Chitinozoan biostratigraphy of the Upper Ordovician D. clingani and P. linearis graptolite biozones on the Island of Bornholm, Denmark

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The last decade saw a revival of the debate on the exact stratigraphical position of the Upper Ordovician P. linearis graptolite biozone. Chitinozoan biostratigraphy can be useful to help address this question. Here, we provide a high-resolution chitinozoan biostratigraphy through the Dicellograptus Shale Formation at Vasagård on the Island of Bornholm (Denmark), which recently also was subject to a thorough revision of its graptolite fauna, representing the Dicellograptus folicaceus, Dicranograptus clingani and Pleurograptus linearis biozones. We have identified close to 9000 individual chitinozoan vesicles from 26 samples through the upper c. 9m of the Dicellograptus Shale Formation. The Spinachitina cervicornis, Fungochitina spinifera and Tanuchitina bergstroemi chitinozoan biozones are identified, and their boundaries carefully calibrated against the revised graptolite biostratigraphy. A correlation with the chitinozoan biozonation in the British Cautley district, which has a predominantly Baltoscandian, mid-latitude signature and is well-correlated with the graptolite and shelly fauna biozones described from the historical type region, is established.