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Major tectonostratigraphic units of the Bohemian Massif

By
Josef Chaloupský
Josef Chaloupský
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Published:
January 01, 1989

The Bohemian Massif, the largest outcropping part of the central European Variscides, is divisible into five major tectonostratigraphic units: Moldanubicum, Bohemicum, Saxothuringicum-Lugicum, Brunovistulicum, and Rhenohercynicum. All the units except the external Rhenohercynian zone have contacts within Czechoslovakia. The units are mostly bounded by steep faults and thrusts and show marked contrasts in geology on either side. However, they cannot be classified as terranes spaced widely apart at any time of their geological history. They are autochthonous units whose lateral movement was greatly restricted and whose contrasts in the Late Proterozoic and Paleozoic development were brought about by pre-existing inhomogeneities of the underlying Precambrian continental crust.

The pre–upper Proterozoic (Moldanubian) basement in the interior part of the massif resembles the Sveconorvegides of southwestern Scandinavia. Its pre-Cadomian fold structures have north-northeast–south-southwest to north-south trends. The western tectonic boundary of the Brunovistulicum unit may represent the southward continuation of the Vättern tectonic zone in south Sweden, thus forming the eastern boundary of the area of Dalslandian (Grenvillian) regeneration of the Precambrian basement rocks in Czechoslovakia.

The Cadomian tectonometamorphic event (650 to 550 Ma) affected with various intensity the whole Bohemian Massif. The center of the Cadomian domain was the Bohemicum—a roughly west-east–trending arched zone of thick, folded, low- to medium-grade metamorphic, upper Proterozoic sedimentary and volcanic rocks of oceanic flavor, which were deposited on an insufficiently developed continental crust.

The Bohemicum also became the center of tectonic activity in the following Paleozoic cycle. From the Bohemicum toward the massif peripheries, a general rejuvenating of both the fills of the Paleozoic sedimentary basins and their main folding can be evidenced. The sedimentary basins developed entirely in an intracontinental environment, mostly along the tectonic boundaries of the Moldanubian and Brioverian units.

The early Caledonian deformations were relatively mild. The late Caledonian (Early Devonian) deformations, locally associated with blueschist-facies metamorphism, were confined only to some west-east to northwest-southeast–trending zones of the Lugicum area. Variscan deformations represented the culmination of a long-term, Late Proterozoic–Paleozoic tectonothermal activity in the massif in which crustal extensions and compressions alternated many times, but never resulted in either crustal separation and oceanic crust generation, or large-scale thrusting.

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GSA Special Papers

Terranes in the Circum-Atlantic Paleozoic Orogens

R. D. Dallmeyer
R. D. Dallmeyer
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Geological Society of America
Volume
230
ISBN print:
9780813722306
Publication date:
January 01, 1989

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