Comparison of gases and source rocks from two tectonically dismembered segments of
Pennsylvanian coal basin
Paszkowski Mariusz1, Matyasik Irena2, Rospondek Mariusz3
1Institute
of Geological Sciences, Polish Academy of Sciences, Kraków Research Center, Senacka 1, 31-002 Kraków,
Poland; 2Instytut Nafty i Gazu, Lubicz 25a, 31-503 Kraków; 3Institute of Geological Sciences, Jagiellonian
University, Oleandry 2a, 30-063 Kraków, Poland; e-mail: m.rospondek@uj.edu.pl
ABSTRACT
A large eastern segment of the Variscan fore-deep coal basin was formed on the Cadomianconsolidated basement composed of terranes: Brno-Upper Silesia-Moesia-Istanbul-Zonguldak. From
Permian to Jurassic this basin was dismembered into two segments by translation along the KrakówHamburg-Dobruja transcontinental strike-slip fault zone. The resulted coal sub-basins were: the Upper
Silesia in the north and the Dobruja with Zunguldak-Amasra in the south. Subsequently, this southern
segment was separated into two pieces during Cretaceous, when one of them was rifed out the European
mainland, due to the formation the Black Sea back-arc basin. Finally, erosional remnants of the
Zonguldak-Amasra basin took rest in its recent position in the western Pontides. Actual extension of the
Upper Silesia coal basin is wider than directly recognized with boreholes. The basin ranges to the
Ukrainian/Romanian border, where its presence is documented by mass occurrences of the
Pennsylvanian low-rank coal clasts in the Carpathian Flysch. The common origin of the rock sequences
in both coal sub-basins: the Zonguldak-Amasra and the Upper Silesia allows us in recent study a
comparison of gases and source rocks between both basins.
Molecular and isotopic composition of the coal associated gases in the Upper Silesia and the
Zonguldak-Amasra areas reveals distinct similarities confirming the common type of source rocks,
maturity and generation history. In the Upper Silesia coal basin gas isotopic composition is in the range
DCH4 –160 to 190‰ and 13C –40 to 70‰ (Kotarba 2001), which is close to analogical values in the
Zonguldak-Amasra basin (DCH4 ca. –180‰ and 13C –50‰; Hoşgörmez et al. 2002). These data
suggest similar proportion of thermogenic and biogenic components in gases of both basins, but higher
variability in the Upper Silesia basin can be attributed to the encountered west to east trend in the
thermal maturity (Rr=0.6-2.0%), perpendicular to the Variscan front. In the Upper Silesia, the further
complications result form the influence of post-Variscian thermal gradients related to deeper burial, e.g.
under the Carpathians nappes. In the Zonguldak-Amasra basin the thermal maturity is generally lower
and more uniform (Rr=0.6-1.0%).
This paper is financed from the Polish Ministry of Science and Higher Education "Gas-prone
Pennsylvanian coal-bearing rocks beyond the known coal basins in Poland".
Kotarba M.J. 2001. Organic Geochemistry 32,163-180. Hoşgörmez, H , Yalcın, M. N, Cramer, B., Gerling, P.,
Faber, E., Schaefer, R.G., Mann, U. 2002. Organic Geochemistry 33, 1429–1439.