International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

LOWER CAMBRIAN SILICICLASTIC SEDIMENTS IN SOUTHERN MORAVIA (CZECH REPUBLIC) AND THEIR PALEOGEOGRAPHICAL CONSTRAINTS

Pages: 67 - 79

Authors: MILADA VAVRDOVA, RADEK MIKULAS, SLAVOMIR NEHYBA

Abstract: Petrological, sedimentological and ichnological studies of cores from the Menin-1 borehole revealed episodic shallow marine influence in the terrestrial clastics underlying the Devonian clastic and carbonate rocks. The organic-walled, acid-resistant microfossils have been recovered from bioturbated beds and have allowed us to determine the age as the earliest Cambrian (most likely Platysolenites antiquissimus faunal Zone). Several index acritarch species justify a preliminary assignment to the Asteridium tornatum – Comasphaeridium velvetum acritarch Zone. The microfossils are very well preserved, without any noticeable thermal alteration (thermal alteration index about 1+) or mechanical damage. The ichnoassemblage contains Diplocraterion isp., Skolithos isp., and Planolites isp. The intensity of bioturbation and ichnofabric patterns correspond well to those described from the Cambrian of the East European Platform. The composition of Cambrian acritarch assemblages, of the ichnotaxa, as well the very low thermal alteration of organic-walled microfossils, link this Moravian sedimentary cover of Brunnia (Brunovistulicum in broader sense of the meaning) to the sediments of the same age which rest on other crustal segments in the southern and central part of Poland and even farther on the Baltica Paleocontinent. This indicates a connection rather than separation of these Cambrian "Gondwanan parts" and Baltica by the Trans-European Suture Zone.

Keywords: Early Cambrian, paleogeography, sedimentology, acritarchs, ichnofossils

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