Castle Conglomerate Unit of the Upper Silesian Basin (Czech Republic and Poland): a record of the onset of Late Mississippian C2 glaciation?

Abstract

The Castle Conglomerate Unit in the Poruba Member (Early Namurian, Mississippian) is a lithosome composed of coarse-grained sandstones and conglomerates. Its thickness, lithology and extensive area make it unique in the paralic sequence of the Ostrava Formation of the Upper Silesian Basin. The unit was studied on the basis of information from exploratory boreholes, mines and its outcrop at the type locality in the Lučina Valley in Silesian Ostrava. Locally, the unit attains a thickness of up to 115 m (average 24.4 m). Its present-day area is approximately 992 km 2 . The axis of the conglomerate facies (with character of interbeds) in the unit has a NNE-SSW alignment and coincides with the axis of the basin's maximum subsidence during the sedimentation of the Poruba Member. The maximum aggregate thickness of the conglomerate facies is 60 m; their present-day area of occurrence is approximately 480 km 2 . The Castle Conglomerate Unit represents deposits of a low-sinuosity river system. The upper part of the multistorey channel fill is characterised by channels filled with sand bedforms and occasional bars. Palaeocurrents show a low spread of vectors, primarily to the NNW. The lower part does not crop out; it is known, therefore, only from boreholes. The presence of the unit's coarse-grained clastics inside the basin filling, which is dominated by siltstone and medium-grained sandstone, indicates a major drop in the base level, which is interpreted here as a drop in the sea level. We correlate this event with the major glacio-eustatic sea level drop at 323 Ma that can be connected with the onset of glaciation interval C2 of the Late Paleozoic Ice Age. Because the resolution of available stratigraphic and geochronologic data is not currently sufficient, an alternative explanation of the tectonic origin cannot be ruled out of the discussion and may also be valid in regard to the active Variscan foreland. •

Coal-bearing capacity of the Petřkovice Member (Ostrava Formation, Serpukhovian, Mississippian) of the Upper Silesian Basin (Czech Republic and Poland)

“…The entire paralic suc ces sion is known as the Ostrava For ma tion in the Czech Re pub lic or the Paralic Se ries in Po land. These units con sist of the Petøkovice, Hrušov, Jaklovec and Poruba members (in Po land, in for mal lithostratigraphic units) and were depos ited in the pe riod from ~330 to ~324 Ma, cov er ing al most the whole Serpukhovian Stage (Jirásek et al, 2013b and un published data of au thors). The youn ger, con ti nen tal de pos its, char ac ter ized by lack of ma rine or brack ish ho ri zons, de pos ited af ter a sig nif i cant strati graphic gap oc cur across the whole basin.…”

“…Sed i men ta tion started at the end of the purely marine siliciclastic flysch sedimention of the Hradec-Kyjovice Forma tion in the Czech Re pub lic or the Malinowice Mem ber in Poland. Zir con age dat ing of the top of the Petøkovice Mem ber gives 327.25 ± 0.15 Ma (Jirásek et al, 2013a), while the base of the unit is ap prox i mately 329.7 Ma (Jirásek et al, 2013b). The…”

Minerals formed by the weathering of sulfides in mines of the Czech part of the Upper Silesian Basin

“…This type of sedimentation is characterized by the cyclic alternation of clastic sediments with coal beds. The formation called the Ostrava Formation (Paralic Series in Poland) consists of the Petřkovice, Hrušov, Jaklovec and Poruba Members, and it was deposited in the period from~330 Ma to~320 Ma (Serpukhovian) (Jirásek et al, 2013). The younger sequences consist of terrestrial continental sediments with freshwater horizons in which volcanoclastic material is also present, and the coal beds are usually thicker (>10 m in some cases).…”

U-Pb zircon age of the Krásné Loučky tuffite: the dating of Visean flysch in the Moravo-Silesian Paleozoic Basin (Rhenohercynian Zone, Czech Republic)

“…De vo nian sed i men ta tion started with pre-flysch car bonates (Bábek et al, 2007) and con tin ued into the ma rine clastic sed i ments of the Car bon if er ous flysch (Kumpera, 1983;Dvoøák, 1994). This so-called Culm fa cies pro vides in di rect ev idence of syn-orogenic sed i men ta tion dur ing the Variscan orogeny from pos si bly as early as the Tournaisian through the whole of the Visean to the low er most Serpukhovian (Bábek et al, 2007;Jirásek et al, 2013a). The fi nal stages are marked by depo si tion of the coal-bear ing paralic and terrigenous molasse of the Up per Silesian Ba sin.…”