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At least 757 records · Page 42Linked to original sources
USGS1973

Pliocene marine fossils in the Paso Robles Formation, California

Marine invertebrates from the Paso Robles Formation recently discovered near Atascadero, Calif., indicate that the basal part of this chiefly nonmarine deposit is of provincial early Pliocene age. Heretofore the lack of direct fossil or radiometric evidence of the age of the Paso Robles has made it a difficult unit to place in the late Cenozoic history of the Coast Ranges. The assemblage is dominated by Ostrea vespertina and by Nettastomella rostrata , a rock-boring bivalve; its mode of preservation indicates that the fossils are in place and have not been recycled from older marine formations. This occurrence suggests that during the early Pliocene a seaway connected the present southern Salinas Valley area with the northern part of the Santa Maria basin; the fossils occur about halfway between the southernmost exposures of the Pancho Rico Formation near San Miguel and fossiliferous strata east of Pismo Beach, both marine units of early Pliocene age.

California↗
USGS1973

Galkhaite, (Hg,Cu,Tl,Zn) (As,Sb)S2, from the Getchell mine, Humboldt County, Nevada

The first reported occurrence in the United States of galkhaite (Hg,Cu,Tl,Zn)(As,Sb)S 2 is at the Getchell mine, Humboldt County, Nev. The mineral occurs as brownish-black cubes associated with graphite, pyrite, and realgar. In polished section galkhaite is grayish white and isotropic with a deep-red internal reflection; reflectivity at 590 nm is 21.6 percent. Spectrographic analysis gave Hg 42 percent, Cu 5 percent, Zn 1.5 percent, Fe 0.7 percent, Tl 5 percent, As 24 percent, Sb 0.3 percent, and S (by difference) 21.3 percent. The mineral is cubic, a=10.36, and the strong lines of the X-ray powder pattern are 2.99 (100), 4.21 (90), 2.76 (80), 1.831 (70), 7.25 (60), 2.58 (40), 1.561 (40). The pattern is very similar to that of tetrahedrite except for the strong lines at 7.25, 4.21, and 2.76.

Nevada↗
USGS1973

Disseminated pyrite in a latite porphyry at Texan Mountain, Hudspeth County, Texas

A pyrite-bearing latite porphyry that contains fragments of syenite and a quartz porphyry intruded into the Cretaceous Cox Sandstone are well exposed in a roadcut at Texan Mountain, Hudspeth County, Tex. The pyrite, which occurs along tiny fractures as well as disseminated, and the multiple episodes of intrusion, coupled with copper minerals in veins in the overlying Cox Sandstone, indicate a slight potential for porphyry-type copper or molybdenum deposits at depth.

Texas↗
USGS1973

Soda Creek springs - metamorphic waters in the eastern Alaska Range

The Soda Creek springs are a group of small, cold mineral springs on the southern flank of the eastern Alaska Range. The spring waters contain anomalous concentrations of carbon dioxide, sodium, chlorine, sulfate, boron, and ammonia and are actively precipitating deposits of calcite and aragonite. Sparingly present in these deposits are mixed-layer illite-montmorillonite clays and zeolite minerals. Low-temperature metamorphic reactions in subjacent marine sedimentary rocks of Jurassic and Cretaceous age may have produced the fluids and silicate minerals. With only a few exceptions, cool bicarbonate-rich springs in Alaska are concentrated south of the Denali fault system in south-central Alaska, southeastern Alaska, and along the Kaltag-Tintina fault system. These areas are characterized by active or recently active tectonism, major faults and folds, and an abundance of marine sedimentary rocks.

