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USGS1976

Fresh ground water found deep beneath Nantucket Island, Masachusetts

In a deep water-resources and stratigraphic test well near the center of Nantucket Island, about 30 miles (48 kilometres) off the New England coast, freshwater has been found at greater depths than predicted by the Ghyben-Herzberg principle. An uppermost lens of freshwater, which occupies relatively permeable glacial-outwash sand and gravel to a depth of 520 feet (158 metres), is believed to be in hydrodynamic equilibrium with the present level of the sea and the height of the water table. However, two zones of freshwater at 730 to 820 ft (222-249 m) and 900 to 930 ft (274-283 m) are anomalously deep. Although several explanations are possible, the most likely is that the entire surface of the Continental Shelf was exposed to recharge by precipitation during long periods of low sea level in Pleistocene time. After the last retreat of glacial ice, seawater rapidly drowned the shelf around Nantucket Island. Since then, about 8,000 years ago, the deep freshwater zones which underlie dense clay layers have not had time to adjust to a new equilibrium. Under similar circumstances, freshwater may remain trapped under extensive areas of the Continental Shelf wherever clay confining beds have not permitted saltwater to intrude rapidly to new hydrodynamic equilibria positions. The implications are far reaching because all continental shelves worldwide were exposed to similar hydrologic influences during Pleistocene time.

Massachusetts↗

USGS1976

Improving estimates of streamflow characteristics by using Landsat-1 imagery

Imagery from the first Earth Resources Technology Satellite (renamed Landsat-1) was used to discriminate physical features of drainage basins in an effort to improve equations used to estimate streamflow characteristics at gaged and ungaged sites. Records of 20 gaged basins in the Delmarva Peninsula of Maryland, Delaware, and Virginia were analyzed for 40 statistical streamflow characteristics. Equations relating these characteristics to basin characteristics were obtained by a technique of multiple linear regression. A control group of equations contains basin characteristics derived from maps. An experimental group of equations contains basin characteristics derived from maps and imagery. Characteristics from imagery were forest, riparian (streambank) vegetation, water, and combined agricultural and urban land use. These basin characteristics were isolated photographically by techniques of film-density discrimination. The area of each characteristic in each basin was measured photometrically. Comparison of equations in the control group with corresponding equations in the experimental group reveals that for 12 out of 40 equations the standard error of estimate was reduced by more than 10 percent. As an example, the standard error of estimate of the equation for the 5-year recurrence-interval flood peak was reduced from 46 to 32 percent. Similarly, the standard error of the equation for the mean monthly flow for September was reduced from 32 to 24 percent, the standard error for the 7-day, 2-year recurrence low flow was reduced from 136 to 102 percent, and the standard error for the 3-day, 2-year flood volume was reduced from 30 to 12 percent. It is concluded that data from Landsat imagery can substantially improve the accuracy of estimates of some streamflow characteristics at sites in the Delmarva Peninsula.

Maryland, Delaware, Virginia↗

USGS1976

Field verification of method for distributing flow through multiple-bridge openings

Field data collected at three sites in Louisiana having multiple-bridge openings were used to check a method of distribution of flow through two or more bridges. Actual peak discharges in the various main and overflow bridges ranged from 878 to 11,055 cubic feet per second (24.9 to 313 m 2 /s). The error of the computed discharge to the actual discharge ranged between -20 and +6 percent, with the exception of one opening that had an error of +101 percent.

Louisiana↗

USGS1976

Confidence limits for flood-frequency curves computed from samples from Pearson type III populations

A study of T -year events computed from samples drawn from Pearson type III populations of known skew indicates that for skew coefficients between -1.0 and 1.0, confidence limits can be derived from the confidence limits computed for frequency curves based on samples from normal distributions. For samples from populations with skew coefficients between -0.5 and 0.5, the ratios of the standard deviates of the confidence limits to the standard deviates of the underlying frequency curve are approximately the same as for samples from normal distributions. A table provides adjustments required to make the ratios for normal distributions more applicable to distributions with skews in the range -1.0 to 1.0.

