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Subsurface correlations and sequence stratigraphic interpretations of lower Silurian strata in the Appalachian Basin of northeast Ohio, southwest New York, and northwest Pennsylvania
Significant quantities of recoverable natural gas resources are estimated to be in the regionally extensive Lower Silurian Medina Group and “Clinton” sandstone of the Appalachian Basin (Gautier and others, 1995; Ryder and others, 1996; Ryder, 1998). In order to assess these accumulations of natural gas more accurately, the U.S. Geological Survey (USGS) has investigated the Silurian stratigraphy along six lines of cross section located in New York, Pennsylvania, Ohio, and West Virginia (fig. 1). Cross section A–A' extends about 375 mi from northeast to southwest and is oriented approximately parallel to the nearby paleoshoreline of the Silurian epeiric sea. The remaining cross sections extend about 100–200 mi from northwest to southeast and are oriented nearly perpendicular to the paleoshoreline. Stratigraphic investigations along A–A' were reported by Ryder (2000), correlations along D–D' were reported by Keighin (1998), and investigations along E–E' and F–F' were in progress at the time of this publication. This report provides correlations for Silurian strata along cross sections B–B' and C–C', which are located in the northern part of the Appalachian Basin (figs. 1 and 2). Cross section B–B' extends about 140 mi from Chautauqua County, N.Y., to Clinton County, Pa., and C–C' extends about 200 mi from Lake County, Ohio, to Clinton County, Pa. Correlations are made along B–B' and C–C' for the Lower Silurian Medina and Clinton Groups, Lower Silurian Tuscarora and Rose Hill Formations, and Lower and Upper Silurian Lockport Group and Mifflintown Formation (lower part). Emphasis is placed on the Medina Group because it is the principal natural gas reservoir in the Silurian deposit.
Interpretive geologic map of the bedrock showing radioactivity, and aeromagnetic map of the Salisbury, Southmont, Rockwell, and Gold Hill quadrangles, Rowan and Davidson counties, North Carolina
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Gravity anomaly and interpretation map of the Chignik and Sutwik Island quadrangles, Alaska
The gravity field of the Chignik and Sutwik Island quadrangles near the center of the Alaska Peninsula represents a complex series of transitions between probable continental crust on the north, probable oceanic crust on the south, sedimentary basins on each side of the peninsula, and a central structural high and volcanic arc. The resulting gravity field may be generalized as a central southwest- to northeast-trending gravity high bordered on both sides by flanking gravity lows over sedimentary basins underlying the lowlands and continental shelf. All three gravitational features show discontinuities and magnitude variations that reflect the complex geologic setting. Data concerning this complex gravity field have accumulated slowly and intermittently since an initial measurement was made at Port Heiden more than 25 years go (Thiel and others, 1958, 1959). A few reconnaissance measurements by R. V. Allen and an offshore traverse conducted by the U.S. Coast and Geodetic Survey R/V Surveyor were made in the early 1960's (Barnes and others, 1966; Barnes, 1967). At about the same time, Gulf Oil Corp. contracted for a relatively detailed survey of the lowlands on the north shore of the peninsula; the map prepared from this survey is now available (Gulf Oil Corp., Port Moller Development Contract Report, available at U.S. Geological Survey, Anchorage, Alaska). In the early 1970's, a few new land measurements were made by P. L. Dobey, of the Alaska Division of Geological and Geophysical Surveys, and an offshore traverse was completed by the R/V C. Greene on contract to the U.S. Geological Survey (Fisher, 1979, and M. A. Fisher, written commun., 1977). The most recent measurements, the basis for this map, were made by M. E. Yount, D. L. Detra, D. R. Jefferis, and J. E. Case during the mineral assessment of the two quadrangles. D. F. Barnes, R. L. Morin, D. R. Jefferis, and R. F. Sikora have shared in the data compilation. Geologic background for the text was provided by R. L. Detterman, T. P. Miller, E. Young, and F. H. Wilson (1979, 1981).
