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At least 505 records · Page 28Linked to original sources
USGS1976

Non-radiometric borehole geophysical detection of geochemical halos surrounding sedimentary uranium deposits

Roll-type uranium deposits are formed by the concentration of uranium by ground water in geochemical cells. Non-uranium minerals having different solubilities may be deposited ahead of or behind the uranium minerals, forming halos that surround the ore. In addition, oxidizing and reducing environmental conditions may cause zones of mineral alteration to develop beyond the limits of the uranium deposit. Certain physical property anomalies that are commonly associated with halos can be detected by relatively fast and inexpensive borehole geophysical measurements made either in individual holes, or between two adjacent holes. Borehole measurements that have been found to be useful include electrical resistivity, induced polarization, and magnetic susceptibility. Electrical resistivity is increased by the presence of calcite and other cementing minerals that sometimes create permeability barriers in the neighborhood of uranium deposits. Induced polarization (IP) response is increased by sulfide and clay minerals that are commonly found in anomalous concentrations near roll-type deposits. Magnetic susceptibility is usually decreased by the oxidation of magnetite to hematite or limonite in the zone of chemical alteration that is left as a trail behind roll fronts. Borehole measurements of electrical resistivity, induced polarization and magnetic susceptibility were made in the vicinity of a uranium roll-type deposit in south Texas. Results indicate that mineral halos can be detected by borehole measurements made. in wide-spaced drill holes, and that the total amount of drilling needed to find a deposit can be reduced substantially by this exploration approach.

Open-File Report↗
USGS1976

Progress report on geology of the Edwards aquifer, San Antonio area, Texas, and preliminary interpretation of borehole geophysical and laboratory data on carbonate rocks

This report describes the geology and porosity of the rocks of the Edwards aquifer, with particular attention to the eastern half of the San Antonio area. The data were obtained from geologic and geophysical studies of nine cored test holes, from laboratory analyses of samples of the aquifer materials, and from recent stratigraphic studies by other investigators. The Georgetown Formation and the Edwards Group or their equivalent stratigraphic units are extensively exposed in central Texas and they occur in the subsurface throughout southern Texas. They consist of a complex sequence of carbonate rocks deposited during Early Cretaceous time under different depositional conditions. Within the study area, the thickness of the carbonate rocks ranges from less than 400 feet (122 m) in the eastern part of the area to more than 600 feet (183 m) in the southwestern part. The depositional environments significantly affected the texture and the composition of the sediments. The Maverick Basin in the southwestern part of the study area was a euxinic basin surrounded by a barrier rudistid reef. Fine-grained carbonates and some associated evaporites occur within this basin. The San Marcos Platform in the eastern part of the study area was intermittently submerged by a transgressing continental sea. Much of the sediments are extensively reworked and burrowed by marine organisms. Several thick sequences of dolomites, evaporites, and associated collapsed deposits occur on the San Marcos Platform. The carbonates of the San Marcos Platform are extensively dissolved within the fresh-water zone. Much of the dissolution is selective of beds containing evaporites or porous dolomites. The dominant structural feature of the study area is a broad homocline that extends from nearly flat-lying beds on the Edwards Plateau to steeply dipping beds of the deep subsurface of the Gulf Coastal Plain. The homocline is interrupted by the Balcones Fault Zone, which is a zone of normal faults that extend across the study area. The intensity and complexity of faulting increases eastward as part of a progression from gentle flexures in the southwestern part of the study area to a complex pattern of tilted fault blocks on the San Marcos Platform.

Texas↗
USGS1977

A multi-channel digital telemetry system for low frequency geophysical data

An inexpensive general purpose digital telemetry system for collection of low frequency geophysical data from U.S. Geological Survey instruments (eg. tilt, strain, gravity, creep, water level, radon, magnetic field, resistivity, telluric current, temperature, etc.) has been designed and built. This system provides data for a more general interactive data acquisition, retrieval and analysis system. The field stations are self-contained, battery operated and housed in weather proof containers. Each accepts up to 15 analog data inputs in the range of -5 to +5 volts. The dynamic range is 70db. The units transmit information as FSK (Frequency Shift Keyed) tones onto either a phone line or radio link with up to 150 transmitters sharing one line. The average power consumption is 0.06 nR watts where n is the 1 number of input channels transmitted and R is the sample rate in minutes -1 . The central receiver-recorder unit accepts and decodes the FSK tones and converts, formats and records the digital data together with time information and station identification on IBM combatible magnetic tape. The digital data are also converted and recorded in analog form for visual monitoring.

