in each hole is commonly only about 10 percent of the highest interval; the changes in gradient at interval boundaries are commonly interpreted as channels of near-boiling water or of cooler meteoric water. Temperature reversals are probably related to inflowing cooler water rather than to transient effects from recent changes. Some temperatures plot on curved segments that probably indicate dispersed convective upflow and boiling of water in ground penetrated by the drill hole. Other similar curved segments are too low in temperature for local boiling and are probably on the margins of hot upflow zones, reflecting conductive cooling of flowing water. The conifers of Yellowstone National Park (mainly lodgepole pine) seem to have normal growth characteristics where near-surface conductive heat flow is below about 200 heat-flow units (1 HFU = 10 -6 cal/cm 2 = 41.8 mW/m 2 ). Most areas of abnormal "stunted" trees (low ratio of height to base diameter, and low density of spacing) are characterized by conductive heat flows of about 250 to 350 HFU. The critical factor affecting growth is probably the seasonal maximum soil temperature at the root depths preferred by each form, rather than the heat flow as such. Heat flows up to 300 HFU are greatly dominated near the surface by conduction and are little affected by convection within the measured intervals. With increasing total heat flow above 300 HFU, the convection component, as indicated by snowfall calorimetry, becomes increasingly important. Snowfall calorimetry and tree growth as related to heat flow are calibrated by the heat-flow data considered here. Both snowfall calorimetry and tree growth patterns can be extrapolated rapidly, although without high precision, to thermal areas that lack subsurface data.

Wyoming↗
USGS1978

Upper Devonian radiolarians separated from chert of the Ford Lake Shale, Alaska

Leaching of black bedded chert from the Ford Lake Shale, Kandik Basin, Alaska, with dilute hydrofluoric acid resulted in the complete separation of moderately well preserved radiolarians. Preliminary study of an assemblage obtained from the lower half of the formation revealed six to eight forms apparently identical to specimens previously known from the Tournaisian of southern France and northwestern Turkey, including four genera not previously described from North America. Sparse, poorly preserved conodonts in the same sample are of Late Devonian age. We conclude that certain radiolarian species, hitherto known only from the early Carboniferous, span the Devonian-Carboniferous boundary. The radiolarian assemblage of the Ford Lake Shale sample contrasts markedly with Late Devonian assemblages known from the Canol Shale of northern Canada and the Huron Member of the Ohio Shale; the Ford Lake Shale fauna may reflect greater oceanic influences than these other localities, which lie farther inland from the Devonian continental margin.

Alaska↗
USGS1978

A reexamination of the Pennsylvanian trace fossil Olivellites

The original interpretation of Olivellites plummeri Fenton and Fenton as the trace of an infaunal gastropod, is reconsidered and rejected. The original slab bearing several examples of O. plummeri has been reexamined and reillustrated. The slab came from the type-locality of O. plummeri in Eastland County, Tex., and is a shallow sub tidal sandstone of the Graham Formation; the sandstone, which has yielded additional specimens, is presumably a reworked delta-front deposit. Olivellites was also observed in the Caddo Creek Formation in Stephens County, Tex., but, to date, it has not been found elsewhere in north-central Texas. Interpretation of Paleozoic ichnofossils by analogy with modern traces is limited; behavioral characteristics may be the products of post-Paleozoic innovation. The internal morphology and path of Olivellites are unlike those of any modern gastropod trail, and the genus is removed from the Mollusca.

Texas↗
USGS1978

lowaphyllum (rugose coral) from the Upper Devonian of Arizona

The rugose coral genus lowaphyllum is uncommon but widely distributed in rocks of Devonian age. It is here reported for the first time from western North America (Late Devonian). lowaphyllum is also known from the late Middle and Late Devonian of Eastern North America, but the lack of Early and early Middle Devonian species anywhere in North America leaves open the question of derivation of these forms and their relationship to Early Devonian species in Europe and Australia.

