Early to early Middle Ordovician conodont biostratigraphy of the Gillberga quarry, northern Öland, Sweden

The Gillberga quarry in northern Öland provides a c. 16 m thick sequence through middle Volkhov to upper Kunda (mid-Arenig to early Llanvirn) beds. The section has been sampled for conodonts and its temporal faunal changes have been investigated on the basis of fiftynine samples yielding over 300,000 conodont elements. Conodont zones earlier recognized in south-central Sweden and ranging from the middle of the Baltoniodus navis Zone to the middle or upper part of the Microzarkodina ozarkodella Subzone of the Eoplacognathus pseudoplanus Zone were encountered at Gillberga. The temporal changes in relative frequencies of the most abundant conodont genera were calculated throughout the sequence and are presented in frequency diagrams. A new species, Microzarkodina bella, from the lower Kunda has been identified and is described.