Paleozoic evolution of the Moravosilesian Basin
| Authors | |
|---|---|
| Year of publication | 2000 |
| Type | Article in Periodical |
| Magazine / Source | Geolines |
| MU Faculty or unit | |
| Citation | |
| Field | Geology and mineralogy |
| Keywords | Brunovistulian terrane; extension; rifting; Devonian; Carboniferous |
| Description | The Brunovistulian Terrane (BT) is a fragment of northern Gondwana margin regarded as a part of Avalonian group of terranes (KALVODA 1995). The lithological record of the Cambrian marine sediments may indicate the extension and rifting connected with the fragmentation of Gondwana. It is assumed that BT was amalgamated to Baltica along the TESZ in Lower Paleozoic and during the Variscan orogeny was a southern promontory of Laurussia. The Devonian extension is assumed to be connected with intraplate stresses due to the collision of the Brunovistulian promontory with Moldanubian and Armorican Superterrane. Orogeny leads to rifting at high angle to the compression direction and rifts form first near the collision site and propagate later away from it. As a consequence, the amount of total extension and correlatively, the magnitude of the total subsidence, is commonly greatest near the suture and decreases away from it. The Moravosilesian basin bears features of both impactogen and strike-slip related rifting. During the rifting old basement faults of approximately NW-SE direction paralleling the Teisseyre-Tornquist Zone and Kraków-Lubliniec Zone were reactivated. The remnants of the extensional zones can be distinguished in the Nesvačilka, Jablůnka, Jablůnkov and other halfgrabens in the east, while more to the west detached sediments and their basement were incorporated in the complicated mosaic of the Moravo-Silesian shear Zone. The development of similar halfgraben basins can be traced also in southern Poland and shows a distinct S-N polarity. The compression in Moravosilesian foreland basin started in the Tournaisian (Moravia) while in southern Poland extension still took place. During the compression former extensional faults served often as overthrust zones. The Variscan flysch in Moravia can be subdivided in the inner belt (including the Protivanov and partly Rozstání Formation in the Drahany Upland and the Andělská Hora and Horní Benešov Formation in the Nízký Jeseník Mountains) and outer belt (including the Myslejovice Formation in the Drahany Upland and the Moravice and Hrádek-Kyjovice Formation in the Nizký Jeseník Mountains). The inner belt was characterized by prominent dextral translation on nappe units and Brunovistulian affinity of source rocks while the outer belt shows the decreasing extent of overthrusting to the east (even passing in paraautochthonous and autochthonous units), important role of Moldanubian source rocks and prominent S-N grain size distribution. The evolution of the Moravosilesian foreland basin was governed by the interaction of Brunovistulian Terrane with Moldanubian Superterrane in the Drahany area, Armorican Superterrane in the Jeseníky area as well as with Malopolska Terrane in the north. In this respect the evolution of the Moravosilesian foreland basin is more complex than in western Europe where the collision of Avalonian foreland with Armorican Superterrane took place. The dextral translation was characteristic both for the contact with Malopolska Terrane (Kraków-Lubliniec Zone) and for the whole TESZ (Grygar, Vavro 1995). The close affinity of the Devonian and Carboniferous foraminiferal fauna of Brunovistulian Terrane with the Dnieper-Donets Basin supports this idea. Consequently, the Brunovistulian Terrane may be regarded as a separate terrane within the Avalonian group of terranes showing similar tectonic position (Rhenohercynian Zone) but different paleogeographic evolution as Eastern Avalonian Terrane in Germany. Summarizing we assume a more important role of terranes in the origin of the Middle European Variscides analogous to the evolution of Appalachians. |
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