Alaska↗
USGS1973

A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3 (CO3)4 , and artinite, Mg2(OH)2 CO3 * 3H2O, and their standard Gibbs free energies of formation

The enthalpies of formation, ΔH° f, of huntite, CaMg 3 (CO 3 ) 4 , and artinite, Mg 2 (OH) 2 CO 3 * 3H 2 O, have been determined by HCl solution calorimetry using a constant-volume isoperibol reaction calorimeter. For the reaction CaO(c) + 3MgO(c) + 4CO 2 (g) = CaMg 3 (CO 3 ) 4 (c), the enthalpy change at 298.15 K, ΔH° 298 , is -123,203±145 cal mol -1 . For the reaction 2MgO(c) + 4H 2 O(l) + CO 2 (g)=Mg 2 (OH) 2 CO 3 * 3H 2 O(c), we obtained -45,132±100 cal mol -1 . These results combined with the standard enthalpies of formation of CaO, MgO, H 2 O, and CO 2 lead to ΔH° 298 (huntite) = -1,082,600±375 cal mol -1 and ΔH° 298 (artinite) = -698,043±170 cal mol -1 . Using recently determined values for the standard entropies of huntite, CaMg 3 (CO 3 ) 4 , and artinite, Mg 2 (OH) 2 CO 3 * 3H 2 O, and of Mg, Ca, C, O 2 , and H 2 , we calculate ΔG° f,298 (huntite) = -1,004,707±390 cal mol -1 and ΔG° f,298 (artinite) = -613,924±180 cal mol -1 .

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

The enthalpies of formation of nesquehonite, MgCO3 * 3H2O, and hydromagnesite, 5MgO * 4CO2 * 5H2O

The enthalpies of formation, ΔH° f , of nesquehonite, MgCO 3 * 3H 2 O, and hydromagnesite, 5MgO * 4CO 2 * 5H 2 O, have been determined by HCl solution calorimetry. For the reaction MgO(c) + CO 2 (g) + 3H 2 O(l) = MgCO 2 * 3H 2 O(c), the enthalpy change at 298.15 K is -29,781*40 cal mor' . For the reaction 5MgO(c) + 4CO 2 + 5H 2 O = 5MgO * 4CO 2 * 5H 2 O, the enthalpy change at 298.15 K is -120,310±120 cal. For MgCO 3 * 3H 2 O the standard molar enthalpy and standard Gibbs free energy of formation, ΔH° f,298 and ΔG° f,298 are -472,576+110 and 412,040±120 cal. ΔH° f,298 and ΔG° f,298 for 5MgO * 4CO 2 * 5H 2 O are -1,557,090±250 and -1,401,71 0±250 cal.

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

Chemical analysis of rutile - a pyrocatechol violet spectrophotometric procedure for the direct microdetermination of zirconium

The ZrO 2 content of rutile is determined spectrophotometrically by a direct pyrocatechol violet procedure. The sample is decomposed by potassium pyrosulfate fusion in a transparent quartz crucible, and a sulfuric acid solution of the melt is used for the determination at a pH of 5.1. Of the elements commonly present in rutile, only titanium and niobium occur in concentrations large enough to interfere. Titanium and niobium interference is overcome by adding the titanium and niobium contents of the sample to the standard zirconium solutions used for the standard zirconium curve. The absorbance is measured at 570 nm. Beer's law is obeyed within the range of 0.05-1.50 ppm ZrO 2 . In the presence of 50 ppm TiO 2 , the range is 0.15-1.50 ppm ZrO 2 . The tolerances of 47 elements were determined. The sensitivity is 0.0058 ug Zr/cm 2 . The variables in the method were studied, and typical results are given for commercial rutile concentrates.

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

Spectrophotometric determination of tungsten in rocks by an isotope dilution procedure

Samples are decomposed with hydrofluoric acid and perchloric acid in the presence of W 181 tracer. Molybdenum is extracted from a hydrochloric acid solution with tributyl phosphate. Tungsten is separated from most other elements by extraction of the a-benzoinoximate into chloroform. Stannous chloride in concentrated hydrochloric acid is used to strip tungsten and reduce it to W +5 . The amount of tungsten is determined spectrophotometrically after extraction as the thiocyanate complex into amyl alcohol. The correction for chemical losses is determined by counting W 181 .

