The Lower Ordovician Tøyen Shale succession in the Fågelsång-3 drill core, Scania, Sweden

Abstract

The Ordovician Tøyen Shale Formation of the recently retrieved Fågelsång-3 drill core provides some important information on the graptolite biostratigraphy of the unit and its completeness in the region. The drill core reached downwards into the Kiaerograptus supremus Biozone of late Tremadocian age. Above a major fault zone, faunas with a number of specimens referred to Pseudophyllograptus densus are indicative of a late Dapingian age. Rare specimens of Azygograptus sp. also help constrain the age. The presence of Arienigraptus zhejiangensis indicates that the base of the Darriwilian Komstad Limestone Formation is of Levisograptus austrodentatus Biozone age. Specimens of Tetragraptus cor and Levisograptus sinicus in a shale bed within the lower part of the Komstad Limestone Formation can be referred to the upper subzone of the L. austrodentatus Biozone, the Levisograptus sinicus Subzone. This fauna represents the youngest graptolite fauna beneath the massive Komstad Limestone Formation. The Tøyen Shale Formation can be shown to be highly incomplete in Scania, possibly due to post-depositional tectonic deformation and faulting.

Keywords:

• Graptolites
• biostratigraphy
• Lower Ordovician
• Middle Ordovician
• Scania
• Sweden

Acknowledgements

We acknowledge grants from the Gyllenstierna Krapperup’s Foundation for defraying the cost of the Fågelsång-3 drilling and supporting our research (grants KR2012-0079, 2014-0100 and 2017-0108 to Ahlberg). Fisnik Balija kindly assisted in the drawing of Fig. 1. We also thank two anonymous reviewers for critically reading and improving the manuscript. This paper is a contribution to IGCP project 653 – “The onset of the Great Ordovician Biodiversification Event”.