Arizona↗
USGS1978

Inventory of land use and land cover of the Puget Sound region using Landsat digital data

Landsat multispectral scanner digital data from four bands were analyzed using computers to produce land use and land cover information of the Puget Sound region, Wash., for use by agencies in that area. The data were first geographically registered to map coordinates. This registration enabled samples of known land cover types to be digitized from the maps. Samples of the same land cover were grouped together and then subdivided by cluster analysis into spectrally similar classes. Spectral categories were associated with specific land cover classes and used to determine spectral signatures for classification of the entire region. Reclustering and reclassification techniques were developed and then employed to minimize certain classification errors. The classified data were displayed in color using a film recorder. This color image was enlarged photographically to a 1:100000 scale to match new base maps of the region. Although the result resembles a conventional polygonal land use and land cover map, certain image-like qualities remain and yield additional information about the landscape.

Washington↗
USGS1978

Application of four input-output models for nutrients in Lake Okeechobee, Florida

R. A. Vollenweider's (1975) nonconservative model described concentrations of nitrogen and phosphorus for 1969-70 in Lake Okeechobee, Fla., better than the models of F. Biffi in 1963, R. H. Rainey in 1967, and R. Piontelli and V. Tonolli in 1964. Vollenweider's model predicted concentrations of 1.4 milligrams per liter of total nitrogen and 0.09 mg/L of total phosphorus in the lake. The concentration of nitrogen could be approximated with conservation models but phosphorus required a nonconservative model. Unless variations in input concentrations and flow rate of the tributaries are modeled, only short-term predictions of lake concentrations can be made because of variations in inflow concentrations and because of the short time required (400 days) for the lake to be flushed by its inflow.

Florida↗
USGS1977

Simulation of flow from an aquifer to a partially penetrating trench

Construction of the Tennessee-Tombigbee Waterway in northeast Mississippi will involve dewatering as much as 46 m of an unconfined aquifer near the Tennessee Valley divide. Dewatering by trenching is one of the proposed methods. Methods of calculating effects of dewatering by trenching have been heretofore limited to situations where ideal conditions such as isotropic aquifers and fully penetrating trenches occur. In order to study the effects of trenching on the water table in the more complicated hydrologic system in northeast Mississippi, a two-dimensional cross-sectional digital model was developed from an existing two-dimensional digital model. To make the solutions obtained from the model applicable to any aquifer thickness or other hydrologic condition, a technique for nondimensional simulation was developed. With these techniques, nondimensional water-surface profiles were generated for given stages of trench penetration of the aquifer and for different ratios of anisotropy.

Mississippi↗
USGS1977

A method for adjusting values of Manning's roughness coefficient for flooded urban areas

A method is presented for adjusting values of Manning's roughness coefficient for flooded urban areas on the basis of the density of buildings on a flood plain and verified roughness coefficients for natural conditions. An urban roughness coefficient can be calculated to emulate the water-surface profiles to within 0.06 meter for depths of flow less than 0.6 meter and plus or minus 10 percent for depths between 0.6 and 2 meters.

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

Periphyton and phytoplankton in the Sacramento River, California, May 1972 to April 1973

Periphyton and phytoplankton samples were collected monthly at five sites in the Sacramento River between May 1972 and April 1973. Periphyton were analyzed for species identification and biomass, and phytoplankton were analyzed for species identification and concentrations. The results were used to assess biological water-quality conditions in the river and to compare phytoplankton types and concentrations at three sites with those in 1960-61. Diatoms were the dominant group in both numbers and types of periphyton and phytoplankton. The number of genera and frequency of occurrence of periphyton increased downstream. The periphyton biomass decreased downstream and with succeeding monthly sampling periods. The highest productivity was at site B, below Red Bluff, probably because the Red Bluff Diversion Dam provides optimum conditions for periphyton growth. The decreasing productivity downstream is probably a function of higher sediment concentrations. The periphyton biomass ranged from 0.00 to 0.56 grams per square meter per day throughout the study period. Phytoplankton concentrations and diversity increased downstream. The highest phytoplankton concentration was 980 organisms per milliliter at site D, above Knights Landing, in September. The diversity indices ranged from 0.95 to 3.88 for all sites throughout the study period. Fewer phytoplankton genera were collected in 1972-73 than in 1960-61, but the generic composition was similar. Total phytoplankton concentrations were nearly always higher in 1960-61 than in 1972-73. Green algal concentrations were significantly higher ( p <0.05) at site C and diatoms were significantly higher at all three sites in 1960-61. Blue-green algal concentrations were higher in 1972-73, but differences between the two time intervals were not significant.

