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At least 37 records · Page 2Linked to original sources
USGS1977

Land use and land cover changes: A framework for monitoring

Information on the rate and kind of change in the use of land resources is essential to-the proper planning, management, and regulation of the use of such resources. Starting in 1975, the U.S. Geological Survey has been engaged in mapping and inventory of land use and land cover at a scale of 1:250000 with plans to change to new 1:100000 base maps as they become available. Such scales are-appropriate for acquiring benchmark or baseline data on land use and land cover on a nationwide basis with a reasonable degree of standardization and accuracy, within a practical time frame of 6 to 7 years, and at a reasonable level of detail in categorization. Changes in land use and land cover occur at highly variable rates from place to place. Thus variations, in the intervals between updates of land use and land cover data should be carefully evaluated in order to provide an appropriate frame of reference for the systematic updating of such data. A methodological framework is needed for monitoring changes in land use and land cover that will be timely, relatively inexpensive, and appropriate for widely varying needs at national, interstate-regional, state, multicounty, county, and city levels. In this article a partial framework for monitoring land use and land cover changes is provided with opportunity to extend its use to greater levels of detail in categorization and shorter intervals of frequency when needed for selected areas.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Geology of a system of submarine canyons south of Puerto Rico

A strongly dendritic submarine canyon system with four major canyons occupies a 30-km indentation in the insular shelf off the south coast of Puerto Rico between Guanica and Ponce. Each canyon has several headward branches at depths of 100 to 1,100 m. Each of the five major rivers that reach the coast between Guanica and Ponce is opposite a canyon head, and off each of the rivers a channel 20 to 30 m deep is incised into the insular shelf. The entire canyon system is 40 km long and terminates at a depth of about 3.3 km; no fan or other constructional feature appears to have been formed. A 410-km continuous seismic profiling survey shows that three unconformable stratigraphic units underlie the canyon area. One sample of indurated clay of probable Miocene age was dredged from a canyon-wall outcrop of the middle stratigraphic unit. The three stratigraphic units may be roughly correlative with (in ascending order) the Juana Diaz Formation, the Ponce Limestone, and an unnamed upper section found in a nearby drill hole ashore. Canyon-axis sediment at depths of 700 to 2,200 m is entirely of pelagic origin, indicating that sediment is not now being transported down the canyons.

Guanica, Ponce↗
USGS1975

Applications of remote sensing to structural interpretations in the southern Appalachians

Remote sensing is the technology of studying distant objects by measuring and recording energy from one or more segments of the electromagnetic spectrum. Imaging sensors which operate from medium- and high-altitude aircraft or from spacecraft can provide a synoptic view of large areas and of surface phenomena not evident in the field. Image-acquiring systems and instruments have been designed to partially automate data collection and to reduce the time devoted to analysis, information extraction, and detection of changes of surface phenomena. Among these phenomena are the surface distribution of heat, moisture, snow, water, vegetation, and cultural features. When coupled with ancillary data, including field surveys, sensor data provide useful information for the recognition and mapping of regional structure, jointing patterns, drainage patterns, fault and fracture traces, and rock types. The recognition of several major linear surface features, two of which proved to be traces of previously unrecognized faults (the Canebrake and the Coeburn faults) in the Appalachian Plateaus, demonstrates the pragmatic application of aircraft and spacecraft remote sensing to geological investigations in the Appalachians.

Virginia, West Virginia↗
USGS1977

Cauldron subsidence of Oligocene age at Mount Lewis, Shoshone Range, Nevada: A reasonable interpretation

James Gilluly has rejected the interpretation of Wrucke and Silberman (U.S. Geol. Survey Prof. Paper 876, 1975) that a thrust fault and tear fault mapped by Gilluly and Gates (U.S. Geol. Survey Prof. Paper 465, 1965) as structures bounding the upper plate of the Roberts Mountains thrust at Mount Lewis are parts of a ring fracture around an area that underwent volcanic collapse. In his discussion (this volume) of our paper, Gilluly fails to consider important questions that we presented in support of the subsidence hypothesis. Instead of answering these critical questions, Gilluly merely recapitulates the interpretations that he and Gates gave in Professional Paper 465. We presented new information, including a map of one critical area along the cauldron boundary where, among other significant differences in geologic interpretation, we found the ring fault where previously no steep fault was shown. Gilluly believes that the paucity of dikes along the ring fracture at Mount Lewis is highly anomalous for cauldrons. However, the amount of dike rock is comparable to that in known cauldrons (some cauldrons have none) and is what might be expected at high levels in subsidence structures that have undergone relatively little resurgent igneous activity after collapse. Gilluly concludes that in formulating our interpretation of volcanic collapse, we have ignored much evidence that he and Gates have presented on thrust faulting; in the Shoshone Range. On the contrary, we have considered their ideas and have reinterpreted them using new evidence that strongly supports the concept of cauldron subsidence at Mount Lewis.

