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Simulated observations of spawning stock size, recruitment, and two random environmental variables were obtained from a density-independent Leslie matrix model. Recruitment to Age 1 was directly proportional to population fecundity but strongly influenced by the effects of the random environmental variables. The simulated observations were subjected to multiple regression analysis...

Petroleum resource assessment procedures require the analysis of a large volume of spatial data. The US Geological Survey (USGS) has developed and applied spatial information handling procedures and digital cartographic techniques to a recent study involving the assessment of oil and gas resource potential for 74 million acres of designated...

A 43-acre watershed in Muskingum County, Ohio, was studied to determine the hydrologic consequences of strip mining for coal. A quantitative description of the effects on the ground-water flow components of the hydrologic system has been obtained using digital models.The premining watershed was characterized by...

The chemistry of water in the Cambrian-Ordovician aquifer in six midwestern states has been studied as part of the Northern Midwest Regional Aquifer-System Analysis of the U.S. Geological Survey. Dissolved-solids concentrations generally increase perpendicular to the direction of regional groundwater flow, from less than 400 mg/liter in southeast Minnesota, southwest...

A two-dimensional steady-state model of light-driven phytoplankton productivity and biomass in partially mixed estuaries has been developed. Effects of variations in river flow, suspended sediment concentration, phytoplankton sinking, self-shading and growth rates on distributions of phytoplankton biomass and productivity are investigated.Numerical simulation experiments show that biomass and productivity are particularly...

The amount of thermal energy in high-temperature geothermal systems (>150 degree C) in the United States has been calculated by estimating the temperature, area, and thickness of each identified system. These data, along with a general model for recoverability of geothermal energy and a calculation that takes account of the...

Noble gases have been measured mass spectrometrically in samples collected during 1977 from producing wells at Cerro Prieto. Positive correlations between concentrations of radiogenic (He and 40Ar) and atmospheric noble gases (Ne, Ar and Kr) suggest the following dynamic model: the geothermal fluids originated from meteoric water that penetrated to...

Many large calderas result from the eruption of substantial volumes (tens or hundreds of km3) of silicic pyroclastics. Such events often begin with an airfall phase and progress to the generation of voluminous ignimbrites1-3. We propose here that many such eruptions involve two well-defined stages, based on a simple analysis...

A new photoclinometric technique for extraction of topographic data from single planetary images is presented that overcomes many previous limitations of photoclinometry. The procedure fully compensates for oblique viewing geometry prevalent in spacecraft images. Albedo variations have been one of the most serious obstacles in the application of photoclinometry to...

A digital ground-water flow model of the southern High Plains of Texas and New Mexico has been constructed. The calibrated model with the 1980 water level as the initial condition was used to project water levels to 2020. Estimated future pumpage based on the U. S. Economic Development Administration's economic...

An ion microprobe mass analyzer (IMMA) has been used to analyze semi-quantitatively mineral-rich coal particles from two separate facies of the Upper Freeport coal bed. Accuracy is estimated to be ∓ 20% for those elements making up more than 0.1 wt.%...

Solutions of 30% H2O2 ranging from pH = 0 to pH = 11.5 have been used to oxidize anthracite at room temperature. The inorganic impurities, primarily pyrite, catalysed the oxidation and reduction of H2O2 (the Fenton reaction) to form the hydroxyl radical; the oxidation of the organic matter was minimal and was observed only in strong...

Improved regional and interregional stratigraphic correlations of Pennsylvanian strata permit comparisons of vegetational changes in Euramerican coal swamps. The coal-swamp vegetation is known directly from in situ coal-ball peat deposits from more than 65 coals in the United States and Europe....

Data obtained from 59 Landsat scenes were used to estimate the areal extent of irrigated agriculture over the High Plains region of the United States for a ground-water flow model. This model provides information on current trends in the amount and distribution of water used for irrigation. The analysis and...

The major and minor element composition of ferromanganese nodules from DOMES Site A has been determined by X-ray fluorescence methods. Three phases appear to control the bulk compositions: Mn and Fe oxyhydroxides and aluminosilicates. Relatively wide compositional variations are evident throughout the area. Nodules with high Mn/Fe ratios, high Cu,...

Epidote is a major magmatic mineral in tonalite and granodiorite in a belt coextensive with the Mesozoic accreted terranes between northern California and southeastern Alaska. Textural and chemical evidence indicates that epidote crystallized as a relatively late but magmatic mineral that formed through...

Size and density separates of low-temperature-ashed coal from the Powhatan No. 6 mine, Ohio, have been used to determine the mode of occurrence of 28 minor and trace elements in coal. The size distribution of the major minerals has been determined, and correlations of trace elements with major minerals have...

The Yellowstone Plateau volcanic field has undergone repeated eruption of rhyolitic magma strongly depleted in 18O. Large calderas subsided 2.0, 1.3, and 0.6 Ma ago, on eruption of ash flow sheets that represent at least 2500, 280, and 1000 km3 of zoned magma. More than 60 other rhyolite lavas and tuffs permit...

Analyses of six mineralized and five nonmineralized whole-rock drill core samples from the uranium deposit at Lilljuthatten yield a lead-lead isochron age of 420 + or - 1 m.y. This age corresponds to the last stage of the Caledonian Orogeny. None of the isotopic systems examined have completely retained the...

Side-looking airborne radar has provided a sufficiently detailed synoptic view of the central Appalachian Mountains that the images give an unparalleled representation of the size and nature of the folds within the Valley and Ridge province. The radar data show that fold wavelengths decrease abruptly south of the region of...

Stratiform tourmalinites are significant minor rock types in many regional metamorphic terranes of the world. Tourmalinites are more widespread than previously recognized and are especially common in Proterozoic and early Paleozoic sequences dominated by clastic metasedimentary rocks. They consist of conformable layers made...

Regional studies on the bioavailability of metals at native and disturbed sites were conducted over the past seven years by the USGS. The work was concentrated in the Fort Union, Powder River, and Green River coal resource regions where measures of extractable metals in soils were found to have limited...

Several two- to six-parameter regional water balance models are examined by using 50-year records of monthly streamflow at 10 sites in New Jersey. These models include variants of the Thornthwaite-Mather model, the Palmer model, and the more recent Thomas abcd model. Prediction errors are relatively similar among the models. However, simulated values...

The oxygen isotope compositions and metamorphic mineral assemblages of hydrothermally altered rocks from the Del Puerto ophiolite and overlying volcaniclastic sedimentary rocks at the base of the Great Valley sequence indicate that their alteration occurred in a submarine hydrothermal system. Whole rock δ18O compositions decrease progressively down section (with increasing...

Theories of flow to a well in a double-porosity groundwater reservoir are modified to incorporate effects of a thin layer of low-permeability material or fracture skin that may be present at fracture-block interfaces as a result of mineral deposition or alteration. The commonly used theory for flow in double- porosity...