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The Asturian and Cantabrian floral assemblages with Cordaites from the Plzeň Basin (Czech Republic)

Šimůnek Z.

Studia Geologica Polonica

2008

Vol. 129

51-80

The macrofloras of the Nýřany Member (late Asturian - early Cantabrian age) were studied at five localities and two boreholes in the Plzeň Basin (Western Bohemia). The floras were mostly dominated by Cordaites, and seven species were recognised based mainly on cuticular evidence. Cordaites dobranensis Šimůnek was the most common species and occurred in most of the Asturian-age localities. In addition, an outcrop near Heřmanova Huď yielded C. blazkovicensis Šimůnek, C. wilkischensis Šimůnek and C. pilsensis Šimůnek; and borehole Krašovice Kš 1 yielded C. krasovicensis Šimůnek and C. touskovensis Šimůnek. Cordaites radcicensis nov. sp. was only found in the Cantabrian part of the succession, at the Radčice locality, and shows characters suggesting adaptation to somewhat drier conditions, namely thick cutinisation and proximally oriented projection of the anticlinal cell walls. The most diversified assemblage with 29 species was found at the Dobřany locality, but most other localities yielded only 12 to 18 species. The species-spectrum of individual localities varied according to type of locality, sedimentology and method of collecting. In most localities, cordai- taleans made up 40 to 67% of the macroflora, the only notable exception being the Krimich II mine at Tlučná that yielded only 5% cordaitaleans. The next important plant group was the sphenopsids, which usually comprised about 30% of the macrofloras, with the exception of Heřmanova Huď locality where there were only 3% sphenopsids. The proportion of fern remains varied between localities from 8 to 35%. Lycopsids were usually very rare, except at the Heřmanova Huď locality where 30% of the flora consisted of allochthonous lycopsid fragments. Pteridosperms were very rare and never exceeded 10% of the macroflora. The Westphalian rain forest was not monotonous, but was diversified into several floral assemblages. My work supports the conclusion of previous workers in the area (Šetlík, 1980), that the five most common species in the Nýřany Member of the Plzeň Basin are Pecopteris polypodioides (Presl in Sternberg) Němejc, Sphenophyllum emarginatum (Brongniart) Brongniart, Pecopteris unita, Dicksonites plukenetii and Annularia stellata (Schlotheim) Wood.