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Proterozoic-Paleozoic Géosynclinal and Orogenic Evolution of Central Europe

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Proterozoic-Paleozoic Géosynclinal and Orogenic Evolution of Central Europe WOLFGANG KREBS ) Institut für Geologie und Paläontologie, Technische Universität Braun- HORST WACHENDORF J schweig, D-33 Braunschweig, West Germany Proterozoic-Paleozoic Géosynclinal and Orogenic Evolution of Central Europe ABSTRACT plained in the sense of "the new global tec- tonics." The central European basement is divided into linear domelike zones of crystalline rocks INTRODUCTION that are separated by sedimentary troughs. Until recently, central Europe had not been Analyses of clasts in conglomerates and of touched by the theory of "the new global radiometric dates indicate maximum intensities tectonics." Therefore, it must be determined in of magmatic and metamorphic processes in the what respect, if any, the theory is of importance Proterozoic, at the Cambrian-Ordovician to central European geosynclinal and orogenic boundary, and in the Late Devonian and evolution. Carboniferous. The geosynclinal evolution took The enormous efforts in the exploration of place in an intracontinental area. There is no the ocean floors have led to a new discussion indication of the existence of an oceanic crust of the theory of continental drift. Deep-seated in central Europe. The orogenic events were processes interpreted in the light of newly caused ultimately by vertical rise of light acquired geophysical and petrologic data have buoyant basic magma produced by gravitative required modification of Wegener's classic con- differentiation in the upper mantle. Synkine- ception. Upper-mantle research has verified matically intruded granite masses, which origi- the mobilistic interpretation of lithospheric nated by anatexis of the crust and produced rigid plates above a more plastic asthenosphere. basement uplifts, are surrounded by broad The new model supposes a conveyor-belt metamorphic aureoles, whereas postkinematic mechanism: new sea floor is created at the intrusions are characterized by local zones of mid-oceanic ridge system and diverges from contact metamorphism. As granitic melts rose, the ridges to so-called Benioff zones—subduc- mobile troughs developed in front of the tion zones beneath the deep-sea trenches. How- steep-flanked plutons. Shallow-water deposits, ever, consumption of continental crust by the disconformities, and converging strata are asthenosphere at the subduction zones is ex- typical of the sedimentary cover of the plutons. cluded because this crust is too buoyant to sink. The flanks of the basement uplifts are shown This actualistic model has been proved in the by conglomeratic sediments and by outward Mesozoic and Cenozoic of the Pacific regions, directions of sediment transport. The basins but is applied by many workers to nearly all are shown by uninterrupted sequences of thick orogenic belts of the earth, regardless of their pelagic sediments. ages. These belts are believed to have originated Deformation of the troughs was caused by always by the collision of two lithospheric vertical movements connected with granitic plates. The following specific kinds of collisions intrusion. At the rims of diapiric plutons, can be distinguished (Mitchell and Reading, gravitative sliding of the sedimentary cover 1969, 1971; Dewey and Bird, 1970; Dewey and deep-seated faulting took place, and and Horsfield, 1970; Dickinson, 1971): (1) tholeiitic basalt magmas of continental origin continent-continent (Himalaya, Ural) ; (2) con- altered during processes of spilitization as- tinent-ocean (Andes) ; (3) ocean-island arc cended. Horizontal shortening is only of (western Pacific). subordinate importance, mainly in connection Dewey and Bird (1970) are inclined to with gravity tectonics. The genesis of the explain all phenomena of alpinotype mountain central European basement cannot be ex- belts, including horizontal shortening, magmat- Geological Society of America Bulletin, v. 84, p. 2611-2630, 4 figs., August 1973 2611 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/84/8/2611/3418129/i0016-7606-84-8-2611.pdf by guest on 23 September 2021 2612 KREBS AND WACHENDORF ism, and metamorphism, by plate collision. concept, parts of this rise are superficially ex- They adapted the classic conception of a geo- posed at the southern border of the Hunsriick syncline, as illustrated by Aubouin (1965), to and Taunus, in the Odenwald, Spessart, Ruhla, the model of plate tectonics with emphasis KyfFhauser, and the Wippra zone (southeast upon rise and descent of oceanic material in Harz). Whereas Kossmat (1927), Stille (1951), a convection system. and Dvorak and Paproth (1969) considered Le Pichon (1968) originally assumed :he the crystalline core of the Moldanubian as the existence of seven different