Multiport well design for sampling of ground water at closely spaced vertical intervals
G. N. Delin, M.K. Landon
1996, Ground Water (34) 1098-1104
Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and...
Degassing during magma ascent in the Mule Creek vent (USA)
M.V. Stasiuk, J. Barclay, M.R. Carroll, Claude Jaupart, J.C. Ratte, R. S. J. Sparks, S.R. Tait
1996, Bulletin of Volcanology (58) 117-130
The structures and textures of the rhyolite in the Mule Creek vent (New Mexico, USA) indicate mechanisms by which volatiles escape from silicic magma during eruption. The vent outcrop is a 300-m-high canyon wall comprising a section through the top of a feeder conduit, vent and the base of an...
Deformation-induced changes in hydraulic head during ground-water withdrawal
Paul A. Hsieh
1996, Ground Water (34) 1082-1089
Ground-water withdrawal from a confined or semiconfined aquifer causes three-dimensional deformation in the pumped aquifer and in adjacent layers (overlying and underlying aquifers and aquitards). In response to the deformation, hydraulic head in the adjacent layers could rise or fall almost immediately after the start of pumping. This deformation-induced effect...
Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan
R.B. Symonds, Y. Mizutani, Paul H. Briggs
1996, Journal of Volcanology and Geothermal Research (73) 177-211
This study investigates 31 years of fumarole gas and condensate (trace elements) data from Showa-Shinzan, a dacitic dome-cryptodome complex that formed during the 1943-1945 eruption of Usu volcano. Forty-two gas samples were collected from the highest-temperature fumarole, named A-1, from 1954 (800??C) to 1985 (336??C), and from lower-temperature vents. Condensates...
Weathering rates as a function of flow through an alpine soil
D. W. Clow, J.I. Drever
1996, Chemical Geology (132) 131-141
The effect of flow on release rates of solutes from soil in a 39-m2 alpine catchment in the Colorado Rockies was measured during the summers of 1990-1994. Flow rates through the soil were varied by augmenting natural rainfall with deionized irrigation water. Daily water inputs averaged between 96 and 216...
Spatial partitioning of environmental correlates of avian biodiversity in the conterminous United States
R.J. O’Connor, M.T. Jones, D. White, C. Hunsaker, Tom Loveland, Bruce Jones, E. Preston
1996, Biodiversity Letters (3) 97-110
Classification and regression tree (CART) analysis was used to create hierarchically organized models of the distribution of bird species richness across the conterminous United States. Species richness data were taken from the Breeding Bird Survey and were related to climatic and land use data. We used a systematic spatial grid...
Spatial uncertainty analysis: Propagation of interpolation errors in spatially distributed models
D.L. Phillips, D.G. Marks
1996, Ecological Modelling (91) 213-229
In simulation modelling, it is desirable to quantify model uncertainties and provide not only point estimates for output variables but confidence intervals as well. Spatially distributed physical and ecological process models are becoming widely used, with runs being made over a grid of points that represent the landscape. This requires...
Origin of Bermuda's clay-rich Quaternary paleosols and their paleoclimatic significance
S.R. Herwitz, D.R. Muhs, J.M. Prospero, S. Mahan, B. Vaughn
1996, Journal of Geophysical Research D: Atmospheres (101) 23389-23400
Red clayey paleosols that are chiefly the product of aerosolic dust deposition are interbedded in the Quaternary carbonate formations of the Bermuda oceanic island system. These paleosols provide a basis for reconstructing Quaternary atmospheric circulation patterns in the northwestern Atlantic. Geochemical analyses were performed on representative paleosol samples to identify...
Predicting watershed acidification under alternate rainfall conditions
Thomas G. Huntington
1996, Water, Air, & Soil Pollution (90) 429-450
The effect of alternate rainfall scenarios on acidification of a forested watershed subjected to chronic acidic deposition was assessed using the model of acidification of groundwater in catchments (MAGIC). The model was calibrated at the Panola Mountain Research Watershed, near Atlanta, Georgia, U.S.A. using measured soil properties, wet and dry...
Contrasts between Sm-Nd whole-rock and U-Pb zircon systematics in the Tobacco Root batholith, Montana: Implications for the determination of crustal age provinces
P.A. Mueller, A.L. Heatherington, K. A. D’Arcy, J. L. Wooden, A.P. Nutman
1996, Tectonophysics (265) 169-179
Proper documentation of the extent and age of crust in the western US is critical for constraining a variety of geologic problems ranging from the growth rate of continents to Precambrian continental reconstructions. The secondary isotopic systematics of granitoids have been one of the principal means used to characterize continental...
Clay alteration and gold deposition in the genesis and blue star deposits, Eureka County, Nevada
S. P. Drews-Armitage, S.B. Romberger, C.G. Whitney
1996, Economic Geology (91) 1383-1393
The Genesis and Blue Star sedimentary rock-hosted gold deposits occur within the 40-mile-long Carlin trend and are located in Eureka County, Nevada. The deposits are hosted within the Devonian calcareous Popovieh Formation, the siliciclastic Rodeo Creek unit and the siliciclastic Vinini Formation. The host rocks have undergone contact metamorphism, decalcification,...
Kinetic determinations of trace element bioaccumulation in the mussel Mytilus edulis
W.-X. Wang, N.S. Fisher, S. N. Luoma
1996, Marine Ecology Progress Series (140) 91-113
Laboratory experiments employing radiotracer methodology were conducted to determine the assimilation efficiencies from ingested natural seston, the influx rates from the dissolved phase and the efflux rates of 6 trace elements (Ag, Am, Cd, Co, Se and Zn) in the mussel Mytilus edulis. A kinetic model was then employed to...
