Isotopic evidence for the source of sulfur in the Upper Freeport coal bed (west-central Pennsylvania, U.S.A.)
E.C. Spiker, B.S. Pierce, A. L. Bates, R.W. Stanton
1994, Chemical Geology (114) 115-130
Sulfur isotopic variations were used to determine the sources of sulfur in a medium-sulfur coal (???2 wt%S) that lacked marine influence, which is often cited as a major source of sulfur in coal. Variations in the amount and isotopic composition of the organic and pyritic sulfur among the coal-bed facies...
Seawater as the source of minor elements in black shales, phosphorites and other sedimentary rocks
D.Z. Piper
1994, Chemical Geology (114) 95-114
Many of the minor elements in seawater today have a concentration-depth profile similar to that of the biologically essential nutrients, NO-3 and PO3-4. They show a relative depletion in the photic zone and enrichment in the deep ocean. The difference between their surface- and deep-ocean values, normalized to the change...
Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska
J. M. White, T. A. Ager
1994, Quaternary International (22-23) 43-77
Beds in the Upper Ramparts Canyon of the Porcupine River, Alaska (67?? 20' N, 141?? 20' W), yielded a flora rich in pollen of hardwood genera now found in the temperate climates of North America and Asia. The beds are overlain or enclosed by two basalt flows which were dated...
Six years of change in Lake Nyos, Cameroon, yield clues to the past and cautions for the future
William C. Evans, L. D. White, M. L. Tuttle, G.W. Kling, G. Tanyileke, R. L. Michel
1994, Geochemical Journal (28) 139-162
The catastrophic release of gas from Lake Nyos, Cameroon, in 1986 caused substantial but incomplete mixing of the stratified water column. The post-release evolution of water-column structure has been monitored through April 1992. Changes began immediately after the event as rainfall and inflow brought dilute fluid into the surface layer....
Chemical reaction path modeling of ore deposition in Mississippi Valley-type Pb-Zn deposits of the Ozark region, US midcontinent
G.S. Plumlee, D. L. Leach, A. H. Hofstra, G. P. Landis, E. L. Rowan, J.G. Viets
1994, Economic Geology (89) 1361-1383
The Ozark region of the U.S. midcontinent is host to a number of Mississippi Valley-type districts, including the world-class Viburnum Trend, Old Lead Belt, and Tri-State districts and the smaller Southeast Missouri barite, Northern Arkansas, and Central Missouri districts. There is increasing evidence that the Ozark Mississippi Valley-type districts formed...
An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region
R.B. McCammon, W.I. Finch, J.O. Kork, N.J. Bridges
1994, Nonrenewable Resources (3) 109-122
An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined...
Sediment resuspension and bed armoring during high bottom stress events on the northern California inner continental shelf: Measurements and predictions
P.L. Wiberg, D.E. Drake, D.A. Cacchione
1994, Continental Shelf Research (14) 1191-1219
Geoprobe bottom tripods were deployed during the winter of 1990–1991 on the northern California inner continental shelf as part of the STRESS field experiment. Transmissometer measurements of light beam attenuation were made at two levels and current velocity was measured at...
The geochemical cycling of trace elements in a biogenic meromictic lake
Laurie S. Balistrieri, J.W. Murray, B. Paul
1994, Geochimica et Cosmochimica Acta (58) 3993-4008
The geochemical processes affecting the behavior and speciation of As, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, V, and Zn in Hall Lake, Washington, USA, are assessed by examining dissolved and acid soluble particulate profiles of the elements and utilizing results from thermodynamic calculations. The water column of this...
Modeling the effects of climate change on water resources - a review
G.H. Leavesley
1994, Climatic Change (28) 159-177
Hydrologic models provide a framework in which to conceptualize and investigate the relationships between climate and water resources. A review of current studies that assess the impacts of climate change using hydrologic models indicates a number of problem areas common to the variety of models applied. These problem areas include...
Real-time data collection of scour at bridges
David S. Mueller, Mark N. Landers
1994, Conference Paper, Proceedings of the Symposium on Fundamentals and Advancements in Hydraulic Measurements and Experimentation
The record flood on the Mississippi River during the summer of 1993 provided a rare opportunity to collect data on scour of the streambed at bridges and to test data collection equipment under extreme hydraulic conditions. Detailed bathymetric and hydraulic information were collected at two bridges crossing the Mississippi River...
Uranium(VI) adsorption to ferrihydrite: Application of a surface complexation model
T.D. Waite, J.A. Davis, T.E. Payne, G.A. Waychunas, N. Xu
1994, Geochimica et Cosmochimica Acta (58) 5465-5478
A study of U(VI) adsorption by ferrihydrite was conducted over a wide range of U(VI) concentrations, pH, and at two partial pressures of carbon dioxide. A two-site (strong- and weak-affinity sites, FesOH and FewOH, respectively) surface complexation model was able to describe the experimental data well over a wide range...
Ionic strength and DOC determinations from various freshwater sources to the San Francisco Bay
Y.R. Hunter, J.S. Kuwabara
1994, Bulletin of Environmental Contamination and Toxicology (52) 311-318
An exact estimation of dissolved organic carbon (DOC) within the salinity gradient of zinc and copper metals is significant in understanding the limit to which DOC could influence metal speciation. A low-temperature persulfate/oxygen/ultraviolet wet oxidation procedure was utilized for analyzing DOC samples adapted for ionic strength from major freshwater sources...
Salinity increases in the navajo aquifer in southeastern Utah
D. L. Naftz, L.E. Spangler
1994, Water Resources Bulletin (30) 1119-1135
Salinity increases in water in some parts of the Navajo aquifer in southeastern Utah have been documented previously. The purpose of this paper is to use bromide, iodide, and chloride concentrations and del oxygen-18 and deuterium values in water from the study area to determine if oil-field brines (OFB) could...
