Restoring marsh elevation in a rapidly subsiding salt marsh by thin-layer deposition of dredged material
M.A. Ford, Donald R. Cahoon, J.C. Lynch
1999, Ecological Engineering (12) 189-205
Thin-layer deposition of dredged material on coastal marsh by means of high-pressure spray dredging (Jet-Spray??2) technology has been proposed as a mechanism to minimize wetland impacts associated with traditional bucket dredging technologies and to restore soil elevations in deteriorated marshes of the Mississippi River delta. The impact of spray dredging...
The evolutionary history of steelhead (Oncorhynchus mykiss) along the US Pacific Coast: Developing a conservation strategy using genetic diversity
J.L. Nielsen
1999, ICES Journal of Marine Science (56) 449-458
Changes in genetic variation across a species range may indicate patterns of population structure resulting from past ecological and demographic events that are otherwise difficult to infer and thus provide insight into evolutionary development. Genetic data is used, drawn from 11 microsatellite loci amplified from anadromous steelhead (Oncorhynchus mykiss) sampled...
Temporal and spatial variability of the sediment grain-size distribution on the Eel shelf: The flood layer of 1995
D.E. Drake
1999, Marine Geology (154) 169-182
Sediment grain-size characteristics observed on the Eel shelf have been analyzed using a wet-sieving technique that minimizes breakage of aggregates. At several sites on the 70-m isobath north of the river, where a 1995 flood layer attained a maximum thickness of about 9 cm, replicate box cores were collected on...
Influence of the Atlantic inflow and Mediterranean outflow currents on late Quaternary sedimentary facies of the Gulf of Cadiz continental margin
C.H. Nelson, J. Baraza, A. Maldonado, J. Rodero, C. Escutia, J. H. Barber Jr.
1999, Marine Geology (155) 99-129
The late Quaternary pattern of sedimentary facies on the Spanish Gulf of Cadiz continental shelf results from an interaction between a number of controlling factors that are dominated by the Atlantic inflow currents flowing southeastward across the Cadiz shelf toward the Strait of Gibraltar. An inner shelf shoreface sand facies...
Effects of humic substances on the bioconcentration of polycyclic aromatic hydrocarbons: Correlations with spectroscopic and chemical properties of humic substances
M. Haitzer, G. Abbt-Braun, W. Traunspurger, C.E.W. Steinberg
1999, Environmental Toxicology and Chemistry (18) 2782-2788
The presence of dissolved humic substances (HS, fulvic and humic acids) generally reduces the up take of hydrophobic organic compounds into aquatic organisms. The extent of this effect depends both on the concentration and on the origin of the HS. The aim of this study was to investigate the role...
Quantification of aerobic biodegradation and volatilization rates of gasoline hydrocarbons near the water table under natural attenuation conditions
Matthew A. Lahvis, Arthur L. Baehr, Ronald J. Baker
1999, Water Resources Research (35) 753-765
Aerobic biodegradation and volatilization near the water table constitute a coupled pathway that contributes significantly to the natural attenuation of hydrocarbons at gasoline spill sites. Rates of hydrocarbon biodegradation and volatilization were quantified by analyzing vapor transport in the unsaturated zone at a gasoline spill site in Beaufort, South Carolina....
The search for a source rock for the giant Tar Sand triangle accumulation, southeastern Utah
J. E. Huntoon, P. L. Hansley, N. D. Naeser
1999, American Association of Petroleum Geologists Bulletin (83) 467-495
A large proportion (about 36%) of the worlds oil resource is contained in accumulations of heavy oil or tar. In these large deposits of degraded oil, the oil in place represents only a fraction of what was present at the time of accumulation. In many of these deposits, the source...
A record of estuarine water contamination from the Cd content of foraminiferal tests in San Francisco Bay, California
A. VanGeen, S. N. Luoma
1999, Marine Chemistry (64) 57-69
A five-year dissolved Cd time series from San Francisco Bay and adjacent coastal water shows that the composition of surface water towards the mouth of the estuary is determined largely by the effect of coastal upwelling. Cd concentrations inside and outside the estuary (0.2-1.0 nmol/kg) increase as Cd-rich deep water...
