Die zeitgleichen floren des europäischen oberkarbons und die mesophile flora des ostrau-karwiner stein- kohlenreviers

Abstract

The recently published geobotanical units of the European Upper Carboniferous flora are compared (p.248) and author's geobotanical classification completed ( Havlena, 1970). In the sphere of deposition the basin floral formation occurs including the hygrophilous and the mesophilous flora. The first covers the most humid environment of the coal basin and displays three fundamental associations (Lepidophyta, Articulata and Pteridophylla). The mesophilous flora is believed to represent the floral cover either of those places in the coal basin which have not been favourable for the hygrophilous flora or of the hills surrounding the basin. In the sphere of denudation the extra-basin floral formation extends including the extra-basin mesophilous flora (= denudo-mesophilous flora) and the extra-basin xerophilous flora (= denudo-xerophilous flora). The lower part of the cyclically arranged Ostrava Formation (Upper Silesian Basin) that represents the E 1-Zone of the Namurian A displays apart from a rich hygrophilous flora numerous remains of a mesophilous flora. The Ostrava hygrophilous flora carries a lot of index fossil plants evidencing very precisely its Namurian A age. The Ostrava mesophilous flora listed on p. 257, however, displays the Lower Carboniferous character; its index species are in particular Rhodea moravica ( Ettingshausen) Stur, Sphenopteridium bifidum ( Lindley et Hutton) Benson, Sphenocyclopteridium bertrandii Stockmans et Willière and Aphlebia ostraviensis Gothan. The predominance of the Rhodea representatives indicates the close similarity of the assemblage examined to the Namurian A flora of Belgium. The geological coherence of the Upper Silesian Basin with the North Variscan foredeep seems herewith to be well ascertained. The mesophilous flora is found always as drifted fragments (Plate I, 1–5; Plate II, 2, 3, 6) occurring exclusively in the highest siltstone layers of each cyclotheme. These rocks are supposed to be deposited in a shallow lagoon. No mesophilous remains, however, have been hitherto ascertained among the hygrophilous compressions of the non-marine roof claystones. Examining the areal distribution of the size-classified fragments of the mesophilous flora the northern direction of the Namurian A drift at Ostrava ( Unrug, 1967; Jansa, 1967) has been repeatedly confirmed. The largest fragments were deposited in a calm area of the above lagoon. To this calm place the mesophilous fragments were drifted from the borden of the Upper Silesian Basin exposed in the southwestern surroundings of the Ostrava-Karviná Coal District. The calm area strikingly coincides with the lowermost sand-content line given by Zeman-Kupka (1959) for the sequence examined (Fig.4).