Terminal Ordovician stratigraphy of the Siljan district, Sweden

The late Katian (Pirgu) age of Holorhynchus in the Siljan district is clear and its co-occurrence with the chitinozoan Belonechitina gamachiana in Estonia supports a Katian age for this zone. The base of the Ozarkodina hassi Biozone may occur within units B–C of the Upper Boda Member and in the upper part of the Loka Formation and most likely is correlated with the M. persculptus Biozone. The Hirnantia – Dalmanitina faunas reported from the lowermost part of the Loka Formation and units B–D of the Upper Boda Member seem to range through all the Hirnantian, but detailed morphological studies allow to distinguish an older ( = extraordinarius ) and a younger ( = persculptus ) fauna.