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Creator | Title | Description | Subject | Date |
51 |
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Brown, Francis Harold | Geological development of the Omo-Turkana Basin during the pliocene and pleistocene epochs | Pliocene and Pleistocene deposits of the Omo-Turkana Basin extend from 6?N latitude to about 2?N latitude (-450 km), and laterally from about 35.5?E to 36.5?E. Sediments are brought to the basin by the Omo River which rises in Ethiopia, and by the Turkwel and Kerio Rivers which rise in Kenya and Uga... | | 2004 |
52 |
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Chapman, David S. | Air, ground, and groundwater recharge temperatures in an alpine setting, Brighton Basin, Utah | Noble gases are useful tracers for constraining groundwater recharge temperature and elevation, critical in determining source areas of groundwater recharge in mountainous terrain. A monitoring network in the alpine Brighton Basin in the Wasatch Mountains of northern Utah, USA, was established to ex... | | 2012-01-01 |
53 |
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Zhdanov, Michael | Contraction integral equation method in three-dimensional electromagnetic modeling | The integral equation method has been proven to be an efficient tool to model threedimensional electromagnetic problems . Owing to the full linear system to be solved, the method has been considered effective only in the case of models consisting of a strongly limited number of cells. However, recen... | | 2002-01-01 |
54 |
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Zhdanov, Michael | Discussion and reply: comments on "electromagnetic geophysics: notes from the past and the road ahead" | The direct current and electromagnetic methods have been around for almost 180 years and have been applied successfully in mining, petroleum, geotechnical, engineering, environmental, groundwater, and tectonic studies. Over such a long period of time, it is possible to lose track of who the pioneers... | | 2012-01-01 |
55 |
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Zhdanov, Michael S. | Quasi-analytical approximation and series in electromagnetic modeling | The quasi-linear approximation for electromagnetic forward modeling is based on the assumption that the anomalous electrical field within an inhomogeneous domain is linearly proportional to the background (normal) field through an electrical reflectivity tensor ˆλ. In the original formulation of... | Electromagnetic modeling; Quasi-linear approximation; Quasi-analytical approximation; Quasi-analytical series | 2000 |
56 |
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Jarrard, Richard D. | Exceptionally preserved jellyfishes from the Middle Cambrian | Cnidarians represent an early diverging animal group and thus insight into their origin and diversification is key to understanding metazoan evolution. Further, cnidarian jellyfish comprise an important component of modern marine planktonic ecosystems. Here we report on exceptionally preserved cnida... | Jellyfishes; Metazoan evolution; Jellyfish fossils; Marjum Formation; Utah; Middle Cambrian | 2007-10-31 |
57 |
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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 |
58 |
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Brown, Francis Harold | Chronology | The boundaries of the Lower Omo Basin have been mapped by Fuchs (1939) and by Butzer (1970, 1971) in a general way. The structural features and physiography of the eastern and central part of the Lower Omo Basin are best expressed on the maps of Davidson et al. (1973). Walsh and Dodson (1969) have m... | | 1983 |
59 |
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Fernandez, Diego P. | Deep-sea scleractinian coral age and depth distributions in the Northwest Atlantic over the last 225,000 years | Deep-sea corals have grown for over 200,000 yrs on the New England Seamounts in the northwest Atlantic, and this paper describes their distribution both with respect to depth and time. Many thousands of fossil scleractinian corals were collected on a series o f cruises from 2003- 2005; by contrast,... | Desmophyllum dianthus; Scleractinian coral; Seamounts; Northwest Atlantic | 2007 |
60 |
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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 |
61 |
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Zhdanov, Michael | Cross-well electromagnetic imaging in three dimensions | In this paper, we develop a new technique for 3D cross-well electromagnetic tomography, based on an EM borehole survey consisting of a moving vertical magnetic dipole transmitter, located in one or several boreholes, and a tri-axial induction receiver, located in the other boreholes. The method is b... | | 2003 |
62 |
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Brown, Francis Harold | Dating | There are basically three lines of investigation that are involved in geochronology ? the dating of rocks and other earth materials. First, there are the physical and chemical dating methods which give us numerical estimates of age. Second, there is the reconstruction of the order of events in sec... | | 1984 |
63 |
