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Creator | Title | Description | Subject | Date |
26 |
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Jarrard, Richard D. | High-resolution geochemical variations at Sites 723, 728, and 731: a comparison of X-ray fluorescence and geochemical logs | Geochemical logging is a routine part of the Ocean Drilling Program, yet the reliability of ODP geochemical logs has rarely been evaluated quantitatively. On ODP Leg 117, geochemical logs were obtained at Sites 723, 728, and 731. We report here an evaluation of ODP geochemical log quality based on h... | | 1991 |
27 |
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Jarrard, Richard D. | Geophysical properties of oceanic crust at Sites 768 and 770 | Velocity, density, resistivity, and neutron-porosity logs were recorded in virtually the entire 222-m-thick section of basaltic back-arc crust drilled at Site 768 and through the 106-m section of MORB crust at Site 770. Our analysis of these logs and comparison with measurements on discrete cores pe... | | 1991 |
28 |
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Jarrard, Richard D. | Electrical properties of basalts from Sites 768 and 770 | Conductivity of 54 basalt samples from ODP Sites 768 and 770 was measured as a function of temperature and fluid salinity. Porosity was also measured for all samples, and cation exchange capacity was measured for 46 of the samples. Porosity measurements indicated that porosity is underestimated fo... | | 1991 |
29 |
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Brown, Francis Harold | Correlation of tephra layers from the Western Rift Valley (Uganda) to the Turkana Basin (Ethiopia/Kenya) and the Gulf of Aden | Four volcanic ashes have been mapped in Albertine Group strata (Warwire, Kaiso Village and Nyabusosi Formations) Western Rift Valley, Uganda. Three of these tuffs have geochemical fingerprints similar to tuffs in the Turkana Basin (Ethiopia, Kenya), in Afar (Ethiopia) and the Gulf of Aden, permitti... | | 1991 |
30 |
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Brown, Francis Harold | Methods of dating | The fossil record of primates begins in the latest Cretaceous period, so primate palaeontologists are interested in techniques of dating applicable over the past 70 million years. Fossil bones themselves are rarely datable with any precision, and these are mainly of late Pleistocene or Holocene age.... | | 1992 |
31 |
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Jarrard, Richard D. | Geometry of Pleistocene facies on the Great Barrier Reef outer shelf and upper slope - seismic stratigraphy of sites 819, 820, and 821 | Seismic stratigraphic analysis of the sedimentary succession intersected in Ocean Drilling Program (ODP) Sites 819, 820, and 821, on the outer shelf and upper slope seaward of the Great Barrier Reef, provides a clear indication of the importance of sediment supply and depositional base-level as two ... | | 1993 |
32 |
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Jarrard, Richard D. | Velocity and density of carbonate-rich sediments from northeastern Australian margin: integration of core and log data | During Ocean Drilling Program (ODP) Leg 133, shipboard scientists obtained a remarkable quantity of both core and log measurements of the physical properties of carbonate-rich sediments. This suite of measurements provides a unique opportunity to evaluate the robustness of each measurement technique... | | 1993 |
33 |
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Jarrard, Richard D. | Resistivity/porosity/velocity relationships from downhole logs: an aid for evaluating pore morphology | Relationships between downhole resistivity/velocity logs and porosity styles, controlled by cementation/dissolution/recrystallization, are investigated using core and downhole logging data from the carbonate-rich sediments encountered during Leg 133 of the Ocean Drilling Program (ODP), northeastern ... | | 1993 |
34 |
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Jarrard, Richard D. | Sedimentology and downhole log analysis of Site 820, central Great Barrier Reef outer shelf: the factors controlling Pleistocene progradational and aggradational seismic geometry | The textural and compositional characteristics of the 400 m sequence of Pleistocene wackestones and packstones intersected at Ocean Drilling Program (ODP) Site 820 reflect deposition controlled by fluctuations in sea-level, and by variations in the rate of sediment supply. The development of an effe... | | 1993 |
35 |
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Jarrard, Richard D. | Origin of seismic reflectors within carbonate-rich sediments from northeastern Australian margin | We use continuous velocity records from 12 sites and continuous density records from 9 sites from Ocean Drilling Program (ODP) Leg 133 to examine both direct and indirect controls on seismic reflectors and depth-to-time conversion for the northeastern Australian margin. In these carbonate-rich sedim... | | 1993 |
36 |
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Jewell, Paul | Paleoredox conditions and the origin of bedded barites along the Late Devonian North American continental margin | The most important controls of the redox state of natural waters are the flux of organic matter from the photic zone, the degree of physical mixing, and oxygen concentrations of any connecting water masses. In coastal upwelling zones, these factors can be described with a simple box model constraine... | Bedded barites; Late Devonian; Continental margin; Redox state | 1994 |
37 |
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Zhdanov, Michael | Resistivity imaging by time domain electromagnetic migration (TDEMM) | One of the most challenging problems of electrical geophysical methods is the interpretation of time domain electromagnetic (TDEM) sounding data in the areas with the horizontally inhomogeneous geoelectrical structures. This problem is of utmost importance in mining exploration and environmental stu... | | 1995 |
38 |
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Jewell, Paul | Circulation, salinity, and dissolved oxygen in the Cretaceous North American seaway | Critical paleoceanographic problems regarding the maximum transgressive phase of the Cretaceous North American seaway have been studied with a three-dimensional ocean circulation model. Four simulations employing minimum and maximum solar insolation winds from the Cretaceous and a wide range of pre... | Cretaceous North American Seaway | 1996 |