Nevada↗
USGS1974

Time of travel and dye dosage for an irrigation canal system near Duchesne, Utah

Fracturing and subsidence of the land surface in the Milford area oil Utah have resulted from the decline of water levels due to pumping in unconsolidated deposits of Quaternary age. To the writers’ knowledge, these are the first such effects of ground-water withdrawal reported in Utah. The fracturing is in an area about 1 mile (1.6 km) wide and 11 miles (18 km) long near Milford, in an unsaturated clay-silt zone (locally peaty at top) in the upper part of the principal ground-water reservoir. The fractures range in length from several feet to more than 100 feet (30 m), and their maximum measured depth in 1972 was 4 feet (1.2 m). Land subsidence in the Milford area is demonstrated by three lines of evidence: (1) collapse structures, (2) well casings that protrude higher above the land surface than when first placed in the borehole, and (3) lower elevations at National Ocean Survey (formerly U.S. Coast and Geodetic Survey) bench marks in 1970 than in 1908. This evidence shows that land subsidence in the Milford area is of two types, each having a different origin. One type has a near-surface origin in the clay-silt zone in the upper part of the principal groundwater reservoir, and the other is in the lower artesian aquifers of the principal ground-water reservoir. The amount of observed subsidence ranges from 0.05 foot (0.015 m) at the bench mark at Read to about 6 feet (1.8 m) at collapse structures in the Hay Springs area.

Utah↗
USGS1976

Fracturing and subsidence of the land surface caused by the withdrawal of ground water in the Milford area, Utah

Fracturing and subsidence of the land surface in the Milford area of Utah have resulted from the decline of water levels due to pumping in unconsolidated deposits of Quaternary age. To the writers' knowledge, these are the first such effects of ground-water withdrawal reported in Utah. The fracturing is in an area about 1 mile (1.6 km) wide and 11 miles (18 km) long near Milford, in an unsaturated clay-silt zone (locally peaty at top) in the upper part of the principal ground-water reservoir. The fractures range in length from several feet to more than 100 feet (30 m), and their maximum measured depth in 1972 was 4 feet (1.2 m). Land subsidence in the Milford area is demonstrated by three lines of evidence: (1) collapse structures, (2) well casings that protrude higher above the land surface than when first placed in the borehole, and (3) lower elevations at National Ocean Survey (formerly U.S. Coast and Geodetic Survey) bench marks in 1970 than in 1908. This evidence shows that land subsidence in the Milford area is of two types, each having a different origin. One type has a near-surface origin in the clay-silt zone in the upper part of the principal groundwater reservoir, and the other is in the lower artesian aquifers of the principal ground-water reservoir. The amount of observed subsidence ranges from 0.05 foot (0.015 m) at the bench mark at Read to about 6 feet (1.8 m) at collapse structures in the Hay Springs area.

Utah↗
USGS1977

Microwave radiometric survey of the San Joaquin nuclear project site, Kern County, California

An airborne microwave survey was made in the region of the San Joaquin nuclear project site near Bakersfield, Calif. The purpose of the study was to determine if the variability of soil emissivity due to moisture content is a valid near-surface expression of buried fault systems. The results showed the existence of linear-emissivity anomalies paralleling, and to some extent, overlying the Greeley and Pond-Poso Creek faults. The anomalies seem to be direct expressions of silt-filled, northwesterly trending channels of the Pond-Poso Creek-Tulare Lake distributary system. The location, orientation, and linearity of the distributary channels suggest an association with buried faults, but no relationship has yet been determined.

California↗
USGS1975

Preliminary results of a gravity survey of the Henrys Lake quadrangle, Idaho and Montana

A gravity survey of the Henrys Lake quadrangle shows that a gravity low with about 10 milligals of closure coincides with the Henrys Lake basin. The low is interpreted to reflect a basin fill of 1,100 m or more of Cenozoic sediments and volcanic rock. The data indicate that on the east and probably on the west the basin is bounded by northwest- and north-trending faults, and near its waist by the east-trending Centennial fault. A model constructed across the Henrys Lake basin suggests a northwest-trending fault, located near the southeast corner of Henrys Lake and concealed beneath the basin fill. The sparse gravity data east of the Centennial Mountains are not sufficient to provide any evidence on the extension of the Centennial fault across the Henrys Lake basin.

