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At least 577 records · Page 32Linked to original sources
USGS2005

Mudstone sedimentation at high latitudes: Ice as a transport medium for mud and supplier of nutrients

Controls on mudstone deposition at high latitudes are poorly known relative to low latitudes. In recent sediments deposited in these environments, ice significantly influences sediment transport and primary productivity. The products of ice transport are relatively well known in glacimarine settings, but are less well known from below melting sea ice. This latter setting is significant as today it is associated with high primary organic productivity. The aim of this study is to assess how sea ice might have controlled lithofacies variability and organic-matter distribution and preservation in an ancient marine, siliciclastic mudstone-dominated succession deposited at high latitudes. Combined sedimentary logging, optical and electron optical (back-scatte red electron imagery), geochemical, and isotopic methods were used to determine sample variability in forty-five samples collected from the Lower Cretaceous succession in the Mikkelsen Bay State #1 borehole (North Slope, Alaska). The succession overall fines upward and contains muddy sandstones and sand- and silt-bearing, clay-rich mudstones towards its base in contrast to clay-rich and clay-dominated mudstones towards its top. Some of the mudstone units exhibit thin (< 5 mm), relic-beds that fine upward weakly. In some units small (0.5 mm), bed-parallel silt-filled microburrows disrupt depositional laminae whereas in others pervasive burrowing completely obliterates original depositional textures. Many of the units are pelleted. These mudstones are unusual in that they contain minor but very striking outsize grains, composed of subrounded to rounded sand and granule-size material. In addition, they are good petroleum source rocks, with between 2.8 and 5.9 wt % total organic carbon, of predominantly Type II kerogen. The organic matter has an isotopic signature ranging from -25.4??? ??13C to -28.1??? ??13C. Thin tuffs (< 20 mm) and carbonate-cemented units are also present. Given the absence of significant polar ice in the Early Cretaceous the outsized grains are interpreted to have been deposited from a combination of melting, dirty anchor, and fast ice. The mud fraction, which forms the bulk of the sediment, is interpreted to have been deposited from melting, sediment-laden frazil ice, and fast ice. After deposition sediments were partially reworked by bottom currents generated by brine rejection during sea ice formation. Sympagic organisms, grazing on algae and bacteria both within and below the ice, pelleted the sediment. Bioturbation, which varies through the succession, indicates that sedimentation probably occurred beneath a predominantly oxic or dysoxic water column. In this setting productivity was fueled by nutrients released from melting sea ice in the marginal ice zone. The good petroleum source potential of these mudstones is attributed to high organic productivity coupled to episodic and rapid sedimentation rather than existence of bottom-water anoxia linked to upwelling. Because sea-ice rafting was probably the dominant sediment transport mechanism it is not appropriate to use sequence stratigraphic methodology to predict lithofacies variability in this environment. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

Journal of Sedimentary Research↗
USGS2010

Stratigraphic response across a structurally dynamic shelf: The latest guadalupian composite sequence at Walnut Canyon, New Mexico, U.S.A

The uppermost Yates and Tansill formations (Late Permian), as exposed along Walnut Canyon in Carlsbad Caverns National Park, New Mexico, USA, provide a unique opportunity to document the depositional architecture of a progradational, oversteepened, and mechanically failure-prone carbonate platform. Detailed facies mapping permitted critical assessment of depositional processes operating along this structurally dynamic platform margin. At the shelf crest, thick (12 m), vertically stacked fenestral-pisolite-tepee complexes indicate a stable shoreline. Early lithification of sediments and extensive cementation fostered rapid vertical accretion and allowed the shelf crest to easily adjust to base-level oscillations by stepping landward, stepping seaward, or aggrading. This production imbalance-in combination with syndepositional brittle failure and down-to-the-basin tilting(< 5??)-generated 22 m of depositional relief as measured from nearly horizontal (< 2??) shelf-crest toplap to an outer-shelf downlap surface (< 1??). Mechanical failure of Capitan-equivalent back-reef strata is constrained by stratigraphic architecture, fracture properties, and a highly refined fusulinid biostratigraphic framework. Where fractures tip out, down-to-the-basin rotation is often observed with concurrent seaward thickening of overlying beds, indicating that such fractures functioned as a syndepositional hinge. A facies disjunction and horizontally juxtaposed fusulinid zonation were documented across an 80?? seaward-dipping dilational fracture filled with polymict breccia. An overlying damage zone consisting of spar-cemented fractures nested within silt-filled fractures illustrates periodic reactivation. Field relationships indicate that the dilational fracture approximates a paleoescarpment that resulted from catastrophic failure of the Capitan platform margin. Younger strata onlapped the paleoescarpment and gradually filled the reentrant. This mechanically compromised paleoescarpment was subsequently reactivated during the latest Guadalupian lowstand and was subaerially filled by siliciclastics and polymict breccia derived from the platform top. Results from Walnut Canyon indicate that shelf crest aggradation dominantly controlled the shelf-crest to outer-shelf profile, although this was temporarily modified by brittle failure and down-to-the-basin tilting, and mass wasting. Copyright ?? 2010, SEPM (Society for Sedimentary Geology).

