New Tertiary stratigraphy for the Florida Keys and southern peninsula of Florida
K.J. Cunningham, D.F. McNeill, L.A. Guertin, P.F. Ciesielski, T.M. Scott, L. De Verteuil
1998, Geological Society of America Bulletin (110) 231-258
Seven lithologic formations, ranging in age from Oligocene to Pleistocene, were recently penetrated by core holes in southernmost Florida. From bottom to top, they are the early Oligocene Suwannee Limestone; late-early Oligocene-to-Miocene Arcadia Formation, basal Hawthorn Group; late Miocene Peace River Formation, upper Hawthorn Group; newly proposed late Miocene-to-Pliocene Long...
Episodic plate separation and fracture infill on the surface of Europa
R. Sullivan, R. Greeley, K. Homan, J. Klemaszewski, M. J. S. Belton, M. H. Carr, C. R. Chapman, R. Tufts, J. W. Head III, R. Pappalardo, Jeff Moore, P. Thomas
1998, Nature (391) 371-373
Images obtained by the Voyager spacecraft revealed dark, wedge-shaped bands on Europa that were interpreted as evidence that surface plates, 50- 100 km across, moved and rotated relative to each other. This implied that they may be mechanically decoupled from the interior by a layer of warm ice or liquid...
A geologic history of the north-central Appalachians, part 3. The Alleghany orogeny
R. T. Faill
1998, American Journal of Science (298) 131-179
The north-central Appalachians occupy a critical position within the 3000+ km-long Appalachian orogen, lying southwest of the boundary between the central and northern Appalachians (CNAB). The one-billion-year-long history of tectonic activity in eastern Laurentia includes the creation and evolution of the Appalachian orogen during the Paleozoic and the Mesozoic transformation...
Detrital zircon U-Pb geochronology of Cambrian to Triassic miogeoclinal and eugeoclinal strata of Sonora, Mexico
G. E. Gehrels, John H. Stewart
1998, Journal of Geophysical Research B: Solid Earth (103) 2471-2487
One hundred and eighty two individual detrital zircon grains from Cambrian through Permian miogeoclinal strata, Ordovician eugeoclinal rocks, and Triassic post-orogenic sediments in northwestern Sonora have been analyzed. During Cambrian, Devonian, Permian, and Triassic time, most zircons accumulating along this part of the Cordilleran margin were shed from 1.40–1.45 and...
A comparison of zero-order, first-order, and monod biotransformation models
B.A. Bekins, E. Warren, E.M. Godsy
1998, Ground Water (36) 261-268
Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K(s), this assumption is often made without verification of...
Evolution of cutoffs across meander necks in Powder River, Montana, USA
G.R. Gay, H.H. Gay, W.H. Gay, H. A. Martinson, R.H. Meade, J. A. Moody
1998, Earth Surface Processes and Landforms (23) 651-662
Over a period of several decades, gullies have been observed in various stages of forming, growing and completing the cutoff of meander necks in Powder River. During one episode of overbank flow, water flowing over the down-stream bank of the neck forms a headctu. The headcut migrates up-valley, forming a...
Review of magnetic field monitoring near active faults and volcanic calderas in California: 1974-1995
R.J. Mueller, M.J.S. Johnston
1998, Physics of the Earth and Planetary Interiors (105) 131-144
Differential magnetic fields have been monitored along the San Andreas fault and the Long Valley caldera since 1974. At each monitoring location, proton precession magnetometers sample total magnetic field intensity at a resolution of 0.1 nT or 0.25 nT. Every 10 min, data samples are transmitted via satellite telemetry to...
Solution of the advection-dispersion equation in two dimensions by a finite-volume Eulerian-Lagrangian localized adjoint method
Richard W. Healy, T.F. Russell
1998, Advances in Water Resources (21) 11-26
We extend the finite-volume Eulerian-Lagrangian localized adjoint method (FVELLAM) for solution of the advection-dispersion equation to two dimensions. The method can conserve mass globally and is not limited by restrictions on the size of the grid Peclet or Courant number. Therefore, it is well suited for solution of advection-dominated ground-water...
