Palaeofloristics of Middle Pennsylvanian medullosaleans in Variscan Euramerica

Abstract

Medullosaleans were an abundant and widely distributed group of seed-plants in the Moscovian palaeotropical wetland forests (‘coal forests’). Using mainly a combination of cluster analysis and Detrended Correspondence Analysis, the distribution of medullosalean species has revealed five distinct palaeofloristic units within Variscan Euramerica. Two palaeofloristic units characterise lowland paralic areas: the Rhine Palaeoprovince found in parts of the Variscan Foreland and the Donets Basin; and the Iberia Palaeoprovince found in northern Spain and Portugal. The Silesia Palaeoprovince represents somewhat lower-diversity medullosalean macrofloras, mainly associated with more marginal areas of the Variscan Foreland. Intramontane basins are characterised by two palaeofloristic units that are quite distinct from those of the more lowland areas, and to a lesser-extent different from each other: the Saar-Lorraine and Central Bohemia Palaeoprovinces (the latter found in the Intrasudetic Basin and Zwickau, as well as Central Bohemia). Except for the appearance of the Iberia Palaeoprovince in late Moscovian times, the basic palaeofloristic structure of Variscan Euramerica remained essentially unchanged through the Moscovian Age. Those palaeofloristic changes that did take place mainly reflect localised increased influxes of sediment or changes in water-table. The palaeofloristic data provides no evidence of regional-scale environmental changes taking place, such as marked climate-change, regional uplift, or major palaeolatitudinal change.