Isotopic and chemical constraints on the petrogenesis of Blackburn Hills volcanic field, western Alaska
E. J. Moll-Stalcup, Joseph G. Arth
1991, Geochimica et Cosmochimica Acta (55) 3753-3776
The Blackburn Hills volcanic field is one of several Late Cretaceous and early Tertiary (75–50 Ma) volcanic fields in western Alaska that comprise a vast magmatic province extending from the Arctic Circle to Bristol Bay. It consists of andesite flows, rhyolite domes, a central granodiorite to quartz monzonite pluton, and...
Estimating estuarine flushing and residence times in Charlotte Harbor, Florida, via salt balance and a box model
R. L. Miller, B. F. McPherson
1991, Limnology and Oceanography (36) 602-612
The new concept is that, over many tidal cycles, the tidally averaged "flow' (Qg) of water from the Gulf of Mexico, with a salinity of 35???, can be treated as a constant at any point in the estuary. This flow is used in a simple mixing equation to predict salinity...
High-frequency spectral falloff of earthquakes, fractal dimension of complex rupture, b value, and the scaling of strength on faults
A. Frankel
1991, Journal of Geophysical Research (96) 6291-6302
The high-frequency falloff ω−γ of earthquake displacement spectra and the b value of aftershock sequences are attributed to the character of spatially varying strength along fault zones. I assume that the high frequency energy of a main shock is produced by a self-similar distribution of subevents, where the number...
Oligocene basaltic volcanism of the northern Rio Grande Rift: San Luis Hills, Colorado
R. A. Thompson, C.M. Johnson, H. H. Mehnert
1991, Journal of Geophysical Research (96) 13577-13592
The inception of the Rio Grande rift in northern New Mexico and southern Colorado was accompanied by voluminous mafic volcanism preserved in part as erosional remnants on an intrarift horst within the current axial rift graben of the San Luis Valley. Oligocene (∼26 Ma) volcanic...
Jurassic normal and strike-slip faults at Crater Island, northwestern Utah
D. M. Miller, R.W. Allmendinger
1991, Geological Society of America Bulletin (103) 1239-1251
At Crater Island, northern Silver Island Mountains, northwestern Utah, an unbroken Tertiary fault block within the Basin and Range province exhibits Jurassic or older structures that are virtually unmodified by subsequent tectonism, providing an opportunity to examine the tectonics of the Jurassic back arc of the Cordillera. Widespread high-angle faults,...
Seabed measurements of modern corrosion rates on the Florida escarpment
C. K. Paull, R.F. Commeau, Joseph R. Curray, A.C. Neumann
1991, Geo-Marine Letters (11) 16-22
A mooring containing diverse carbonate and anhydrite substrates was exposed to bottom waters for 9 months at the base of the Florida Escarpment to determine the influence of dissolution on the development of this continental margin. Weight loss was measured on all samples. Etching, pitting, and loss of the original...
Genesis and continuity of quaternary sand and gravel in glacigenic sediment at a proposed low-level radioactive waste disposal site in east-central Illinois
K. G. Troost, B. Brandon Curry
1991, Environmental Geology and Water Sciences (18) 159-170
The Illinois Department of Nuclear Safety has characterized the Martinsville Alternative Site (MAS) for a proposed low-level radioactive waste disposal facility. The MAS is located in east-central Illinois approximately 1.6 km (1 mi) north of the city of Martinsville. Geologic investigation of the 5.5-km2 (1380-acre) site revealed a sequence of...
Analysis of borehole expansion and gallery tests in anisotropic rock masses
B. Amadei, W. Z. Savage
1991, International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (28) 383-396
Closed-form solutions are used to show how rock anisotropy affects the variation of the modulus of deformation around the walls of a hole in which expansion tests are conducted. These tests include dilatometer and NX-jack tests in boreholes and gallery tests in tunnels. The effects of rock anisotropy on the...
Metasomatic oxidation of upper mantle periodotite
A. V. McGuire, M.D. Dyar, J. E. Nielson
1991, Contributions to Mineralogy and Petrology (109) 252-264
Examination of Fe3+ in metasomatized spinel peridotite xenoliths reveals new information about metasomatic redox processes. Composite xenoliths from Dish Hill, California possess remnants of magmatic dikes which were the sources of the silicate fluids responsible for metasomatism of the peridotite part of the same xenoliths. Mo??ssbauer spectra of mineral separates...