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

Spectrochemical computer analysis - argon-oxygen d-c arc method for silicate rocks

Use of an argon-oxygen atmosphere eliminates the interference of cyanogen bands with many sensitive analytical lines. The jet-controlled atmosphere also improves the stability of the arc. These procedural changes, coupled with computerized analysis of the spectra, result in increased detectability, precision, and speed as compared to the former visual semiquantitative technique.

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

Bathymetry of the continental margin off Liberia, West Africa

A bathymetric map based on new data allows examination of geomorphic features on the narrow continental margin off Liberia. The continental shelf in this region is relatively flat and featureless. The northwestern part of the continental slope, off Monrovia and Cape Mount, shows complex slump features and two submarine valleys. The central part of the slope is smoother, apparently as a result of progradation. The southeastern part of the slope, near Cape Palmas, is crossed oblique to the shoreline by a structural valley that has been modified by large slumps or landslides. This valley may be the termination, at the continental margin, of an oceanic fracture zone. The major slumplike features of the Liberian continental margin appear to be surface manifestations of deep faulting which has been partially masked by sedimentation.

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

Ice ages and the thermal equilibrium of the earth

A model for climatic change, and particularly for the changes of the late Cenozoic, involves as its primary variables the albedo of the earth and the heat storage characteristics of the oceans. Geography exerts a strong influence. The model proposed does not require metaphysical causes or astronomical events other than known variations in the earth's orbit.

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

Aquifer diffusivity of the Ohio River alluvial aquifer by the flood-wave response method

Aquifer diffusivity (T/S) was calculated for 10 sites in the alluvial aquifer adjacent to the Ohio River by observing the response of the aquifer to a flood wave in the river. The calculated type curves matched the observed aquifer response reasonably well at eight of the 10 sites. The diffusivities ranged from 0.4 ft 2 sec -1 to 10.3 ft 2 sec -1 and were generally in agreement with diffusivity values calculated from pump-test methods at two of the sites. Interference from pumping 1/2 mile upstream from one site and localized aquifer inhomogeneity at another site precluded calculation of diffusivity. Determining the shape of the ground-water recession curve may be difficult, but it can be done satisfactorily by collecting water-level data during an extended period of ground-water discharge and transposing the average recession curve to the flood period being analyzed. The flood-wave response method for estimating aquifer diffusivity provides a relatively inexpensive technique for obtaining a significant part of the data needed to predict the aquifer's response to river and pumping stresses.

Ohio River↗
USGS1973

A study of the distribution of the polychlorinated biphenyls in the aquatic environment

Data gathered from monitoring activities and project studies indicate the ubiquitous occurrence and distribution of polychlorinated biphenyls in the aquatic environment. Residues have been detected in samples from 19 States, representing nearly every region of the country. Concentrations ranged from 0.1 to 4.0 ug/l in unfiltered water samples and 5.0 to 3,200 ug/kg in bottom sediments. PCB residues were also found in fish and aquatic plants. Samples were prepared by the same techniques used for general chlorinated insecticide detection, with special attention to cleanup and separation of PCB's from other compounds. Basic identification and quantification were made by dual-column electron-capture gas chromatography and confirmed by gas chromatography mass spectrometry whenever possible. The sampling program is expected to be broadened geographically in 1973 and increased in successive years in order to more adequately define the distribution of PCB residues in the major drainage basins of the United States.

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

Remote sensing of turbidity plumes in Lake Ontario

High-altitude photography provides an effective method of monitoring the spatial extent of turbidity plumes in Lake Ontario. Large plumes generated by the Niagara, Genesee, and Oswego Rivers are identifiable on photographs obtained from about 60,000 feet above the lake on July 6, 1970, October 19, 1970, and May 29, 1971. The Niagara plume, covering as much as 43 sq mi of the lake's surface, is the largest turbidity feature. The configuration of the plumes is a function of river discharge, level of turbidity, and wind speed and direction.

