Floras of clastic and peat-forming Pennsylvanian wetlands: are they different? A case study from the Upper Radnice Coal (late Duckmantian), Kladno Coalfield, Czech Republic

Resumen

Floras of two ecologically and taphonomically different fossiliferous horizons associated with the late Duckmantian Upper Radnice Coal in the Kladno Coalfield are compared. Observations made in coal mines suggest that the Velká opuka bears autochthonous in situ preserved peat-forming vegetation, whereas the Mydlák ins a lacustrine sediment that contains mostly drifted allochthonous and locally parautochthonous plant associations derived from coastal mostly clastic wetlands. Material from museum collections and our own field data show that floras of both fossiliferous horizons consist of representatives of the same families and genera but differ in their proportions and to a large part in species compositions. This is demonstrated by only 40 % overlap of 89 plant species identified in both horizons. Flora of the Velká opuka is dominated by lycopsids, either by arborescent lepidodendrids or by the sub-arborescent genus Omphalophloios. Co-dominant are sphenopsids and locally common are ferns and cordaitaleans. The Mydlák flora is more diverse and dominates by pteridosperms, whereas the proportion of lycopsids is lower and their composition partly different. Taxa abundant in the Velká opuka and nearly absent in the Mydlák include Omphalophloios feistmantelii, Lepidodendron longifolium and L. ophiurus. Abundant in the Mydlák and mostly missing in the Velká opuka are Laveineopteris tenuifolia, L. bohemica, Sphenopteris spiniformis, Eusphenopteris nummularia, Lepidodendron aculeatum and L. mannebachense. Prevalence of pteridosperms in clastic wetland floras of the Mydlák is in agreement with existing observations