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

USGS1976

Volcanic rocks of the eastern and northern parts of the San Francisco volcanic field, Arizona

The eastern and northern parts of the San Francisco volcanic field, between San Francisco Mountain and the Little Colorado River, contain about 175 cinder cones, many with one or more associated lava flows, and one center of silicic volcanism, O'Leary Peak. Basaltic flows and cones are divided into five groups, primarily on the bases of stratigraphic and physiographic relations, degree of weathering and erosion, K-Ar and tree-ring age determinations, and, in part, chemical and petrographic data: Basaltic rocks of Sunset age -------- A.D. 1064-1065 Holocene. Basaltic rocks of Merriam age ----- <100,100 years Pleistocene. Basaltic rocks of Tappan age ------- 0.2-0.7 m.y. Do. Basaltic rocks of Woodhouse age --- 0.8-3.0 m.y. Pliocene and Pleistocene. Basalt of Cedar Ranch --------------- 5.5 m.y. Pliocene. The flows and cones are predominantly alkali olivine basalt, commonly nepheline normative, and characterized by a single Ca-rich pyroxene phase and the absence of the olivine-pyroxene reaction relation. By depletion in olivine and pyroxene these basalts grade into alkali-rich high-alumina basalts; the most silicic of which contain both Ca-rich and Ca-poor pyroxene but show no olivine reaction. By relative enrichment in K 2 O and SiO 2 , alkali olivine basalts grade into intersertal basaltic andesites that contain, in addition to olivine, two pyroxene phases and minor primary cristobalite. Volcanic rocks of O'Leary Peak consist largely of rhyodacite domes, flows, and minor pyroclastic deposits. An andesite flow underlies the rhyodacites and andesitic cinders mantle the rhyodacite porphyry dome that forms O'Leary Peak. This dome, 0.23±0.04 m.y. old, is both underlain and overlain by Tappan-age basaltic rocks. Variation diagrams that include data from the dominantly andesitic to rhyolitic San Francisco Mountain as well as from the mapped area show the differentiated and consanguineous character of the lavas, which are chemically intermediate between typical calc-alkalic and alkalic suites. Sr 87 /Sr 86 ratios of 0.7026 to 0.7050 suggest a mantle origin with little contamination by upper crustal material. Ultramafic and mafic xenoliths with cumulus texture may represent crustal intrusions related to the volcanic rocks. Eruption of intermediate to silicic magmas was generally localized in a few centers such as San Francisco Mountain and O'Leary Peak. In the same general time interval, basaltic eruptions dominated in the surrounding areas.

Arizona↗

USGS1976

Prehnite in plutonic and metamorphic rocks of the northern Santa Lucia Range, Salinian block, California

Prehnite is abundant as monomineralic veins, as lenses in biotite, and as discrete patches and apparent primary crystals in both plutonic and metamorphic rocks along the west edge of the Salinian block in the northern Santa Lucia Range. The prehnite appears to be concentrated near the Sur fault zone but is very rare in Franciscan rocks west of the fault zone. The prehnite does not appear to have been derived by local alteration of minerals in the country rocks (either plutonic or metamorphic). I suggest that solutions, derived from a "substratum" (possibly Franciscan graywacke) beneath the tectonically thinned west margin of the Salinian block, migrated through the fractured rocks of the Salinian block near the Sur fault zone and that the chemical and physical nature of these rocks favored selective prehnite deposition.

