Flora from the Líně Formation (Czech Republic) as an example of floristic dynamics around the Carboniferous/Permian boundary
Abstract
Characterised is a climatic signal and biotic response recorded in the sediments of the latest Pennsylvanian Líně Formation, the youngest unit in the continental basins of the central and western Czech Republic. It consists dominantly of fluvial red beds intercalated with several tens of meters of thick gray-colored strata, locally bearing poorly developed coals.
The significant part of these gray strata was deposited in lacustrine environments. Lithological climatic indicators (e.g. calcic vertisols, freshwater limestones and cherts, silicification of stems, etc.) suggest seasonal climate with variations in degree of seasonality throughout the formation.
Floristic and palynological records indicate presence of at least 40 plant taxa. Data from boreholes suggest the existence of two ecologically different and probably spatially separated plant assemblages representing wetland and dryland floras, the former preserved usually as coalified plant compressions in gray-colored to variegated mudstones or lacustrine limestones and the latter preserved as plant impressions in red mudstones or silicified stems in coarse-grained channel facies.
The wetland assemblage is dominated by calamites and tree and herbaceous ferns with subdominant medullosan and callystophytalean pteridosperms and rare herbaceous and arborescent lycopsids. Some palynomorph assemblages from thin coals intercalated with nearshore/offshore lacustrine strata are dominated by the miospore genus Lycospora.
The dryland assemblage occurs in red mudstones and is composed of conifers and cordaitalean impressions; silicified stems of these plants occur in coarsegrained fluvial sediments associated with the red mudstones. Rare conifers and cordaitaleans, as well as their spores, occur in gray lacustrine strata, however, suggesting occasional coexistence of both assemblages, possibly within the basin lowland.