Baltica: A mid Ordovician diversity hotspot

Abstract

A detailed bed-by-bed study of late Early—early Mid Ordovician Eastern Baltic brachiopods has been used to construct an α-diversity curve through the upper Billingen—Kunda regional stages (Arenig–early Llanvirn). Surprisingly the main peak in diversity does not occur until the Volkhov–Kunda boundary, whereas global data indicate a peak in the mid Volkhov. On Baltica especially the orthidines show a time lag compared with the global data. This study is based more than 30 000 specimens collected from argillaceous limestones with interfingering marls at eight different localities in the East Baltic area.

Keywords:

• Early–Mid Ordovician
• brachiopods
• α-diversity
• Baltic

Acknowledgements

We thank Andrei Dronov and Peter Fedorov, both St. Petersburg State University, for logistic help during field-work. Further, they are thanked for their extensive aid with targeting and measuring the bed-by-bed lithology in the Volkhov and Kunda sections. Thanks are also due to Arne Thorshøj Nielsen and Kristian Grube Jakobsen, both University of Copenhagen, and Thomas Hansen, Natural History Museum, University of Oslo, for companionship and enlightening discussions both during fieldwork and subsequent laboratory work. Furthermore DATH and JH would like to thank the Carlsberg Foundation for financial support. Finally, we would like to thank Matthew A. Parkes and Leonid E. Popov, for their very constructive reviews. This paper is a contribution to IGCP 503 ‘Ordovician palaeogeography and palaeoclimate’.