Evaluation of Some Devonian Standard Boundaries

Some Devonian standard boundaries, namely the Silurian-Devonian, Lochkovian-Pragian, Pragian-Emsian, Zlichovian-Dalejan, Emsian-Eifelian, and Eifelian-Givetian, are reviewed and discussed according to their identification and practicability. Whereas the lower system limit and the majority of stage boundaries possess more or less sufficient criteria for their recognition, the lower Eifelian and particularly the lower Emsian boundaries are less usable and the latter even vague. The Lower-Upper Emsian, i.e. the Zlichovian-Dalejan limit, merits an international standardization as a stage or substage boundary.