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    Wyświetlanie 1-6 z 6
    Tytuł:
    Palaeozoic orogeneses in the Sudetes: a geodynamic model
    Autorzy:
    Cymerman, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059384.pdf
    Data publikacji:
    2000
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Sudetes
    Variscan
    Palaeozoic
    transpression
    extension
    orogeny
    Opis:
    The Palaeozoic geodynamic evolution of the Sudetes resulted from two successive orogenic events: (1) Ordovician-Silurian geotectonic processes (pre-Variscan stages), and (2) the Variscan orogeny. Early Palaeozoic rifting of Cadomian crustal segments and opening of the Ligerian (Galicia-Massif Central) and/or Saxothuringian Ocean occurred in Ordovician-Silurian times on the northern (peri-Gondwana) periphery of the Bohemian Massif. At the same time, the Góry Sowie terrane with a magmatic arc affinity quite probably developed on the SW margin of Baltica due to subduction of the Tornquist Ocean. Two major structural events characterised the Variscan evolution of the Sudetes: (1) regional-scale ductile thrusting of Late Devonian-Early Carboniferous age, and (2) Early Carboniferous-Early Permian regional extension. Ductile thrusting is characterised by: (I) a general NNE-directed, dextral transpressional stacking of ductile nappes due to oblique collision of the Moldanubian and Moravian microplates in the Eastern Sudetes, and (II) SW- to NW-directed, sinistral transpressional stacking of ductile nappes due to westward lateral extrusion of continental crust in the Central and Western Sudetes, itself a result of oblique indentation of the Central Sudetic oceanic lithosphere. The first Variscan deformation in the Sudetes might reflect a purely convergent setting that evolved into a transpressive setting during oblique convergence. Special attention is given to the geometry and kinematics of intraplate tectonic escape and a model of indentation processes in the Sudetes. The presented new geotectonic model for the Variscan evolution of the Sudetes is consistent with lateral escape of the Saxothuringian terrane as an important way of accommodating Variscan strain in the NE part of the Bohemian Massif. This model explains the lateral expulsion (escape) process as due to the indentation of the Central Sudetic terrane along with the Góry Sowie terrane and by the oblique subduction of the Ligerian/Saxothuringian Ocean(s) (now tectonically dismembered ophiolitic rocks of the Central Sudetic terrane).
    Źródło:
    Geological Quarterly; 2000, 44, 1; 59-80
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Variscan Orogen in Poland
    Autorzy:
    Mazur, S.
    Aleksandrowski, P.
    Kryza, R.
    Oberc-Dziedzic, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058949.pdf
    Data publikacji:
    2006
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Bohemian Massif
    Sudetes
    Palaeozoic
    terranes
    metamorphism
    magmatism
    Opis:
    The structure and evolution of the Polish part of the Variscan Orogenic Belt is reviewed, based on published data and interpretations. The Sudetic segment of the Variscides, together with adjacent areas, experienced multi-stage accretion during successive collisional events that followed the closure of different segments of the Rheic Ocean. In SW Poland, Variscan tectono-stratigraphic units are tectonically juxtaposed and often bear record of contrasting exhumation/cooling paths, constrained by palaeontological and geochronological data. This points to the collage-type tectonics of this area. A three-partite subdivision of the Sudetes is proposed that reflects timing differences in deformation and exhumation of the respective segments. The Central,West and East Sudetes were deformed and amalgamated during the Middle/Late Devonian, at the turn from the Devonian to Carboniferous and during Early Carboniferous times, respectively. Problems in extending the classical tectono-stratigraphic zonation of the Variscides into the Sudetes are discussed and attributed to activity along Late Palaeozoic strike-slip faults and shear zones, disrupting and dispersing the initially more simply distributed tectono-stratigraphic units into the present-day structural mosaic. Relationships between the Variscan Externides and the foreland basin are explored. Sediments of the foreland basin locally onlap the external fold-and-thrust belt that had undergone an earliest Carboniferous partial tectono-thermal overprint. During the Late Carboniferous, the SW part of the foreland basin was heavily affected by thrusting and folding and incorporated into the Externides. DuringWestphalian C to Early Permian times, localized folding and thrusting affected the distal parts of the foreland basin, probably in response to dextral transpressional movements along NW–SE trending basement faults.
