Inversion tectonics at the northern margin of the North German Basin: Cretaceous to recent reactivation of Triassic normal faults (iTec-NGB)
Geophysics
Final Report Abstract
The reactivation of faults and possible impact on barrier integrity marks a critical aspect for investigations on subsurface usage capabilities. Glacial isostatic adjustments, originating from repeated Quaternary glaciation of Northern Europe, cause tectonic stresses on preexisting fault systems and structural elements of the North German and Norwegian Danish Basins. Notably, our current understanding of the dynamics and scales of glacially induced fault reactivation is rather limited. In course of this project, a high-resolution 2D seismic dataset acquired offshore northeastern Langeland Island allowed the investigation of a fault and graben system termed the Langeland Fault System. Seismo-stratigraphic interpretation of reflection seismic data in combination with diffraction imaging reveal the spatial character of the Langeland Fault System along an elevated basement block of the Ringkøbing-Fyn High. In combination with sediment echosounder data, the dataset helps visualise the continuation of deep-rooted faults up to the seafloor. Initial Mesozoic faulting occurred during the Triassic. Late Cretaceous inversion reactivated a basement fault flanking the southern border of the elevated basement block of the Ringkøbing-Fyn High while inversion is absent in the Langeland Fault System. Here, normal faulting occurred in the Maastrichtian-Danian. We show that a glacial or post-glacial fault reactivation occurred within the Langeland Fault System as evident by the propagation of the faults from the deeper subsurface up to the seafloor, dissecting glacial and post-glacial successions. Our findings suggest that the Langeland Fault System was reactivated over a length scale of a minimum of 8.5 km. We discuss the causes for this Quaternary fault reactivations in the context of glacially induced faulting and the presentday stress field. The combination of imaging techniques with different penetration depths and vertical resolution used in this study is rarely realized on the hinterland. It can therefore be speculated that many more inherited, deep-rooted faults were reactivated in Pleistocene glaciated regions.
Publications
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The Langeland Fault System unravelled: Quaternary fault reactivation along an elevated basement block between the North German and Norwegian–Danish basins. Boreas, 52(3), 381-401.
Ahlrichs, Niklas; Hübscher, Christian; Andersen, Theis Raaschou; Preine, Jonas; Bogner, Laura & Schäfer, Wiebke