Idaho, Montana, Wyoming↗
USGS1978

Reconnaissance for microbial activity in the Magothy aquifer, Bay Park, New York, four years after artificial recharge

Tertiary-treated sewage effluent was injected into the Magothy aquifer at Bay Park, Long Island, N.Y., between 1968 and 1973. In 1977, the microbial flora in water samples from the injection well and from three nearby wells were surveyed. Differences in the composition of the microbial flora among the four wells were found. A bacterial community dominated by facultative and obligate anaerobes, including two Clostridium species and methanogenic bacteria, was found at a well 6.1 m from the injection well. By contrast, except for isolation of Clostridium sphenoides from a well 30 m away, only obligate aerobes and facultative anaerobes were found in water from the injection well and the 30 m well. Only a small number of obligate aerobes were found in samples from a well 61 m away. These results suggest that nutrients in the recharge water formed an organically enriched zone to at least a distance of 6.1 m from the point of injection but not as far as 61 m. Extensive pumping at the end of the injection program apparently removed exogeneous nutrients near the injection well.

New York↗
USGS1975

Lithium in sediments and brines--how, why and where to search

The possibility of using lithium in batteries to power electric vehicles and as fuel for thermonuclear power has focused attention on the limited resources of lithium other than in pegmatite minerals. The Clayton Valley, Nev., subsurface lithium brine has been the major source of lithium carbonate since about 1967, but the life of this brine field is probably limited to several more decades at the present rate of production. Lithium is so highly soluble during weathering and in sedimentary environments that no lithium-rich sedimentary minerals other than clays have been identified to date. The known deposits of lithium, such as the clay mineral hectorite and the lithium-rich brines, occur in closed desert basins of the Southwest in association with nonmarine evaporites. However, the ultimate source for the lithium in these deposits may be from hydrothermal solutions. The search for previously unreported deposits of nonpegmatitic lithium should consider its probable association, not only with nonmarine evaporite minerals, but also with recent volcanic and tectonic activity, as well as with deposits of boron, beryllium, fluorine, manganese, and possibly phosphate.

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

Analyses and economic potential of monazite in Liberia

Eleven monazite samples from Liberia, including seven from beach sands, were analyzed by the X-ray fluorescence method. The monazite samples, containing only one-half percent impurities, were obtained by use of a hot Clerici-solution procedure for purification which was devised by the author. The percentage of the rare-earth elements in Liberian monazite concentrates does not differ greatly from that of monazite sands elsewhere in the world. The average of the 11 samples shows less praseodymium and neodymium than Russian and American monazites, but more cerium. Liberian coastal sands apparently contain sufficient reserves of monazite (and other heavy minerals of commerce) to encourage mining. A feasibility study of production and marketing of monazite from Liberian beach sands is recommended.

Journal of Research of the U.S. Geological Survey↗
USGS1976

Textural distribution of sea-floor sediments, south Texas Outer Continental Shelf

The general texture of sea-floor sediments along the south Texas Outer Continental Shelf was evaluated in terms of gravel, sand, silt, and clay components. The gravel component is quantitatively minor and is concentrated mainly in the southern sector; it consists, for the most part, of relict biogenic detritus dominated by molluscan shells. The sand component consists of terrigenous and biogenic detritus. Modern sand is localized along the shoreface sector, whereas palimpsest and relict sands characterize the northern and southern sectors, which are the respective locations of the ancestral Brazos-Colorado 'and Rio Grande deltas. The central sector contains an extensive modern mud blanket that appears to be migrating southward over relict deposits of the ancestral Rio Grande delta. The silt fraction is the highly dominant component of the mud blanket; silt appears to be hydraulically trapped within the shelf environment and constitutes the most abundant detrital component within the Outer Continental Shelf region. The subordinate clay component of the mud blanket is concentrated toward the shelf break and may be largely escaping into deeper water environments.

Texas↗
USGS1976

Exploration for porphyry copper deposits in Pakistan using digital processing of Landsat-1 data

Rock-type classification by digital-computer processing of Landsat-1 (formerly ERTS-1) multispectral scanner data has been used to select 23 prospecting targets in the Chagai District, Pakistan, 5 of which have proved to be large areas of hydrothermally altered porphyry containing pyrite. The known porphyry copper deposit at Saindak was used as a control area. Empirical maximum and minimum apparent reflectance limits were selected for each multispectral scanner band in each rock type classified, and a relatively unrefined classification table was prepared. Where the values for all four bands fitted within the limits designated for a particular class, a symbol for the presumed rock type was printed by the computer at the appropriate location; these symbols formed a classification map. Drainage channels, areas of mineralized quartz diorite, areas of pyrite-rich rock, and the approximate limit of propylitic alteration were very well delineated on the computer-generated map of the test area. The classification method was then used to evaluate 2,100 km 2 in the Mashki Chah region, east of the test area, and a partial check of the results was made in the field. The results of the experiment show that outcrops of hydrothermally altered and mineralized rock can be identified from Landsat-1 data under favorable conditions. The empirical method of digital computer classification of the multispectral scanner data was relatively unrefined and rapid. The five mineralized prospecting sites identified are in locations that I would not have selected as favorable on the basis of geologic knowledge or photogeologic interpretation at the time of the investigation.

