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At least 361 records · Page 20Linked to original sources
USGS1978

Preliminary report on the coal resources of the National Petroleum Reserve in Alaska

NPR-A, located on the Arctic slope of Northern Alaska, is underlain by a thick sequence of sedimentary rocks of Cretaceous age which attain a thickness of as much as 4600 m (15,000 feet). The bulk of the coal resources occurs in rocks of the Nanushuk Group of Early and Late Cretaceous age. The Nanushuk Group is a wedge-shaped unit of marginal marine and nonmarine rocks that is as thick as 3300 m (11,000 feet) just west of NPR-A. Within the reserve, coal occurs primarily in the middle and thicker portions of this clastic wedge and occurs stratigraphically in the upper half of the section. Specific data on individual coal beds or zones are scarce, and estimates of identified coal resources of about 49.5 billion tons represent a sampling of coal resources too small to give a realistic indication of the potential resources for an area so large. Estimates of undiscovered resources suggest hypothetical resources of between 330 billion and 3.3 trillion tons. The wide range in the undiscovered resource estimates reflects the scarcity and ambiguity of the available data but also suggests the presence of a potentially large coal resource.

Open-File Report↗
USGS1978

Cyclic landsliding at Wrightwood, southern California: A preliminary report

Recurring landslide and mudflow events in the Wrightwood area of Southern California are parts of a composite cycle of landslide activity that includes three recognizable stages. The three stages are interdependent, occur in sequence, and are of different duration. Deposits of the first stage--the largest in size--are removed to positions further downstream by the activity of second- and third-stage landslides. First-stage landslides are represented by huge slumped masses derived from steep bedrock slopes in the canyon heads; the material moves down the principal stream drainage, which may be completely filled with debris. Second-stage activity develops as streams cut a network of branching channels into the massive first-stage deposit. The second-stage landslides are chiefly slumps from the older slide mass and from adjacent bedrock slopes. The movement of these slides generally is downslope toward actively eroding drainages. Third-stage activity includes mudflows that accompany the spring melting of snowpack. The debris moves down the stream channels to depositional reaches on major fans. Removal of sufficient amounts of the first-stage landslide mass to the fan by second- and third-stage events resets the bedrock slope of the main drainage for another first-stage event. The first-stage landslides in the Wrightwood area are of prehistoric origin, and their recurrence interval in any one canyon is probably several thousand years. The active duration of a first-stage landslide is one to several thousand years. Second-stage landslides last one to several years and are apparently preceded and triggered by a series of high-precipitation winters. The duration of observed third-stage (spring mudflow) sequences ranges from a few days to as much as six weeks; peak mudflow activity apparently results when a-heavy spring snowmelt occurs during a period of second-stage landslide activity.

California↗
USGS1979

Preliminary report on Tertiary volcanism and uranium mineralization in the Thomas Range and northern Drum Mountains, Juab County, Utah

The Thomas Range and northern Drum Mountains have a history of volcanism, faulting, and mineralization that began about 42 m.y. ago. Volcanic activity and mineralization in the area can be divided into three stages according to the time-related occurrence of rock types, trace element associations, and chemical nature of mineralization. Volcanic activity switched abruptly from rhyodacite-quartz latite (42-39 m.y. ago) to rhyolite (38-32 m.y. ago) to alkali rhyolite stages (21 and 6-7 m.y. ago); these stages correspond to periods of chalcophile and siderophile metal mineralization, no mineralization, and lithophile metal mineralization, respectively. Angular unconformities record episodes of cauldron collapse and block faulting between the stages of volcanic activity and mineralization. The youngest angular unconformity formed between 21 and 7 m.y. ago during basin-and-range faulting. Early rhyodacite-quartz latite volcanism from composite volcanoes and fissures produced flows, breccias, and ash-flow tuff of the Drum Mountains Rhyodacite and Mt. Laird Tuff. Eruption of the Mt. Laird Tuff about 39 m.y. ago from an area north of Joy townsite was accompanied by collapse of the Thomas caldera. Part of the roof of the magma chamber did not collapse, or the magma was resurgent, as is indicated by porphyry dikes and plugs in the Drum Mountains. Chalcophile and siderophile metal mineralization, including copper, gold, and manganese, accompanied early volcanism. The middle stage of volcanic activity was characterized by explosive eruption of rhyolitic ash-flow tuffs and collapse of the Dugway Valley cauldron. Eruption of the Joy Tuff 38 m.y. ago was accompanied by subsidence of this cauldron and followed by collapse and sliding of Paleozoic rocks from the west wall of the cauldron. Landslides in The Dell were covered by the Dell Tuff, erupted 32 m.y. ago from an unknown source to the east. An ash-flow of the Needles Range Formation was erupted 30-31 m.y. ago, probably from a distant source outside the volcanic field. The rhyolitic stage of volcanism was barren of mineralization. The last stage of volcanism was contemporaneous with basin-and-range faulting and was characterized by explosive eruption of ash and pumice, forming stratified tuff, and by quiet eruption of alkali rhyolite as viscous flows and domes. The first episode of alkali rhyolite volcanism deposited the beryllium tuff and porphyritic rhyolite members of the Spor Mountain Formation 21 m.y. ago. After a period of block faulting, the stratified tuff and alkali rhyolite of the Topaz Mountain Rhyolite were erupted 6-7 m.y. ago along faults and fault intersections. Erosion of Spor Mountain may have provided abundant dolomite detritus to the beryllium tuff member. The alkali rhyolite of both formations is fluorine-rich, as is evident from abundant topaz, and contains anomalous amounts of lithophile metals. Alkali rhyolite volcanism was accompanied by lithophile metal mineralization which deposited fluorite, beryllium, and uranium. The structure of the area is dominated by the Thomas caldera, and the younger Dugway Valley cauldron, which is nested within the Thomas caldera; the Thomas caldera is surrounded by a rim of Paleozoic rocks at Spor Mountain and Paleozoic to Precambrian rocks in the Drum Mountains. The Joy fault and Dell fault system mark the ring fracture zone of the Thomas caldera. These structural features began to form about 39 m.y. ago during eruption of the Mt. Laird Tuff and cauldon subsidence. The Dugway Valley cauldron sank along a series of step-like normal faults southeast of Topaz Mountain in response to collapse of the magma chamber of the Joy Tuff. The caldera structure was modified by block faulting between 21 and 7 m.y. ago, the time of widespread extensional faulting in the basin-and-range province. Vents erupted alkali rhyolite 6-7 m.y. ago along basin-and-range faults. Uranium mineralization was associated with the stage of alkali rhyolite volcanism, extensional basin-and-range faulting, and lithophile metal mineralization; it occurred at least 11 m.y. after the end of the caldera cycle. Uranium, derived from alkali rhyolite magma, was concentrated in trace amounts by magmatic fluids and in potentially economic amounts by hydrothermal fluids and ground water. Hydrothermal fluids deposited uraniferous fluorite as pipes in carbonate rocks of Paleozoic age on Spor Mountain and uranium-bearing disseminated deposits of fluorite and beryllium in the beryllium tuff member of the Spor Mountain Formation. Uranium of hydrothermal origin is dispersed in fluorite and opal. Uranium in fluorite may be tetravalent(?) but that in opal is probably hexavalent; no primary minerals of tetravalent uranium are known to occur. Ground waters have concentrated significant ores of hexavalent uranium minerals in the beryllium tuff member of the Spor Mountain Formation at the Yellow Chief Mine, and are probably also responsible for widespread low concentrations (0.0X percent) of uranium that occur separately from beryllium ore in the beryllium tuff member. More deposits of the Yellow Chief type may occur in down-faulted sections of beryllium tuff beneath the Thomas Range. The ground water ores show no evidence of a reducing environment; instead, precipitation of hexavalent uranium minerals occurred by evaporation, decline in concentration of complexing ions such as carbonate, or some other mechanism. Reducing environments for hydrothermal deposits must be sought around rhyolite vents and in a hypothesized pluton of alkali rhyolite composition beneath Spor Mountain; for ground-water deposits, reducing environments may occur in basin fill such as that of the Dugway Valley cauldron.

