In the southern Bergisches Land the Upper Devonian sequence (Frasnian and Lower Famennian) consists mainly of shales, marls and bituminous limestones together with an intercalated biostrome. The acritarch communities identified from these rocks are essentially characterised by members of the Micrhystridium-Veryhachium group.
Sections through the vesicle of Micrhystridium vulgare Stockm̂anns & Willière reveal a simple, dense wall structure, but in the living cyst an exchange of gases was achieved through fine axial canals in its slender spines.
Abundance and diversity of the acritarchs increased off-reef and reflect both the palaeogeography and the depth.
The stable environments on the open marine shelf favoured phytoplanktonic life and also the formation of source rocks for hydrocarbons.
- © 1984 The Micropalaeontological Society