Late Carboniferous palaeodepositional changes recorded by inorganic proxies and REE data from the coal-bearing strata: An example on the Czech part of the Upper Silesian Coal basin (USCB)

Abstract

In the Czech Republic, coal-bearing siliciclastic sediments have been deposited during the Serpukhovian and Bashkirian (Carboniferous). Until now, no attention has been paid to inorganic geochemical assessment of the coals and associated non-coal rocks from the mixed shallow-marine to continental sediments (Ostrava Formation), and continental non-marine settings (Karviná Formation). Samples were collected from a 750 m deep coal exploration borehole at the ČSM Mine. The bulk parameters, total organic carbon TOC, total inorganic carbon TIC, total sulphur TS, major elements, trace elements, and REEs were measured on these samples, and their mineral associations have been investigated using microscopy combined with the principal component analysis (PCA). Common redox proxies V/Cr, U/Th, Ni/Co, Mo/U, and the ratio S/TOC have been tested on the samples to investigate their usefulness for studying anoxia. Research concludes that redox proxies such as U/Th, Ni/Co and V/Cr have been strongly influenced by the clastic input and carbonates, which it hinders for them to be reliable indicators of anoxia. On the basis of Eu anomaly and REEs distribution, the primary source of detrital elements comes from the parent rock, being governed more by physical than redox processes.