As, Bi, Hg, S, Sb, Sn and Te geochemistry of the J-M Reef, Stillwater Complex, Montana: Constraints on the origin of PGE-enriched sulfides in layered intrusions
M. L. Zientek, T. L. Fries, R.W. Vian
1990, Journal of Geochemical Exploration (37) 51-73
The J-M Reef is an interval of disseminated sulfides in the Lower Banded series of the Stillwater Complex that is enriched in the platinum group elements (PGE). Palladium and Pt occur in solid solution in base-metal sulfides and as discrete PGE minerals. PGE minerals include sulfides, tellurides, arsenides, antimonides, bismuthides,...
Deformation monitoring at Nevado del Ruiz, Colombia - October 1985 - March 1988
N.G. Banks, C. Carvajal, H. Mora, E. Tryggvason
1990, Journal of Volcanology and Geothermal Research (41) 269-295
Deformation studies began at Nevado del Ruiz 23 days before the devastating 13 November 1985 eruption, at least 12 months after precursory seismicity and fumarolic activity began. The late start in geodetic monitoring, limited number of stations in the pre-eruption network, and inconsistent patterns in the observed deformation limit conclusions...
Determination of trace levels of herbicides and their degradation products in surface and ground waters by gas chromatography/ion-trap mass spectrometry
W. E. Pereira, C.E. Rostad, T.J. Leiker
1990, Analytica Chimica Acta (228) 69-75
A rapid, specific and highly sensitive method is described for the determination of several commonly used herbicides and their degradation products in surface and ground waters by using gas chromatography/ion-trap mass spectrometry. The compounds included atrazine, and its degradation products desethylatrazine and desisopropylatrazine; Simazine; Cyanazine; Metolachlor; and alachlor and its...
Qualitative and numerical analyses of the effects of river inflow variations on mixing diagrams in estuaries
L.A. Cifuentes, L. E. Schemel, J.H. Sharp
1990, Estuarine, Coastal and Shelf Science (30) 411-427
The effects of river inflow variations on alkalinity/salinity distributions in San Francisco Bay and nitrate/salinity distributions in Delaware Bay are described. One-dimensional, advective-dispersion equations for salinity and the dissolved constituents are solved numerically and are used to simulate mixing in the estuaries. These simulations account for time-varying river inflow, variations...
Carbon isotope constraints on degassing of carbon dioxide from Kilauea Volcano
T.M. Gerlach, B.E. Taylor
1990, Geochimica et Cosmochimica Acta (54) 2051-2058
We examine models for batch-equilibrium and fractional-equilibrium degassing of CO2 from magma at Kilauea Volcano. The models are based on1.(1) the concept of two-stage degassing of CO2 from magma supplied to the summit chamber,2.(2) C isotope data for CO2 in eruptive and noneruptive (quiescent) gases from Kilauea and<li...
Effects of climatic change on the Thornthwaite moisture index
Gregory J. McCabe, David M. Wolock, Lauren E. Hay, Mark A. Ayers
1990, Water Resources Bulletin (26) 633-643
The Thornthwaite moisture index is a useful indicator of the supply of water (precipitation) in an area relative to the demand for water under prevailing climatic conditions (potential evapotranspiration). This study examines the effects of changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the conterminous United...
Comment on "The surface of lo: A new model" by Bruce Hapke
A. S. McEwen, J. I. Lunine
1990, Icarus (84) 268-274
Hapke (1989, Icarus 79, 56–74) proposed that the surface of Io is dominantly basaltic with thin coatings of polysulfur oxide, S2O, ad SO,2. However, observations and models of the active volcanism indicate that volatiles such as sulfur and SO2 must be more abundant than envisioned by Hapke....
Age and paleoclimatic significance of the Stansbury shoreline of Lake Bonneville, Northeastern Great Basin
Charles G. Oviatt, D.R. Currey, D. M. Miller
1990, Quaternary Research (33) 291-305
The Stansbury shoreline, one of the conspicuous late Pleistocene shorelines of Lake Bonneville, consists of tufa-cemented gravel and barrier beaches within a vertical zone of about 45 m, the lower limit of which is 70 m above the modern average level of Great Salt Lake. Stratigraphic evidence at a number...