Journal of Sedimentary Research↗
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

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↗
USGS1989

Behaviour of abandoned room and pillar mines in Illinois

Little comprehensive information has been reported on the behaviour of room-and-pillar mines. The objective of this paper is to present case data on mine failures in the Illinois basin for use in practice. Presented are results of an ongoing study and details on the site characteristics of cases where sags have developed on the surface. Site data are reported to show the geologic, mining, and sag conditions that existed. Sags mainly develop from pillar, floor, or pillar-floor failure. The character of the sags depends upon the type of mine failure as well as the overburden response. Preliminary results show that the statistical no-risk tributary pressure decreases over 300% as the mine age increases from about 2 to 100 years at a long-term value of approximately 300 psi (2070 kPa). As more information is collected and more analysis is done, the allowable tributary pressure can be determined for different site conditions. A plot is also reported that depicts the relationship of the maximum subsidence to site conditions. It was found that the modified subsidence factor was heavily dependent upon the overburden rock thickness. ?? 1989 Chapman & Hall Ltd.

International Journal of Mining and Geological Eng↗
USGS1984

Water-resources reports prepared by or in cooperation with the U.S. Geological Survey, Kansas, 1886-1983

Water-resources data and the results of hydrologic investigations in Kansas are published or released by the U.S. Geological Survey, by cooperating State or Federal agencies, or by technical or scientific journals. This report lists more than 800 water-resources reports prepared by or in cooperation with the U.S. Geological Survey in Kansas for 1886 through 1983. The reports are listed by author, publication series, year of publication, and subject. The first water-resources investigations by the U.S. Geological Survey in Kansas was completed by A.C. Peale in 1886. The first cooperative program with a State agency was initiated 9 years later in 1895 and included the first stream-gaging stations operated by the Survey in western Kansas. The U.S. Geological Survey continues to investigate the occurrence, quantity, quality, distribution, and movement of surface and ground waters within the State. (USGS)

Open-File Report↗
USGS1974

Chemical variations across the Alaska-Aleutian Range batholith

A study of 79 chemical analyses of plutonic rocks in the northern part of the Alaska-Aleutian Range batholith shows that K 2 O and SiO 2 in Late Cretaceous and Tertiary rocks decrease toward the Pacific margin and that Al 2 O 3 and CaO increase. Plots for Fe 2 O 3 , FeO, MgO, and TiO 2 suggest a possible increase toward the Pacific margin; Na 2 O, H 2 O+, and MnO show no significant trends across the batholith. Oxide trends for groups of plutons in the western and eastern parts of the batholith in general are opposite that of the groups combined. For the Jurassic plutonic rocks, K 2 O may decrease toward the Pacific margin; other oxides show considerable scatter, and meaningful trends are not readily apparent. The oxide trends across the batholith are similar to trends across the central Sierra Nevada batholith of California, with the exception of SiO 2 and A1 2 O 3 , which show no significant changes. In the Coast Range batholith of British Columbia, potassium also increases away from the Pacific margin. The increase in K 2 O toward the continent in the Alaska-Aleutian Range batholith is similar to that found across Quaternary volcanic island arcs, where K 2 O content increases directly with increasing depth to inclined seismic zones. This increase suggests that generation of magma may have taken place along, or above, a paleoseismic zone. Geologic evidence supports such a model for the Jurassic plutonic rocks, which represent the roots of an early Mesozoic magmatic arc that probably formed above a descending oceanic plate. However, the hypothesis that magma for Late Cretaceous and Tertiary plutonic rocks was generated along seismic zones does not fit available geologic evidence, and an anatectic model cannot be ruled out.

