Secular, annual, and semiannual changes in the baseline level of the earth's magnetic field at North American locations
W.H. Campbell
1980, Journal of Geophysical Research Solid Earth (85) 6557-6571
Secular, annual, and semiannual changes were obtained from the midnight values of field on specially determined days of quiet magnetospheric conditions. From a selection of North American observatories the latitude variation of these changes was evaluated from 20° to 65°. Results for the active and quiet sun years (1958 and...
Tectonic state: its significance and characterization in the assessment of seismic effects associated with reservoir impounding
R. O. Castle, M. M. Clark, A. Grantz, J.C. Savage
1980, Engineering Geology (15) 53-99
Any analysis of seismicity associated with the filling of large reservoirs requires an evaluation of the natural tectonic state in order to determine whether impoundment is the basic source, a mechanically unrelated companion feature, or a triggering stimulus of the observed seismicity. Several arguments indicate that the associated seismicity is...
Asymmetric measures of association, closed data, and multivariate analysis
M. Hohn, E.B. Nuhfer
1980, Journal of the International Association for Mathematical Geology (12) 235-246
The association between constant-sum variables Xiand Xjexpressed as percentages can be calculated as a product-moment correlation between Xiand Xj/(100 - Xi) and a correlation between Xjand Xi/(100 - Xj). An asymmetric, square matrix may be formed from these coefficients, and multivariate analysis performed by two methods: singular value decomposition and...
Origin of gasoline-range hydrocarbons and their migration by solution in carbon dioxide in Norton basin, Alaska.
Keith A. Kvenvolden, George E. Claypool
1980, American Association of Petroleum Geologists Bulletin (64) 1078-1086
Carbon dioxide from a submarine seep in Norton Sound, Alaska, carries a minor component of gas- and gasoline-range hydrocarbons. The molecular and isotopic compositions of the hydrocarbon gases and the presence of gasoline-range hydrocarbons indicate that these molecules are derived from thermal alteration of marine and/or nonmarine organic matter buried...
Sedimentary masses and concepts about tectonic processes at underthrust ocean margins
D.W. Scholl, Roland E. von Huene, T.L. Vallier, D. G. Howell
1980, Geology (8) 564-568
Tectonic processes associated with subduction of oceanic crust, but unrelated to the collision of thick crustal masses or microplates, are presumed by many geologists to significantly affect the formation and deformation of large sedimentary bodies at underthrust ocean margins. More geologists are familiar with the concept of subduction accretion, which describes...
The morphology of the Martian surface
M. H. Carr
1980, Space Science Reviews (25) 231-284
Most of the southern hemisphere of Mars is densely cratered and stands 1-3 km above the topographic datum. The northern hemisphere is more sparsely cratered and elevations are generally below the datum. A broad rise, the Tharsis bulge, centered at 14?? S, 101?? W, is 8000 km across and 10...
Scaling variables and interpretation of eigenvalues in principal component analysis of geologic data
A.T. Miesch
1980, Journal of the International Association for Mathematical Geology (12) 523-538
The dominant feature distinguishing one method of principal components analysis from another is the manner in which the original data are transformed prior to the other computations. The only other distinguishing feature of any importance is whether the eigenvectors of the inner product-moment of the transformed data matrix are taken...
Stable isotope and fluid inclusion studies of carbonate deposits from the Tolfa Mountains mining district (Latium, central Italy)
U. Masi, V. Ferrini, J. R. O’Neil, J. N. Batchelder
1980, Mineralium Deposita (15) 351-359
Carbon and oxygen isotope analyses were made of representative samples of calcite and quartz from the carbonate deposits in the Tolfa Mountains mining district. Measurements were also made of hydrogen isotope compositions, filling temperatures and salinities of fluid inclusions in these minerals. There are three stages of mineralization at Tolfa....
Direct computation of the sensible heat flux
K. Watson
1980, Geophysical Research Letters (7) 616-618
An algorithm to determine the sensible heat flux from simple field measurements (wind speed, air and ground temperatures) has been developed. It provides a direct solution, in parametric form, which can be displayed graphically or tabularly. This method has an advantage over the previous iterative solution...
