Geological mapping of Mezozoic deposits along the eastern margin of the Rønne Graben, offshore Bornholm, Denmark

Detailed shallow seismic investigations of the eastern Ronne Graben, offshore Bornholm have resulted in the recognition of characteristic seismic facies which are subdivided into seismostratigraphic units. The seismostratigraphic units are correlated with known lithostratigraphic units on Bornholm, thus permitting detailed geological mapping along the eastern margin of the Ronne Graben. In contrast to the sequence on Bornholm, it appears that there was continuous sedimentation from the Ronne Formation (Lower Jurassic) to the Rabekke Formation (Lower Cretaceous), while the Robbedale and Jydegard Formations (Lower Cretaceous) are absent in the Ronne Graben. In the area mapped in detail the youngest Pre-Quaternary sediments are the Arnager Greensand, the Arnager Limestone and Bavnodde Greensand Formations (Upper Cretaceous). All the Mesozoic deposits were affected by transpressional tectonic activity during the Upper Cretaceous-Lower Tertiary. The structural relationships show a characteristic pattern consisting of the main fault on the eastern side of the Ronne Graben and a system of en echelon reverse faults. This pattern probably formed as a result of northeast-southwest wrench movements in a compressional dextral strike slip system. -Authors