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Research about United States of America

Source-linked reports with geographic coverage including United States of America.

52 records · Page 3Linked to original sources
USGS1973

Metamorphic facies indicated by vein minerals in basal beds of the Great Valley sequence, northern California

A reexamination of reported blueschist mineral localities in the basal strata of the Great Valley sequence revealed only prehnite-pumpellyite facies minerals. Franciscan graywacke thrust below the Great Valley rocks contains lawsonite-quartz blueschist assemblages. At a common pressure of about 4 kb, the Franciscan blueschists formed at lower temperatures than the overlying Great Valley prehnite-bearing rocks, lending support to tectonic models that involve rapid subduction of the Franciscan rocks.

California↗
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

Use of machine-processable field notes in a wilderness mapping project (Granite Fiords area), southeastern Alaska

For reconnaissance geologic mapping and mineral resource evaluation of the Granite Fiords wilderness study area, we developed and used a system of machine-processable field notes. Preprinted field forms standardize notes and serve as checklists that insure collection of all available data. The use of this system cut in half the time required to record data at an outcrop. The system consists of three related but different types of preprinted field sheets, a key to abbreviations and codes, and a set of written instructions. The field sheets include a station sheet for basic outcrop data, a specimen sheet for rock samples, and a geochemical sheet for materials to be chemically analyzed. Data on the field sheets are keypunched on standard IBM cards, then arranged in subfiles and retrieved by using a card sorter. Our system is designed specifically for a region of granitic and metamorphic rocks but is easily modified for use in different geologic terranes. We offer four guidelines for developing a system of machine-processable field notes: (1) Time and money spent to develop the system must be worth its anticipated benefits. (2) The system should be as flexible as possible. (3) It is necessary to tailor the system to a particular geologic terrane or project objective. (4) The system should be as simple and self-explanatory as possible.

Alaska↗
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

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↗
USGS1973

Loss of volatiles during fountaining and flowage of basaltic lava at Kilauea Volcano, Hawaii

The amount of water and sulfur in pumice erupted during periods of vigorous activity during the 1969-71 Mauna Ulu eruption varied inversely with fountain height because of degassing during the fountaining. The pumice lost about 0.05 wt percent water and 0.003 wt percent sulfur during fountaining to heights of 400-540 m. Analyses suggest that the initial volatile content of Mauna Ulu lava was greater immediately preceding periods of high fountaining than during weak activity between those periods or after the last high fountains on December 30, 1969. Water and sulfur were systematically depleted during nearly isothermal flowage in lava tubes. Rapidly quenched samples of dipped melt show losses of about 0.03-0.04 wt percent water and 0.007-0.008 wt percent sulfur during flowage for several hours through a distance of 12 km. Glassy skins on cooled pahoehoe flows contain about 0.002-0.003 wt percent less sulfur than quenched melt at comparable distances from the vent, because of continued degassing under natural cooling conditions. Chlorine shows similar but less well defined trends. Pumice erupted in high fountains becomes more strongly oxidized than the parent magma, because of mixing with air while still at high temperatures.

Hawaii↗
USGS1973

Radioelement distribution in the basement complex of the Yukon-Tanana upland, Eielson deep test hole, Alaska

Uranium, thorium, and potassium contents were determined in 94 samples of drill cuttings from a 9,774-foot-deep exploratory hole drilled entirely in crystalline schists of the basement complex of the Yukon-Tanana Upland. The data indicate two distinctively different rock types and reflect differences in the calcite content of the rock. Zones of anomalously high concentrations of the radioelements probably reflect the effects of the emplacement of the nearby Eielson pluton.

Alaska↗
USGS1973

Early Pleistocene(?) pollen spectra from near Lake Tahoe, California

Fossil pollen was recovered at Tahoe City, Calif., from beneath a 1.9-m.y.-old volcanic flow. Pollen counts of four fossil samples are compared with soil-surface pollen samples from the Sierra Nevada. The presence of Picea (spruce) pollen in the fossil samples suggests that summer drought conditions in the central Sierra Nevada were less severe prior to 1.9 m.y. ago than they are now.

California↗
USGS1973

Effects of migratory waterfowl on water quality at the Montezuma National Wildlife Refuge, Seneca County, New York

This study was done in response to the shellfish industry's concern that bacteria in effluent from the national wildlife refuges along the northeast coast of the United States may be adversely affecting the harvest of shellfish. A line graph shows inconsistent relationships between bird population at the Montezuma refuge and total coliform, fecal coliform, and fecal Streptococci counts. Salmonella were found in only one of 17 samples of water taken within the refuge. Counts of nonpathogenic bacteria in the two major streams flowing into the refuge, Black Brook and White Brook, were greater than they were in water flowing out of the refuge. Specific conductance of water flowing out of the refuge was less than that of water flowing into the refuge, although the effluent had higher concentrations of phosphorus and nitrogen than the influent. A settling-pond effect in the quiet water of the refuge may help explain the improvement in the quality of the water leaving the refuge. The study shows how its quality changes both chemically and biologically as water flows through the refuge. Further study is needed, however, to determine the effects that a similar effluent would have on a coastal habitat of shellfish.

New York↗