Nd-isotopes in selected mantle-derived rocks and minerals and their implications for mantle evolution
A. R. Basu, M. Tatsumoto
1980, Contributions to Mineralogy and Petrology (75) 43-54
The Sm-Nd systematics in a variety of mantle-derived samples including kimberlites, alnoite, carbonatite, pyroxene and amphibole inclusions in alkali basalts and xenolithic eclogites, granulites and a pyroxene megacryst in kimberlites are reported. The additional data on kimberlites strengthen our earlier conclusion that kimberlites are derived from a relatively undifferentiated chondritic...
Gas and hydrogen isotopic analyses of volcanic eruption clouds in Guatemala sampled by aircraft
W.I. Rose Jr., R.D. Cadle, L.E. Heidt, I. Friedman, A.L. Lazrus, B.J. Huebert
1980, Journal of Volcanology and Geothermal Research (7) 1-10
Gas samples were collected by aircraft entering volcanic eruption clouds of three Guatemalan volcanoes. Gas chromatographic analyses show higher H2 and S gas contents in ash eruption clouds and lower H2 and S gases in vaporous gas plumes. H isotopic data demonstrate lighter isotopic distribution of water vapor in ash...
The 1977 eruption of Kilauea volcano, Hawaii
R. B. Moore, Rosalind Tuthill Helz, D. Dzurisin, G. P. Eaton, R. Y. Koyanagi, P. W. Lipman, J. P. Lockwood, G. S. Puniwai
1980, Journal of Volcanology and Geothermal Research (7) 189-210
Kilauea volcano began to erupt on September 13, 1977, after a 21.5-month period of quiescence. Harmonic tremor in the upper and central east rift zone and rapid deflation of the summit area occurred for 22 hours before the outbreak of surface activity. On the first night, spatter ramparts formed along...
Thickness change involved in the peat-to- coal transformation for a bituminous coal of Cretaceous age in central Utah
Thomas A. Ryer, A.W. Langer
1980, Journal of Sedimentary Petrology (50) 987-992
The ratio of the thicknesses of a layer of peat and the coal bed formed from that peat has been calculated for a bituminous coal bed in central Utah. The method used involves comparison of the thickness of peat eroded by a laterally...
Use of altered volcanic ash falls in stratigraphic studies of coal-bearing sequences: an example from the Upper Cretaceous Ferron Sandstone Member of the Mancos Shale in central Utah.
Thomas A. Ryer, R.E. Phillips, B.F. Bohor, R. M. Pollastro
1980, Geological Society of America Bulletin (91) 579-586
The Ferron consists of 5 delta cycles, each of which includes one coal zone which contains at least one, and usually several, laterally persistent kaolinitic claystone partings. Laboratory study of the partings demonstrates that they represent altered volcanic ash falls. These partings have proven particularly useful in reconstructing the depositional...
Compositional controls on spinel clouding and garnet formation in plagioclase of olivine metagabbros, Adirondack Mountains, New York
J. M. McLelland, P.R. Whitney
1980, Contributions to Mineralogy and Petrology (73) 243-251
Olivine metagabbros from the Adirondacks usually contain both clear and spinel-clouded plagioclase, as well as garnet. The latter occurs primarily as the outer rim of coronas surrounding olivine and pyroxene, and less commonly as lamellae or isolated grains within plagioclase. The formation of garnet and metamorphic spinel is dependent upon...
Goat paddock cryptoexplosion crater, Western Australia
J.E. Harms, D.J. Milton, J. Ferguson, D.J. Gilbert, W.K. Harris, B. Goleby
1980, Nature (286) 704-706
Goat Paddock, a crater slightly over 5 km in diameter (18??20??? S, 126??40???E), lies at the north edge of the King Leopold Range/Mueller Range junction in the Kimberley district, Western Australia (Fig. 1). It was noted as a geological anomaly in 1964 during regional mapping by the Bureau of Mineral...
Inland (non-tidal) wetland mapping.
W.R. Steward, V. Carter, P. D. Brooks
1980, Photogrammetric Engineering and Remote Sensing (46) 617-628
The US Geological Survey has prepared three experimental wetland maps for the Auburndale, Florida 1:24,000-scale quadrangle. Wetland classes and boundaries were interpreted from quad centered high altitude color infrared and superwide black and white panchromatic photographs onto a black and white orthophoto base map made from a color infrared photograph....