Open-File Report↗
USGS1978

Geophysical data from the 1975 cruise of the NOAA ship Surveyor in northern Gulf of Alaska

In April and Flay 1975, a U.S. Geological Survey marine geology field party under the leadership of Bruce F. Molnia and Paul R. Carlson collected geophysical data from the N.O.A.A. ship Surveyor. The cruise, which consisted of 3 legs, studied the area between Cross Sound and Seward (Figure 1). Maps 1, 2, and 3 (scale 1:250,000) show the location of track lines and ship positions for the 3 legs.

Alaska↗
USGS1980

Borehole geophysical measurements for hole UE25-3, Nevada Test Site, Nuclear Waste Isolation Program

Borehole geophysical measurements made in drill hole UE25a-3 with a U.S. Geological Survey research well-logging truck are presented in this paper. The purpose of these logging measurements is to provide in-situ physical properties information that is not commercially available on drill hole UE25a-3. Well logs are presented in this paper for dual-detector density, normal resistivity, gamma-ray, neutron-neutron, induced polarization, and magnetic susceptibility measurements. These data are analyzed for correlations with the core lithology. Hole-to-surface measurements made from drill hole UE25a-3 indicate the presence of two resistive bodies at depth. The deeper resistive anomaly may be related to a granitic intrusion.

Nevada↗
USGS1980

Instrument specifications and geophysical records for airborne electromagnetic survey of parts of Iron, Baraga, and Dickson Counties, Michigan

The data presented herein is from an airborne electromagnetic INPUT* survey conducted by Geoterrex Limited of Canada for the U.S. Geological Survey. The survey area is located in the central part of the Upper Peninsula of Michigan, within parts of Iron, Baraga, and Dickinson Counties. The general area covered is between 46°00' and 46°30' latitude and 88°00' and 88°30' longitude (fig. 1). The INPUT survey was flown as part of a U.S. Geological Survey CUSMAP (Conterminous United States Mineral Appraisal Program) project focusing on the Iron River 2° quadrangle. The survey was flown in order to provide geophysical information which will aid in an integrated geological assessment of mineral potentials of this part of the Iron River 2° quadrangle. The flight line spacing was chosen to maximize the areal coverage without a loss of resolution of major lithologic and structural features. East-west flight lines were flown 400 feet above ground at 1/2 mile intervals. Aerial photos were used for navigation, and the flight path was recorded on continuous-strip film. A continuously recording total field ground magnetic station was used to monitor variations in the Earth's magnetic field. One north-south line was flown to provide a tie for the magnetic data, which was recorded simultaneously with the electromagnetic data by a sensor mounted in the tail of the aircraft. This report is one of two open-file reports. The map in the other report Heran and Smith (1980) shows locations of the fiducial points, the flight lines, preliminary locations of anomalies and conductive zones; all plotted on an air photomosaic. The latitude and longitude ticks marked on this map are only approximate due to distortion in air photos used to recover the flight line position. This map is preliminary and is not to be considered a final interpretation. The present report contains a description of the instrument specifications, a copy of the ground station magnetic data, and a record of the electromagnetic and magnetic data, with reference to the digital data of the flight records. The purpose of two reports is to make the analog and magnetic records available separate from the anomaly map. The following sections on the general description of the INPUT system are abridged from a typical interpretation report prepared by Geoterrex Limited of Ottawa, Canada for the U.S. Geological Survey.

Michigan↗
USGS1980

Preliminary field geotechnical and geophysical logs from a drill hole in the Capps coal field, Cook Inlet region, Alaska

The drilling and logging activity described in this report was undertaken in August 1979, as part of the Energy Lands program of the U.S. Geological Survey. The general objectives of the project, of which this work is a part, are to provide an understanding of the nature, location, and extent of the engineering and environmental concerns in potential coal-development areas of the Cook Inlet region, Alaska. The geotechnical and geophysical logs presented in this report provide some of the basic physical-property and engineering data needed to evaluate geologic hazards, and to predict the response of geologic materials to large-scale coal mining and related development in the Capps coal field of the Beluga coal area. Specifically, the information may be used to help determine such things as natural- and cut-slope stability, spoil-pile stability, ground response to seismic activity, blasting effects, excavatability, bulking characteristics, ground-water conditions, and erosion potential.

