Chemistry of rocks Březina and Podolí Formations – dinantian–culmian transition facies of Drahany Upland ViséanArticle PDF
Chemistry of rocks Březina and Podolí Formations – dinantian–culmian transition facies of Drahany Upland Viséan
Březina and Podolí Formations represent a transition from the Lower Carboniferous calciturbiditic sedimentation in the Moravian Karst (Líšeň Formation) to the Upper Viséan siliciclastic turbidite flysch facies (Culm facies of the Rozstání Formation). The Březina shales are relatively variable in mineral and chemical composition especially in the content of carbonates (CaO = 0.53 to 0.98 wt. %). Compared with Podolí shales and typical Culmian facies shales, the clastic component of Březina shale exhibits higher degree of chemical weathering and sometimes contains admixture of volcanic material and is intercalated by volcaniclastic deposits (individual beds). Chemistry of volcaniclastics indicates rhyolitic composition and tectonic setting of active continental margin. Contents of Pb, Cu, As, Zn, Cd, Se and Sr depend on the amount of carbonate in the Březina shale. Březina shales have lower contents of Zr, Hf, and often also P, Ti. Shales of Rozstání and Podolí formations have compositions, which indicate rapid deposition of fresh clastic material in environments that were more oxygen-rich than it was in the case of Březina shale.
David Buriánek*, Helena Gilíková, Jiří Otava, Czech Geological Survey, Branch Brno, Leitnerova 22, 658 69 Brno, Czech Republic, * e-mail: email@example.com