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At least 991 records · Page 55Linked to original sources
USGS1977

Use of infrared imagery in bank-storage studies

The use of thermal infrared imagery as a reconnaissance tool to identify bank seepage was investigated at Franklin D. Roosevelt Lake in northeastern Washington. The banks of the lake are generally composed of glacial lacustrine sediments deposited when the Cordilleran ice sheet dammed the Columbia River at least three times during the Pleistocene. The existence of a significant amount of bank storage was suspected. An airborne scanner having a spectral coverage of 8.5 to 11 micrometres and continuous filmstrip output was used in two test flights of March 27 and April 24, 1973. These flights were made during the reservoir drawdown when groundwater flow was from the banks to the reservoir and the ground water was warmer than the lake. The imagery shows temperatures in the lake ranging from 5° to 13° C. The lighter tones of the imagery show lake circulation patterns and extensive areas of bank seepage, spring discharge, stream inflow, and subsurface discharge which are all distinguishable from the darker tones of the colder lake surface. Bank seepage and ground-water discharge generally are evident where unconsolidated glacial sediment rather than bedrock is present.

Washington↗
USGS1977

Transverse mixing in the Mobile River, Alabama

Transverse dispersion in the Mobile River was measured by (1) ground-based techniques using water samples and a fluorometer and (2) by aerial photography. Magnitude of the transverse mixing coefficient obtained by the two methods was 6.2 feet squared per second (0.58 metre squared per second) and 5.0 feet squared per second (0.46 metre squared per second), respectively. The value of the numerical coefficient k , which relates the transverse mixing coefficient E , to shear velocity U * and average depth of flow, d , by the relationship k = E z / U * d , was 7.2.

Alabama↗
USGS1978

An "optimal" filter for maps showing nominal data

An "optimal" filtering technique for use with nominal data, such as land use and land cover categories, has been developed. This method is based on the conditional probability joins of neighboring data elements. In addition to its use in performing filtering, the method can be used to calculate the likelihood of each data element being properly classified. The technique was tested on a land use data set for an area in Walnut Valley, Calif. The computer program performing the filtering process proved to be computationally efficient and produced satisfactory results. Useful statistics of the error estimation process were also generated. Future applications of the method to spectrally classified Landsat data are being explored.

Journal of Research of the U.S. Geological Survey↗
USGS1978

Accuracy of selected land use and land cover maps in the Greater Atlanta region, Georgia

The land use and land cover maps at 1:100000 scale and at 1:24 000 scale in the Greater Atlanta Region were tested for accuracy. At 1:100 000 scale, 381 points were selected using a stratified systematic unalined sampling technique. Of these 381 points, 343 points or 90 percent were found to be correct. At 1:24 000 scale, 71 points were tested for accuracy. Of these 71 points, 62 points or 87 percent were found to be accurate. Confidence intervals were determined based on the assumption that the data exhibited a binomial distribution. With 95-percent confidence the accuracy of the 1:100 000-scale maps was between 87 and 93 percent, and the accuracy of the 1:24 000-scale maps was between 79 and 96 percent. The accuracy of the interpretations was consistent from category to category.

Georgia↗
USGS1978

Blue Ribbon Lineament, an east-trending structural zone within the Pioche mineral belt of southwestern Utah and eastern Nevada

The Blue Ribbon lineament is an east-west structural zone that is about 25 kilometers wide and passes through the Pioche mineral belt at about 38°10' N. It is best known in Utah, where it is at least 190 km long, and extends from the southern Sevier Plateau in the High Plateaus westward and across southern Mountain Home (Needle) Range in the Great Basin. It probably continues westward an additional 170 km into Nevada, where it connects with the eastern end of the 230-km Warm Springs lineament. The Blue Ribbon lineament is defined by range terminations and east-trending valleys, alinement of eruptive centers of middle Miocene (20 million years) to Pliocene(?) (5-1.8 m.y.) alkalic rhyolite, alinement of areas of middle Miocene to Pliocene mineralized rocks (mostly fluorine, uranium, tungsten) and hydrothermally altered rocks, east-trending magnetic highs and interruptions of magnetic anomalies, and east-striking basin-range faults of late Tertiary and Quaternary age. Mountains south of the lineament are topographically and structurally lower than those to the north. North-striking Quaternary basin-range faults, the Thermo hot springs area, several warm springs and former hot springs, and numerous dacitic to andesitic volcanic centers of early to middle Miocene age (26-20 m.y.) occur along the lineament. The Blue Ribbon lineament is believed to be a deep crustal fault zone dating from at least middle Miocene time and possibly much earlier. It thus developed generally coincident with northerly trending classical basin-range faults. Its fracture system was an important, long-lived conduit for mineralizing fluids, and it should be an attractive target for minerals exploration in the future. The lineament could be due to an east-trending warp in the subducting mantle plate, or it could be part of a past or present intracontinental transform fault that locally gets younger eastward and dies out eastward in the western Colorado Plateaus province.

