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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 103 (1990), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The main features of the crustal structure of the Karelian and Svecofennian provinces are discussed on the basis of data obtained from deep seismic sounding (DSS) profiles across the SE Fennoscandian Shield. The data show that in the ancient Karelian province the crust is thinner (about 40 km), the average velocity is lower (about 6.4 km s-1) and the Moho boundary is a sharp discontinuity which produces strong reflections. The high-velocity layer in the lower crust, if it exists at all, is thin. In the younger Svecofennian province, crustal thickness averages about 45 km with a velocity of 6.6–6.8 km s-1. The reflectivity of the Moho is usually weak and a high-velocity layer with velocities greater than 7 km s-1 is ubiquitous in the lower crust. High velocities in the lower crust and upper mantle are found in deep Moho areas. Beneath the younger granitic intrusions, Gothian complex and Vyborg Rapakivi granites, the crust is thinner than on average.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 101 (1990), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The 430 km long DSS Baltic profile in SE Finland runs through the Rapakivi intrusion, the Svecokarelian geosynclinal complex, including the Ladoga-Bothnian Bay zone, and the Archean basement complex. A brief description of field operations in 1982 is presented. Record sections of P- and S-waves were used for the interpretations. A starting model was constructed by inverse methods and improved by dynamic ray tracing modelling. Three blocks are indentified on the cross-section from SW to NE. These are the southern, associated with the Rapakivi Massif, depth to Moho (M) about 40 km; the central, Ladoga-Bothnian Bay zone, with M of approximately 55-60 km, and the northern, Archean crystalline basement, with M about 40-45 km. The average crustal velocity is 6.6-6.7 km s−1. The crustal structure along the Baltic profile is compared with the surrounding DSS profiles, Finnish Sveka and Soviet Kem-Tulos and Ladoga profiles. The eastern border of the Ladoga-Bothnian Bay zone was located and specific features of the crust and uppermost mantle along the profile area are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 26 (1978), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Magneto-telluric experiments were performed in August 1974 in the Muhos Jotnian sedimentary formation and the Koillismaa Precambrian basement complex by the Centre de Recherches Géophysiques, Garchy, and the Department of Geophysics, University of Oulu, employing the “Résistivimètre magnéto-tellurique”, an instrument which permits apparent resistivity values to be observed at eight pre-selected frequencies between 8–1700 Hz.Preliminary soundings were made on the Muhos formation and on its surroundings, after which a magneto-telluric profile was measured involving eleven sites on a line 13 km long extending across the formation. Some further soundings were made at certain sites of known stratigraphy. The resistivity values in the sedimentary formation were found to vary between 10 ωm and 200 ωm, while those in the basement were markedly higher. This resistivity contrast suggests that the method seems to be suitable for delimiting the sedimentary formation.Soundings made on the basement at Koillismaa show apparent resistivity values in the range 1000–20000 ωm. The interpretation of these soundings was in agreement with other, independently obtained geophysical results.
    Type of Medium: Electronic Resource
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