Correlation of the Scandinavian Middle Ordovician with the graptolite succession

Abstract

A correlation of the Scandinavian Middle Ordovician shelly and graptolitic facies has been made based on new graptolite material and reinvestigation of most of the previous graptolite material of stratigraphic importance. The Crassicauda limestone is shown to be the equivalent of the subzone of Climacograptus haddingi instead of the zone of Nemagraptus gracilis as previously thought. Thus both the Schrocteri and Crassicauda limestones correspond to the Llandeilian. The main part of the Ludibundus limestone falls within the zone of Nemagraptus gracilis. It is impossible at present owing to insufficient material to use any graptolite zones for correlation between N. gracilis and D. clingani beds.