Journal of Research of the U.S. Geological Survey↗
USGS1975

A model for earthquakes near Palisades Reservoir, southeast Idaho

The Palisades Reservoir seems to be triggering earthquakes: epicenters are concentrated near the reservoir, and quakes are concentrated in spring, when the reservoir level is highest or is rising most rapidly, and in fall, when the level is lowest. Both spring and fall quakes appear to be triggered by minor local stresses superposed on regional tectonic stresses; faulting is postulated to occur when the effective normal stress across a fault is decreased by a local increase in pore-fluid pressure. The spring quakes tend to occur when the reservoir level suddenly rises: increased pore pressure pushes apart the walls of the graben flooded by the reservoir, thus decreasing the effective normal stress across faults in the graben. The fall quakes tend to occur when the reservoir level is lowest: water that gradually infiltrated poorly permeable (fault-gouge?) zones during high reservoir stands is then under anomalously high pressure, which decreases the effective normal stress across faults in the poorly permeable zones.

Idaho↗
USGS1976

A portable helium sniffer

A portable helium sniffer has been developed for field use. The instrument is mounted in a four-wheel-drive pickup truck and can detect 50 parts per billion of helium in soil gas. The usefulness of helium sniffing in soil is being investigated as a prospecting tool in gas, oil, uranium, and geothermal prospecting as well as in earthquake prediction.

Journal of Research of the U.S. Geological Survey↗
USGS1976

Rise of a variable-viscosity fluid in a steadily spreading wedge-shaped conduit with accreting walls

Relatively rigid plates making up the outer 50 to 100 km of the Earth are steadily separating from one another along narrow globe-circling zones of submarine volcanism, the oceanic spreading centers. Continuity requires that the viscous underlying material rise beneath spreading centers and accrete onto the steadily diverging plates. It is likely that during the rise the viscosity changes systematically and that the viscous tractions exerted on the plates contribute to the unique pattern of submarine mountains and earthquake faults observed at spreading centers. The process is modeled by viscous creep in a wedge-shaped conduit (with apex at the sea floor) in which the viscosity varies as r m where r is distance from the apex and m is a parameter. For these conditions, the governing differential equations take a simple form. The solution for the velocity is independent of r and of the sign of m . As viscous stresses vary as r m-1 , the pattern of stress on the conduit wall is sensitive to viscosity variation. For negative m , the viscous pressure along the base of the conduit is quite uniform; for positive m , it falls toward zero in the axial region as the conduit base widens. For small opening angles, viscous forces push the plates apart, and for large ones, they oppose plate separation. Though highly idealized, the solution provides a tool for investigating tectonic processes at spreading centers.

Journal of Research of the U.S. Geological Survey↗
USGS1975

Possible extension of mineral belts, northern part of Coeur d'Alene district, Idaho

The ore deposits in the northern part of the Coeur d'Alene district are located within rocks of the Belt Supergroup that have been intruded by Cretaceous quartz monzonites. Lead-zinc-silver replacement veins constitute most of the deposits. The geometry of the district has been modified by post-ore faulting along the Osburn, Dobson Pass, and other faults. The original position of the Gem stocks, before their separation from the Diego Peak stocks by the Dobson Pass fault, can be approximately reconstructed by moving the truncated stocks and associated geochemical dispersion patterns back into matching positions. The known mineral belts are defined by dispersion patterns of both lead and the Pb:Zn ratio. Similar dispersion patterns of lead and the Pb:Zn ration northwest of the original position of the Gem stocks suggest that the mineral belts extend into that area.

Idaho↗
USGS1976

A geochemical study of oil in metalliferous veins, Idarado Mine, San Juan Mountains, Colorado

A tarry, benzene-soluble material is present in metal-rich veins in the Idarado mine, Ouray County, Colo., in an area not known to have petroleum resources. The material was compared chemically, spectometrically, and chromatographically with oils from four fields in the nearby Paradox basin. Each of these oil fields contains reservoir rocks equivalent to rock units known to extend beneath volcanic rocks near the mine. Carbon and sulfur isotope data and gas chromatographic data indicate a similarity between the oil from the nearby Sierra field and the oil from the mine. Thus, it seems both geologically and chemically possible that oil in the mine originated in Cretaceous sediments. Variations in the composition of oil from the mine and differences between the mine oil and Sierra oil, notably in the distributions of hydrocarbons, are attributed to bacterial degradation.

Colorado↗