USGS Science⌕ Search

SEARCH · USGS Science

Results for “Explorer”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,405 records · Page 78Linked to original sources

Diamond drilling at the Ma'milah Mine, Kingdom of Saudi Arabia

The Ma'millah gold mine is about 90 km southeast of At Ta'if at lat 21°03'N., long 41°18'E., in southwestern Saudi Arabia. The deposit, which was worked extensively by ancient miners, consists of several veins and massive lenses of quartz along a regional fault. The extensive ancient mine workings, large size of some quartz outcrops, and significant gold content of several samples indicated that subsurface exploration was warranted. Accordingly, two holes were drilled into the deposit during the interval December 1972 to February 1973. The drill findings were disappointing; the grade of vein material was found to be too low to be of economic interest and the quartz bodies were found to pinch out both along strike and downdip. The drilling program therefore was terminated. The deposit is not worth further exploration

Ma'milah Mine↗

Integration of geological remote-sensing techniques in subsurface analysis

Geological remote sensing is defined as the study of the Earth utilizing electromagnetic radiation which is either reflected or emitted from its surface in wavelengths ranging from 0.3 micrometre to 3 metres. The natural surface of the Earth is composed of a diversified combination of surface cover types, and geologists must understand the characteristics of surface cover types to successfully evaluate remotely-sensed data. In some areas landscape surface cover changes throughout the year, and analysis of imagery acquired at different times of year can yield additional geological information. Integration of different scales of analysis allows landscape features to be effectively interpreted. Interpretation of the static elements displayed on imagery is referred to as an image interpretation. Image interpretation is dependent upon: (1) the geologist's understanding of the fundamental aspects of image formation, and (2.) his ability to detect, delineate, and classify image radiometric data; recognize radiometric patterns; and identify landscape surface characteristics as expressed on imagery. A geologic interpretation integrates surface characteristics of the landscape with subsurface geologic relationships. Development of a geologic interpretation from imagery is dependent upon: (1) the geologist's ability to interpret geomorphic processes from their static surface expression as landscape characteristics on imagery, (2) his ability to conceptualize the dynamic processes responsible for the evolution 6f interpreted geologic relationships (his ability to develop geologic models). The integration of geologic remote-sensing techniques in subsurface analysis is illustrated by development of an exploration model for ground water in the Tucson area of Arizona, and by the development of an exploration model for mineralization in southwest Idaho.

Open-File Report↗

Geological reconnaissance of some Uruguayan iron and manganese deposits in 1962

The Valentines iron deposit, Florida, Uruguay This report is the result of a request by the Uruguayan Government for technical assistance in the field of geology by the U.S. Geological Survey under the auspices of the U.S. Agency for International Development and the Corps of Engineers, United States Army. Geological reconnaissance was made in the Departamentos (counties) of Florida, Tacuarembo, Rivera, and Cerro Largo from January 5-15, 1962. The Valentines iron deposit is located about 261 km north of Montevideo, Uruguay. Exploration of the deposit was started about three years ago by Ingeniero Juan H. Caorsi and Q.I. Don Juan C. Goni of the Instituto Geologico del Uruguay. The deposit contains an estimated 23,500,000 tons of hematite-martite-magnetite iron ore that averages about 40 percent Fe. The ore occurs in highly metamorphosed itabirite of Precambrian age that is surrounded by coarse-grained metasomatized granite. The itabirite formation is about 50 meters thick and has been encountered down dip at a depth of 240 meters below its surface exposure. A few granite and amphibolite sills, commonly less than 1 m wide, lie within the itabirite. The deposit has been separated into three distinct parts along strike by small right-lateral slip faults or normal faults; the northern Apretado body, the central Aurora body, and the southern Esabella body. The orebody lies on the western flank of a gently plunging NNW-trending anticline. Mining of the ore and its transportation by railroad to Montevideo would present no special difficulties, but shipping by small barges should be investigated. Geological reconnaissance in the Tacuarembo and Rivera Departamentos Three mineralized areas lie in an area near the town of Minas de Corrales in the Departamento de Rivera; they are the Cerro Amelia, the Cerro de Papagayo, and the Cerro Iman. The Cerro Amelia is composed of small bands of iron-rich rock separated by an amphibolitic or mafic rock. Selective mining would be necessary to extract the 31,000 tons per meter of depth of iron-rich rock that ranges from 15 to 40 percent metallic iron. The Cerro de Papagayo district contains many small, rich deposits of ferruginous manganese ore. The ratio of Mn to Fe varies widely within each small deposit as well as from deposit to deposit. Some ferruginous manganese ore contains 50-55 percent manganese dioxide. Although there are many thousands of tons of ore in the district, small-scale mining operations are imperative. One deposit, the Cerro Avestuz manganese mine, was visited. The manganese ore body lies within contorted highly metamorphosed itabirite that contains both hard low grade and soft high grade ferruginous manganese ores estimated to average 40 percent Mn. About 38,000 tons of manganese ore is present in this deposit. The Cerro Iman is a large block of itabirite that contains about 40 percent Fe. The grade is variable and probably runs from less than 35 percent Fe to more than 50 percent Fe. No exploration has been done on this deposit. It is recommended that the Cerro de Iman area be geologically mapped in detail, and that a geological reconnaissance be made of the area that is between the Cuchilla de Corrales and the Cuchilla de Areycua/Cuchilla del Cerro Pelado area.