Maps showing interpretation of Landsat imagery of the Chignik and Sutwik Island quadrangles, Alaska
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Maps showing aeromagnetic survey and geologic interpretation of the Lake Clark Quadrangle, Alaska
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Map showing interpretation of Landsat imagery of the Lake Clark Quadrangle, Alaska
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Interpretation of an aerial radiometric survey of the San Gorgonio Wilderness Area and vicinity, San Bernardino County, California
The aerial radiometric data for the San Gorgonio Wilderness Area show slight correlation with mapped geology and contain no information of economic significance. Precambrian and modified Precambrian crystalline rocks have more eTh compared to Mesozoic plutonic rocks and one rock unit mapped as a pluton has slightly more K. These rocks have essentially uniform ratios of eU/eTh and eU/K despite their different origins. The ratios and also show that part of the granodiorite of Manzanita Springs could be somewhat deficient in eTh and K. It is concluded that the mapped radioelement distributions are within reasonable limits for the rock types involved, and there is no immediate evidence on any anomalous concentrations of radioactive minerals within the Wilderness Area.
Map and interpretation of the structural geology of the Survey Pass Quadrangle, Brooks Range, Alaska
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Maps showing aeromagnetic survey and interpretation of the Survey Pass Quadrangle, Brooks Range, Alaska
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Maps and interpretation of geochemical anomalies in the John Muir Wilderness, Fresno, Inyo, Madera and Mono counties, California
A geochemical survey of the John Muir Wilderness was conducted by the U.S. Geological Survey between 1969 and 1978. The 755-mi 2 (1,956-km 2 ) wilderness is located in the central Sierra Nevada, Calif. (fig. 1). Stream-sediment samples were collected at 1,434 sites in the wilderness and immediately adjacent areas. Analytical data for these samples and a map of smapling sites are presented by du Bray and Dellinger (1980) and Diggles and others (1981). A geologic map of the area was compiled by du Bray (1981). These maps and tables present the results of the analysis of geochemical data for lead, zinc, gold, silver, arsenic, chromium, molybdenum, manganese, tungsten, tin, copper, and nickel. These are elements of economic interest which have historically been found in mineral deposits of the Sierra Nevada or other geologically similar areas.
Map showing aeromagnetic interpretation of the Baker-Cypress BLM Instant Study Area and Timbered Crater Forest Service Further Planning Areas, Modoc, Shasta, and Siskiyou counties, California
The data for the aeromagnetic map of the Baker-Cypress and Timbered crater areas were collected in 1978 and compiled at a scale of 1 :62,500 (U,S, Geological Survey, 1979). East-west traverses were spaced at 0.8-km intervals at a constant altitude of 1370 m (4500 ft) above sea level, Contour interval is 20 and 100 gammas, depending upon the steepness of local gradients in the Earth's magnetic field. A regional magnetic field (the International Geomagnetic Reference Field - 1975, updated to the month flown) of approximately 5-6 gammas/km was removed from the data be fore con touring.
Map showing aeromagnetic interpretation of the Golden Trout Wilderness, Tulare and Inyo counties, California
The Golden Trout Wilderness covers 457 mi 2 in the rugged forested part of the southern Sierra Nevada. It is bounded on the east by Owens Valley, on the north by Sequoia National Park, and on the west and south by U.S. Forest Service multiple-use lands. The east side of the area is accesible from U.S. Highway 395, while the remainder is reached by state, county, and Forest Service roads from the San Joaquin Valley.
Maps showing structural interpretation of magnetic lineaments in the northern Gulf of Alaska
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Preliminary aerial photographic interpretative map showing features related to the May 18, 1980 eruption of Mount St. Helens, Washington
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Interpretation of graphic data on potential geologic hazards on the southeastern United States Atlantic continental shelf
This report presents and analyzes seismic-survey data and bottom-instrument data as they pertain to a regional assessment of potential geologic hazards and other constraints to petroleum exploration and development on the southeastern United States Continental Shelf (see fig. 1).
Map and interpretation of aeromagnetic data for the Wild Rogue Wilderness, Coos and Curry Counties, Oregon
The Wild Rogue Wilderness is located in Coos and Curry Counties, southwestern Oregon and covers part of the Bone Mountain, Marial, and Agness 15-minute quadrangles (fig. 1). It is an elongate area 19 mi by 1 to 3 mi (31 km by 1.3 to 5 km) and covers approximately 35,818 acres extending from the town of Agness to Mount Bolivar. The mapped geology of the Wild Rogue Wilderness (Gray and others, 1982) consists of a tectonic wedge of volcanic and intrusive rocks of Jurassic age surrounded on all sides by thick sequences of Jurassic, Creacetous, and Tertiary sedimentary rocks. Normally, volcanic and intrusive rocks are more magnetic than sedimentary rocks, a property which should be reflected by the areomagnetic data. We conclude, however, that most of the magnetic anomalies of the Wild Rogue Wilderness are caused by magnetic rocks that are not exposed but which occur at relatively shallow depth below the topographic surface.