Alaska↗
USGS2013

Web-based flood database for Colorado, water years 1867 through 2011

In order to provide a centralized repository of flood information for the State of Colorado, the U.S. Geological Survey, in cooperation with the Colorado Department of Transportation, created a Web-based geodatabase for flood information from water years 1867 through 2011 and data for paleofloods occurring in the past 5,000 to 10,000 years. The geodatabase was created using the Environmental Systems Research Institute ArcGIS JavaScript Application Programing Interface 3.2. The database can be accessed at http://cwscpublic2.cr.usgs.gov/projects/coflood/COFloodMap.html. Data on 6,767 flood events at 1,597 individual sites throughout Colorado were compiled to generate the flood database. The data sources of flood information are indirect discharge measurements that were stored in U.S. Geological Survey offices (water years 1867–2011), flood data from indirect discharge measurements referenced in U.S. Geological Survey reports (water years 1884–2011), paleoflood studies from six peer-reviewed journal articles (data on events occurring in the past 5,000 to 10,000 years), and the U.S. Geological Survey National Water Information System peak-discharge database (water years 1883–2010). A number of tests were performed on the flood database to ensure the quality of the data. The Web interface was programmed using the Environmental Systems Research Institute ArcGIS JavaScript Application Programing Interface 3.2, which allows for display, query, georeference, and export of the data in the flood database. The data fields in the flood database used to search and filter the database include hydrologic unit code, U.S. Geological Survey station number, site name, county, drainage area, elevation, data source, date of flood, peak discharge, and field method used to determine discharge. Additional data fields can be viewed and exported, but the data fields described above are the only ones that can be used for queries.

Colorado↗
USGS2024

Evaluation of coal mine drainage and associated precipitates for radium and rare earth element concentrations

Coal mine drainage (CMD) and associated metal-rich precipitates have recently been proposed as unconventional sources of rare earth elements (REEs). However, the potential occurrence of radium (Ra), a known carcinogen, with the REE-bearing phases has not been investigated. We hypothesized that Ra may occur in solids that are precipitated from CMD as a “radiobarite” solid solution ((Ba,Sr,Ra)SO 4 ) and/or adsorbed with hydrous metal oxides. REEs have been documented to sorb or co-precipitate with iron (Fe), manganese (Mn), and aluminum (Al) oxyhydroxide in CMD solids. Likewise, Ra has been documented to sorb to hydrous Fe and Mn oxides especially where sulfate (SO 4 ) and/or barium (Ba) concentrations are insufficient to precipitate radiobarite. Thus, we conducted the first-ever survey of Ra concentrations in corresponding CMD water and solid samples in the United States. Samples were analyzed from 4 untreated and 9 treated CMD sites in both the bituminous and anthracite coal regions of Pennsylvania across a range of pH and SO 4 concentrations. The dissolved Ra in CMD was relatively low (<0.5 Bq/L), consistent with radiobarite solubility; however, CMD solids were largely composed of amorphous Fe, Al, and Mn oxyhydroxide and silicate minerals. Ra was associated with Mn-enriched CMD solids, upwards of 875 Bq/kg. Total REE + yttrium (Y) content in the CMD solids was enriched upwards of 3600 mg/kg and was significantly correlated with Al content. These preliminary results suggest that REE extraction may target Al-rich solids to avoid Ra in Mn-rich solids.