Cerro Largo;Florida;Rivera;Tacuarembo↗

Mineral resources of Elko County, Nevada

Of the 66 named mining districts in Elko County, 56 have been productive of one or more of 19 different commodities: 11 metals--copper, gold, silver, lead, zinc, mercury, tungsten, manganese, iron, uranium, and antimony; 8 nonmetals--sand and gravel, stone, barite, diatomite, gems, oil shale, volcanic ash, and clay. In addition to the commodities produced, at least 5 others--beryllium, molybdenum, tin, phosphorite, and petroleum, occur in amounts sufficient to warrant exploration. The other districts have been explored, but no production has been recorded. Total value-when-sold of production recorded through 1969 was nearly $91 million; actual production was considerably greater, especially if sand and gravel, barite, and other nonmetallic products before 1953 are included. In value of metals produced, the five highest districts are Mountain City ($26 million), Tuscarora ($11 million), Jarbidge ($10 million), Aura ($6 million), and Railroad (nearly $5 million). The Rio Tinto copper mine in the Mountain City district yielded $21 million. Of the 17 districts that produced nonmetallic minerals, Bootstrap .is the largest producer, containing the Rossi mine, one of the two largest barite mines in the United States. Most of /he metals produced name from veins and replacement deposits in limestone or dolomite near granitic stocks; exceptions are manganese and mercury, which are not associated with known or inferred stocks; mercury is further excepted because it occurs in volcanic rocks, as do a few deposits of the major metals. The largest deposit--the Rio Tinto lode--was a combination of fissure filling and replacement along a bedding plane shear zone 150 ft wide and 1,200 ft long in carbonaceous shale of the Valmy Formation; this deposit is apparently older than the Mountain City stock and its mineralization may be related to Paleozoic mafic volcanism later than a major thrust fault, inferred to underlie the area at a depth of about 5,000 ft. Most of the nonmetallic minerals mined were sedimentary bedded deposits, but mica was mined from pegmatite deposits, and turquoise from both placer and hydrothermal deposits. The largest known reserves of metals (1973) are of porphyry copper in the Dolly Varden district and gold in the Bootstrap district. Reserves of barite also are presumed to be large. The greatest potential for future production of metals, notably copper and gold, appears to be in the known districts or extensions of them and peripheral to deposits that are related to known or concealed plutons and thrust faults. Potential resources in deposits too low in grade to be worked profitably at the present time include all commodities that have been produced and, in addition, known, deposits of beryllium, molybdenum, tin, and phosphorite. Speculative resources in undiscovered deposits may reasonably be predicted to include all known commodities as well as others that are unsuspected. Petroleum may yet be produced from the Elko Formation and geothermal energy from the Ruby Valley and Elko areas.