California↗

USGS1976

Bulk chemical analyses of petrographic thin sections of rocks of the Samli area, western Turkey

Petrographic thin sections have been analyzed for their major-element composition using a fusion-dilution technique and measuring the intensity of X-rays by means of the electron microprobe. The balsam-mounted thin sections were removed from the glass slides by soaking them in methylene chloride. The freed sections were mixed with twice their weight of Li 2 B 4 O 7 , and fused at 1100° C. A fragment of the resulting glasslike bead was mounted for probe analysis. Both wavelength and energy-dispersive detector systems were used for quantitative determinations of elements sodium through iron. Because the samples and standards are diluted and fused, powdered rock standards may be used as reference materials. The calibration curves obtained by plotting X-ray intensity versus concentration of the analyte are linear over the concentration ranges used in this work and have an overall range of error of 2 to 8 percent. Although some of the analytical values show excessive scatter for petrographically similar rocks, in general the analyses are acceptable given the sample size and analytical uncertainties. Bulk chemical analyses were made of 18 thin sections, including altered diabase, amphibolite, and calc-silicate hornfels produced by progressive contact metamorphism and associated with metasomatic magnetite deposits in the Samli area, western Turkey. Normative plots indicate that (1) diabase and amphibolite are compositionally related and are similar to average compositions of basalts and orthoamphibolites, and (2) calc-silicate hornfels appears to have been derived in part from amphibolite and in part from crystalline limestone that underlies much of the region.

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

USGS1976

Brown, yellow, orange, and greenish-black thorites from the Seerie pegmatite, Colorado

Four types of thorite - brown, yellow, orange, and greenish-black - occur together in narrow fracture fillings rich in brown fluorite near the outer edge of the Seerie pegmatite. The brown thorite is by far the most abundant. The thorites are remarkably similar in composition except for their Fe 2 O 3 and UO 2 contents. The common brown thorite contains about 5 percent Fe 2 O 3 , but the other types have only about 0.3 percent. The greenish-black thorite contains about 15 percent UO 2 ; the yellow and orange, about 7 percent; and the brown, about 3 percent. All four thorites have high total rare-earth oxide contents, which vary from 17.3 to 20 percent. The rare-earth assemblage is unusual in that the heavy rare earths predominate, ytterbium being the most abundant lanthanide. Unheated brown and yellow thorites gave thorite X-ray patterns, but the orange and greenish-black types are metamict. All the thorites gave a ThO 2 -UO 2 X-ray pattern as well as a thorite pattern after heating in air for 1- and 2-hour periods at 1,000°C. In addition, the pattern of the greenish-black thorite contained peaks which we ascribe to a second UO 2 compound. Minute black inclusions present in the greenish-black thorite were identified as uraninite by microprobe analysis.

Colorado↗

USGS1976

Compositional variations in wolframite from the Hamme (Tungsten Queen) mine, North Carolina

A microprobe study of wolframite from the Tungsten Queen mine, Hamme district, North Carolina, proves it to be almost pure huebnerite. Concentric zoning, which shows up as light-brown and dark-brown bands, indicates small variations in the content of FeO. There is no apparent correlation between the small variations in the composition of the wolframite and its position in the mine. The Fe/Mn ratio of the wolframite is not indicative of the temperature of crystallization.

North Carolina↗

USGS1976

Gamma-ray spectrometer measurement of 238 U/ 235 U in uranium ore from a natural reactor at Oklo, Gabon

About 20 years ago, Kuroda theorized that a high-grade uranium deposit emplaced about 2x10 9 years ago could achieve criticality and sustain a nuclear chain reaction, given a sufficient thickness of high-grade ore and an appropriate water content. Such a natural reactor was found in 1972 at the Oklo deposit, Gabon. The ore contains as much as 60 percent uranium, but the isotopic abundance of 235 U is as little as 0.4 percent in contrast to the normal abundance of 0.7110 percent 235 U. A sample from the Oklo deposit containing about 0.51 atom percent 235 U (by mass spectrometer) was analyzed by a gamma-ray spectrometer system, using a high-purity planar germanium detector. The 235 U was determined from its daughter's ( 234 Th) 63.3 keV photopeak; the 235 U was determined from its 143.8 and 163.4 keV photopeaks. The ratios of these photopeaks were compared with that from a standard having normal uranium isotopic content; the resulting calculations give a 235 U abundance of 0.54 atom percent in the Oklo sample. The gamma-ray spectrum also contains lines from five other isotopes in the uranium series, which indicate the Oklo sample to be at or near secular equilibrium, as the time elapsed since the nuclear reaction ended was sufficient to permit the daughters to achieve equilibrium.

