Basin-ring spacing on the Moon, Mercury, and Mars
R.J. Pike, P. D. Spudis
1987, Earth, Moon and Planets (39) 129-194
Radial spacing between concentric rings of impact basins that lack central peaks is statistically similar and nonrandom on the Moon, Mercury, and Mars, both inside and outside the main ring. One spacing interval, (2.0 ?? 0.3)0.5D, or an integer multiple of it, dominates most basin rings. Three analytical approaches yield...
Some effects of quiet geomagnetic field changes upon values used for main field modeling
W.H. Campbell
1987, Physics of the Earth and Planetary Interiors (48) 193-199
The effects of three methods of data selection upon the assumed main field levels for geomagnetic observatory records used in main field modeling were investigated for a year of very low solar-terrestrial activity. The first method concerned the differences between the year's average of quiet day field values and the...
Coal deposits of the United States
Nelson W. John
1987, International Journal of Coal Geology (8) 355-365
The coal fields of the Unites States can be divided into six major provinces. The Appalachian and Interior Provinces contain dominantly bituminous coal in strata of Pennsylvanian age. The coal seams are relatively thin and are mined both by surface and...
APPALACHIAN FOLDS, LATERAL RAMPS, AND BASEMENT FAULTS: A MODERN ENGINEERING PROBLEM?
Howard A. Pohn
1987, Transportation Research Record 132-133
Field studies and analysis of radar data have shown that cross-strike faulting in the central and southern Appalachians has affected geologic structures at the surface. These basement faults appear to have been active through much of geologic time. Indeed, more than 45 percent of modern earthquakes occur along these narrow...
Chemical structural studies of natural lignin by dipolar dephasing solid-state 13C nuclear magnetic resonance
Patrick G. Hatcher
1987, Organic Geochemistry (11) 31-39
Two natural lignins, one from a gymnosperm wood the other from angiosperm wood, were examined by conventional solid-state and dipolar dephasing 13C nuclear magnetic resonance (NMR) techniques. The results obtained from both techniques show that the structure of natural lignins is consistent with models of softwood and hardwood lignin. The dipolar...
Modeling and analysis of direct-current electrical resistivity in the Durham Triassic basin, North Carolina
C. Erwin Brown
1987, Geoexploration (24) 429-440
Sixty-two Schlumberger electrical soundings were made in the Durham Triassic basin in an effort to determine basin structural geometry, depth of the sedimentary layers, and spatial distribution of individual rock facies. A digital computer program was used to invert the sounding curves of apparent resistivity versus distance to apparent resistivity...
Sedimentation across the central California oxygen minimum zone: an alternative coastal upwelling sequence
T. L. Vercoutere, H.T. Mullins, K. McDougall, J.B. Thompson
1987, Journal of Sedimentary Petrology (57) 709-722
Distribution, abundance, and diversity of terrigenous, authigenous, and biogenous material provide evidence of the effect of bottom currents and oxygen minimum zone (OMZ) on continental slope sedimentation offshore central California. Box core samples and bottom photographs collected across the oxygen minimum zone of...
Assessment of models proposed for the 1985 revision of the international geomagnetic reference field
N.W. Peddie, A.K. Zunde
1987, Physics of the Earth and Planetary Interiors (48) 330-337
Geomagnetic measurements from land, marine and aerial surveys conducted in the years 1945-1964 were used to test the 14 models proposed as additions, for that period, to the series of definitive geomagnetic reference field (DGRF) models. Overall, NASA's 'SFAS' models and the BGS (British Geological Survey) models agree best with...
The geomagnetic jerk of 1969 and the DGRFs
D. Thompson, J.C. Cain
1987, Physics of the Earth and Planetary Interiors (48) 386-388
Cubic spline fits to the DGRF/IGRF series indicate agreement with other analyses showing the 1969-1970 magnetic jerk in the h ??12 and g ??02 secular change coefficients, and agreement that the h ??11 term showed no sharp change. The variation of the g ??01 term is out of phase with...
Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica
Keith A. Kvenvolden, John B. Rapp, Margaret Golan-Bac, Frances D. Hostettler
1987, Organic Geochemistry (11) 291-302
Normal alkanes (n-C13n-C36), isoprenoid hydrocarbons (i-C15, i-C16, i-C18, i-C19, and i-C20) triterpanes (C27C32), and (C27C29) are present in low concentrations offshore Antarctica in near-surface, Quaternary sediment of the Wilkes Land continental margin and of the western Ross Sea. The distributions of these...
Chalcopyrite disease in sphalerite: pathology and epidemiology.
P. B. Barton Jr., P. M. Bethke
1987, American Mineralogist (72) 451-467
This descriptive paper identifies three widely occurring textures designated as 'watermelon', 'dusting' and 'bimodal' that characterize the replacement of original Fe-bearing sphalerite by an aggregate of chalcopyrite and low-Fe sphalerite as an integral part of the mineralization process. Replacement probably predominates over alternative modes of origin for small chalcopyrite blebs...
Evaluation of the 1985-1990 IGRF secular variation candidates
J.C. Cain, C. Kluth
1987, Physics of the Earth and Planetary Interiors (48) 362-378
The IGRF secular variation model for 1985-1990 was adopted by the International Association of Geomagnetism and Aeronomy at its Prague meeting in August 1985 as an average of the three candidate models submitted to the committee. We compared the three models at epoch 1985.0 against each other and against a...