Open-File Report↗

The Lisburne Group: A potential major hydrocarbon objective of the Arctic Slope, Alaska

The Lisburne Group, a thick carbonate rock unit of Mississippian and Pennsylvanian age, is one of the most widespread potential reservoir rock units in northern Alaska. A comprehensive review of the Lisburne in the subsurface of the eastern Arctic Slope indicates attractive reservoir characteristics in a favorable source and migration setting where numerous trapping mechanisms appear to be available. Evaluation of this group as a potential exploration objective is particularly timely in view of impending offshore sales in the Beaufort Sea and current exploration programs underway in the Prudhoe Bay area and the Naval Petroleum Reserve. Dolomite and sandstone have been identified as reservoir rocks. Oolitic grainstone is a common rock type, but all observations to date indicate little reservoir potential owing to complete void filling by calcite cement. The most important reservoir rock as judged by thickness, areal extent, and predictability is microsucrosic (10-30 μ) dolomite of intertidal to supratidal origin. It is present throughout the Lisburne and is most abundant near the middle of the sequence. Northward it decreases in thickness from 1,000 feet (300 m) to less than 100 feet (30 m). Porosity of the dolomite as determined in selected wells averages between 10 and 15 percent and attains a maximum of slightly more than 25 percent. Net thickness of reservoir rocks (i.e., rocks with greater than 5 percent porosity) varies in these wells from 140 feet (40 m) to 390 feet (120 m). Oil shows are common, and drill-stem tests have yielded as much as 1,600 bbls/day oil and 22 MMcf/day gas in the Lisburne pool of the Prudhoe Bay Field and as much as 2,057 bbls/day saltwater outside the field area. The occurrence of dolomite over such a large area makes its presence in the offshore Beaufort Sea and adjacent Naval Petroleum Reserve No. 4 fairly certain. The occurrence of sandstone as thick as 140 feet (40 m) in the middle and upper part of the Lisburne in two coastal wells suggests that larger areas of sandstone may be found to the north in offshore areas. Shows of oil and gas and a saltwater flow of 1,470 bbls/day have been recorded from this sandstone facies. Shales of Permian and Cretaceous age unconformably overlie the Lisburne, providing adequate sealing beds above potential reservoirs. Impermeable limestone (completely cemented grainstone) and thin beds of shale may serve as seals within the Lisburne, but the possibility of fractures in these units may negate their sealing capability. The most favorable source rock for Lisburne hydrocarbons appears to be Cretaceous shale that unconformably overlies the Lisburne east of Prudhoe Bay. This shale is reported by Morgridge and Smith (1972) to be a rich source rock and is the most likely source for the entire Prudhoe Bay Field. A source within the Lisburne or within the underlying Kayak Shale is postulated to explain oil shows in the southernmost Lisburne wells. This postulated source may be in a more basinal facies of the Lisburne and may be similar to dark shale in the upper Lisburne found in thrust slides in the Brooks-Range. Coal in the underlying Endicott Group is a possible source for dry gas. It is inferred that at the present time much of this coal is in a gas—generating regime downdip from the Prudhoe Bay Field area. Stratigraphic traps involving the Lisburne Group may exist as a result of widespread Permian and Cretaceous unconformities. Structural traps related to normal faulting may occur along the trend of the Barrow Arch, and faulted anticlines are numerous in the foothills of the Brooks Range. Combination traps are possible along the trend of the Barrow Arch at places where both stratigraphic and structural trap might exist.

Alaska↗

In situ analysis of coal using a 252CF-Ge(Li) borehole sonde

A borehole sonde using a 252 Cf neutron source and a Ge(Li) gamma-ray detector was field tested in a coal bed in Belmont County, Ohio, to ascertain whether such a device could be useful as a coal-exploration tool. In continuous motion, the sonde was used to accumulate successive spectra over short time intervals. The intensities of the capture gamma rays from hydrogen and of the decay gamma rays from aluminum were determined simultaneously in each spectrum. A log of the intensities versus depth shows the depth and thickness of the coal bed. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. These experiments show that it is feasible to use a 252 CfGe(Li) borehole sonde as an aid in coal exploration.