Mapping the rupture process of moderate earthquakes by inverting accelerograms
M. Hellweg, J. Boatwright
1999, Journal of Geophysical Research B: Solid Earth (104) 7319-7328
We present a waveform inversion method that uses recordings of small events as Green's functions to map the rupture growth of moderate earthquakes. The method fits P and S waveforms from many stations simultaneously in an iterative procedure to estimate the subevent rupture time and amplitude relative to the Green's function event. We invert...
Mid-Pleistocene cosmogenic minimum-age limits for pre-Wisconsinan glacial surfaces in southwestern Minnesota and southern Baffin Island: A multiple nuclide approach
P.R. Bierman, K.A. Marsella, Chris Patterson, P.T. Davis, M. Caffee
1999, Geomorphology (27) 25-39
Paired 10Be and 26Al analyses (n = 14) indicate that pre-Wisconsinan, glaciated bedrock surfaces near the northern (Baffin Island) and southern (Minnesota) paleo-margins of the Laurentide Ice Sheet have long and complex histories of cosmic-ray exposure, including significant periods of partial or complete shielding from cosmic rays. Using the ratio,...
Application of geologic map information to water quality issues in the southern part of the Chesapeake Bay watershed, Maryland and Virginia, eastern United States
L. McCartan, J. D. Peper, L. J. Bachman, J. Wright Horton Jr.
1999, Journal of Geochemical Exploration (64) 355-376
Geologic map units contain much information about the mineralogy, chemistry, and physical attributes of the rocks mapped. This paper presents information from regional-scale geologic maps in Maryland and Virginia, which are in the southern part of the Chesapeake Bay watershed in the eastern United States. The geologic map information is...
Evidence for recent volcanism on mars from crater counts
W.K. Hartmann, M. Malin, A. McEwen, M. Carr, L. Soderblom, P. Thomas, E. Danielson, P. James, J. Veverka
1999, Nature (397) 586-589
Impact craters help characterize the age of a planetary surface, because they accumulate with time. They also provide useful constraints on the importance of surface erosion, as such processes will preferentially remove the smaller craters. Earlier studies of martian crater populations revealed that erosion and dust deposition are important processes...
Analysis of pumping tests: Significance of well diameter, partial penetration, and noise
M. Heidari, K. Ghiassi, E. Mehnert
1999, Journal of the American Water Resources Association (35) 333-347
The nonlinear least squares (NLS) method was applied to pumping and recovery aquifer test data in confined and unconfined aquifers with finite diameter and partially penetrating pumping wells, and with partially penetrating piezometers or observation wells. It was demonstrated that noiseless and moderately noisy drawdown data from observation points located...
Calibrating Late Quaternary terrestrial climate signals: radiometrically dated pollen evidence from the southern Sierra Nevada, USA
Ronald J. Litwin, Joseph P. Smoot, Nancy J. Durika, George I. Smith
1999, Quaternary Science Reviews (18) 1151-1171
We constructed a radiometrically calibrated proxy record of Late Pleistocene and Holocene climate change exceeding 230,000 yr duration, using pollen profiles from two cores taken through age-equivalent dry lakes - one core having greater age control (via 230Th alpha mass-spectrometry) and the other having greater stratigraphic completeness. The better dated...
The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO2 in the United States
H. Tian, J. M. Melillo, D. W. Kicklighter, A. D. McGuire, J. Helfrich
1999, Tellus, Series B: Chemical and Physical Meteorology (51) 414-452
We use the Terrestrial Ecosystem Model (TEM, Version 4.1) and the land cover data set of the international geosphere-biosphere program to investigate how increasing atmospheric CO2 concentration and climate variability during 1900-1994 affect the carbon storage of terrestrial ecosystems in the conterminous USA, and how carbon storage has been affected...
Responses of riparian cottonwoods to alluvial water table declines
M. L. Scott, P.B. Shafroth, G.T. Auble
1999, Environmental Management (23) 347-358
Human demands for surface and shallow alluvial groundwater have contributed to the loss, fragmentation, and simplification of riparian ecosystems. Populus species typically dominate riparian ecosystems throughout arid and semiarid regions of North American and efforts to minimize loss of riparian Populus requires an integrated understanding of the role of surface...