Thermal infrared exploration in the Carlin trend, northern Nevada
K. Watson, F.A. Kruse, S. Hummer-Miller
1990, Geophysics (55) 70-79
Experimental Thermal Infrared Multispectral Scanner (TIMS) aircraft data have been acquired for the Rodeo Creek NE 7 1/2 minute quadrangle, Eureka County, northern Nevada, covering the Carlin gold mine. A simple model has been developed to extract spectral emissivities for mapping surface lithology and alteration based on the physical properties...
Petrology, isotope characteristics, and K-Ar ages of the Maranhão, northern Brazil, Mesozoic basalt province
R.V. Fodor, A.N. Sial, S.B. Mukasa, E.H. McKee
1990, Contributions to Mineralogy and Petrology (104) 555-567
Northern Brazil contains remnants of Mesozoic flood basalts and hypabyssal rocks that were apparently emplaced during tectonism related to opening of the Atlantic Ocean. Analyses and new K-Ar ages reveal that this ∼700x250 km Maranhão province (5°–8°S) has low-Ti basalts (∼1.1 wt% TiO2) in the western part that range...
The extraordinary radar echoes from Europa, Ganymede, and Callisto: A geological perspective
S.J. Ostro, E.M. Shoemaker
1990, Icarus (85) 335-345
This outline of plausible geologic explanations for the icy Galilean satellites' radar properties takes into consideration electromagnetic scattering models for the echoes, available empirical and theoretical information about regolith formation, and ice physics. The...
Metal and nutrient behavior in the Raritan estuary, New Jersey, U.S.A.: The effect of multiple freshwater and industrial waste inputs
A.S. Maest, D.A. Crerar, R.F. Stallard, J. N. Ryan
1990, Chemical Geology (81) 133-149
A geochemical analysis of the Raritan estuary during high and low river flow is presented. Several statistical and graphical approaches, in addition to a hydrodynamic model of the Raritan estuary, are used to demonstrate the effects of lateral inputs on trace-element distribution in a complicated fluvial-marine system. Results from factor...
Iberian plate kinematics: A jumping plate boundary between Eurasia and Africa
S.P. Srivastava, Hans Schouten, W.R. Roest, Kim D. Klitgord, L.C. Kovacs, J. Verhoef, R. Macnab
1990, Nature (344) 756-759
THE rotation of Iberia and its relation to the formation of the Pyrenees has been difficult to decipher because of the lack of detailed sea-floor spreading data, although several models have been proposed1-7. Here we use detailed aeromagnetic measurements from the sea floor offshore of the Grand Banks of Newfoundland...
Climatic change and permafrost. Record from surficial deposits
L. David Carter
1990, Journal of Cold Regions Engineering (4) 43-53
The physical and chemical characteristics of surficial deposits and the floral and faunal remains they contain provide information that is useful for interpreting both paleoclimate and past permafrost conditions. Surficial deposits thus provide a record of climatic change and permafrost history. This record suggests that initiation of permafrost in lowland...
Relationships among macerals, minerals, miospores and paleoecology in a column of Redstone coal (Upper Pennsylvanian) from north-central West Virginia (U.S.A.)
W.C. Grady, C.F. Eble
1990, International Journal of Coal Geology (15) 1-26
Two distinct paleoenvironments are represented in vertical succession in a column of Redstone coal in north-central West Virginia as indicated by a study of 37 consecutive 3-cm (0.1 ft) increments analyzed for ash yield, petrographic composition, low-temperature ash mineralogy and palynomorph...
A quantitative micropaleontologic method for shallow marine peleoclimatology: Application to Pliocene deposits of the western North Atlantic Ocean
T. M. Cronin, H.J. Dowsett
1990, Marine Micropaleontology (16) 117-147
A transfer function was developed to estimate summer and winter paleotemperatures for arctic to tropical regions of the western North Atlantic Ocean using fossil ostracode assemblages. Q-mode factor analysis was run on ostracode assemblages from 100 modern bottom sediment samples from continental shelves of North America, Greenland and the Caribbean...