Open-File Report↗

Geological and geochemical investigations of uranium occurrences in the Arrastre Lake area of the Medicine Bow Mountains, Wyoming

Metasedimentary rocks of Precambrian X age in and near the Snowy Range wilderness study area of southeastern Wyoming are lithologically and chronologically similar to those on the north shore of Lake Huron in Canada. The rocks in Canada contain major deposits of uranium in quartz-pebble conglomerates near the base of the metasedimentary sequence. Similar conglomerates in the Deep Lake Formation in the Medicine Bow Mountains of southeastern Wyoming are slightly radioactive and may contain deposits of uranium and other valuable heavy metals. During the summer of 1976, a geological and geochemical pilot study was conducted in the vicinity of Arrastre Lake in the Medicine Bow Mountains to determine the most effective exploration methods for evaluating the uranium potential of the Snowy Range wilderness study area. The area around Arrastre Lake was selected because of the presence of a radioactive lens within a quartz-pebble conglomerate of the Deep Lake Formation. The results of the survey indicate possible uranium mineralization in the subsurface rocks of this formation. The radon content of the dilute waters of the area is much higher than can be accounted for by the uranium content of the surface rocks. Two sources for the high content of the radon are possible. In either case, the high values of radon obtained in this study are a positive indication of uranium mineralization in the subsurface rocks. The determination of the radon content of water samples is the recommended geochemical technique for uranium exploration in the area. The determination of uranium in water and in organic-rich bog material is also recommended.

Wyoming↗

Seismic model study of Patrick Draw field, Wyoming: a stratigraphic trap in the Upper Cretaceous Almond Formation

The Patrick Draw field, located on the eastern flank of the Rock Springs uplift in the Washakie basin of southwestern Wyoming, was discovered in 1959 without the use of geophysical methods. The field is a classic example of a stratigraphic trap, where Upper Cretaceous porous sandstone units pinch out on a structural nose. Two-dimensional seismic modeling was used to construct the seismic waveform expressions of the Patrick Draw field, and to better understand how to explore for other 'Patrick Draw' fields. Interpretation of the model shows that the detection of the reservoir sand is very difficult, owing to a combination of acoustic contrasts and bed thickness. Because the model included other major stratigraphic units in the subsurface, several stratigraphic traps are suggested as potential exploration targets.

Open-File Report↗

Comparison of the Wilfley concentration table and hand panning for concentration of heavy minerals prior to geochemical analysis

Chemical analysis of heavy—mineral concentrates of stream sediments is a common geochemical exploration technique used by the U.S. Geological Survey. Generally these concentrates are prepared by hand panning at streamside or in a washtub and then further concentrated using heavy—liquid (bromoform) techniques in a laboratory. Concentration using heavy liquids is slow, tedious, and expensive for large surveys such as mineral evaluation of wilderness areas. In addition the cost of bromoform is expected to increase greatly because most if not all chemical companies in the United States have ceased production of the compound due to problems in meeting the safety standards of the U.S. Environmental Protection Agency (E.P.A.). Preliminary studies by the E.P.A. suggest a severe health hazard may be incurred by inhaling vapors of or contacting the skin with chemicals like bromoform. Heavy—liquid concentration of thousands of heavy— mineral samples carries an unavoidable risk of exposure to bromoform. The risk, expense, and time required by routine heavy—liquid concentration of heavy minerals should be eliminated by finding other methods to satisfactorily concentrate minerals whenever it is possible. Heavy—mineral concentrates can be used in several ways in geochemical exploration and each way has certain standards for the nature and quality of the mineral concentration required. The nature of the concentration refers to whether the heavy minerals are analyzed in bulk or whether they are split into magnetic fractions using a hand magnet and possibly a Frantz Isodynamic Magnetic Separator.