plates. Since then, central crest of the Variscan orogen (Hercynian the number of plates postulated has increased orogen in the sense of English and American considerably. In the Mediterranean, especially, literature), others have regarded the central tectonically active plates are reported to be German crystalline rise as the central massif very numerous, their relative movements seem of the Vtriscan orogen, depending on the atti- extremely complicated, and the distinction of tude of the axial planes and the source areas oceanic and continental crust is controversial. of flysch and related sediments. It is contro- The concepts of plate tectonics and the new versial waether the central German crystalline global tectonics have also been adapted to the rise trended continuously southwest-northeast Caledonian geosyncline of North America and during the whole geosynclinal period or was northwestern Europe. Here, various opinions only a submarine elevation of the basement and views regarding the positions of the sub- that protruded above sea level as separate islands. To the east, the Moldanubian is termi- duction zones have been discussed (Dewey, nated by the Moravo-Silesian or East Sudetan 1969; Bird and Dewey, 1970; Fitton and zone which is characterized by crystalline mas- Hughes, 1970; Mitchell and Reading, 1971). sifs, pre-flysch, flysch, and molasse sediments The discussion that follows emphasizes that of Devonian to late Carboniferous age. there is no proof for the existence of relics of an oceanic crust in the whole area of central The boundaries between the zones intro- Europe. Furthermore, there is no sign of a duced by Kossmat are in part arbitrary and Variscan continental margin that coincides hypothetical, especially the boundary between with the Hercynian or Alpine ophiolite line as the Saxothuringian and Moldanubian. Instead Smith (1971), Laurent (1972), and Nicolas of forming elongated sedimentary troughs, the (1972) suggested, using a controversial analogy sub-Variscan and East Sudetan are both com- with the American Cordillera based chiefly on monly confined to primarily elliptical basins. the presence of calc-alkalic plutonic and vol- Furthermore, the Proterozoic Barrandian sedi- canic rocks. On the contrary, in the Carnic ments in central Bohemia are completely sur- Alps, late Carboniferous molasse sediments rounded by the metamorphic series of the derived from the north indicate continental Moldanubian (Fig. 2). This wedge-shaped ob- conditions in that direction (Schonenberg, long structure of the Barrandian does not con- 1970). Analysis of the basement relations in tinue to the east and west. A marked fault that region is basic to the understanding of zone, which can be followed over a distance of the continental underpinnings of central 200 km, predominates along the Elbe River. Europe. The area east of the Elbe valley, which differs in many aspects from the Saxothuringian, has CENTRAL EUROPEAN BASEMENT: been termed "Lugikum" (Lugian). On ac- PROBLEMS OF SUBDIVISION count of this difference, several interpretations In accordance with the classic work of of eastward continuation of the Saxothuringian Kossmat (1927), we distinguish the Moldanu- sedimentary troughs have been discussed (for bian in the central part of the central European example, Hirschmann, 1965; Mobus, 1968; Proterozoic-Paleozoic basement. Adjacent to Dvorak and Paproth, 1969). the north of the Moldanubian, the Saxothu- The Saxothuringian and the East Sudetan ringian, Rhenohercynian, and sub-Variscan fore- are divided into small individually developed deeps follow in broad to wedge-shaped belts sedimentary troughs and domelike to elon- (Fig. 1). Between the Rhenohercynian and gated elevations of metamorphic and magmatic Saxothuringian, the central German crystalline complexes. Therefore, in central Europe, a rise (Mitteldeutsche Kristallin-Schwelle), con- distinction between isolated sedimentary sisting of magmatic and metamorphic com- troughs that contain thick, folded Proterozoic plexes, is recognized. According to Kossmat's to Paleozoic sediments, and crystalline massifs Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/84/8/2611/3418129/i0016-7606-84-8-2611.pdf by guest on 23 September 2021 GEOSYNCLINAL AND OROGENIC EVOLUTION—CENTRAL EUROPE 2613 Figure 1. Index map of the central European Pro- tioned in the text. • = distinct localities; x = moun- terozoic-Paleozoic tectonic zones and localities men- tain ranges. consisting of metamorphic series and granitoid tites occurred over a long time in some areas intrusions, is more realistic than the homoge- and emplacement cannot be assigned to any one neous and uniform arcs of Kossmat (1927, Fig. distinct orogenic phase (for example, the 3, Table 1). Erzgebirge). Geochronologic analysis shows Deformation within the sedimentary troughs magmatic activity
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