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We examined 14 archived samples of shale for the chemical and 13C isotopic composition of residual gases produced as part of rock-crushing operations at a hammer mill. Results were compared with data on maturity from Rock-Eval pyrolysis and vitrinite reflectance measurements. The samples originated from three different formations (Mikulov Marls, Ostrava Formation, and Liteň Formation) located in the Czech Republic. For comparison, we examined a gas-prone shale sample from the Polish Silurian. We used changes in the chemical and isotopic composition of released gases to evaluate the isotope fractionation during gas loss and retroactively calculated the initial content of gas in the shale samples. The gas content estimates (in L of gas per ton of rock) correspond with the maturity parameters of the shales. Calculated isotope fractionation for the gas release was −3‱ for both methane and ethane. The archived samples primarily lost methane (up to 90%), with subsequent changes in the content of ethane and higher hydrocarbon levels.

After briefly introducing the sedimentology of two Eifelian-Frasnian carbonate sections in Belgium and Moravia, this paper focuses on the comparison of the magnetic susceptibility (MS) curves. The Ardennes section shows highly variable facies, with an alternation of ramp, platform and mound environments. Detrital inputs are locally very important. Time-equivalent facies in the area of the Moravian Karst correspond to rather pure carbonate platform facies, mostly composed of Amphipora beds. The first analysis of long-term trends in Devonian MS in Belgium and Moravia shows a remarkable similarity, despite a very different background of palaeogeographical setting, facies, sedimentary rate and retrogradation-progradation history. However, a relative independence of the MS and the distal-proximal curves, deduced either from the microfacies record (Ardennes) or from shoreline shifts (Moravia) is observed. This questions the nature of the forcing mechanisms that must at least be active at the inter-regional scale. Moravia and the Ardennes are located along the same palaeolatitude, perhaps suggesting some climatically driven mechanisms, responsible for the input of the detrital fraction responsible for the MS in these sediments. Trade winds are potentially responsible for transportation of dust and its widespread distribution in intertropical areas. [ABSTRACT FROM AUTHOR]