Michael Tuomey's 1848 geological survey of South Carolina
P.G. Nystrom Jr.
1999, Southeastern Geology (38) 189
One hundred and fifty years ago, Michael Tuomey completed his 'Report on the Geology of South Carolina,' the result of four years of arduous labor. The report is the first detailed and comprehensive geological description of the entire state, and it includes a geological map that shows the distribution of...
Determining travel time and stream mixing using tracers and empirical equations
Ingrid M. Verstraeten, P. J. Soenksen, G.B. Engel, L.D. Miller
1999, Journal of Environmental Quality (28) 1387-1395
Water-supply managers need adequate warning to protect water supplies if a contaminant is spilled in an upgradient tributary. The city of Lincoln draws water from alluvium associated with the Platte River near Ashland, eastern Nebraska. Using constant-rate injection methods and a conservative tracer, travel time and...
A record of hydrocarbon input to San Francisco Bay as traced by biomarker profiles in surface sediment and sediment cores
F. D. Hostettler, W. E. Pereira, K.A. Kvenvolden, A. VanGeen, S. N. Luoma, C. C. Fuller, R. Anima
1999, Marine Chemistry (64) 115-127
San Francisco Bay is one of the world's largest urbanized estuarine systems. Its water and sediment receive organic input from a wide variety of sources; much of this organic material is anthropogenically derived. To document the spatial and historical record of the organic contaminant input, surficial sediment from 17 sites...
Atmospheric transmission of North Atlantic Heinrich events
S. W. Hostetler, P.U. Clark, P. J. Bartlein, A.C. Mix, N.J. Pisias
1999, Journal of Geophysical Research D: Atmospheres (104) 3947-3952
We model the response of the climate system during Heinrich event 2 (H2) by employing an atmospheric general circulation model, using boundary conditions based on the concept of a “canonical” Heinrich event. The canonical event is initialized with a full-height Laurentide ice sheet (LIS) and CLIMAP sea surface temperatures (SSTs),...
Test of two methods for faulting on finite-difference calculations
D.J. Andrews
1999, Bulletin of the Seismological Society of America (89) 931-937
Tests of two fault boundary conditions show that each converges with second order accuracy as the finite-difference grid is refined. The first method uses split nodes so that there are disjoint grids that interact via surface traction. The 3D version described here is...
Ontogeny of a flood plain
J. A. Moody, J.E. Pizzuto, R.H. Meade
1999, Geological Society of America Bulletin (111) 291-303
The ontogeny of five flood-plain segments is described for a period of 18 yr following a major flood in 1978 on the Powder River in southeastern Montana. The flood plains developed on relatively elevated sand and gravel deposits left within the channel by the 1978 flood. In cross section, the...
Active Volcanism on Io: Global Distribution and Variations in Activity
R. Lopes-Gautier, A. S. McEwen, W.B. Smythe, P.E. Geissler, L. Kamp, A. G. Davies, J.R. Spencer, L. Keszthelyi, R. Carlson, F.E. Leader, R. Mehlman, L. Soderblom
1999, Icarus (140) 243-264
Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the near-infrared mapping spectrometer (NIMS) for the first 10 orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI) and from groundbased observations, and...
Comparison of post-fire seedling establishment between scrub communities in mediterranean and non-mediterranean climate ecosystems
M.E. Carrington, Jon E. Keeley
1999, Journal of Ecology (87) 1025-1036
I Both fire regimes and the conditions under which fires occur vary widely. Abiotic conditions (such as climate) in combination with fire season, frequency and intensity could influence vegetation responses to fire. A variety of adaptations facilitate post-fire recruitment in mediterranean climate ecosystems, but responses of other communities are less...
Frequency-magnitude statistics and spatial correlation dimensions of earthquakes at Long Valley caldera, California
D.J. Barton, G.R. Foulger, J. R. Henderson, B.R. Julian
1999, Geophysical Journal International (138) 563-570
Intense earthquake swarms at Long Valley caldera in late 1997 and early 1998 occurred on two contrasting structures. The first is defined by the intersection of a north-northwesterly array of faults with the southern margin of the resurgent dome, and is a zone of hydrothermal upwelling. Seismic activity there was...