Large-scale variation in lithospheric structure along and across the Kenya rift
C. Prodehl, J. Mechie, W. Kaminski, K. Fuchs, C. Grosse, H. Hoffmann, R. Stangl, R. Stellrecht, M.A. Khan, Peter K.H. Maguire, W. Kirk, Gordon R. Keller, A. Githui, M. Baker, Walter D. Mooney, E. Criley, J. Luetgert, B. Jacob, H. Thybo, M. Demartin, S. Scarascia, A. Hirn, J. R. Bowman, I. Nyambok, S. Gaciri, J. Patel, E. Dindi, D.H. Griffiths, R.F. King, A. E. Mussett, L.W. Braile, G. Thompson, K. Olsen, S. Harder, R. Vees, D. Gajewski, A. Schulte, J. Obel, F. Mwango, J. Mukinya, D. Riaroh
1991, Nature (354) 223-227
The Kenya rift is one of the classic examples of a continental rift zone: models for its evolution range from extension of the lithosphere by pure shear1, through extension by simple shear2, to diapiric upwelling of an asthenolith3. Following a pilot study in 19854, the present work involved the shooting...
Multicycle slip distribution along a laboratory fault
Chi-Yu King
1991, Journal of Geophysical Research (96)
Slip distribution along a laboratory fault, which consists of eight spring-connected blocks that are elastically driven to slide on a frictional surface, has been examined for a “long” sequence of slip events to test the applicability of some conceptual models proposed recently in the literature. The...
Marinas, mines, and mudpots. Building a feature-based production system at the U.S. geological survey
Gary B. Chappell, Kathryn C. Neff
1991, Conference Paper, GIS/LIS 1991 ACSM-ASPRS Fall Convention
By the mid-1990's, the U.S. Geological Survey expects to produce spatial data according to its new data model, Digital Line Graph-Enhanced (DLG-E). This new data model currently defines more than 200 unique feature types that describe the geographic phenomena portrayed on the series of 1:24,000-scale topographic maps. Characteristics of features...
A statistical approach to the interpretation of aliphatic hydrocarbon distributions in marine sediments
J. B. Rapp
1991, Chemical Geology (93) 163-177
Q-mode factor analysis was used to quantitate the distribution of the major aliphatic hydrocarbon (n-alkanes, pristane, phytane) systems in sediments from a variety of marine environments. The compositions of the pure end members of the systems were obtained from factor scores and the distribution of the systems within each sample...
Chemical equilibrium and mass balance relationships associated with the Long Valley hydrothermal system, California, U.S.A.
A. F. White, M. L. Peterson
1991, Journal of Volcanology and Geothermal Research (48) 283-302
Recent drilling and sampling of hydrothermal fluids from Long Valley permit an accurate characterization of chemical concentrations and equilibrium conditions in the hydrothermal reservoir. Hydrothermal fluids are thermodynamically saturated with secondary quartz, calcite, and pyrite but are in disequilibrium with respect to aqueous sulfide-sulfate speciation. Hydrothermal fluids are enriched in...
Photometric functions for photoclinometry and other applications
A. S. McEwen
1991, Icarus (92) 298-311
Least-squared fits to the brightness profiles across a disk or “limb darkening” described by Hapke's photometric function are found for the simpler Minnaert and lunar-Lambert functions. The simpler functions are needed to reduce the number of unknown parameters in photoclinometry, especially...
National aerial photography program as a geographic information system resource
Donald L. Light
1991, Conference Paper, GIS/LIS 1991 ACSM-ASPRS Fall Convention
The National Aerial Photography Program (NAPP) is jointly funded by Federal agencies and States that choose to participate in a 50-50 cost sharing cooperative arrangement. The NAPP is designed to acquire black-and-white (B&W) or color infrared (CIR) photography at a scale of 1:40,000. The status of NAPP flying, now going...
Brine evolution and mineral deposition in hydrologically open evaporite basins
W. E. Sanford, W.W. Wood
1991, American Journal of Science (291) 687-710
A lumped-parameter, solute mass-balance model is developed to define the role of water outflow from a well-mixed basin. A mass-balance model is analyzed with a geochemical model designed for waters with high ionic strengths. Two typical waters, seawater and a Na-HCO3 ground water, are analyzed to illustrate the control that...