Utah↗
USGS1977

Dating and recurrence frequency of prehistoric mudflows near Big Sur, Monterey County, California

Botanical evidence based on the dendrochronology and root horizons of redwoods ( Sequoia sempervirens ) and radiocarbon dating were used to date prehistoric mudflows near Big Sur, Calif. At least three periods of mudflow activity were delineated for the approximate prehistoric period 1370-1800. Two historic periods of mudflow activity have occurred, 1908-10 and 1972-73. The documentation of mudflows as characteristic surficial processes in the Santa Lucia Range indicates a hazard to development on recent mudflow deposits in this region.

California↗
USGS1978

A tuya in Togiak Valley, Southwest Alaska

The shape, composition, structure, and location of a conspicuous flat-topped mountain in the lower Togiak Valley, southwest Alaska, all indicate that it formed by a subglacial volcanic eruption of olivine basalt. Volcanoes of this type are known as "tuyas." The Togiak tuya erupted into an intraglacial lake in a hole thawed through a glacier that occupied Togiak Valley in Pleistocene time. The eruption was localized along the Togiak fault, which defines the east side of a shallow graben that is floored by older olivine basalt flows. The tuya, which has an area of 15 square kilometers, is a parallelogram. The flat summit, about 300 meters above the valley floor, is capped by glassy, fine-grained subaerial flows of alkali olivine basalt. To the north, the capping flows overlie palagonitized glassy tuffs; to the south, they overlie pillow basalts and breccia. The elevation of the pillow basalts indicates that surface of the melt-water lake was at least 250 m above present-day sea level. Basalt xenoliths in the tuffs and comparison with other better exposed tuyas suggest that the tuffs probably overlie an older pile of subaqueous pillow basalts that erupted beneath the intraglacial lake. The tuya overlies and is much younger than the preglacial flows on valley floor that yielded a potassium-argon age of 0.758±0.2 million years.

Alaska↗
USGS1978

Origin of two clay-mineral facies of the Potomac Group (Cretaceous) in the Middle Atlantic States

Sedimentary clay that crops out in the coastal plains of New Jersey, Delaware, the part of Maryland north and east of Washington, B.C., and the northeast half of Washington, D.C., in the nonmarine Cretaceous Potomac Group is predominantly kaolinite and illite. In contrast, in part of southeastern Maryland, the southwest half of Washington, D.C., and most of eastern Virginia, Potomac Group clay is predominantly montmorillonite. Kaolinite and illite were probably derived by intense acid weathering of metamorphic and granitic rocks to the west during the Cretaceous and were deposited in a well-drained basin. Montmorillonite was most likely produced by deep weathering of a mainly granitic source. Poor drainage and alkaline surface- and ground-water conditions probably accompanied the production, transportation, deposition, and burial of the montmorillonite. Kaolinization of the montmorillonite is taking place now at the surface in northern Virginia.