Pennsylvania↗
USGS1955

Geologic investigations of radioactive deposits, semiannual progress report for June 1 to November 30, 1955

This report is a statement of progress during the six-months period from June 1 to November 30, 1955 on investigations of radioactive materials in the United States and Alaska, undertaken by the U.S. Geological Survey under the sponsorship of the U.S. Atomic Energy Commission. During the period the Geological Survey's program has been directed to an increasing extent toward the understanding of geologic conditions favorable for the concentration of uranium, rather than the search for minable deposits as such. This shift in emphasis is reflected in the decreased amount of exploration drilling during the period, and the accompanying increase in geologic programs of a long-range nature. The program is now directed toward a comprehensive understanding of the many factors involved in uranium geology, and the publication of reports that will make available information on all phases of the uranium program. Many investigations have progressed to the point where final reports are in preparation for future publication with the permission of the Atomic Energy Commission; for other investigations of a continuing nature it will be several years before final reports can be prepared. Formal publications (as distinguished from administrative Trace Elements Reports) published during the period include 10 Geological Survey Bulletins or Bulletin Chapters; 116 Geological Survey maps; 15 reports published in scientific journals; seven Trace Elements Reports sent to the Technical Information Service of the Atomic Energy Commission for distribution and sale to the public; and four Trace Elements reports placed on open file. In addition, a large number •of papers by geologists in the program were presented before scientific societies, and the 61 papers prepared for the United Nations International Conference .on the Peaceful Uses of Atomic Energy during the preceding report period were published by the United Nations.

Trace Elements Investigations↗
USGS1975

A computer-assisted procedure for information processing of geologic field data

We have examined several computer systems to see how they could aid information processing of geologic field data. The processing procedure we have chosen combines a systematic note-taking technique, a computer text-editor for creating files of data, and automated printing of selected data or of complete file copies. Traditional text notes are the foundation of each station record, and no coding of data is required. The text-editor used is an interactive computer system that allows any individual with typing skills to build and use data files. On the basis of our experience, an interactive text-editor can readily fulfill the data-handling needs of most geologic field projects and offers important advantages over other systems that were examined.

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

Remote-sensing methods for monitoring surface coal mining in the northern Great Plains

Recent studies at a large surface coal mine in southern Montana confirm that remote sensing is both feasible and effective for gathering land-use and environmental data (spatial, dynamic, and seasonal) for large-scale surface mines in the northern Great Plains. The Western Energy Co.'s Rosebud mine near Colstrip, Mont., was selected as a test site because it typifies surface operations in the Powder River Basin of Montana and Wyoming and elsewhere in the northern Great Plains. Several basic interpretive and analytical remote-sensing techniques were used to identify and delineate various categories of surface-mining operations and concurrent stages of reclamation that characterize most, if not all, such mining operations. Color infrared and black-and-white aerial photographs and a black-and-white band 5 Landsat image were used to identify (1) high wall and bench areas, (2) ungraded spoils, (3) graded and recontoured areas, (4) revegetated recontoured areas, (5) natural and impounded surface water, and (6) miscellaneous areas. Over the lifespan of an extensive surface mine, cultural and natural processes and cumulative environmental effects can be monitored by capitalizing on the close correlation between enhanced satellite imagery, infrared and (or) black-and-white aerial photography, standard large-scale topographic maps (such as U.S. Geological Survey 7½-minute quadrangle maps), and results of onsite inspection of mining and reclamation by Federal or State agencies.

Montana↗
USGS1974

Spectrophotometric determination of niobium in rocks

After acid decomposition and evaporation to volatilize silica, samples containing 0.5 6 μ g Nb are fused with pyrosulfate and dissolved in hydrochloric acid tartaric acid. Niobium is separated by thiocyanate extraction with amyl alcohol and back-extracting from the organic solvent with dilute hydrofluoric acid. Niobium is reacted with 4-(2-pyridylazo)-resorcinol to obtain a colored species. Analytical error, estimated from replicate analyses of eight U.S. Geological Survey standard rocks, ranges from 2.9 to 6.4 percent at the 1 27 μ g/g Nb level.

Journal of Research of the U.S. Geological Survey↗
USGS2003

Liquefaction potential index: Field assessment

Cone penetration test (CPT) soundings at historic liquefaction sites in California were used to evaluate the predictive capability of the liquefaction potential index (LPI), which was defined by Iwasaki et al. in 1978. LPI combines depth, thickness, and factor of safety of liquefiable material inferred from a CPT sounding into a single parameter. LPI data from the Monterey Bay region indicate that the probability of surface manifestations of liquefaction is 58 and 93%, respectively, when LPI equals or exceeds 5 and 15. LPI values also generally correlate with surface effects of liquefaction: Decreasing from a median of 12 for soundings in lateral spreads to 0 for soundings where no surface effects were reported. The index is particularly promising for probabilistic liquefaction hazard mapping where it may be a useful parameter for characterizing the liquefaction potential of geologic units.