Open-File Report↗

A statistical summary and listing of the spectrographic analyses of heavy mineral concentrate and conventional, sieved stream-sediment samples, Silver City area, New Mexico

Geochemical sampling of a tier of eight 7 1/2-minute quadrangles bordered by latitudes 32° 45'and 33° 00' N. and longitudes 108° 00' and 108° 30' W. was begun in the fall of 1974 and continued seasonally until completion in the fall of 1976. These quadrangles are in southwest New Mexico and include the well-known mineral deposits of the Silver City area. The sampling was designed to gain semidetailed information on the metal-anomaly characteristics of the strongly mineralized area surrounding Silver City, New Mexico, and to seek geochemical clues for the continuation of these mineral deposits beneath overlying Tertiary volcanic rocks to the north. The data obtained within areas of known mineral deposits provide information on the metallogenic processes and metal suites that both relate and distinguish metal systems. Evaluation of this information relative to the regional geologic framework and the distribution of known mineral deposits will result in the identification of additional target areas for exploration, as well as further our understanding of the geochemical characteristics of mineralized areas. Extrapolation of models developed from the study of areas of known, exposed mineralization to areas covered by Tertiary volcanic rocks, such as the northern part of this tier of quadrangles, is a promising procedure for continuing research into geochemical-anomaly characteristics of covered mineral deposits. Preliminary interpretation of the data indicates that the southern part of the area in which Paleozoic-Mesozoic rocks and mineral deposits are exposed, should be reassessed to the classification and genesis of some of the deposits and to the types of mineral commodities that may be present. Some wholly new exploration targets within these areas are also indicated by some of the data. In addition, geochemical clues to buried mineral deposits, possibly representing continuation northward of some features of the Silver City mining district, have been observed in data from the northern, Tertiary volcanic areas. The meanings of these clues are still speculative. For this study, 917 stream-sediment and 921 stream-sediment concentrate samples were collected. The stream-sediment-concentrate samples, which consist of heavy minerals, were split into magnetic and nonmagnetic fractions, each of which was analyzed. This resulted in the analysis of 1,842 heavy-mineral and 917 sieved stream-sediment samples. Analytical results for all of the sample types are summarized statistically on table 1 and tabulated in their entirety on table 2.

New Mexico↗

Geologic conditions in the Baltimore Canyon Trough area: A summary of U.S.G.S. second-year environment studies

Geologic studies of the outer Continental Shelf off the Middle Atlantic States (Baltimore Canyon Trough Area) have been carried out for two years to assess conditions and hazards which might cause or distribute oil spills and other potential pollution associated with petroleum exploration and development. These detailed investigations were requested and funded by the Bureau of Land Management to carry out its responsibility under the Outer Continental Shelf (OCS) Lands Act (67 Stat 462) of 1953 and the National Environmental Policy Act of 1969. Because of the energy crisis, these studies had to be mounted quickly so that a substantial body of data would be available for making decisions concerning environmental constraints on potential lease tracts. Indeed, pertinent data were available prior to Lease Sale #40 in the Middle Atlantic in August 1976. This was in part due to the alacrity of BLM's Environmental Division management, and in part due to the depth of USGS' experience in the area. For example, geophysical data and bottom samples had been collected since 1962 as part of the Geological Survey's role to "conduct geological and geophysical exploration in the Outer Continental Shelf" (43 U.S.C. 1340). At the advent of the energy crisis, the Atlantic-Gulf Coast Branch focused in-house resources and environmental assessment efforts on the Middle Atlantic OCS area. Thus, considerable information was available to guide the needed detailed studies.

Baltimore Canyon Trough area↗

Coal resources of southeastern Massachusetts assessed in 1942

Large easily mined coal deposits of usable quality would be of great value to Massachusetts, particularly in war time. Every effort has been made in this study to evaluate the probable occurrence, quantity, and quality of the coal deposits in southeastern Massachusetts but unfortunately it is impossible from surface observations alone to ascertain adequately the coal resources of this area. Only by means of widespread and systematic underground exploration, accomplished best by core drilling, can the coal resources be determined. All the available data concerning the coal resources is analyzed in this report in order to indicate the feasibility of such an exploration program and where it is most likely to be successful.

