Biostratigraphy of the Furongian (upper Cambrian) Alum Shale Formation at Degerhamn, Öland, Sweden

Abstract

The Furongian (upper Cambrian) Alum Shale at Degerhamn, southern Öland, Sweden, has been systematically sampled for macrofossils. Two sections were investigated, one in a large abandoned Alum Shale quarry and one in a nearby road section. The 6.25 m thick succession comprises the Olenus, Parabolina, Leptoplastus, Protopeltura and Peltura superzones. The Olenus gibbosus, Olenus truncatus, Olenus attenuatus, Parabolina spinulosa, Leptoplastus crassicornis–Leptoplastus angustatus, Sphaerophthalmus flagellifer, Ctenopyge tumida, Ctenopyge linnarssoni and Parabolina lobata zones have been identified in addition to the informal Olenus rotundatus and Sphaerophthalmus modestus zones. The informal Olenus rotundatus biozone is assumed corresponding in age to the Olenus scanicus Chronozone and the informal Sphaerophthalmus modestus biozone is assumed corresponding in age to the Ctenopyge (Mesoctenopyge) similis Chronozone; S. modestus has not previously been reported from Öland. The uppermost parts of the O. gibbosus, O. truncatus, P. spinulosa and C. tumida zones are reworked. Peltura minor may range into the basal C. linnarssoni Zone; alternatively it is also reworked. Ctenopyge (Ctenopyge) directa, Triangulopyge humilis, Triangulopyge major and Ctenopyge (Ctenopyge) fletcheri are here reported from the C. linnarssoni Zone; none of these species have previously been described from Öland. Furthermore, this zone yielded indeterminable fragments of ‘exotic’ non-olenid trilobites. The uppermost level preserved at Degerhamn is the Parabolina lobata Zone where common Peltura scarabaeoides westergaardi is recorded for the first time from this locality.

Keywords:

• Cambrian
• Furongian
• Alum Shale
• biostratigraphy
• trilobites
• Öland
• Sweden
• Scandinavia

Acknowledgements

We would like to thank Cementa AB for access and permission to sample in the quarry. We also thank Timothy Topper for improving the written English. We are grateful for comments on the manuscript by editor Christian Skovsted and referees Anna Żylińska and Jorge Esteve, which improved the final version. This paper is part of a PhD study by BWR. Sampling work was undertaken by all three authors. Determination of the material and writing the paper was undertaken by BWR under supervision of ATN; all authors contributed to editing and refinement of the paper.