Journal of Geotechnical and Geoenvironmental Engin↗
USGS2010

Viscosity and finite strength of the mantle as determined from water and ice loads

Some recent examples of transient Earth loads (Lake Bonneville, Utah; Glacier Bay, Alaska; northeast Greenland) indicate that both the viscosity and finite strength of the mantle are lower than is commonly presumed. A time constant (1/ e ) of 4000 years is estimated for Lake Bonneville, and of 1000 years for northeast Greenland. A strain rate of 10 −14 is typical. These figures imply viscosities in a homogeneous half space ranging from 10 20 to 10 21 poises. An upper limit of finite strength is set by Lake Bonneville at a few times 10 6 dyn/cm 2 . If mountain ranges like the Sierra Nevada or Himalaya are regarded as dynamically supported rather than static systems, this low value is not incompatible with other geologic observations.

Alaska, Utah↗
USGS1983

Correlation of metal occurrence and terrane attributes in the northwestern conterminous United States

The regional distribution patterns for 20 critical metals derived by an areal-pattern recognition technique leads me to conclude that metals are regularly distributed preferentially in the accreted and cratonic terranes studied in and surrounding the state of Oregon in the northwestern United States. The distribution patterns along distinctively different zones differ in these contrasting crusts across a concealed boundary that is established by strontium isotope data. Copper and gold appear to be abundant in both terranes; nickel, cobalt, chromium, and the platinum-group metals predominate in accreted terranes; lead, zinc, tin, and tungsten are concentrated locally along the boundary zone along the edge and in the interior of the cratonic terrane. The association of metals with accreted terranes and with restricted areas or lineaments in the craton further supports the metallogenetic hypothesis that metal materials are derived mainly from underlying ensialic and ensimatic crusts, and anticipates the possibility for remobilization of these materials along the same broad linear zones over geologic time.

California, Idaho, Montana, Nevada, Oregon, Utah, ↗
USGS1973

Use of machine-processable field notes in a wilderness mapping project (Granite Fiords area), southeastern Alaska

For reconnaissance geologic mapping and mineral resource evaluation of the Granite Fiords wilderness study area, we developed and used a system of machine-processable field notes. Preprinted field forms standardize notes and serve as checklists that insure collection of all available data. The use of this system cut in half the time required to record data at an outcrop. The system consists of three related but different types of preprinted field sheets, a key to abbreviations and codes, and a set of written instructions. The field sheets include a station sheet for basic outcrop data, a specimen sheet for rock samples, and a geochemical sheet for materials to be chemically analyzed. Data on the field sheets are keypunched on standard IBM cards, then arranged in subfiles and retrieved by using a card sorter. Our system is designed specifically for a region of granitic and metamorphic rocks but is easily modified for use in different geologic terranes. We offer four guidelines for developing a system of machine-processable field notes: (1) Time and money spent to develop the system must be worth its anticipated benefits. (2) The system should be as flexible as possible. (3) It is necessary to tailor the system to a particular geologic terrane or project objective. (4) The system should be as simple and self-explanatory as possible.

Alaska↗
USGS1975

An integrated-intensity method for emission spectrographic computer analysis

An integrated-intensity method has been devised to improve the computer analysis of data by emission spectrography. The area of the intensity profile of a spectral line is approximated by a rectangle whose height is related to the intensity difference between the peak and background of the line and whose width is measured at a fixed transmittance below the apex of the line. The method is illustrated by the determination of strontium in the presence of greater than 10 percent calcium. The Sr 3380.711-A line, which is unaffected by calcium and which has a linear analytical curve extending from 100-3,000 ppm, has been used to determine strontium in 18 standard reference rocks covering a wide range of geologic materials. Both the accuracy and the precision of the determinations were well within the accepted range for a semiquantitative procedure.

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