Abstract
A 558 m long, complete section of the Lower Palaeozoic succession preserved onshore southern Bornholm has been compiled from five fully cored scientific wells, carried out between 2005 and 2012. The scientific programme included coring and geophysical logging of the five scientific wells that yielded a total of c. 750 m of partially overlapping cores as well as re-logging of water wells and acquisition of shallow seismic data. The last well drilled, the Sommerodde-1, cored the youngest preserved Silurian strata on Bornholm including strata not exposed in outcrops. The well penetrated 168.1 m of Silurian shales, 42.7 m of Upper Ordovician shales and 27.9 m of Alum Shale before it terminated at a depth of 250.3 m in the Lower Cambrian Norretorp Member of the Læså Formation. Th e Sommerodde-1 well documents that the Lower Silurian Cyrtograptus shale is at least 91.7 m thick and that the Rastrites shale is 76.4 m thick. The complete Lower Cambrian succession has previously been covered by the 316.0 m deep Borggård-1 well that terminated in basement rocks (Nielsen et al. 2006).
Highlights
A 558 m long, complete section of the Lower Palaeozoic succession preserved onshore southern Bornholm has been compiled from five fully cored scientific wells, carried out between 2005 and 2012
The Lower Palaeozoic is very thick in Denmark, locally more than 4 km thick, and the deposition marks the transition from passive margin to a rapidly subsiding foreland basin developed in front of the Caledonian orogen towards the south and west (Lassen & Thybo 2012)
The well was drilled as close as technically possible to the Sommerodde beach locality described by Bjerreskov & Jørgensen (1983) where the youngest Silurian strata onshore Bornholm are exposed at low tide
Summary
The Lower Palaeozoic is very thick in Denmark, locally more than 4 km thick, and the deposition marks the transition from passive margin to a rapidly subsiding foreland basin developed in front of the Caledonian orogen towards the south and west (Lassen & Thybo 2012). Contemporaneous strata throughout most of central and western Denmark are deeply buried and have only been reached by a few deep exploration wells (Fig. 1), and the succession is rather poorly known. In Slagelse-1 and Terne-1 in Kattegat have the Palaeozoic shales been fully penetrated whereas only the topmost parts of the Silurian shales were reached by the Rønde-1, Nøvling-1, Pernille-1 and Stina-1 wells (Fig. 1). A new shale gas exploration well, Vendsyssel-1, is planned to be drilled in 2015 and is expected to penetrate the entire Lower Palaeozoic shale sequence in northern Jylland (Fig. 1). The well was drilled as close as technically possible to the Sommerodde beach locality described by Bjerreskov & Jørgensen (1983) where the youngest Silurian strata onshore Bornholm are exposed at low tide.
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