Geologica Belgica

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Leona KOPTIKOVA, Jindrich HLADIL, Ladislav SLAVIK, Petr ČEJCHAN & Ondřej BÁBEK

Fine-grained non-carbonate particles embedded in neritic to pelagic limestones (Lochkovian to Emsian, Prague synform, Czech Republic): composition, provenance and links to magnetic susceptibility and gamma-ray logs

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Mots-clés : Lower Devonian, limestones, magnetic susceptibility, non-carbonate impurities, gamma-ray spectrometry, REE distributions, atmospheric dust, Prague Synform.

Abstract

Variations in non-carbonate impurities trapped in the Lower Devonian limestone stratal successions in the Prague Synform are studied, with particular emphasis on the composition and quantities of fine-mineral grain assemblages. Different assemblages are encountered for the Lochkovian, lower Emsian and Pragian. The Lochkovian (represented by the Lochkov Formation) is characterized by pyrite–pyrrhotite assemblages with lower abundance of iron oxides and oxyhydroxides (mostly goethite) whereas the Pragian (represented by the Praha Formation) shows relatively abundant iron oxides and oxyhydroxides (mostly hematite). Major changes in magnetic susceptibility and gamma-ray spectrometric logs also coincide with the Lochkovian/Pragian boundary. Maximum values of magnetic susceptibility and relatively high Th, K concentrations above the boundary correspond to the elevated amounts of barite and Ba concentrations. This level is interpreted as a significant interval with elevated delivery of impurities of aeolian origin, deceleration of sedimentation rate together with decreased carbonate productivity. REE distributions in the Lochkovian to lower Emsian are indicative of the aeolian origin of trapped impurities. Detrital zircons found in all three stages are considered to be also of aeolian origin.

To cite this article

Leona KOPTIKOVA, Jindrich HLADIL, Ladislav SLAVIK, Petr ČEJCHAN & Ondřej BÁBEK, «Fine-grained non-carbonate particles embedded in neritic to pelagic limestones (Lochkovian to Emsian, Prague synform, Czech Republic): composition, provenance and links to magnetic susceptibility and gamma-ray logs», Geologica Belgica [En ligne], volume 13 (2010), number 4 - Magnetic susceptibility, correlations and Palaeozoic environments, 407-430 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=3113.

About: Leona KOPTIKOVA

Institute of Geology AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic. E-mail: koptikova@gli.cas.cz

About: Jindrich HLADIL

Institute of Geology AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic

About: Ladislav SLAVIK

Institute of Geology AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic

About: Petr ČEJCHAN

Institute of Geology AS CR, v.v.i., Rozvojová 269, 165 00 Prague 6, Czech Republic

About: Ondřej BÁBEK

Department of Geological Sciences, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic