Search USGS⌕ Search

SEARCH · Search USGS

Results for “Journal of Geology”

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 721 records · Page 40Linked to original sources
USGS1973

Cretaceous mafic conglomerate near Gualala offset 350 miles by San Andreas fault from oceanic crustal source near Eagle Rest Peak, California

Upper Cretaceous mafic conglomerate and quartz-plagioclase arkose that crop out on the southwest side of the San Andreas fault near Gualala, Calif., may have been eroded from a gabbroic terrane that now lies about 350 miles to the southeast, on the opposite side of the San Andreas fault. The plagioclase arkose near Gualala contains little or no K-feldspar, and the conglomerate is characterized by quartz-bearing mafic rocks that lack K-feldspar volcanic rocks, diabase, and diorite to gabbro. Hornblendes from these clasts yield K/Ar ages of 141±4,175±7, and 186±7 m.y. The arkose and conglomerate appear to have been eroded from a chert-poor ophiolite (oceanic crust) sequence that, according to paleocurrent evidence, lay east of the present San Andreas fault. Near Eagle Rest Peak, 350 miles southeast of Gualala, similar mafic quartz-bearing volcanic rocks, diabase, and gabbro are exposed in a small structurally isolated area that abuts the San Andreas fault on the southwest. These rocks yield hornblende K/Ar ages of 134±4, 165±4, and 207±10 m.y. They may also be the source of two small fault slivers of similar mafic rocks, which yield hornblende K/Ar ages between 144 and 172 m.y. These slivers now lie 100 and 200 miles to the northwest along the San Andreas fault at Gold Hill and Logan.

California↗
USGS1973

Blueschist metamorphism in the Yreka-Fort Jones area, Klamath Mountains, California

Blueschist is plentiful in the Yreka-Fort Jones area, eastern Klamath Mountains, adjacent to a belt of serpentinite that marks the boundary between two fundamental lithologic units, an eastern belt of early Paleozoic sedimentary and metamorphic rocks, and a western greenstone-chert assemblage of late Paleozoic and Triassic(?) age. The blueschists, which contain lawsonite and glaucophane or crossite, occur with phyllitic quartzite and siliceous phyllite of the Stuart Fork Formation, which is overthrust northwestward on the greenstone-chert terrane. The blueschist facies metamorphism probably was synchronous with Middle and Late Jurassic metamorphism of the Stuart Fork Formation. The blueschist-serpentinite terrane possibly marks the site of collision between the eastern Klamath plate and an oceanic western Paleozoic and Triassic plate.

California↗
USGS1973

Dolomitization model for Upper Cambrian and Lower Ordovician carbonate rocks in the eastern United States

Existing models for dolomitization emphasize that penecontemporaneous dolomitization can occur in both subtidal and supratidal environments if the necessary chemical and physical factors favorable for the development of magnesium-rich hypersaline waters exist. Holocene shallow-water hypersaline environments that have the potential to produce dolomite without deposition of more soluble evaporite minerals are found in Shark Bay, Australia, and on the Great Bahama Bank. These hypersalinity systems are characterized by near-vertical isosalinity layers of increasing concentration landward from the open ocean and show little or no relationship to bottom topography. I suggest that a similar but larger scale epicontinentalsalinity system covering the Late Cambrian and Early Ordovician carbonate continental shelf produced a broad wedge of subtidally deposited dolomite in the eastern half of the United States from Mexico to Canada. The distribution of limestone and dolomite in this region is closely keyed to the salinity gradient and accounts for the natural progression from a normal marine limestone facies through a transition zone to a highly saline dolomite facies phase. Algal stromatolite mats and domes occupied low-energy niches in both the limestone and dolomite facies, whereas stratiform algal stromatolites were confined to the areas of moderate energy within the dolomite facies.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Determination of gold in phosphates by activation analysis using epithermal neutrons

A simple method is described for determining gold in phosphates and phosphatic materials. Samples in a cadmium container are irradiated with epithermal neutrons to minimize the formation of 32 P, while permitting the formation of adequate amounts of 198 Au. Fire assay-radiochemical methods are used to separate the 198 Au. Concentrations as low as 0.1 ppb can be determined readily while maintaining low radiation levels.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Rapid determination of sulfur in rocks

Sulfur is determined turbidimetrically as barium sulfate after an aqua regia attack. The turbidity is formed in an ammoniacal solution from which R2O3 has been centrifuged. Reproducibility of turbidity is obtained by adding barium chloride as a solid rather than as a solution. Sulfur is determined in the range 0.01-4 percent within ±0.02 absolute, or approximately 5 percent of the amount present, whichever is larger. A 100-mg sample is used for sulfur concentrations of up to 0.50 percent S, a 20-mg sample for higher levels. A determination requires about 5 minutes.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Antimony-bearing orpiment, Carlin gold deposit, Nevada

Orpiment, As 2 S 3 , containing up to 1.5 percent antimony has been recognized in carbonaceous arsenic-rich gold ores in the unoxidized East ore body of the Carlin gold deposit. Associated hydrothermal minerals include realgar (AsS) and quartz. Stibnite, commonly associated with realgar in the ores, has not been observed associated with this type of orpiment.

Nevada↗
USGS1973

Accessory apatite from hybrid granitoid rocks of the southern Snake Range, Nevada

Analytical data, optical properties, and unit-cell parameters are presented for 24 samples of accessory apatites recovered from hybrid granitoid rocks of the southern Snake Range, Nev. A complete chemical analysis is given for one. In the Snake Creek-Williams Canyon outcrop area, where the hybrid rocks grade from granodiorite with 63 percent SiO 2 to a quartz monzonite with 76 percent SiO 2 within a horizontal distance of about 3 miles, abundance and crystal habit of the apatite change with rock chemistry. The apatite probably is slightly more than 90 mole percent fluorapatite in the most felsic rocks, slightly less in the most mafic. The range of F->OH substitution in apatite from this outcrop area is much smaller than in the coexisting biotites. Except for manganese, strontium, sodium, and the rare earths, there is very limited substitution for calcium in the crystal structure of these apatites. Apatites from the more mafic rocks tend to contain a lighter, more basic assemblage of rare earths, in agreement with results obtained for coexisting allanites, monazites, and zircons.

Nevada↗
USGS1973

New data on cuprobismutite

Cuprobismutite from Tunnel Extension Number Two mine, Ohio mining district, Utah, was chemically analyzed using the electron microprobe. Its empirical formula was determined to be Cu 20.8 Ag 0.97 Pb 0.35 Mn 0.22 Bi 26.7 Sb 0.06 Te 0.05 Se 0.55 S 50.4. The tentative conclusion is that unsubstituted cuprobismutite has the chemical formula 6Cu 2 S*6Bi 2 S 3 rather than the previously ascribed formula 6Cu 2 S*6Bi 2 S 3 and that cuprobismutite is therefore not dimorphous with emplectite.

Utah↗
USGS1973

Chemical composition of a saline lake on Enderbury Island, Phoenix Island Group, Pacific Ocean

Ion activity products for the dissolution of calcite, aragonite, gypsum, monetite, brushite, dolomite, magnesite, hydroxyapatite, and fluorapatite were calculated for a South Pacific guano island brine with an ionic strength of 6.4. Environmental conditions for the brine at the time of analysis and of sampling indicated saturation with respect to calcite, aragonite, gypsum, hydroxyapatite and fluorapatite; a comparison of the ion activity products and equilibrium constants indicated saturation or supersaturation with respect to most minerals found in lake sediments or elsewhere on the island. The results suggest that chemical thermodynamic calculations for brines may have some usefulness despite the many assumptions and estimations that must be made.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Effect of septic-tank wastes on quality of water, Ipswich and Shawsheen River basins, Massachusetts

Many housing projects in the metropolitan area of Boston are beyond the reach of municipal sewer systems. Waste water disposed of through septic-tank or cesspool systems percolates to ground-water reservoirs and eventually reaches the streams. The dissolved-solids load in the streams receiving septic-tank effluent is increased by an amount that can be predicted from the housing density. In the study area, highway deicing salts are the only materials other than septic-tank discharge that contribute to water-quality degradation. The effect of these salts on the relationship with housing density is eliminated by subtracting the specific conductance due to sodium chloride from the measured specific conductance of a water sample. The difference is called residual conductance and is proportional to the dissolved-solids content minus the concentration of sodium chloride.

Massachusetts↗
USGS1973

The Great Tunisian Flood

In the autumn of 1969, unusual meteorological conditions over Europe and northern Africa caused an enormous persistent desert storm in Tunisia and eastern Algeria. Poorly developed drainage patterns and gypsum-encrusted surfaces of these desert regions intensified effects of the storm and contributed to the heavy loss of life and property. Destruction of Roman bridges suggests that such storms may have recurrence probabilities of several thousands of years. The event also suggests that, although desert storms are less frequent than those of temperate regions, they can be similar in magnitude.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Hydraulic sand-model studies of miscible-fluid flow

