Correlation of Neoproterozoic conglomerates of the Barrandian, Saxothuringian and Moldanubian units


Authors: Klápová H, Hyršl J

Published in: Bulletin of Geosciences, volume 75, issue 3; pages: 217 - 228;

Keywords: conglomerates, metaconglomerates, Neoproterozoic, Bohemicum, Barrandian, Teplá-Barrandian Zone, Saxothuringicum, Saxolugicum, Moldanubicum, Armorica, Avalonia, turbidites, glacioeustatic movements, Protogondwana,

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The development of Neoproterozoic petromictic conglomerates in the Barrandian, Saxothuringicum and likely even in the southwestern part of the Moldanubicum is generally uniform. Local variations in composition and overall character of the conglomerates do not differ considerably from other Neoproterozoic coarse clastic sediments in the Perigondwanan domain either in the earlier or later phases of the Cadomian Orogeny. Small petrographic differences were observed between the eastern Barrandian complex of conglomerates (Dobříš conglomerates) and Saxothuringian metaconglomerates (Přísečnice and Saxolugian conglomerates). The Dobříš conglomerates contain more clasts of greywackes; Saxothuringian metaconglomerates are dominated by clasts of shales, rhyolites, keratophyres and granites. The highest contents of acid volcanics are known from metaconglomerates near Nákří in the Moldanubicum. An exceptional association of crystalline rocks occurs in the Hudlice conglomerates in the western Barrandian. The REE analyses show similar data for granite pebbles in all conglomerates tested. The CIA weathering index of matrix in the Barrandian and Přísečnice conglomerates oscillates between 56.2 and 66.7. This is in agreement with the presumed cold climate during the conglomerate sedimentation. A two-phase model is considered for conglomerate formation during the glaciation in the Sturtian and Vendian.