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

USGS1976

Pre-Eocene rocks of Java, Indonesia

The exposed pre-Eocene rocks of Java can be divided into two compound units for purposes of reconnaissance mapping and structural interpretation: a sedimentary sequence and melange. The sedimentary sequence consists of moderately deformed and little-metamorphosed conglomerate, sandstone, mudstone, claystone, chert, and limestone. The melange consists of a chaotic mechanical mixture of rocks identical to those of the sedimentary sequence and their metamorphic equivalents, such as schist, phyllite, quartzite, and marble. In addition, it contains a large proportion of quartz porphyry and smaller amounts of granite, basalt, gabbro, peridotite, pyroxenite, and serpentinite. The sedimentary sequence is at least partly of Early Cretaceous age and the melange is of Early Cretaceous to very early Paleocene age. They are overlain unconformably by Eocene rocks. The presence in the melange of blocks of quartz porphyry and granite is not easily reconcilable with current plate tectonic concepts in which the sites of formation of melange and plutonic rocks should be hundreds of kilometres apart.

Java↗

USGS1976

Sedimentary depositional environments of uranium and petroleum host rocks of the Jackson Group, south Texas

Determination of depositional environments in rocks of the Jackson Group of late Eocene age aids in the exploration for uranium and petroleum in south Texas. During deposition of the Jackson Group, conditions were similar to those existing along the modern Gulf Coast of Texas except for a less arid climate and a greater supply of volcanic sediment. Sedimentary depositional environments recognized in both the modern coast and the Jackson rocks, in order from sea toward land, are: shoreface, beach, lagoon and bay, and paludal. Sediment deposited in these environments in places is interbedded with or transected by fluvial sediment. Both uranium and petroleum are found in the shoreface, beach, and fluvial facies. These facies are characterized by permeable well-sorted sandstone, which is commonly overlain and underlain by less permeable mudstone. A typical vertical sequence in ascending order through a unit containing a beach sandstone facies is (1) lagoonal or paludal clay stone and siltstone, (2) crossbedded fine-grained beach sandstone which contains Ophiomorpha burrows and, which, in places, is locally interbedded with lacustrine or lagoonal mudstone, (3) weakly laminated beach sandstone which contains root impressions at the top and Ophiomorpha , and (4) lagoonal or paludal claystone and siltstone. Gulfward, the beach sandstone apparently grades into highly burrowed, generally finer grained, more poorly sorted, less porous shoreface rocks. The beach facies may include barrier island beaches and mainland beaches, some of which were probably cheniers. Beach facies sandstone units extend many miles along the depositional strike, which nearly parallels the present outcrop strike, but extend only a mile or two (2-3 km) normal to the depositional strike into the subsurface. Recognition of the various facies in outcrops and drill holes is necessary for determination of true stratigraphic relations and for aid in exploration for beach and fluvial sandstone favorable for uranium and petroleum accumulations.

Texas↗

USGS1973

A rapid method for the determination of radioactive cesium isotopes in water

Radioactive cesium in water is concentrated by ion-exchange on finely divided ammonium hexacyanocobalt ferrate (NCFC), and then determined by beta counting. No carrier is added, and the method can be used to determine beta-emitting cesium isotopes at the 10-pCi/l level using a 100-ml sample. Five samples can be prepared for counting, in approximately 3 hours, and the method is applicable to fresh and saline waters.