Massachusetts↗

Investigations needed to stimulate the development of Jordan's mineral resources

The level of living that any society can attain is a direct function of the use it makes of all kinds of raw materials (soil, water, metals, nonmetals, etc.), all kinds of energy (both animate and inanimate), and all kinds of human ingenuity; and is an inverse function of the size of the population that must share the collective product. The relation between raw materials, energy and ingenuity is such that use of a large amount of one may offset the need for large amounts of others. The most vital raw materials are water, soil, and construction materials, for these are needed in large quantities and are hard to import. Metals, chemicals, and inanimate energy are necessary for industrialization. The more of these minerals a nation possess, the better, but not nation can hope to be self-sufficient in all of the m and therefore must trade for some essential materials. Jordan’s natural resources have been little explored. The grantitc-metamorphic terrane in the southeastern part of the Kingdom could contain deposits of tungsten, rare earths, feldspar, mica, fluorite etc. and the sedimentary terrane over much of the rest of the county is favorable for the occurrence of oil. Even if none of these minerals is found, however, Jordan’s other mineral resource, if fully explored and developed in the light of modern technology, will support a far higher level of living than her people now enjoy. Very likely she can increase her rainfall by about 10 percent by cloud seeding, and she undeveloped supplies in both surface and ground water that are sufficient to nearly double her usable water supply. Even if she does not have oil or have it in large quantities, she can buy it cheaply from neighboring counties, and in addition has undeveloped sources of hydroelectric power, large reserves of bituminous limestone, large reserves of nuclear power as uranium in phosphate rock, and can use solar and wind power for special purposes. Her large supplies of construction, fertilizer, and other chemical raw materials will not only satisfy her own needs, but will yield both raw materials and some manufactured products for export. And she has valuable resource of touristic interest in the form of incomparable scenery, antiquities, and holy places, which, if properly advertised, could well become her largest single source of foreign currency. Revenues obtained from this source and from the export of agricultural products, nonmetallic minerals, and mineral products should support foreign oil purchase of oil, machinery, and other products not mined or produced internally. Full development of Jordan’s economic potential will take years to achieve and involves many complex activities. One of the most essential is one that can be pressed in the early years, namely the gathering of facts and basic data concerning the character, extent, and distribution of her resources, and the uses that can be made of them. Without each fundamental data or the understanding of their meaning or the ways to use and apply them, costly developmental projects and similar efforts to raise the level of living are likely to have limited success at best. Basic data and mineral resources are best gathered and published by permanent government agencies, for private organizations and individual cannot afford to take the risks involved in gathering data that may not have an immediate economic return; and even if private parties do collect such data they are not likely to make them general available. Of the activities needed in the field of mineral resources, some are already underway as the established function of government agencies. No bureau however, seems to have responsibility for making geologic maps and for gathering data on such things as steam flow, composition and properties of minerals and rocks, or for investigating the uses to which Jordan’s minerals might be put. To satisfy these needs, a Geological Survey and a Bureau of Mineral Industries should be formed and placed in operation as quickly as possible. The task of collecting and interpreting basic data or mineral resources must be done largely by Jordanians, for only in this way will Jordan acquire the technical competence needed to use the information. Few Jordanians have enough training or experience to work independently in these fields now, however, so help from outside technicians would be necessary over an initial training period of several years. But the number of outside technicians should never exceed the number of Jordanian technicians, and for this reason, neither organization could have a staff of more than a few people during the early years of operation.