Sedimentary and structural patterns on the northern Santa Rosa-Cortes Ridge, southern California
Michael E. Field, William C. Richmond
1980, Marine Geology (34) 79-98
The Santa Rosa-Cortes Ridge is an 1800 m high, 180 km long feature lying approximately 90 km off the coast of southern California and directly south of the northern group of Channel Islands. Geophysical profiling and sampling cruises to the northern part of the ridge, an area of recent and...
Shallow, low-permeability reservoirs of northern Great Plains: Assessment of their natural gas resources.
Dudley D. Rice, George W. Shurr
1980, American Association of Petroleum Geologists Bulletin (64) 969-987
Major resources of natural gas are entrapped in low-permeability, low-pressure reservoirs at depths less than 4,000 ft (1,200 m) in the northern Great Plains. This shallow gas is the product of the immature stage of hydrocarbon generation and is referred to as biogenic gas. Prospective low-permeability, gas-bearing reservoirs range in...
A lead isotope study of mineralization in the Saudi Arabian Shield
J. S. Stacey, B. R. Doe, R. J. Roberts, M.H. Delevaux, J. W. Gramlich
1980, Contributions to Mineralogy and Petrology (74) 175-188
New lead isotope data are presented for some late Precambrian and early Paleozoic vein and massive sulfide deposits in the Arabian Shield. Using the Stacey Kramers (1975) model for lead isotope evolution, isochron model ages range between 720 m.y. and 420 m.y. Most of the massive sulfide deposits in the...
A generalized garnet-forming reaction for metaigneous rocks in the Adirondacks
J. M. McLelland, P.R. Whitney
1980, Contributions to Mineralogy and Petrology (72) 111-122
A generalized reaction is presented to account for garnet formation in a variety of Adirondack metaigneous rocks. This reaction, which is the sum of five partial reactions written in aluminum-fixed frames of reference, is given by: 4(y+1+w)Anorthite+4 k(y+1+2 w)Olivine +4(1-k)(y+1+2 w)Fe-oxide+(8(y+1) -4 k(y+1+2 w))Orthopyroxene = 2(y+1)Garnet +2(y+1+2 w)Clinopyroxene+4 wSpinel where...
Deep-sea spherules from Pacific clay: Mass distribution and influx rate
M.T. Murrell, P.A. Davis Jr., K. Nishiizumi, Hugh T. Millard Jr.
1980, Geochimica et Cosmochimica Acta (44) 2067-2074
From 411 kg of Pacific clay, 22 mg of stony spherules and 50 mg of iron spherules larger than 150 μm were concentrated. The extraterrestrial origin of these particles was evaluated with the aid of both optical and electron microscopy as well as atomic absorption elemental analysis. The integral number...
Radioactivity method
J. S. Duval
1980, Geophysics (45) 1690-1694
Radioactivity measurements have played an important role in geophysics since about 1935, and they have increased in importance to the present. The most important areas of application have been in petroleum and uranium exploration. Radioactivity measurements have proved useful in geologic mapping, as well as in specialized applications such as...
Stable isotope variations in the Quaternary epithermal calcite-fluorite deposit at Monte delle Fate near Cerveteri (Latium, central Italy)
U. Masi, J. R. O’Neil
1980, Mineralium Deposita (15) 41-45
Carbon, oxygen and hydrogen isotope variations have been measured in samples from the epithermal fluorite vein deposit at Monte delle Fate, Latium. The ranges in ?? 13C and ??18O of calcite are -1.3 to 3.4 and 9.5 to 17.3, respectively. ??D values of water extracted from fluid inclusions are -49...
Crustal parameters estimated from P-waves of earthquakes recorded at a small array
J.N. Murdock, J.A. Steppe
1980, Pure and Applied Geophysics PAGEOPH (118) 1179-1190
The P-arrival times of local and regional earthquakes that are outside of a small network of seismometers can be used to interpret crustal parameters beneath the network by employing the time-term technique. Even when the estimate of the refractor velocity is poorly determined, useful estimates of the station time-terms can...
