Graptolite biostratigraphy of the lower Silurian of the Sommerodde-1 core, Bornholm, Denmark

Abstract

The Sommerodde-1 core provides a continuous record through the subsurface of southern Bornholm from the Wenlock Series (Silurian) through to the Lower Cambrian. The Silurian graptolite biostratigraphy of the core is described. For the Rhuddanian and Aeronian (lower and middle Llandovery), the succession and thickness of biozones are very similar to those in the Øleå rivulet nearby. For the upper Llandovery, the lower Telychian Spirograptus guerichi and Sp. turriculatus biozones are significantly thicker in the core than in Øleå, whilst the uppermost Telychian (represented by more than 30 m of strata in nearby sections) is largely absent in the core. This is likely to be a reflection of synsedimentary faulting influencing deposition. It has previously been suggested that much of the Sheinwoodian is missing on Bornholm; this is not the case. The Sheinwoodian is represented by an apparently continuous sequence, at least 31 m thick, in the Sommerodde-1 core.