Open-File Report↗

Impact of coastal processes on resource development with an example from Icy Bay, Alaska

The coastline of Alaska is dynamic and continually readjusting to changes in the many processes that operate in the coastal zone. Because of this dynamic nature, special consideration must be made in planning for development, and. caution must be exercised in site selection for facilities to be emplaced in the coastal zone. All types of coastal processes from continuously active normal processes to the low frequency-high intensity rare event must be considered. Site-specific evaluation-s considering the broad range of possible processes must precede initiation of development. An example of the relation between coastal processes and a proposed resource treatment facility is presented for Icy Bay, Alaska. Icy Bay is the only sheltered bay near many of the offshore tracts leased for petroleum exploration in the 1976 northern Gulf of Alaska OCS (Outer Continental Shelf) lease sale. Consequently, it has been selected as a primary onshore staging site for the support of offshore exploration and development. The environment of Icy Bay has many potentially hazardous features, including a submarine moraine at the bay mouth and actively calving glaciers at the bay's head which produce many icebergs. But most significant from the point of view of locating onshore facilities and pipeline corridors are the high rates of shoreline erosion and sediment deposition. If pipelines or any onshore staging facilities are to be placed in the coastal areas of Icy Bay, then the dynamic changes in shoreline position must be considered so that man-made structures will not be eroded away or be silted in before the completion of development.

Open-File Report↗

Final executive summary report; environmental studies, southeastern United States Atlantic Outer Continental Shelf, 1977; geology

Starting in mid 1976 and continuing into 1977 a variety of geological studies were carried out by the U. S. Geological Survey on the southeastern U. S. Atlantic Continental Margin to assess conditions and hazards that might cause or distribute oil spills or other pollutants, or constrain petroleum exploration or development of the area. These detailed investigations were requested and funded by the Bureau of Land Management to carry out its responsibility under the Outer Continental Shelf (OCS) Lands Act of 1969. Because of the energy crisis the decision had been made to lease on the southeastern continental shelf. A variety of studies had to be mounted quickly for input into decisions concerning the environment that would affect or constrain which lease tracks would be offered. The first lease sale, Lease Sale 43, took place in March 1978, and the environmental information on which this lease sale was based came in part from this initial effort and in part from a wide variety of pertinent data assembled from the literature by the Bureau of Land Management's Environmental Assessment Division. The compilation of relevant data for the Environmental Impact Statement for Lease Sale 43 also pointed up deficiencies in environmental knowledge in a number of areas. The Bureau of Land Management's environmental program for the Southeast Atlantic OCS was initiated to fill gaps in the environmental data base and to detect and assess impacts from oil and gas exploration and production.

Florida, North Carolina, South Carolina↗

Lemhi Pass drilling project, Montana

The Lemhi Pass district has the largest thorium resources of any vein district in the United States (Staatz and others, 1979, p. 10). Most of the resources occur in veins that have an average grade of between 0.1 and 2.0 percent Th0 2 . More than 200 thorium-bearing veins have been mapped in this district (Staatz, 1979, p. A34). The Lemhi Pass thorium district lies astride the Continental Divide in the east-central part of the Beaverhead Mountains along the Idaho-Montana State line. Although the area in which thorium veins are found covers more than 150 square miles, the drilling project was confined to three veins in the northwestern part of this district on the Montana side of the Continental Divide (fig. 1). An unimproved dirt road that crosses the Continental Divide at Lemhi Pass furnishes access to the drilling area. This road connects Idaho State Highway 28 at Tendoy, Idaho, 13 miles west of Lemhi Pass, with Interstate Highway 15 at the Clark Canyon reservoir/dam, 31.5 miles east of Lemhi Pass. Salmon, Idaho, the principal town to the west, is 19 miles northwest of Tendoy; and Dillon, Mont., the principal town to the east, is 18 miles northeast of Clark Canyon Reservoir. The drilling project was proposed by the Department of Energy headquarters personnel in Washington, D.C., during the spring of 1978. The purpose of the project was to demonstrate downward extension of the veins. Drilling was proposed to indicate whether several veins had a depth of 500 feet or more. Little exploration has been carried out on thorium veins. The lack of a ready market for thorium has resulted in little economic incentive for exploration. Most veins in this district are covered by 50 feet of soil.