Utah↗
USGS1979

Preliminary report on the energy resource position of the Republic of Korea

The Republic of Korea has meager resources of energy minerals. Only hydroelectric power and coal were listed as sources of energy indigenous to Korea in the report of the 1967 World Energy Conference. Small reserves of thorium have been estimated and the discovery of uranium was reported in 1977 (A. W. Noonan, Jr., U.S. Department of State, written commun., 1977). Petroleum, natural gas, and geothermal energy sources possibly exist in South Korea, but their potential for development is not considered to be great. About 55 percent of the energy in the Republic is produced from petroleum, most of which is imported as crude and is refined in-country. Domestically produced coal supplies about 32 percent of the energy demand, hydroelectric power about 4 percent, and other sources (firewood, charcoal, and dung) about 9 percent. South Korea's latest energy program stresses construction of additional hydroelectric power installations, increased production of coal, initiation of energy production by atomic reactors, onshore and offshore exploration for petroleum and natural gas, generation of energy by tidal power, and energy savings through conservation (R. A. Stella, written commun., 1977).

Korean Penninsula↗
USGS1979

Preliminary report on the petrography and geochemistry of basalt from the Pribilof Islands and vicinity, southern Bering Sea

Alkali basalt from the Pribilof Islands has been described by several workers (Washington and Keyes, 1930; Barth, 1956; Cox and others, 1966; and Kay, 1977). This report complements the previous reports by providing new petrographic and geochemical data for samples from St. Paul and St. George Islands and from two dredge hauls near St. George Island (Fig. 1). The geologic setting of the Pribilof Islands region is given by Barth (1956), Hopkins and Einarsson (1965), Cox and others (1966), Hopkins and others (1969), Marlow and others (1976), and Hopkins and Silberman (1978). Quaternary basalt (Table 1) (Cox and others, 1966; Hopkins, 1976; Simpson and others, 1979) is extruded onto the structurally high Pribilof Ridge (Marlow and others, 1976) which consists of rocks as old as late Jurassic (Vallier and others, 1979). Barth (1956) recognized the structural implication of alkalic volcanism in back-arc environments. We plan to interpret alkalic volcanism in the Pribilof Islands within the context of recent tectonic and petrologic findings in the southern Bering Sea. Funds for this project were provided jointly by the U.S. Geological Survey and Bureau of Land Management. Funds from the Bureau of Land Management were managed by the Outer Continental Shelf Environmental Assessment Program (OCSEAP) office of the National Oceanic and Atmospheric Administration (NOAA).

Alaska↗
USGS1980

Preliminary report on the mineral resource potential of the Red Rocks Escarpment Instant Study area, Clark County, Nevada

The Red Rocks Escarpment Instant Study area in Clark County, Nevada, is 2 mi (32 km) west of Las Vegas and covers about 31,000 acres (12,500 ha) of the rugged Sandstone Bluffs area in the Spring Mountains (fig. 1). It includes the crest of the range, which is slightly higher than 7,200 ft (2,190 m), the Sandstone Bluffs east of the crest where steep cliffs as high as 2,500 ft (760 m) occur, and part of the gently sloping western range front. The Instant Study area (fig. 2) is within land administered by the U.S. Bureau of Land Management.

Nevada↗