    Źródło:
    Geological Quarterly; 2006, 50, 1; 89-118
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Seismic refraction investigations in Poland (1964-1978) and their use in continuing studies
    Autorzy:
    Młynarski, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059904.pdf
    Data publikacji:
    2002
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Precambrian Platform
    Palaeozoic Platform
    Carpathians
    refraction seismic surveys
    Opis:
    Seismic refraction investigations, performed in Poland between 1964 and 1978, are reviewed. Examples selected from the many seismic profiles, totalling approximately 15 000 km in length, are shown. The most useful profiles as regards geological interpretation are in the Precambrian Platform and along its southwestern edge. Both the top of the crystalline basement and a system of faults, downfaulting the basement towards the south-west, can be identified in that area. In the Carpathians and its foreland, the top of this basement may be identified together with the bases of thrust flysch nappes. In the Fore-Sudetic Monocline, the top of folded Carboniferous deposits can be determined. The most ambiguous results were obtained from the Palaeozoic Platform.
    Źródło:
    Geological Quarterly; 2002, 46, 3; 247-254
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Development of Trans-European Suture Zone in Poland: from Ediacaran rifting to Early Palaeozoic accretion
    Autorzy:
    Nawrocki, J.
    Poprawa, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2058943.pdf
    Data publikacji:
    2006
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Early Palaeozoic
    Trans-European Suture Zone
    Ediacaran, terrane
    rifting
    accretion
    Opis:
    This contribution summarizes selected results of the “Palaeozoic Accretion of Poland” Project. Emphasis is placed on geochronological, geochemical and palaeomagnetic constraints on the Late Neoproterozoic to Early Palaeozoic development of the Trans-European Suture Zone (TESZ). During the Late Neoproterozoic break-up of Rodinia, a major rift developed in the area of the future TESZ along which Baltica was separated from peri-Gondwana and Laurentia, resulting in opening of the Tornquist Ocean and development of the southwestern Baltica passive margin. This was paralleled by the development of the Cadomian orogenic system along the margin of Gondwana and the eastern and southern margins of Baltica. Some tectonic units involved in the TESZ, such as the Brunovistulian Terrane and the Małopolska Massif characterized by Cadomian basement, were derived fromthe internal and external parts of the Cadomian Orogen, presumably somewhere at the SE or SW corners of Baltica. Determination of areas where these terrains were originally located depends strongly on the Ediacaran plate model that is adopted for Baltica. The Małopolska Massif was reaccreted to Baltica, presumably due to latest Ediacaran strike-slip tectonics, during the late Middle to Late Cambrian, causing at that time an interruption of its passive margin subsidence pattern and minor erosion. During Late Ordovician to Silurian times, the Caledonian collision of Gondwana-derived East Avalonia Terrane with Baltica gave rise to the development of a foredeep basin along the southwestern margin of Baltica. The proximal part of this foredeep corresponds to the Pomeranian region to the Koszalin-Chojnice Zone, and its distal parts to the Baltic Basin, both of which developed on Baltica basement. During Ordovician and Silurian times clastics were shed into the Koszalin-Chojnice Zone and the Baltic Basin from the evolving Caledonian orogenic wedge, consisting of a subduction-related volcanic arc, obducted ophiolites and accretionary prism, as well as crustal units that were detached from basement of Baltica and Avalonia. The Brunovistulian Terrane was accreted to theMałopolskaMassif at the turn from the Silurian to the Devonian. Proximal terranes, such as the Pomerania and Łysogóry units remained after Late Neoproterozoic rifting in a position close to the relatively mobile SW margins of Baltica.
    Źródło:
    Geological Quarterly; 2006, 50, 1; 59-76
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Hydrothermal veins linked with the Variscan structure of the Prague Synform (Barrandien, Czech Republic): resolving fluid-wall rock interaction
    Autorzy:
    Halavínová, M.
    Melichar, R.