Montana↗

Evaluation of radar imagery for geological and cartographic applications

The House/Senate conference report on H.R. 4930 (96th Congress), the Department of the Interior and Related Agencies Appropriations bill, 1980, stated that the U.S. Geological Survey should "begin the use of side-looking airborne radar imagery for topographic and geological mapping, and geological resource surveys in promising areas, particularly Alaska." In response to this mandate, the Survey acquired radar data and began scientific studies to analyze and interpret these data. About 70 percent of the project funding was used to acquire radar imagery and to evaluate Alaskan applications. Results of these studies indicate that radar images have a unique incremental value for certain geologic and cartographic applications but that the images are best suited for use as supplemental information sources or as primary data sources in areas of persistent cloud cover. The value of radar data is greatest for geologic mapping and resource surveys, particularly for mineral and petroleum exploration, where the objective is to locate any single feature or group of features that may control the occurrences of these resources. Radar images are considered by oil and gas companies to be worth the cost of data acquisition within a limited area of active exploration. Radar images also have incremental value for geologic site studies and hazard mapping. The need in these cases is TO inventory all geologic hazards to human life, property, resources, and the environment. For other geologic applications, radar images have a relatively small incremental value over a combination of Landsat images and aerial photographs. The value of radar images for cartographic applications is minimal, except when they are used as a substitute for aerial photographs and topographic maps in persistently cloud-covered areas. If conventional data sources are not available, radar images provide useful information on terrain relief, landforms, drainage patterns, and land cover. Screen less lithography is a low-cost method of reproducing the images. The images from modern, commercially available radar systems have good visual quality; they also have better geometric accuracy and higher information content than images from older systems. Images from modern systems, however, also have some of the same disadvantages as those from older systems. The most serious problem is that considerable information is lost in the process of recording the radar return on film. Another problem is that the oblique radar view of the landscape results in interpretations that are biased by look direction. A compromise antenna depression angle also commonly results in inadequate or excessive shadowing in parts of the image. There is a need for high-resolution digital data, not currently available from the private sector, to significantly improve the utility of radar data for geologic and cartographic applications.

Open-File Report↗

South Atlantic summary report 2: A revision of Outer Continental Shelf oil and gas activities in the South Atlantic (U.S.) and their onshore impacts, a summary report, July 1980

The search for oil and gas on the Outer Continental Shelf (OCS) in the South Atlantic Region began in 1960, when geophysical surveys of the area were initiated. In 1977, a Continental Offshore Stratigraphic Test (COST) well was drilled in the Southeast Georgia Embayment. In March 1978, the first lease sale, Sale 43, was held, resulting in the leasing of 43 tracts. Approximately a year later, in May 1979, the first exploratory drilling began, and by February 1980, six exploratory wells had been drilled by four companies. Hydrocarbons were not found in any of these wells. Lease Sale 56, the second lease sale in the South Atlantic Region, was held in August 1981. The sale resulted in the leasing of 47 tracts. Most of the leased tracts are in deep water along the Continental Slope off North Carolina. To date, no drilling has occurred on these tracts, but it is likely that two wells will be drilled or will be in the process of being drilled by the end of 1982. Reoffering Sale RS-2 is scheduled for July 1982, and it will include tracts offered in Lease Sale 56 that were not awarded leases. Lease Sale 78 is scheduled to be held in July 1983. The most recent (March 1982) estimates of risked resources for leased lands in the South Atlantic OCS are 27 million barrels of oil and 120 billion cubic feet of gas. To date, onshore impacts resulting from OCS exploration have been minimal, and they were associated with Lease Sale 43 exploratory activities. Tenneco, using existing facilities, established a support base in Savannah, Georgia; Getty, Transco, and Exxon used a support base established for them by the city of Brunswick, Georgia. The port at Morehead City, North Carolina, is expected to provide the onshore facilities for exploration in the near future on Lease Sale 56 tracts. Arrangements for the use of these facilities are currently being negotiated. In June 1981, the South Atlantic Regional Technical Working Group prepared a Regional Transportation Management Plan for the South Atlantic OCS. The plan is principally an integration of regulatory frameworks, policies, and plans that are applicable to pipeline siting from each of the South Atlantic coastal States and Federal agencies with jurisdiction in the area.

Outer Continental Shelf, South Atlantic↗