A model of geomagnetic secular variation for 1980-1983
N.W. Peddie, A.K. Zunde
1987, Physics of the Earth and Planetary Interiors (48) 324-329
We developed an updated model of the secular variation of the main geomagnetic field during 1980 through 1983 based on annual mean values for that interval from 148 worldwide magnetic observatories. The model consists of a series of 80 spherical harmonics, up to and including those of degree and order...
Generation of liquid water on Mars through the melting of a dusty snowpack
G.D. Clow
1987, Icarus (72) 95-127
The possibility that snowmelt could have provided liquid water for valley network formation early in the history of Mars is investigated using an optical-thermal model developed for dusty snowpacks at temperate latitudes. The heating of the postulated snow is assumed to...
Rainfall, ground-water flow, and seasonal movement at Minor Creek landslide, northwestern California: Physical interpretation of empirical relations
R.M. Iverson, J. J. Major
1987, Geological Society of America Bulletin (99) 579-594
Simple ground-water flow analyses can clarify complex empirical relations between rainfall and landslide motion. Here we present detailed data on rainfall, ground-water flow, and repetitive seasonal motion that occurred from 1982 to 1985 at Minor Creek landslide in northwestern California, and we interpret these data in the context of physically...
Transport of reacting solutes subject to a moving dissolution boundary: Numerical methods and solutions
Catherine Willis, Jacob Rubin
1987, Water Resources Research (23) 1561-1574
A moving boundary problem which arises during transport with precipitation-dissolution reactions is solved by three different numerical methods. Two of these methods (one explicit and one implicit) are based on an integral formulation of mass balance and lead to an approximation of a weak solution. These methods are compared to...
Moment tensor solutions estimated using optimal filter theory for 51 selected earthquakes, 1980-1984
S.A. Sipkin
1987, Physics of the Earth and Planetary Interiors (47) 67-79
The 51 global events that occurred from January 1980 to March 1984, which were chosen by the convenors of the Symposium on Seismological Theory and Practice, have been analyzed using a moment tensor inversion algorithm (Sipkin). Many of the events were routinely analyzed as part of the National Earthquake Information...
On regional geomagnetic charts
L.R. Alldredge
1987, Journal of Geomagnetism & Geoelectricity (39) 723-738
When regional geomagnetic charts for areas roughly the size of the United States were compiled by hand, some large local anomalies were displayed in the isomagnetic lines. Since the late nineteen sixties, when the compilation of charts using computers and mathematical models was started, most of the details...
Evaluation of the stability of gas hydrates in Northern Alaska
A. Kamath, S. P. Godbole, R. D. Ostermann, T. S. Collett
1987, Cold Regions Science and Technology (14) 107-119
The factors which control the distribution of in situ gas hydrate deposits in colder regions such as Northern Alaska include; mean annual surface temperatures (MAST), geothermal gradients above and below the base of permafrost, subsurface pressures, gas composition, pore-fluid salinity and the soil condition. Currently existing data on the above...
EFFECT OF AN ACID RAIN ENVIRONMENT ON LIMESTONE SURFACES.
Victor G. Mossotti, James R. Lindsay, Michael F. Hochella Jr.
1987, Materials Performance (26) 47-52
Salem limestone samples were exposed to weathering for 1 y in several urban and one rural environments. Samples exposed in the rural location were chemically indistinguishable from the freshly quarried limestone, whereas all samples collected from urban exposure sites developed gypsum stains on the ground-facing surfaces where the stones were...
15N/14N variations in Cretaceous Atlantic sedimentary sequences: Implication for past changes in marine nitrogen biogeochemistry
G.H. Rau, M.A. Arthur, W.E. Dean
1987, Earth and Planetary Science Letters (82) 269-279
At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds (“black shales”) were found to have significantly lower δ15N values (lower15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in...
Compositional evidence regarding the origins of rims on Semarkona chondrules
J. N. Grossman, J. T. Wasson
1987, Geochimica et Cosmochimica Acta (51) 3003-3011
The compositions of the interiors and abraded surfaces of 7 chondrules from Semarkona (LL3.0) were measured by neutron activation analysis. For nonvolatile elements, the lithophile and siderophile element abundance patterns in the surfaces are generally similar to those in the corresponding interiors. Siderophile and chalcophile concentrations are much higher in...
Phytoplankton productivity in relation to light intensity: A simple equation
D. H. Peterson, M.J. Perry, K.E. Bencala, M.C. Talbot
1987, Estuarine, Coastal and Shelf Science (24) 813-832
A simple exponential equation is used to describe photosynthetic rate as a function of light intensity for a variety of unicellular algae and higher plants where photosynthesis is proportional to (1-e−β1). The parameter β (=Ik−1">=Ik−1) is derived by a simultaneous curve-fitting method, where I is incident...
Man-induced gradient adjustment of the South Fork Forked Deer River, west Tennessee
A. Simon, C. H. Robbins
1987, Environmental Geology and Water Sciences (9) 109-118
Channel modifications from 1968 to 1969 on the South Fork Forked Deer River in western Tennessee have caused upstream degradation, downstream aggradation, and bank failures along the altered channels, adjacent reaches, and tributaries. The result of these adjustments is a general decrease in gradient as the channel attempts to absorb...
A study of metal ion adsorption at low suspended-solid concentrations
Cecily C.Y. Chang, J.A. Davis, James S. Kuwabara
1987, Estuarine, Coastal and Shelf Science (24) 419-424
A procedure for conducting adsorption studies at low suspended solid concentrations in natural waters (<50 mg l−1) is described. Methodological complications previously associated with such experiments have been overcome. Adsorption of zinc ion onto synthetic colloidal titania (TiO2) was studied as a function...
