The Frasnian Upper Kellwasser event and a lower Famennian stratigraphic gap in Calabria (southern Italy)

The identification of three late Frasnian conodont biozones (MN 11–12 and 13, as defined in the Montagne Noire, France) and of several Famennian conodont biozones (Early, Late, and Latest marginifera, and Late postera zones of the standard zonation) in the Palaeozoic record of the Stilo Unit (southern Calabria, southern Italy) indicates the existence of a stratigraphic gap during the early Famennian (triangularis, crepida and rhomboidea zones). In the studied section, this gap occurs above a thin, black, pelitic horizon that appears just on top of the uppermost sample dated as late Frasnian. The conodonts obtained from the beds underlying this black horizon are all highly pyritized, unlike the few Famennian conodonts found in the limestone bed immediately overlying this horizon, which is richer in organic matter. Both stratigraphic features (the black pelitic horizon and the gap in the conodont record) are interpreted as being related to the Upper Kellwasser Anoxic Event. These new data indicate that this important biotic crisis was also evident in the pelagic environments of the Palaeozoic succession of the Stilo Unit at the very end of the Frasnian.