Terrestrial radioisotopes as paleoenvironmental proxies in sedimentary formations

The presence of anomalous terrestrial radioisotopes must be suspected in black shale-hosted manganese ore deposits, based on high organic matter content, which is useful tool in genetic, among them paleoenvironmental investigations. Our work aims at the characterization of the paleoredox conditions of the Urkut Manganese Formation based on comparison of terrestrial radioisotopes and selected element ratios. Paleoredox indicators were estimated on U/Th, delta U, Ni/Co, V/Cr, V/(V + Ni) and Ce*. The results of paleoredox indicator element ratios show, that these methods must be used with caution (microbial selective element enrichments, mobilizations), and the complex interpretation using mineralogy and microtexture can be recommended.