Importance of hydrologic data for interpreting wetland maps and assessing wetland loss and mitigation
V. Carter
1991, Biological Report - US Fish & Wildlife Service (90) 79-85
The US Geological Survey collects and disseminates, in written and digital formats, groundwater and surface-water information related to the tidal and nontidal wetlands of the United States. This information includes quantity, quality, and availability of groundwater and surface water; groundwater and surface-water interactions (recharge-discharge); groundwater flow; and the basic surface-water...
A geochemical model of the Platanares geothermal system, Honduras
C. J. Janik, A.H. Truesdell, F. Goff, L. Shevenell, M.L. Stallard, P.E. Trujillo Jr., D. Counce
1991, Journal of Volcanology and Geothermal Research (45) 125-146
Results of exploration drilling combined with results of geologic, geophysical, and hydrogeochemical investigations have been used to construct a geochemical model of the Platanares geothermal system, Honduras. Three coreholes were drilled, two of which produced fluids from fractured Miocene andesite and altered Cretaceous to Eocene conglomerate at 450 to 680...
Tidal stirring and phytoplankton bloom dynamics in an estuary
J. E. Cloern
1991, Journal of Marine Research (49) 203-221
In South San Francisco Bay, estuarine phytoplankton biomass fluctuates at the time scale of days to weeks; much of this variability is associated with fluctuations in tidal energy. During the spring seasons of every year from 1980-1990, episodic blooms occurred in which phytoplankton biomass rose from a baseline of 2-4mg...
Re - Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Colombia: Os isotopic evidence for ancient heterogeneities in the mantle
R.J. Walker, L.M. Echeverria, S.B. Shirey, M.F. Horan
1991, Contributions to Mineralogy and Petrology (107) 150-162
The Re - Os isotopic systematics of komatiites and spatially associated basalts from Gorgona Island, Colombia, indicate that they were produced at 155??43 Ma. Subsequent episodes of volcanism produced basalts at 88.1??3.8 Ma and picritic and basaltic lavas at ca. 58 Ma. The age for the ultramafic rocks is important...
Preliminary palynological zonation of the Chinle formation, southwestern U.S.A., and its correlation to the Newark supergroup (eastern U.S.A.)
R. J. Litwin, A. Traverse, S.R. Ash
1991, Review of Palaeobotany and Palynology (68) 269-287
Three informal palynological assemblage zones can be distinguished in samples from Chinle Formation outcrops in Utah, Arizona and New Mexico. The oldest zone (zone I) is in the Temple Mountain Member in southeastern Utah; the middle zone (zone II) is in the Shinarump, Moss Back, Monitor Butte and (lower part...
In situ measurement of methane oxidation in groundwater by using natural-gradient tracer tests
R. L. Smith, B.L. Howes, S. P. Garabedian
1991, Applied and Environmental Microbiology (57) 1997-2004
Methane oxidation was measured in an unconfined sand and gravel aquifer (Cape Cod, Mass.) by using in situ natural-gradient tracer tests at both a pristine, oxygenated site and an anoxic, sewage-contaminated site. The tracer sites were equipped with multilevel sampling devices to create target grids of sampling points; the injectate...
Uranium and minor-element partitioning in Fe-Ti oxides and zircon from partially melted granodiorite, Crater Lake, Oregon
T.Z.L. Tourrette, D.S. Burnett, C. R. Bacon
1991, Geochimica et Cosmochimica Acta (55) 457-469
Crystal-liquid partitioning in Fe-Ti oxides and zircon was studied in partially melted granodiorite blocks ejected during the climactic eruption of Mt. Mazama (Crater Lake), Oregon. The blocks, which contain up to 33% rhyolite glass (75 wt% SiO2), are interpreted to be portions of the magma chamber walls that were torn...
A giant submarine slope failure on the northern insular slope of Puerto Rico
W. C. Schwab, W. W. Danforth, Kathryn M. Scanlon, D.G. Masson
1991, Marine Geology (96) 237-246
A large amphitheater-shaped scarp, approximately 55 km across, was imaged on the northern insular slope of Puerto Rico using long-range sidescan sonar and bathymetric data. This scarp results from the removal of more than 1500 km3 of Tertiary strata. A review of seismic-reflection profiles, stratigraphic data, and subsidence models of the...