Delaware, Maryland, New Jersey, Pennsylvania, Virg↗
USGS1978

Heavy-mineral variability in the Baltimore Canyon trough area

Petrographic analyses of bottom sediments from 87 stations within a relatively large subarea (1700 square kilometers) define the local variability and the distributional processes of heavy minerals in the Baltimore Canyon Trough area (13500km 2 ). Of the 29 mineral groups that were identified, those most diagnostic of differences between stations were opaque minerals, garnet, hornblende, orthopyroxene, other amphiboles, and staurolite. Some of the common components cannot be used to define areal trends. The association of minerals by their specific gravities reflects the modern reworking and sorting of sediments in this area. The poor correlation between mineral abundance and the ridge-and trough topography suggests either that our analyses and samples did not resolve bathymetrically induced changes or that smaller bed forms (such as ripples) largely control the heavy-mineral distribution. Data from this study provide a baseline for evaluating manmade disturbances of the bottom sediments and show that relatively large changes in the heavy mineral composition can take place over small distances on this part of the Continental Shelf.

Baltimore Canyon Trough↗
USGS1977

Application of a hydrometeorological model to the south-central Sierra Nevada of California

A hydrometeorological streamflow-prediction model (HM model) developed for the North Cascades of Washington has been tested in the south-central Sierra Nevada of California. Twenty-four drainages ranging in mean altitude from 770 to 3,160 metres, including several of the major ones such as those of the Kern, Kings, and Merced Rivers, were examined. Eight U.S. National Oceanic and Atmospheric Administration precipitation stations were evaluated. Of these, three proved to be of significant value for nearly all the drainages used. Results are given for predictions on February 1, March 1, and April 1 of monthly runoff of five major drainages for the April-September season. Also demonstrated is the April 1 prediction of a daily hydrograph for the April-September season for 2 diverse years. The altitude distribution of storage and runoff, both observed and predicted, is determined by using several drainages with different area-altitude profiles. Results of this calculation for two drainages show that, on the average, approximately 50 percent of the April-July runoff originates above 2,800 m. The influence of subsequent precipitation on prediction accuracy is determined by relating prediction error and actual precipitation occurring after the prediction day. Results for three basins show that about 75 percent of the error of a January-September prediction on January 1 is due to precipitation occurring during the prediction season. Comparisons of prediction accuracy are made for five major drainages: the Kern River near Kernville; the Kings River below North Fork, near Trimmer (inflow to Pine Flat Dam); the Kings River at Piedra; the Merced River at Pohono Bridge, near Yosemite; and the Merced River below Merced Falls Dam, near Snelling. The accuracy of the HM model appears to be about 24 percent higher than existing operational methods in predicting the April-July runoff on April 1.

California↗
USGS1978

Stable isotope studies of bedded barite at East Northumberland Canyon in Toquima Range, central Nevada

Several beds of barite occur in the Slaven Chert at East Northumberland Canyon in the Toquima Range of central Nevada. Most of the barite is internally laminated but shows massive weathering. However, rosette, disseminated, conglomeratic, and concretionary varieties also occur. New fossil evidence from conodonts and brachiopods indicates a Late Devonian age for the Slaven Chert at East Northumberland Canyon. Preliminary δ 34 S values of most disseminated and massive-laminated barite within the Slaven Chert average about 25 permil; these are within the range of values that is typical of sulfate from Late Devonian seawater and are distinctly different from δ 34 S values of most crosscutting hydrothermal barite veins in the area. Primary δ 34 S values of the bedded barite appear to be retained during recrystallization and hydrothermal alteration, suggesting that δ 34 S data of bedded barites could be developed into a useful stratigraphic tool. The δ 34 S values of rosette and concrectionary barites range from 29.1 to 56.3 permil and indicate that these varieties of barite formed in restricted microenvironments where extensive bacterial reduction of seawater sulfate occurred. The δ 18 O data on cherts associated with the barite beds and δ 14 C and δ 18 O data on carbonate beds within the Slaven Chert indicate that the depositional environment at tames had restricted communication with normal seawater of the open ocean.

Nevada↗
USGS1977

Procedure for estimating the temperature of a hot-water component in a mixed water by using a plot of dissolved silica versus enthalpy

A graphical method using a plot of dissolved silica versus enthalpy allows quick determination of the temperature of the hot-water component of a nonboiling thermal spring. The method is applicable to warm spring waters that either have not lost heat before mixing or have lost heat by separation of steam before mixing.