California↗
USGS1977

Feasibility and technology for making remote measurements of solutes in water

An indepth evaluation of the available technology in the field of laser-Raman spectroscopy indicates that a TV-type detector, a single monochromator with a holographic grating, an entrance slit filter blocking the Rayleigh light, and a pulsed laser coupled to signal averaging electronics is the best combination of commercial equipment that is presently available for building a remote water-quality sensor. The resultant sensor would be capable of measuring oxyanions in water at concentrations from 10 to 50 milligrams per liter at distances from ground level to 30 meters above the sample. The main interferences would be ambient light, bioluminescence, and natural fluorescence, all of which are minimized when taking advantage of the signal generating and readout capability contained in this equipment package.

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

Chemical structure of humic acids - Part 1, a generalized structural model

A new model is proposed for the structure of humic acids. In this model humic acid is pictured as being made up of a hierarchy of structural elements. At the lowest level in this hierarchy are simple phenolic, quinoid, and benzene carboxylic acid groups. These groups are bonded covalently into small particles. Particles of similar chemical structure are linked together by weak bonds to form "homogeneous" aggregates. Two or more different types of aggregates may be linked together to form mixed aggregates. Complexes of humic acid and clay minerals are also formed.

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

Chemical structure of humic acids - Part 2, the molecular aggregation of some humic acid fractions in N, N-dimethylformamide

Humic acid fractions form molecular aggregates in solution. In previous studies we have shown by small angle X-ray scattering that the size of these aggregates is a function of pH. In this study we have found that the size of the aggregates of two humic acid fractions in water and buffers and in dimethylformamide solutions can be changed by oxidation with molecular oxygen and air. These results cast new light on the bonding mechanisms that cause aggregation of the humic acid particles in solution. We have interpreted the changes in aggregation sizes as being brought about by changes in intermolecular and intramolecular hydrogen bonding of the humic particles. Solvation of the humic molecules by dimethylformamide interferes with some of the hydrogen bonding reactions between proton donor and acceptor groups on the same humic acid molecules or on different molecules.

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

Thallium contents of 16 USGS standard rocks

Thallium was determined in 16 USGS standard rocks by atomic absorption spectroscopy in which a heated graphite atomizer was used after extraction as thallium iodide into amyl acetate. Four subsamples from four bottles of each standard sample, except G-1 and W-1, were analyzed in random order, and the average thallium contents in parts per million (as Tl) were AGV-1, 0.41; GSP-1, 1.63; G-2, 1.08; BCR-1, 0.35; SDC-1, 0.80; MAG-1, 0.79; BHVO-1, 0.049; SCO-1, 0.79; SGR-1, 0.34; QLO-1, 0.23; RGM-1, 1.07 ; STM-1, 0.30; DTS-1, <0.005; and PCC-1, <0.005. The analysis of variance showed that all samples may be considered homogeneous at F 0.975 and only GSP-1 may be considered heterogeneous at F 0.95 . The Tl contents of G-1 and W-1 are 1.0 and 0.12 ppm, respectively.

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

A combustimetric method for determining the total carbon content of geologic materials

A modified LEGO WR-12 carbon determinator is used in a combustimetric determination of total carbon in geologic materials. A thermal conductivity cell is used as the sensing device. International reference samples are analyzed and compared to results previously published. Three new standards from the Canadian Certified Reference Materials Project were received and analyzed for the total carbon content.

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