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

USGS1973

Effects of laboratory treatments on silver and other elements in native gold

Interpretation of the element content of gold and of alloy proportions of gold and silver may have useful applications in prospecting and ore genesis studies. The commonly used methods of concentration and recovery of gold for analysis (acid leach, roasting, or amalgamation), however, alter the content of silver and other elements in the gold. The treatment of gold with four mineral acids (HF, HCL, H 2 S0 4 , and HNO 3 ) and combinations of these acids, amalgamation of the gold, and roasting the gold in a muffle furnace at 650°C for 8 hours caused losses of 0-100 percent of the elements studied. In some of the samples studied these treatments also caused losses totaling as much as 50 percent, by weight, of the silver content (which made up 20 percent of the total sample weight). The other elements studied show similar behavior to a lesser extent. The results of these studies show that before one interprets compositional analyses for prospecting or other applications he must know to what extent a recovery treatment changes the composition of the elements.

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

USGS1973

Tests of rhodamine WT dye for toxicity to oysters and fish

Because of the toxicity to oyster larvae and eggs of rhodamine B dye in concentrations greater than 1 mg/l in earlier tests, there was a concern that rhodamine WT, a similar tracer dye, would have a detrimental effect on marine life being developed under the aquaculture program of the Lummi Indian Tribe near Bellingham, Wash. Tests showed that 48-hour exposures at 24° C of 11,000 oyster eggs per liter and 6,000 12-day-old larvae per liter, in sea water with concentrations of rhodamine WT ranging from 1 μg/l to 10 mg/l, resulted in development of the eggs to normal straight-hinge larvae and no abnormalities in the larvae development. Tests made on the smolt of both silver salmon and Donaldson trout, with the fish held for 17.5 hours in a tankfull of sea water with a dye concentration of 10 mg/l at 22°C showed no mortalities or respiratory problems. With the concentration increased to 375 mg/l, and the time extended an additional 3.2 hours, still no mortalities or abnormalities were noted. The fish remained healthy in dye-free water when last checked a month after the test.

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

USGS1973

An accurate Invar-wire extensometer

Stevens Type F water-level recorders have been modified to measure changes in the distance between two points, with amplification of up to 10 times. Such recorders are capable of measuring strains of 10 -5 and possibly 10 -6 over 10-m distances when corrections are made for frictional effects and temperature. In two field experiments, one on Kilauea Volcano in Hawaii, and the other on the San Andreas fault in central California, measurements by the recorders agree well with those by several different methods for the same episodes of ground deformation. Equipment for the entire system costs about $300 and requires 1 to 2 man-days for installation.

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

USGS1973

Notes on the bromine pentafluoride technique of oxygen extraction

The necessity to use a dry box when loading silicate samples into reaction vessels prior to fluorination is eliminated by the use of a simple loading technique. Data presented show the reproducibility of the fluorination reaction using this technique. Sodium fluoride, when added to saline waters prior to fluorination, improves the precision of the overall technique.

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

USGS1974

Stabilities of calcite and aragonite

A revaluation of the 25° C activity-product constants of calcite ( K C ) and aragonite ( K A ) was made on the basis of the known solubilities of these phases for which the activity of total dissolved calcium was corrected for the presence of the ion pair CaHCO 3 + in the aqueous phase. The value of the dissociation constant of CaHCO 3 + was taken to be 10 -1.225±0.02 . This value, combined with values of the analytical concentrations in solutions with partial pressure P CO2 =0.97 atmosphere, leads to K C =l0 -8.52±0.04 and K A = 10 -8.36±0.04 . Based on these K values, standard free energies of formation of calcite and aragonite were calculated to be -270,144±375 and -269,926±375 calories mole -1 , (-1,130,282±1,569 and -1,129,370±1,569 joules mole -1 ), respectively. From the 25°C K values, using appropriate entropy and heat capacity data, values of K C and K A were calculated over the temperature range 0° to 200°C. Possible errors in interpretation of measured pH values and inferred P CO2 values and the bearing of these errors on calculations of K values are discussed.

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