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

Method for estimating the diversion potential of streams in eastern Massachusetts and southern Rhode Island

A simple method is proposed for estimating the probable magnitude and frequency of streamflow that is in excess of predetermined minimum streamflows required downstream in eastern Massachusetts and southern Rhode Island. Regional curves relate these annual volumes of streamflow excess to the average annual discharge and the median 7-day annual minimum flow of the site. Use of the curves is illustrated by a hypothetical example.

Massachusetts, Rhode Island↗
USGS1973

Changes in floodflow characteristics of a rectified channel caused by vegetation, Jackson, Mississippi

Extreme changes in velocity, stage, and Manning's roughness coefficient, n , were observed during the first year after canalization of Hanging Moss Creek at Jackson, Miss. Additional changes were observed during the following 8 years. The channel, constructed during the summer of 1963, had a 50-foot-wide bottom, 2:1 side slopes, and 12-foot depth. In March 1964, average velocities of 7.8 feet per second were measured at a 5 1/2-foot depth in the clean channel and Manning's n was computed to be 0.022. In October 1964 the average velocity was 3.2 fps at a 5 1/2-foot depth and Manning's n was 0.045. The channel was then lined with fairly thick vegetation consisting of small willows, weeds, and grass. In October 1970 (summer foliage existing) the average velocity was 2.0 fps at a 5 1/2-foot depth and Manning's n was 0.07. Willow trees, 8 to 10 feet high, then lined the channel. In March 1971 (barren foliage), Manning's n was 0.05. In March 1972 (barren foliage), Manning's n was increased to 0.07. These observations indicate that the commonly used values of Manning's n for channel rectification (0.02-0.03) are low and that the carrying capacity of earthen channels may be reduced 50 percent as a result of only 1 year's growth of vegetation and 70 percent as a result of 8 year's growth. The carrying capacity during summer foliage is approximately two-thirds the carrying capacity during barren winter foliage.

Mississippi↗
USGS1973

Revised volcanic history of the San Juan, Uncompahgre, Silverton, and Lake City calderas in the western San Juan Mountains, Colorado

The sequence of mid-Cenozoic volcanic events in the western San Juan Mountains is closely analogous to that elsewhere in the San Juan volcanic field. The Lake Fork, Picayune, and San Juan Formations were erupted from a cluster of central volcanoes from 35 to 30 m.y. ago, when dominant activity shifted to more silicic ash-flow eruptions with accompanying caldera collapses. The Uncompahgre and San Juan calderas, each about 20 km across, formed mainly from eruption of the 28-m.y.-old Sapinero Mesa Tuff. Collapse occurred concurrently with eruption, and intracaldera tuffs accumulated to a thickness of more than 700 m. Both calderas were resurgently domed together; the northeast-trending Eureka graben formed along the distended crest of that dome. The Uncompahgre caldera was then flooded by several 27- to 28-m.y.-old ash-flow sheets from easterly sources, and also by one apparently erupted from the Silverton caldera nested within the older San Juan caldera. The Lake City caldera, located within the older Uncompahgre caldera, formed about 22.5 m.y. ago in response to eruption of the Sunshine Peak Tuff.

Colorado↗
USGS1973

Sr87/Sr86, K, Na, Rb, and Sr in some eclogites and associated basalts from California and southwestern Oregon

Six samples of group C eclogites from California and southwestern Oregon have initial Sr 87 /Sr 86 ratios in the range of 0.7028 to 0.7051; Rb contents from less than 1 to 53.4 ppm; and Sr contents from 147 to 270 ppm. These data and major-element compositions suggest that the eclogites were derived from basalts older than but similar in composition to those intercalated with Mesozoic cugeosynclinal sedimentary rocks in California and western Oregon. The isotopic heterogeneity of the eclogites and associated graywackes contrasts with a uniformity of Sr 87 /Sr 86 in many younger calc-alkaline volcanic rocks of the circum-Pacific province. Derivation of the younger volcanic rocks from an eclogite-blueschist melange isotopically similar to those investigated here would require isotopic homogenization or integrated partial melting over sufficient volumes so as to reduce these variations in the derived melts.

California, Oregon↗