The Taylor Creek Rhyolite of New Mexico: a rapidly emplaced field of lava domes and flows
W. A. Duffield, G. B. Dalrymple
1990, Bulletin of Volcanology (52) 475-487
The Tertiary Taylor Creek Rhyolite of southwest New Mexico comprises at least 20 lava domes and flows. Each of the lavas was erupted from its own vent, and the vents are distributed throughout a 20 km by 50 km area. The volume of the rhyolite and genetically associated pyroclastic deposits...
Thermal maturity of Jurassic shales from the Newark Basin, U.S.A.: Influence of hydrothermal fluids and implications to basin modeling
C.C. Walters, R. K. Kotra
1990, Applied Geochemistry (5) 211-225
Organic geochemical investigations were conducted on a series of cores that systematically sampled the uppermost Jurassic strata from the northern Newark Basin. Each sedimentary unit consists of fluvial red sandstones and siltstones with cyclic deposits of interbedded black lacustrine shales and...
Sediment movement along the U.S. east coast continental shelf-II. Modelling suspended sediment concentration and transport rate during storms
V.D. Lyne, B. Butman, W.D. Grant
1990, Continental Shelf Research (10) 429-460
Long-term near-bottom wave and current observations and a one-dimensional sediment transport model are used to calculate the concentration and transport of sediment during winter storms at 60-80 m water depth along the southern flank of Georges Bank and in the Mid-Atlantic Bight. Calculations are presented for five stations, separated by...
Cosmic ray exposure dating with in situ produced cosmogenic 3He: Results from young Hawaiian lava flows
Mark D. Kurz, D. Colodner, T.W. Trull, Richard B. Moore, K. O’Brien
1990, Earth and Planetary Science Letters (97) 177-189
In an effort to determine the in situ production rate of spallation-produced cosmogenic 3He, and evaluate its use as a surface exposure chronometer, we have measured cosmogenic helium contents in a suite of Hawaiian radiocarbon-dated lava flows. The lava flows, ranging in age...
Reaction paths and equilibrium end-points in solid-solution aqueous-solution systems
P. D. Glynn, E.J. Reardon, Niel Plummer, E. Busenberg
1990, Geochimica et Cosmochimica Acta (54) 267-282
Equations are presented describing equilibrium in binary solid-solution aqueous-solution (SSAS) systems after a dissolution, precipitation, or recrystallization process, as a function of the composition and relative proportion of the initial phases. Equilibrium phase diagrams incorporating the concept of stoichiometric saturation are used to interpret possible reaction paths and to demonstrate...
A comparison of two- and three-dimensional stochastic models of regional solute movement
A.M. Shapiro, V.D. Cvetkovic
1990, Transport in Porous Media (5) 1-25
Recent models of solute movement in porous media that are based on a stochastic description of the porous medium properties have been dedicated primarily to a three-dimensional interpretation of solute movement. In many practical problems, however, it is more convenient and consistent with measuring techniques to consider flow and solute...
Magnetic forward models of Cement oil field, Oklahoma, based on rock magnetic, geochemical, and petrologic constraints
R. L. Reynolds, M. Webring, V. J. S. Grauch, M. Tuttle
1990, Geophysics (55) 344-353
Magnetic forward models of the Cement oil field, Oklahoma, were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of Permian strata contributes to aeromagnetic anomalies at Cement. Six bodies having different magnetizations were constructed for the magnetic models, based on geology...
Order and diversity in the modes of circum-Pacific earthquake recurrence
W. Thatcher
1990, Journal of Geophysical Research Solid Earth (95) 2609-2623
Recurrence characteristics of great circum-Pacific earthquakes and determinations of spatial distribution of seismic moment release are surveyed in order to delineate their general features and relate earthquake slip distribution to models of recurrent rupture. As noted by others, the pattern of moment release is typically very irregular, with strong concentrations...
Equivalent strike-slip earthquake cycles in half-space and lithosphere-asthenosphere earth models
J.C. Savage
1990, Journal of Geophysical Research (95) 4873-4879
By virtue of the images used in the dislocation solution, the deformation at the free surface produced throughout the earthquake cycle by slippage on a long strike-slip fault in an Earth model consisting of an elastic plate (lithosphere) overlying a viscoelastic half-space (asthenosphere) can be duplicated by prescribed slip on...