    Slobodník, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059098.pdf
    Data publikacji:
    2008
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    Bohemian Massif
    Palaeozoic
    Variscan veins
    carbonates
    isotope geochemistry
    fluid systems
    Opis:
    Variscan syntectonic hy dro ther mal veins of the Prague Synform are important traces of small-scale fluid migration in Lower Palaeozoic sedimentary rocks — a process induced by late Variscan tectogenesis. Two main structural types of Variscan syntectonic calcite veins were recognised during fieldwork. Veins of Type I have an irregular or sigmoidal shape and are often arranged in en echelon arrays. A shearing regime during the formation of this type is deduced. Veins of a second structural type (Type II) have a more regular and straight shape relative to those of Type I and in some places form a dense network. The structural position of the Type II veins is related to structural elements of Variscan folds. Veins were formed due to interlayer-slip combined with fold- related fracturing that gave rise to the infilling of dilational structures. A tensional regime also permits growth of the fibrous veins. Two princpal directions were distinguished within the Type II veins. The first one is NNW–SSE and the second one shows a perpendicular ENE–WSW orientation. These directions seem to be parallel and/or perpendicular to the nappearchitec ture of the Prague Synform. Variscan syntectonic veins crystallised in a relatively closed, rock-buf fered system. Extraction of chemical components from surrounding rocks is indicated by a combined microprobe/cathodoluminescent study and by isotope geochemistry. The carbon isotope values of hydrothermal calcites reflect the carbon isotope composition of the host rocks. The delta exp.13C values of vein calcites and their host Silurian rocks are between –0.29 and –1.98‰ PDB. The same relationships were found between the veins and the host Devonian limestones (from 1.72 to 2.52‰ PDB). Samples close to the Silurian/Devonian boundary show transition values between 0.25 and + 1.16‰ PDB. The Sr-isotopic signature supports a genetic link between the calcite veins and the host rocks. The 87Sr/86Sr ra tio in calcites ranges between 0.708619 and 0.708738 and in wall rocks be tween 0.708755 and 0.709355. Aqueous and hydrocarbon-rich fluid systems have been found in fluid inclusions. Liquid hydrocarbons show mostly a light blue fluorescence suggesting the presence of higher hydrocarbons. They are more abundant in dark Silurian rocks, which are rich in organic matter. Lower salinities (0.5–8.9 eq. wt.% NaCl) and homogenization temperatures with a maximum around 140gradeC are typ i cal for the aqueous (H2O–NaCl) system. The oxygen isotopic composition of fluids ranges between –2.80 and +3.33‰ SMOW. This indicates that transformed formation waters in teracted with the host rocks and/or deeply circulating isotopically depleted meteoric waters. Intersections with the isochore specify border trapping temperatures between 127 and 160grade C and pressures from 300 to 1070 bars.
    Źródło:
    Geological Quarterly; 2008, 52, 4; 309-309
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The Late Devonian (Frasnian/Famenian) mass extinction : a proposed test of the glaciation hypothesis
    Autorzy:
    Mc-Ghee, G. R.
    Powiązania:
    https://bibliotekanauki.pl/articles/2059745.pdf
    Data publikacji:
    2014
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Tematy:
    mass extinction
    glaciation
    Late Palaeozoic Ice Age
    Cenozoic Ice Age
    Opis:
    It is argued in this paper that late Frasnian global cooling was the first step in the onset of the Late Palaeozoic Ice Age, and that the late Frasnian extinctions are analogous to the early Oligocene (Oi-1) extinctions that took place in the first step in the onset of the Cenozoic Ice Age. It is argued that the physical evidence for the existence of late Frasnian glaciation, like the Oi-1 glaciation, is largely geochemical: the sharp increases in δ18O values and positive δ13C anomalies that occurred in the late Frasnian and earliest Famennian. In addition to the geochemical evidence, also like the Oi-1 glaciation, stratigraphic calculations indicate a major sea-level fall occurred during the late Frasnian and early Famennian, a sea-level fall that is argued to have been glacially produced. It is here proposed that the best possible independent physical evidence for the existence of late Frasnian glaciation, other than the geochemical and sea-level evidence, would be the discovery of ice-rafted debris in marine sediments of late Frasnian age similar to the ice-rafted debris found in Oi-1 marine sediments (Zachos et al., 1992; Ehrmann and Mackensen, 1992).
    Źródło:
    Geological Quarterly; 2014, 58, 2; 263--268
    1641-7291
    Pojawia się w:
    Geological Quarterly
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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