Hydraulic sand models are useful physical tools in the investigation of the transition zone that occurs between salt and fresh ground water in coastal aquifers. Such models are used to demonstrate the effects of transport mechanisms that influence the dynamic behavior and the shape of the transition zone. The techniques employed in obtaining in-place measurements of solute concentrations are generally the stumbling block in generating data for two-dimensional dispersion systems. Two in-place measurement techniques were used in the studies described: (1) conductivity probes when salt was used as a tracer; and (2) photoelectric cells when organic dye was used as a tracer. Results indicate that conductivity methods are more reliable; however, care must be exercised inasmuch as the probes tend to disturb the fluid flow.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Rapid reaction rates between water and a calcareous clay as observed by specific-ion electrodes

Specific-ion electrodes were used to simultaneously determine the activity changes of calcium, hydrogen, sodium, fluoride, and divalent ions when 50 g of a natural, untreated material containing calcium-rich mixed-layer illite-montmorillonite clay, quartz sand, and calcium carbonate was added to 250 ml of natural Canadian River water containing 220 mg/1 Na. Calcium and magnesium were displaced from the clay by the sodium; the exchanged and dissolved noncarbonate calcium precipitated as calcium carbonate, and the magnesium remained in solution. Fluoride entered into both a rapid reaction and a long-term reaction, indicating solution from the material. The pH decreased rapidly. The reactions for all observed ions, other than fluoride, were faster than the response time of their respective electrodes and were complete in less than one minute. Rapid solution of material containing calcium, magnesium, sodium, and fluoride was also observed when a duplicate sample of the earth material was added to distilled water; pH also changed rapidly in this mixture. These results suggest that many important water-rock reactions can be considered nearly instantaneous for purposes of digital modeling of the geochemical changes during artificial recharge.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Formation of joints in bedrock by moving glacial ice

The orientation of joints in igneous and sedimentary rocks was measured at 21 localities in California, Maine, and New York to investigate the hypothesis that glaciation may open joints in bedrock. A summary of strikes of all joint sets shows the following pattern relative to the direction of glacial advance: two sets, thought to be extension joints, flank the direction of advance and are separated from it by about 10°; two sets, thought to be shear joints, flank the direction of advance by about 40°; and two sets, thought to be release joints, are about 70° to 80° from the direction of advance, or nearly perpendicular to the extension joints. An average of five joint sets, including three or four in this pattern, was found at each locality. The joints are believed to have been opened, in response to stress applied by the moving ice, along preexisting zones of weakness (potential regional joints) in the rock. Some new joints may have formed where no such zone was present near the position required for fracture under the applied stress. Additional investigation of the hypothesis is desirable because of its possible bearing on glacial erosion by quarrying, on interpretation of joint patterns in glaciated regions, and on the nature of aquifers in glaciated bedrock.

California, Maine, New York↗
USGS1973

Radiometric dating of intrusive rocks in the Cottonwood area, Utah

Recently completed fission-track and K-Ar dating of zircon, sphene, apatite, muscovite, biotite, and hornblende indicate that the Clayton Peak stock was intruded 37-41 m.y. ago, the Alta stock about 32-33 m.y. ago, and the Little Cottonwood stock between 24 and 31 m.y. ago. Pb-a ages on zircon, though showing the same sequence, are about twice as great and are inferred to represent a partial mixing of inherited Precambrian zircons. Acceptance of a middle Tertiary age for the Little Cottonwood stock requires revision of earlier interpretations that it could be as old as Late Cretaceous. K-Ar dates also indicate that the Keetley Volcanics are 32 to 35 m.y. old, and a single date of 37.3 m.y. was obtained on the Traverse Volcanics, suggesting that they are more closely related to volcanic activity in the adjoining Oquirrh Mountains.

Utah↗
USGS1973

The concept of growth and maturity of ore-stage pyrite in roll-type uranium deposts

Roll-type uranium deposits contain both ore-stage pyrite and preore or diagenetic pyrite that was present in the host rock before the deposits began to form. Ore-stage pyrite forms as the result of redistribution and accretion from the preore pyrite. Accretion of the ore-stage pyrite seems to be governed by natural laws that limit its concentration to only a few times the concentration of the preore pyrite. Accumulations of ore-stage pyrite build up along the leading edge of a supergene oxidation zone which spreads through the host rocks, literally pushing the ore deposits ahead of it. The ore-stage pyrite probably progresses much as a wave that first grows to a nearly fixed amplitude and thereafter is steadily maintained as the mature deposit continues to advance.

Journal of Research of the U.S. Geological Survey↗
USGS1973

A second specimen of Parahyus vagus Marsh, 1876

The occurrence of the second known specimen of Parahyus vagus , from the Tepee Trail Formation, Wyoming, is recorded. As the first specimen was reported from the lower Eocene, this second occurrence casts doubt on the supposed age ranges of both Parahyus and the Tepee Trail.

Wyoming↗