Detailed observations of California foreshock sequences: Implications for the earthquake initiation process
D.A. Dodge, G. C. Beroza, W.L. Ellsworth
1996, Journal of Geophysical Research B: Solid Earth (101) 22371-22392
We find that foreshocks provide clear evidence for an extended nucleation process before some earthquakes. In this study, we examine in detail the evolution of six California foreshock sequences, the 1986 Mount Lewis (ML = 5.5), the 1986 Chalfant (ML = 6.4), the 1986 Stone Canyon (ML = 4.7), the 1990 Upland (ML =...
Mineralogy and petrology of cretaceous subsurface lamproite sills, southeastern Kansas, USA
R.L. Cullers, M. J. Dorais, P. Berendsen, Sambhudas Chaudhuri
1996, LITHOS (38) 185-206
Cores and cuttings of lamproite sills and host sedimentary country rocks in southeastern Kansas from up to 312 m depth were analyzed for major elements in whole rocks and minerals, certain trace elements in whole rocks (including the REE) and Sr isotopic composition of the whole rocks. The lamproites are...
Comparison of alternative spatial resolutions in the application of a spatially distributed biogeochemical model over complex terrain
D.P. Turner, R. Dodson, D. Marks
1996, Ecological Modelling (90) 53-67
Spatially distributed biogeochemical models may be applied over grids at a range of spatial resolutions, however, evaluation of potential errors and loss of information at relatively coarse resolutions is rare. In this study, a georeferenced database at the 1-km spatial resolution was developed to initialize and drive a process-based model...
20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.
B. F. Molnia, A. Post, P.R. Carlson
1996, Annals of Glaciology (22) 205-210
Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus...
Record of middle Pleistocene climate change from Buck Lake, Cascade Range, southern Oregon - Evidence from sediment magnetism, trace-element geochemistry, and pollen
J. G. Rosenbaum, R. L. Reynolds, D.P. Adam, J. Drexler, A.M. Sarna-Wojcicki, G.C. Whitney
1996, Geological Society of America Bulletin (108) 1328-1341
Comparison of systematic variations in sediment magnetic properties to changes in pollen assemblages in middle Pleistocene lake sediments from Buck Lake indicates that the magnetic properties are sensitive to changes in climate. Buck Lake is located in southern Oregon just east of the...
Outer-sphere Pb(II) adsorbed at specific surface sites on single crystal α-alumina
John R. Bargar, Steven N. Towle, Gordon E. Brown Jr., George A. Parks
1996, Geochimica et Cosmochimica Acta (60) 3541-3547
Solvated Pb(II) ions were found to adsorb as structurally well-defined outer-sphere complexes at specific sites on the α-Al2O3 (0001) single crystal surface, as determined by grazing-incidence X-ray absorption fine structure (GI-XAFS) measurements. The XAFS results suggest that the distance between Pb(II) adions and the alumina surface is approximately 4.2 Å....
The initial cooling of pahoehoe flow lobes
L. Keszthelyi, R. Denlinger
1996, Bulletin of Volcanology (58) 5-18
In this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows. The accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key...
Failure in laboratory fault models in triaxial tests
J.C. Savage, D.A. Lockner, J.D. Byerlee
1996, Journal of Geophysical Research B: Solid Earth (101) 22215-22224
A model of a fault in the Earth is a sand-filled saw cut in a granite cylinder subjected to a triaxial test. The saw cut is inclined at an angle α to the cylinder axis, and the sand filling is intended to represent gouge. The triaxial test subjects the granite...
Uranium adsorption on ferrihydrite - Effects of phosphate and humic acid
T.E. Payne, J.A. Davis, T.D. Waite
1996, Radiochimica Acta (74) 239-243
Uranium adsorption on ferrihydrite was studied as a function of pH in systems equilibrated with air, in the presence and absence of added phosphate and humic acid (HA). The objective was to determine the influence of PO43- and HA on...
Recharge of valley-fill aquifers in the glaciated northeast from upland runoff
J.H. Williams, D. J. Morrissey
1996, ASTM Special Technical Publication (1288) 97-113
Channeled and unchanneled runoff from till-covered bedrock uplands is a major source of recharge to valley-fill aquifers in the glaciated northeastern United States. Streamflow measurements and model simulation of average steady-state conditions indicate that upland runoff accounted for more recharge to two valley-fill aquifers in moderately high topographic-relief settings than...
Use of liquefaction-induced features for paleoseismic analysis
S. F. Obermeier
1996, Engineering Geology (44) 1-76
Liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the Holocene. These features include dikes, craters, vented sand, sills, and laterally spreading landslides. The relatively high seismic shaking level required for their formation makes them particularly valuable...
Integrated high-precision analyses of Holocene relative sea-level changes: Lessons from the coast of Maine
W.R. Gehrels, D. F. Belknap, J. T. Kelley
1996, Geological Society of America Bulletin (108) 1073-1088
A suite of salt-marsh peat samples from four sites along the coast of Maine (Wells, Phippsburg, Gouldsboro, and Machiasport) has been analyzed using high-precision techniques to determine local relative sea-level trends and to evaluate proposed along-coast warping. A spatially variable set of relative sea-level records in Maine would have important...
Unrealistic parameter estimates in inverse modelling: A problem or a benefit for model calibration?
E. P. Poeter, M. C. Hill
1996, IAHS-AISH Publication (237) 277-285
Estimation of unrealistic parameter values by inverse modelling is useful for constructed model discrimination. This utility is demonstrated using the three-dimensional, groundwater flow inverse model MODFLOWP to estimate parameters in a simple synthetic model where the true conditions and character of the errors are completely known. When a poorly constructed...