Occurrence of pesticides in shallow groundwater of the United States: initial results from the National Water-Quality Assessment program
Dana W. Kolpin, Jack E. Barbash, Robert J. Gilliom
1998, Environmental Science & Technology (32) 558-566
The first phase of intensive data collection for the National Water-Quality Assessment (NAWQA) was completed during 1993−1995 in 20 major hydrologic basins of the United States. Groundwater land-use studies, designed to sample recently recharged groundwater (generally within 10 years) beneath specific land-use and hydrogeologic settings, are a major component of...
Relationship between deer mouse population parameters and dieldrin contamination in the Rocky Mountain Arsenal National Wildlife Refuge
D.L. Allen, David L. Otis
1998, Canadian Journal of Zoology (76) 243-250
A small-mammal capture-recapture study was conducted in the Rocky Mountain Arsenal National Wildlife Refuge to quantify the effects of soil contamination with dieldrin on demographic parameters of deer mouse (Peromyscus maniculatus) populations. Increased dieldrin concentrations were significantly associated with larger deer mouse populations, although the size of populations on contaminated...
Microsatellites identify depredated waterfowl remains from glaucous gull stomachs
K.T. Scribner, Timothy D. Bowman
1998, Molecular Ecology (7) 1401-1405
Prey remains can provide valuable sources of information regarding causes of predation and the species composition of a predator's diet. Unfortunately, the highly degraded state of many prey samples from gastrointestinal tracts often precludes unambiguous identification. We describe a procedure by which PCR amplification of taxonomically informative microsatellite loci were...
Geological evidence for solid-state convection in Europa's ice shell
R.T. Pappalardo, J.W. Head, R. Greeley, R.J. Sullivan, C. Pilcher, G. Schubert, W.B. Moore, M. H. Carr, Johnnie N. Moore, M. J. S. Belton, D.L. Goldsby
1998, Nature (391) 365-368
The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water layer. But the mechanisms of interior heat loss...
Structural and kinematic evolution of the Yukon-Tanana upland tectonites, east-central Alaska: A record of late Paleozoic to Mesozoic crustal assembly
V. L. Hansen, Cynthia Dusel-Bacon
1998, Geological Society of America Bulletin (110) 211-230
The Yukon-Tanana terrane, the largest tectonostratigraphic terrane in the northern North American Cordillera, is polygenetic and not a single terrane. Lineated and foliated (L-S) tectonites, which characterize the Yukon-Tanana terrane, record multiple deformations and formed at different times. We document the polyphase history recorded by L-S tectonites within the Yukon-Tanana...
Energy resources - cornucopia or empty barrel?
P.J. McCabe
1998, American Association of Petroleum Geologists Bulletin (82) 2110-2134
Over the last 25 yr, considerable debate has continued about the future supply of fossil fuel. On one side are those who believe we are rapidly depleting resources and that the resulting shortages will have a profound impact on society. On the other side are those who see no impending...
No longer so clueless in seattle: Current assessment of earthquake hazards
C.S. Weaver
1998, Geotechnical Special Publication 39-52
The Pacific Northwest is an active subduction zone. Because of this tectonic setting, there are three distinct earthquake source zones in earthquake hazard assessments of the Seattle area. Offshore, the broad sloping interface between the Juan de Fuca and the North America plates produces earthquakes as large as magnitude 9;...
Soil relative dating of moraine and outwash-terrace sequences in the northern part of the upper Arkansas Valley, central Colorado, U.S.A.
Alan R. Nelson, Ralph R. Shroba
1998, Arctic and Alpine Research (30) 349-361
Profile development indices for soils developed in moraines and outwash near Twin Lakes and in outwash near Leadville support the correlation of moraines with subdued morphology and two high outwash terraces with the Bull Lake glaciation (ca. 130-160 ka) and the correlation of hummocky moraines and two low outwash terraces...
Type curves to determine the relative importance of advection and dispersion for solute and vapor transport
J.A. Garges, A. L. Baehr
1998, Ground Water (36) 959-965
The relative importance of advection and dispersion for both solute and vapor transport can be determined from type curves or concentration, flux, or cumulative flux. The dimensionless form of the type curves provides a means to directly evaluate the importance of mass transport by advection relative to that of mass...
