Caradocian and ashgillian chitinozoan biostratigraphy of the Oslo‐asker and ringerike districts, Oslo region, Norway

Caradocian and Ashgillian chitinozoans from eleven localities in the Oslo‐Asker and Ringerike districts (Oslo Region, Norway) are discussed. 32 species from 13 genera are encountered. The chitinozoan fauna displays pronounced affinities to those in Sweden and Estonia. The local stratigraphie ranges of the chitinozoans are established and compared with the Ordovician chitinozoan standard zonation of Balto‐scandia. Three hiatuses occur, viz. between the middle Keila Stage (Nakk‐holmen Formation) and the Oandu Stage (Solvang Formation), between the Oandu Stage and the Nabala Stage (Venst⊘p Formation), and in the upper Porkuni Stage (upper Lang⊘yene and Langåra Formations).