Journal of Research of the U.S. Geological Survey↗
USGS1978

Factors contributing to the formation of ferromanganese nodules in Oneida Lake, New York

Oneida Lake is a large, shallow, eutrophic lake situated in the Ontario lowlands of central New York State. It contains the most concentrated deposit of freshwater ferromanganese nodules (in terms of amount per unit area) yet reported in the literature. The mineralogy and bulk chemistry of these saucer-shaped nodules are similar to the mineralogy and bulk chemistry of deep-sea ferromanganese nodules, but the nodules in Oneida Lake contain considerably lower concentrations of trace metals, especially cobalt, nickel, and copper. Budgets for iron and manganese in waters from Oneida Lake and its tributaries indicate that approximately 122 t (metric tons) of iron and 23 t of manganese are lost each year from the lake waters, presumably by incorporation into sediments and ferromanganese nodules. Estimates based on nodule abundance and age of the lake suggest that iron and manganese are being incorporated into ferromanganese nodules at rates of 13 and 22 t/yr, respectively. Most iron lost from the lake waters is apparently incorporated into sediments, which contain an average of 10 times more iron than manganese. Most manganese lost from the lake waters is apparently incorporated into ferromanganese nodules, which contain an average of 1.7 times more manganese than iron. In Oneida Lake, very high rates of phytoplankton productivity, combined with almost continuous wind mixing to the bottom, provide high-pH and high-Eh conditions in most of the lake. Algae also provide an effective means of concentrating and transporting iron and manganese and thereby aid in the extensive development of ferromanganese nodule deposits.

New York↗
USGS1977

Geochemistry of amphibolites from the central Beartooth Mountains, Montana-Wyoming

Trends of variation of major- and minor-element contents in amphibolites from the central Beartooth Mountains strongly suggest that these rocks of andesitic composition are derived from a tholeiitic, mafic igneous parent and not from a sedimentary parent. Discriminant functions based on minor-element content also indicate igneous parentage, whereas functions based on major-element content indicate a sedimentary parent, suggesting that the general assumption that the regional metamorphism is isochemical may not be entirely valid. Furthermore, chemical data on the amphibolites do not fit the fractionation curves of average Beartooth metadolerites, the most likely precursor. If, however, it is assumed that regional metamorphism and formation of amphibolites were accompanied by potassium metasomatism, then the higher concentrations of SiO 2 , Al 2 O 3 , K 2 O, and potassium-related minor elements in the amphibolites relative to metadolerite can be explained.

Montana, Wyoming↗
USGS1978

Occurrence and formation of avicennite, Tl2O3 , as a secondary mineral at the Carlin gold deposit, Nevada

Avicennite, Tl 2 O 3 , occurs as grains disseminated in silicified limestones in the upper part of the East ore zone of the Carlin gold deposit, Nevada. The avicennite is formed by the oxidation of carlinite, Tl 2 S, found in primary unoxidized carbonaceous ore immediately below the avicennite. The grains of avicennite closely resemble carlinite in size and shape. Some avicennite occurs as thin coatings on carlinite, but the time of its formation is unclear. Avicennite grains are polycrystalline, porous, dark gray to black, with a hackly fracture but no discernible cleavage. The Mohs hardness is 2.0±0.5; Vickers hardness ranges from 46.0 to 80.5 kg mm -2 . Measured density is distinctly low, 8.9 g cm -3 (or Mg m -3 ), relative to the calculated density, 10.34 g cm -3 . The mineral is isometric, space group Ia 3. a =10.5468±0.0003 angstroms or 1.05468±0.00003 nm, Z =16, and the volume of the unit cell is 1173.17±0.04 Ǻ 3 or 1.17317±0.00004 nm 3 . The most intense X-ray diffraction peaks are 3.044 (100), 1.864 (38), 2.637 (37), and 1.590 (30). In reflected light, avicennite is pale to medium gray and isotropic and lacks discernible bireflectance. Reflectance in air ranges from 10.6 to 13.0 percent. Avicennite is nearly pure Tl 2 O 3 , containing 89.6 weight percent Tl and 10.5 weight percent O by microprobe analysis. Other elements present, detected by emission spectrographic analysis, are: Pb, 300 ppm; Ca, 100 ppm; and Si, Al, Fe, Mg, Ag, Cr, Cu, Ni, and Ti, all <50 ppm.