Prospector II: Towards a knowledge base for mineral deposits
R.B. McCammon
1994, Mathematical Geology (26) 917-936
What began in the mid-seventies as a research effort in designing an expert system to aid geologists in exploring for hidden mineral deposits has in the late eighties become a full-sized knowledge-based system to aid geologists in conducting regional mineral resource assessments. Prospector II, the successor to Prospector, is interactive-graphics...
Profile development for the Spatial Data Transfer Standard
John A. Szemraj, Robin G. Fegeas, Billy R. Tolar
1994, Cartography and Geographic Information Systems (21) 150-154
The Spatial Data Transfer Standard (SDTS), or Federal Information Processing Standard (FIPS) 173, is designed to support all types of spatial data. Implementing all of the standard's options at one time is impractical. Therefore, implementation of the SDTS is being accomplished through the use of profiles. Profiles are clearly defined,...
Earthquake classification, location, and error analysis in a volcanic environment: implications for the magmatic system of the 1989-1990 eruptions at redoubt volcano, Alaska
J.C. Lahr, B. A. Chouet, C.D. Stephens, J.A. Power, R.A. Page
1994, Journal of Volcanology and Geothermal Research (62) 137-151
Determination of the precise locations of seismic events associated with the 1989-1990 eruptions of Redoubt Volcano posed a number of problems, including poorly known crustal velocities, a sparse station distribution, and an abundance of events with emergent phase onsets. In addition, the high relief of the volcano could not be...
A rock-magnetic record from Lake Baikal, Siberia: Evidence for Late Quaternary climate change
J.A. Peck, J.W. King, Steven M. Colman, V.A. Kravchinsky
1994, Earth and Planetary Science Letters (122) 221-238
Rock-magnetic measurements of sediment cores from the Academician Ridge region of Lake Baikal, Siberia show variations related to Late Quaternary climate change. Based upon the well-dated last glacial-interglacial transition, variations in magnetic concentration and mineralogy are related to glacial-interglacial cycles using a conceptual model. Interglacial intervals are characterized by low...
Ductile creep and compaction: A mechanism for transiently increasing fluid pressure in mostly sealed fault zones
Norman H. Sleep, M.L. Blanpied
1994, Pure and Applied Geophysics PAGEOPH (143) 9-40
A simple cyclic process is proposed to explain why major strike-slip fault zones, including the San Andreas, are weak. Field and laboratory studies suggest that the fluid within fault zones is often mostly sealed from that in the surrounding country rock. Ductile creep driven by the difference between fluid pressure...
Fine structure of the landers fault zone: Segmentation and the rupture process
Y.-G. Li, J.E. Vidale, K. Aki, C.J. Marone, W.H.K. Lee
1994, Science (265) 367-370
Observations and modeling of 3- to 6-hertz seismic shear waves trapped within the fault zone of the 1992 Landers earthquake series allow the fine structure and continuity of the zone to be evaluated. The fault, to a depth of at least 12 kilometers, is marked by a zone 100 to...
Digital hum filtering
R.W. Knapp, N.L. Anderson
1994, Computers & Geosciences (20) 881-888
Data may be overprinted by a steady-state cyclical noise (hum). Steady-state indicates that the noise is invariant with time; its attributes, frequency, amplitude, and phase, do not change with time. Hum recorded on seismic data usually is powerline noise and associated higher harmonics; leakage from full-waveform rectified cathodic protection devices...
Developing standards for a national spatial data infrastructure
Kathryn C. Wortman
1994, Cartography and Geographic Information Systems (21) 132-135
The concept of a framework for data and information linkages among producers and users, known as a National Spatial Data Infrastructure (NSDI), is built upon four corners: data, technology, institutions, and standards. Standards are paramount to increase the efficiency and effectiveness of the NSDI. Historically, data standards and specifications have...
Potential-field sounding using Euler's homogeneity equation and Zidarov bubbling
Lindrith Cordell
1994, Geophysics (59) 902-908
Potential-field (gravity) data are transformed into a physical-property (density) distribution in a lower half-space, constrained solely by assumed upper bounds on physical-property contrast and data error. A two-step process is involved. The data are first transformed to an equivalent set of line (2-D case) or point (3-D case) sources, using...
Sensitivity of northern Sierra Nevada streamflow to climate change
L.F.W. Duell
1994, Water Resources Bulletin (30) 841-859
The sensitivity of streamflow to climate change was investigated in the American, Carson, and Truckee River Basins, California and Nevada. Nine gaging stations were used to represent streamflow in the basins. Annual models were developed by regressing 1961-1991 streamflow data on temperature and precipitation. Climate-change scenarios were used as inputs...
Gravitational stresses in long symmetric ridges and valleys in anisotropic rock
E. Pan, B. Amadei, W. Z. Savage
1994, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (31) 293-312
The effect of topography and rock mass anisotropy on gravitational stresses in long isolated symmetric ridges and valleys is modeled using an analytical method proposed earlier by the first two authors. The rock mass deforms under a condition of plane strain. A parametric study is presented on the effect of...
Simulating effects of highway embankments on estuarine circulation
Jonathan K. Lee, Raymond W. Schaffranek, Robert A. Baltzer
1994, Journal of Waterway, Port, Coastal and Ocean Engineering (120) 199-218
A two‐dimensional, depth‐averaged, finite‐difference, numerical model was used to simulate tidal circulation and mass transport in the Port Royal Sound, South Carolina, estuarine system. The purpose of the study was to demonstrate the utility of the Surface‐Water, Integrated, Flow and Transport model (SWIFT2D) for evaluating changes in circulation patterns and...