Variability in nonlinear sediment response during the 1994 Northridge, California, earthquake
S. Hartzell
1998, Bulletin of the Seismological Society of America (88) 1426-1437
Spectral ratios between sediment sites and rock sites for strong and weak ground motion are compared to infer the extent of nonlinear sediment response in the Los Angeles area during the 1994 Northridge earthquake. Northridge mainshock records form the strong-motion database and aftershock...
Liquefaction evidence for strong earthquakes of Holocene and latest Pleistocene ages in the states of Indiana and Illinois, USA
S. F. Obermeier
1998, Engineering Geology (50) 227-254
Sand- and gravel-filled clastic dikes of seismic liquefaction origin occur throughout much of southern Indiana and Illinois. Nearly all of these dikes originated from prehistoric earthquakes centered in the study area. In this area at least seven and probably eight strong prehistoric earthquakes have been documented as occurring during the...
Numerical analysis of seawater circulation in carbonate platforms: I. Geothermal convection
Ward E. Sanford, F. F. Whitaker, P. L. Smart, G. Jones
1998, American Journal of Science (298) 801-828
Differences in fluid density between cold ocean water and warm ground water can drive the circulation of seawater through carbonate platforms. The circulating water can be the major source of dissolved constituents for diagenetic reactions such as dolomitization. This study was undertaken to investigate the conditions under which such circulation...
Geochemical and geochronological constraints on the genesis of Au-Te deposits at Cripple Creek, Colorado
K.D. Kelley, S.B. Romberger, D.W. Beaty, J.A. Pontius, L.W. Snee, H. J. Stein, T.B. Thompson
1998, Economic Geology (93) 981-1012
The Cripple Creek district (653 metric tons (t) of Au) consists of Au-Te veins and disseminated gold deposits that are spatially related to alkaline igneous rocks in an Oligocene intrusive complex. Vein paragenesis includes quartz-biotite-K feldspar-fluorite-pyrite followed by base metal sulfides and telluride minerals. Disseminated deposits consist of microcrystalline native...
How organisms do the right thing: The attractor hypothesis
J.M. Emlen, D.C. Freeman, A. Mills, J.H. Graham
1998, Chaos (8) 717-726
Neo-Darwinian theory is highly successful at explaining the emergence of adaptive traits over successive generations. However, there are reasons to doubt its efficacy in explaining the observed, impressively detailed adaptive responses of organisms to day-to-day changes in their surroundings. Also, the theory lacks a clear mechanism to account for both...
Ecoregions as a level of ecological analysis
R.G. Wright, M.P. Murray, T. Merrill
1998, Biological Conservation (86) 207-213
There have been many attempts to classify geographic areas into zones of similar characteristics. Recent focus has been on ecoregions. We examined how well the boundaries of the most commonly used ecoregion classifications for the US matched the boundaries of existing vegetation cover mapped at three levels of classification, fine,...
Geohistory and thermal maturation in the Cherokee Basin (Mid-Continent, U.S.A.): results from modeling
A. Forster, D. F. Merriam, P. Hoth
1998, American Association of Petroleum Geologists Bulletin (82) 1673-1693
The Cherokee basin in southeastern Kansas contains a stratigraphic section consisting mostly of Permian-Pennsylvanian alternating clastics and thin carbonates overlying carbonates of Mississippian and Cambrian-Ordovician age on a Precambrian crytalline basement. Based on a conceptual model of events of deposition, nondeposition, and erosion, a burial history model for (1) noncompaction,...
Climate variations and changes in mass of three glaciers in western North America
S. M. Hodge, D.C. Trabant, R. M. Krimmel, T.A. Heinrichs, R.S. March, E.G. Josberger
1998, Journal of Climate (11) 2161-2179
Time series of net and seasonal mass balances for three glaciers in western North America, one in the Pacific Northwest and two in Alaska, show various relationships to Pacific hemisphere climate indexes. During the winter season the two coastal, maritime-regime glaciers, over 2000 km apart, are affected almost identically, albeit...