Nevada↗
USGS1977

Geochemical and petrological studies of a uraniferous granite from the Granite Mountains, Wyoming

Granite rocks from the Granite Mountains, Wyo. have been proposed as the source of uranium deposits in the Crooks Gap, Gas Hills and Shirley Basin uranium districts, Wyoming. We have divided these granitic rocks into four units: (1) a biotitic phase which forms the dominant unit at the western end of the Granite Mountains, (2) a leucocratic phase which was found from 215 to 405 metres in drill hole GM-1, (3) silicified zones which crosscut the granitic rocks and form topographic highs, and (4) fractured zones, in drill hole GM-1, which seem to have been hydrothermally altered. The biotitic phase is hypidiomorphic-granular to xenomorphic-granular alkali granite with anomalously high contents of U (10 parts per million), Th (50 ppm), and Pb (50 ppm). Fission-track studies show that uranium is located in zircon, sphene, apatite, monzite, xenotime, biotite, chlorite, epidote, and magnetite; no intergranular uranium was found. The leucocratic phase is mineralogically similar to the biotitic phase, but contains less than half as much iron. It is xenomorphic granular and commonly contains rounded and retrograded garnets, which suggests that this phase is either metamorphic or contaminated with metamorphic materials. The leucocratic phase has anomalously high contents of U (8 ppm) and Pb (55 ppm), but has a low Th content (10 ppm). The silicified phase and fracture zones exhibit cataclastic and crystalloblastic textures and are highly variable in mineralogy. Potassium-bearing minerals are generally absent. Microcline is replaced by albite and (or) quartz, and biotite is replaced by clinozoisite. Uranium values may be anomalously high in the fracture zones. One sample contains 1100 ppm radium-equivalent uranium. In this and other uranium-rich samples from the fracture zones, the uranium is associated with iron oxides which commonly fill microfractures. According to our model and currently available data, an alkali granite is the best crystalline source rock for uranium, especially if it is unmetamorphosed and rapidly exposed to near-surface conditions for the first time when a favorable basin existed nearby.

Wyoming↗
USGS1977

A comparison of some analytical techniques for determining uranium, thorium, and potassium in granitic rocks

Geochemical exploration for uranium requires accurate and precise determinations of low-level concentrations. We have used seven different techniques and four different treatments of the fluorometric method to analyze for uranium in granitic rocks. In addition we have used four analytical techniques for thorium and three analytical techniques for potassium, two elements that are commonly present in anomalous amounts within uranium provinces. Our results show that commonly used techniques for thorium and potassium determinations are both adequately precise and accurate, but that many techniques used for uranium determinations lack the necessary precision or accuracy for complete geochemical prospecting. We suggest that a combination of delayed-neutron determinations for uranium and γ -ray spectrometric analyses for radium equivalent uranium, thorium, and potassium provides the best data base for geochemical exploration for uranium. If more detailed interpretations are desired, the combination of γ -ray spectrometry and α -spectrometry may be best. Carefully done fluorometric analyses should be adequate for water, ore, mineralized rock, and other applications where high precision and accuracy are not required.

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

Some characteristics of Pele's hair

Pele's hair is a filamentous variety of brown sideromelane glass that forms during eruption of basaltic lava. Strands of Pele's hair form from droplets of lava that are spun or stretched into filaments during quenching, and others may form as chilled streamers of lava. Common elongate vesicles, sometimes twisted, indicate extreme stretching and twisting during hair formation. Hair diameter ranges from about 1 to 300 micrometres. Refractive index of hairs decreases with hair diameter and is most probably a function of the process of formation rather than chemical composition. Masses of Pele's hair form natural spun-glass filters that trap small particles and serve as sites for sublimate deposition. Such deposition may begin even while hair is falling to the ground through an eruption fume cloud. Sublimates include carbonates, sulfates, sulfur, and less commonly hydrocarbons, thus complicating the interpretation of volatiles in Pele's hair in terms of original magmatic constituents. Vesicles, which provide the most nearly pure samples of magmatic volatiles, contain mostly H 2 O and CO 2 .

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