Alaska↗
USGS1982

Preliminary geotechnical and geophysical logs from drill hole 2C-80 in the Capps coal field, Cook Inlet region, Alaska

The drilling and logging information provided in this report was collected during September 1980 as part of the Energy Lands program of the U.S. Geological Survey. Drill hole 2C-80 is located in the Capps Coal Field, approximately 100 km (62 mi) west of Anchorage, Alaska (fig. 1). The drilling was undertaken to obtain information on the geotechnical characteristics of a part of the coal-bearing Tyonek Formation and overlying surficial deposits. The preliminary results of a previous drill hole (1C-79), located 1.3 km (0.8 mi) northeast of drill hole 2C-80, were reported by Chleborad and others (1980). The Tyonek Formation is early Oligocene to middle Miocene in age (Wolfe and Tanai, 1980). At the drill site it is overlain by a thin colluvial deposit of Quaternary age. The drilling and continuous core sampling penetrated 19.5 m (63.9 ft) of overburden, a major coal bed (Waterfall bed), and approximately 29 m (95.1 ft) of underlying material, to a total depth of 61 m (200 ft). Drill hole 2C-80 stratigraphically overlaps drill hole 1C-79 and continues down section approximately 33 m (108 ft). A proposed open pit coal-mining plan (Placer Amex, Inc., 1977, status report of December 1977) outlines a sequential mining and reclamation scheme for five areas in the Capps Coal Field. Figure 2 shows the location of drill holes 2C-80 and 1C-79 with respect to the proposed mining areas as well as selected surface features. A general description of the geology and natural hazards of the region are given by Schmoll and others (1981). The generalized lithology interpreted from core obtained from drilling and supplemented by outcrop mapping accomplished during the 1979 and 1980 field seasons is presented in figure 3. A more detailed lithologic log is presented as part of the geotechnical log. The geotechnical and geophysical logs presented herein (pls. 1 and 2) provide basic physical-property and engineering data useful in predicting the response of geologic materials to proposed large-scale coal mining and related development, and in identifying and assessing potential geologic hazards.

Alaska↗
USGS1984

Geophysical well logs for eleven drill holes at the Colorado School of Mines Experimental Mine Site, Idaho Springs, Colorado

The following geophysical well log measurements were made in eleven drill holes above the Colorado School of Mines Experimental Mine at Idaho Springs, Colorado: (1) acoustic velocity (2) resistivity, (3) caliper, (4) gamma-gamma density, (5) neutron-thermal neutron, (6) gamma ray, (7) induced polarization (IP), (8) self potential (SP), and magnetic susceptibility. The density and acoustic velocity logs indicate extensive fracturing in each of the drill holes. Variations in the relative amount of felsic or mafic mineral components in the rocks can be inferred from the magnetic susceptibility and gamma ray well log responses. Zones containing metallic sulfide mineralization are interpreted from the IP well log response.

Open-File Report↗
USGS1983

FFTFIL; a filtering program based on two-dimensional Fourier analysis of geophysical data

The filtering program 'fftfil' performs a variety of operations commonly required in geophysical studies of gravity, magnetic, and terrain data. Filtering operations are carried out in the wave number domain where the Fourier coefficients of the input data are multiplied by the response of the selected filter. Input grids can be large (2=number of rows or columns=1024) and are not required to have numbers of rows and columns equal to powers of two.

Open-File Report↗
USGS1983

Commercial geophysical well logs from the USW G-1 drill hole, Nevada Test Site, Nevada

Drill hole USW G-1 was drilled at Yucca Mountain, Nevada Test Site, Nevada, as part of the ongoing exploration program for the Nevada Nuclear Waste Storage Investigations. Contract geophysical well logs run at USW G-1 show only limited stratigraphic correlations, but correlate reasonably well with the welding of the ash-flow and ash-fall tuffs. Rocks in the upper part of the section have highly variable physical properties, but are more uniform and predictably lower in the section.