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Brown, Francis Harold | The evolution of neogene terrestrial ecosystems in Europe | The Pliocene-Pleistocene chronology of hominid and other vertebrate evolution in East Africa is largely constrained by isotopic dating and regional intercorrelation of volcanic ash layers. Some eruptions were of sufficient magnitude or duration that their widespread tephra dispersal defines a serie... | | 1999 |
64 |
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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 |
65 |
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Chapman, David S.; Picard, M. Dane | Heat flow in the Uinta Basin determined from bottom hole temperature (BHT) data | The thermal resistance (or Bullard) method is used to judge the utility of petroleum well bottom-hole temperature data in determining surface heat flow and subsurface temperature patterns in a sedimentary basin. Thermal resistance, defined as the quotient of a depth parameter AZ and thermal con... | Thermal analysis; Bottom hole temperature | 1984-04 |
66 |
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Jarrard, Richard D. | Milankovitch paleoceanographic cycles in geophysical logs from ODP Leg 105, Labrador Sea and Baffin Bay | Ocean Drilling Program (ODP) Sites 645 and 646, in Baffin Bay and the Labrador Sea, respectively, were logged following drilling during Leg 105. Geophysical logs in ODP drill sites yield long, continuous records of sedimentary sequences and thus provide the opportunity for examining evidence of peri... | | 1990 |
67 |
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Chapman, David S. | Reply to comment by T.J. Osborn and K. R. Briffa on "Mid-Latitude (30?-60?N) climatic warming inferred by combining borehole temperatures with surface air temperatures" | We thank Osborn and Briffa [2002] for their comment regarding our use of the climatic reconstruction of Overpeck et al. [1997]. We [Harris and Chapman, 2001] had taken a proxy, Arctic wide summer-weighted annual temperature reconstruction [Overpeck et al., 1997], given in dimensionless sigma units (... | Surface air temperature; Ground surface temperature; Borehole temperatures; Geothermal observations; Heat transfer | 2002 |
68 |
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Zhdanov, Michael | 3D inversion of airborne electromagnetic data | Time-domain airborne surveys gather hundreds of thousands of multichannel, multicomponent samples. The volume of data and other complications have made 1D inversions and transforms the only viable method to interpret these data, in spite of their limitations. We have developed a practical methodolog... | | 2012-01-01 |
69 |
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Zhdanov, Michael S. | Parameter estimation for 3-D geoelectromagnetic inverse problems | Parameter estimation in geoelectromagnetics aims to obtain the most important parameters of a well-defined conductivity model of the Earth. These parameters are features of typical geological structures, such as depth and size of conductive or resistive targets, angle of dike inclination and its le... | | 1999-01-01 |
70 |
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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 |
71 |
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Brown, Francis Harold | Magnetostratigraphy of the shungura and usno formations, lower Omo Valley, Ethiopia | | | 1976 |
72 |
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Brown, Francis Harold | Observations on the stratigraphy and rediometric age of the omo beds, lower omo basin, southern Ethiopia | During September and October, 1966, the author measured a stratigraphic section for a portion of the Omo Beds, as exposed north of Kalam, Ethiopia. Additional field observations were also made at the time in other parts of the lower Omo Basin. Samples were collected for analysis and for radiometric ... | | 1969 |
73 |
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Chapman, David S.; Harris, Robert N.; Allis, Richard George | Gravity signals at the Geysers geothermal system | Three high-precision gravity and GPS surveys have been conducted over The Geysers geothermal reservoir and surrounding area. These surveys, in September 2000, April 2001, and September 2001, provide an initial baseline for future imaging studies of spatial mass changes from the Santa Rosa Efflu... | Ground water change; Gravity surveys | 2002 |
74 |
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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 |
75 |
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Zhdanov, Michael S. | Fast numerical modeling of multitransmitter electromagnetic data using multigrid quasi-linear approximation | Multitransmitter electromagnetic (EM) surveys are widely used in remote-sensing and geophysical exploration. The interpretation of the multitransmitter geophysical data requires numerous three-dimensional (3-D) modelings of the responses of the receivers for different geoelectrical models of comple... | Multitransmitter electromagnetic data; Numerical modeling; Multigrid quasi-linear approximation; Quasilinear approximation; geophysical exploration; 3-D modeling | 2006-06 |