39 |
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Zhdanov, Michael | Three-dimensional quasi linear electromagnetic inversion | One of the most challenging problems of electromagnetic (EM) geophysical methods is developing three-dimension(a3l- D) EM inversion techniques. This problem is of utmost importance in practical applications because of the 3-D nature of the geological structures.T he main difficulties in 3-D inversio... | | 1996-01-01 |
40 |
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Zhdanov, Michael S. | Underground imaging by frequency-domain electromagnetic migration | A new method of the resistivity imaging based on frequency-domain electromagnetic migration is developed. Electromagnetic (EM) migration involves downward diffusion of observed EM fields whose time flow has been reversed. Unlike downward analytical continuation, migration is a stable procedure tha... | | 1996-01-01 |
41 |
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Zhdanov, Michael S. | Quasi-linear approximation in 3-D electromagnetic modeling | The Born approximation in electromagnetic (EM) numerical modeling has limited application for solving 3-D electromagnetic induction problems, because in structures with high conductivity contrasts and at high frequencies, this approximation is inaccurate. In this paper, we develop a new and rel... | | 1996-01-01 |
42 |
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Zhdanov, Michael S. | New approach to interpretation of airborne magnetic and electromagnetic data | We present a new technique for underground imaging based on the idea of space-frequency filtering and downward continuation of the observed airborne magnetic and electromagnetic data. The technique includes two major methods. The first method is related to the downward analytical continuation and ... | | 1996-01-01 |
43 |
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Chapman, David S. | Thermal analysis of the southern Powder River Basin, Wyoming | Temperature and geologic data from over 3000 oil and gas wells within a 180 km x 30 km area that transect across the southern Powder River Basin in Wyoming, U.S.A., were used to determine the present thermal regime of the basin. Three-dimensional temperature fields within the transect, based on... | Thermal analysis; Inversion; Bottom hole temperature | 1996-11 |
44 |
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Fernandez, Diego P. | Formulation for the static permittivity of water and steam at temperatures from 238 K to 873 K at pressures up to 1200 MPa, including derivatives and Debye- Hückel coefficients | A new formulation is presented of the static relative permittivity or dielectric constant of water and steam, including supercooled and supercritical states. The range is from 238 K to 873 K, at pressures up to 1200 MPa. The formulation is based on the ITS-90 temperature scale. It correlates a selec... | Static relative permittivity; Dielectric constant | 1997 |
45 |
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Zhdanov, Michael | Quasi-linear series in three-dimensional electromagnetic modeling | We have recently introduced a quasi-linear (QL) approximation for the solution of the three-dimension(a3l -D) electromagnetic modeling problem. In this paper we discuss an approach to improving its accuracy by considering the QL approximation so f the higher order. This approach can be considered th... | | 1997-01-01 |
46 |
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Chapman, David S. | Global warming - just hot air? | We know from weather station records that Earth's surface temperature has increased on average by 0.6 degrees C in the last 100 years. The 1990s have been the warmest decade on record. Over the same period, global sea level has increased by 10-20 cm. We know also that planet Earth has an atmosphere ... | Greenhouse Effect; Climate change | 1998 |
47 |
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Chapman, David S.; Allis, Richard George | Late Neogene exhumation patterns in Taranaki Basin (New Zealand): evidence from offset porosity-depth trends | Taranaki Basin, New Zealand, is located adjacent to the Australian-Pacific Plate boundary where the tectonic regime changes from dominantly subduction-related to the north to transpression-related along the Alpine Fault to the south. During the Neogene, burial and exhumation varied extensively, in ... | Neogene; Uplift; Exhumation; Taranaki Basin; New Zealand | 1998 |
48 |
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Chapman, David S. | Geothermics and climate change: 2. Joint analysis of borehole temperature and meteorological data | Long-period ground surface temperature variations contained in bore hole temperature-depth profiles form a complementary climate change record to high-frequency, but noisy surface air temperature (SAT) records at weather stations. We illustrate the benefits of jointly analyzing geothermal and meteo... | Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Heat transfer | 1998 |
49 |
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Chapman, David S. | Geothermics and climate change: 1. Analysis of borehole temperatures with emphasis on resolving power | Temperature-depth data from six boreholes in western Utah and nine boreholes in southeastern Utah are reanalyzed for evidence of ground surface temperature (GST) histories. We invert the temperature-depth data using the functional space inverse algorithm of Shen and Beck [1991, 1992] which we prefer... | Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Geothermics | 1998 |
50 |
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Jewell, Paul | Geochemical variations in an alpine lake and watershed underlain by siliciclastic bedrock, Uinta Mountains, Utah | A small watershed which includes several small lakes in the Uinta Mountains of northern Utah is underlain by monolithologic Precambrian siliciclastic rock with extremely limited buffering capacity. In spite of this, s\ stematic spatial and temporal variations in alkalinity, pH, and major elements oc... | | 1998-01-01 |