Open-File Report↗
USGS1983

Geophysical methods for locating abandoned wells

A preliminary study of the feasibility of using geophysical exploration methods to locate abandoned wells containing steel casing indicated that magnetic methods promise to be effective and that some electrical techniques might be useful as auxiliary methods. Ground magnetic measurements made in the vicinity of several known cased wells yielded total field anomalies with peak values ranging from about 1,500 to 6,000 gammas. The anomalies measured on the ground are very narrow and, considering noise due to other cultural and geologic sources, a line spacing on the order of 50 feet (15.2 m) would be necessary to locate all casings in the test area. The mathematical model used to represent a casing was a set of magnetic pole pairs. By use of a non-linear least squares curve fitting (inversion) program, model parameters which characterize each test casing were determined. The position and strength of the uppermost pole was usually well resolved. The parameters of lower poles were not as well resolved but it appears that the results are adequate for predicting the anomalies which would be observed at aircraft altitudes. Modeling based on the parameters determined from the ground data indicates that all of the test casings could be detected by airborne measurements made at heights of 150 to 200 feet (45.7-61.0 m) above the ground, provided lines spaced as closely as 330 feet (100 m) were used and provided noise due to other cultural and geologic sources is not very large. Given the noise levels of currently available equipment and assuming very low magnetic gradients due to geologic sources, the detection range for total field measurements is greater than that for measurements of the horizontal or vertical gradient of the total intensity. Electrical self-potential anomalies were found to be associated with most of the casings where measurements were made. However, the anomalies tend to be very narrow and, in several cases, they are comparable in magnitude to other small anomalies which are not directly associated with casings. Measurements made with a terrain conductivity meter and slingram system were negative. However, from other work it is known that electrical resistivity and induced polarization measurements can be influenced significantly by the presence of a casing. It is concluded that detailed ground magnetic surveys would be effective in locating casings within relatively small areas. It would be very costly to cover large areas with ground surveys but it appears that airborne surveys may be a cost-effective means of locating wells when the search area is on the order of a few square miles or more. Also, airborne methods could be used in some areas where access to the area on the ground is difficult or impossible.

Open-File Report↗
USGS1983

Preliminary lithologic, geotechnical, and geophysical data from drill hole CW-81-2, Chuitna West coal field, Cook Inlet region, Alaska

The drilling and logging activity described in this report was undertaken in July 1981, as part of the Energy Lands program of the U.S. Geological Survey. The general objectives of the project of which this work is a part are to provide an understanding of the nature, location, and extent of the engineering geology and environmental geology concerns in areas of potential coal development in the Cook Inlet region, Alaska. The lithologic, geotechnical, and geophysical data presented in this report include some of the data needed to evaluate geologic hazards, and to predict the response of geologic materials to large-scale coal mining and related development in the Chuitna West coal field of the Beluga coal resource area. Specifically, the information may be used in evaluation of natural- and cut-slope stability, spoil-pile stability, ground response to seismic activity, blasting effects, excavatability, ground-water conditions, and erosion potential. The drill site (fig. 1, point C), located on the edge of a small, gently sloping basin draining northwestward into the Chuitna River, is approximately 90 km, (55 mi) west of Anchorage, Alaska, and 29 km (18 mi) northwest of Tyonek, a native village on the northwest side of Cook Inlet.

Alaska↗
USGS1983

Geophysical and geologic studies in southern Mecklenburg County and vicinity, North Carolina and South Carolina

