Devonian and early carboniferous coals and the evolution of wetlands

The rise of forests in the Mid and Late Devonian has attracted much attention as potential drivers of the Earth System. In this context it is important to understand what groups contribute to the first wetlands found at the Devonian palaeoequator. A time series of Devonian coals shows that the palaeoequatorial Mid and Late Devonian humic (vitrinite rich) coals are dominated by the lycopod microspore Cymbosporites and megaspore Verrucisporites that can be confidently associated as the spores from Protolepidodendropsis . This plant has successfully colonised and probably created the wetland coal environment by the ability to shallow root and hence anchor the trees above the anaerobic layer. The progymnosperm Archaeopteris is abundant from its spores in Devonian palaeoequatorial sediments but plays no role in these coal forming wetlands. More rigorous age dating shows that there is some evidence for a Tournaisian coal gap.