Geophysical methods consisting of gravity, aeromagnetics and aeroradioactivity have been applied to part of the Charlotte and Carolina slate belts in southern Mecklenburg County and vicinity to help interpret geology, lithology and structure. High aeroradioactivity is associated with potassium-rich granitic plutons, muscovite-rich gneisses, schists, and metavolcanic rocks; positive gravity and magnetic anomalies are associated with gabbro plutons; and negative gravity anomalies are associated with granitic plutons. At the west side of the slate belt, the Tillery phyllite is interpreted as having undergone progressive metamorphism. The underlying Uwharrie Formation extends into the Charlotte belt where it is mapped as metavolcanic rocks. Gravity models of the Carolina slate belt indicate that it is a synform containing a wedge of metasedimentary and volcanoclastic rock on plutonic basement. The basement is exposed in the adjacent Charlotte belt antiform. The northern Charlotte belt contains mainly plutonic rocks which have been divided into 3 supergroups of plutons based upon chemistry, mineralogy, texture, and age. They are: 1. Old Plutonic supergroup - plutons 545-490 m.y. that are medium to coarse-grained tonalite, quartz diorite, and granodiorites. 2. Concord-Salisbury supergroup -- plutons 426-350 m.y. which form sheet-like intrusions of differentiated gabbro; local volcanic centers with ring complexes 13 km in diameter that suggest magma chambers 0 - 8 km deep; smaller bodies of diorite, monzonite, and syenite; and small Salisbury type granodiorites. 3. Landis supergroup -- plutons 350-280 m.y. that are usually very coarse-grained, porphyritic, 'big feldspar,' potassium-rich granites. The Mecklenburg-Weddington gabbro complex of the Concord-Salisbury supergroup, the largest feature in the study area, contains three large gabbro plutons. The gabbro intruded old Plutonic complex rocks and could-have produced the metamorphic reaction K-feldspar + sillimanite quartz + muscovite reflected in the mineral assemblage of adjacent felsic metavolcanic rocks. Gravity models indicate a lopolith 3.5- to 4.5-km thick with a 2 km sill extending to the northeast. Positive magnetic and gravity anomalies suggest the lopolith is. connected with the Concord gabbro complex to the northeast. The sheet-like intrusions of Concord-Salisbury group gabbros, forming the core of the composite 5atholith, have medium-grained Salisbury type granodiorite above, and coarser-grained Landis granite below. The position of the supergroups as presently exposed may be a function of level of erosion versus level of emplacement. The plutons in the composite batholith span 200 m.y. according to current age data and are arranged with the oldest at the top and the youngest at the bottom. However, Rb-Sr and K-At ages in the Piedmont are more likely to reflect age of crustal uplift than the age of metamorphism or intrusion. The Charlotte belt composite batholith, therefore, may very well be the result of a shorter single tectonic event or process.

North Carolina, South Carolina↗
USGS1985

Geophysical well log data for study of water flow in fractures near Mirror Lake, West Thornton, New Hampshire

Four closely spaced boreholes were drilled through approximately 20 meters of till into schist bedrock near Mirror Lake, West Thornton, New Hampshire. The site was selected for borehole geophysical research because it is included in a detailed groundwater study where the effects of flow in fractures on flow in overlying drift deposits is being studied. Three of the boreholes are approximately 100 meters in depth, and the fourth is approximately 230 meters in depth. All four boreholes were logged with caliper, acoustic, gamma, single-point-resistivity, and acoustic televiewer logs. Fracture sets dipping approximately 45 degrees to the east were detected in all four boreholes. Two sets of deeper fractures were detected near the bottom of the deepest borehole. Acoustic waveform logs were obtained in all boreholes using three different source frequencies, 34, 15, and 5 kilohertz, for future comparison with surface to borehole seismic data.

New Hampshire↗
USGS1992

Well-construction, water-level, geophysical, and water-quality data for ground-water monitoring wells for Arnold Air Force Base, Tennessee

Sixty-five wells were installed at 39 sites in the Arnold Air Force Base area in Coffee and Franklin Counties, Tennessee. The wells were installed to provide information on subsurface lithology, aquifer characteristics, ground-water levels, and ground-water quality. Well depths ranged from 11 to 384 feet. Water-quality samples were collected from 60 wells and analyzed for common inorganic ions, trace metals, and volatile organic compounds. The median dissolved-solids concentrations were 60 milligrams per liter in the shallow aquifer, 48 million gallons per liter in the Manchester aquifer, 1,235 milligrams per liter in the Fort Payne aquifer, and 1,712 milligrams per liter in the upper Central Basin aquifer. Caliper, temperature, natural gamma, electric, neutron porosity, gamma-gamma density, and acoustic velocity borehole-geophysical logs were obtained for the six deep wells completed below the Chattanooga Shale. Petrographic and modal analysis were performed on rock samples from each deep well. These six deep wells provide the first information in the study area on hydraulic head and water quality from below the Chattanooga Shale.

Tennessee↗
USGS1993

Data from core analyses, aquifer testing, and geophysical logging of Denver Basin bedrock aquifers at Castle Pines, Colorado

This report contains data pertaining to the geologic and hydrologic characteristics of the bedrock aquifers of the Denver basin at a site near Castle Pines, Colorado. Data consist of a lithologic- description of about 2,400 ft of drill core and laboratory determinations of mineralogy, grain size, bulk and grain density, porosity, specific yield, and specific retention for selected core samples. Water-level data, atmospheric-pressure measurements, aquifer-compression measurements, and borehole geophysical logs also are included.

Open-File Report↗