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Lateglacial neotectonics of the Osning Thrust in northern Germany

Christian Brandes1, Jutta Winsemann1, Julia Roskosch1, Janine Meinsen1, David Tanner2, Manfred Frechen2, Holger Steffen3, Patrick Wu3
1 Institut für Geologie, Leibniz Universität Hannover
2 Leibniz Institute for Applied Geophysics
3 Department of Geoscience, University of Calgary

Key Note 3.1 in Endogene Prozesse (Neotektonik und Vulkanismus)

19.09.2012, 08:30-09:00, H6

 

The Osning Thrust is a 115 km long complex thrust system that represents a key element of the Central European intraplate tectonics. It has been under scientific scrutiny for almost a century. The Osning Thrust underwent a polyphase tectonic evolution in the Mesozoic, which ranged from extensional movements in the Jurassic to reverse faulting and thrusting during inversion in the Late Cretaceous. New outcrop data give evidence for Lateglacial tectonic activity along the Osning Thrust (Brandes et al., 2012). In the vicinity of the fault trace, several complex metre-scale faults and related fold structures are developed in Pleniglacial to Lateglacial alluvial-aeolian sediments of the Upper Senne. Optically-stimulated luminescence (OSL) ages of the fault-related growth strata (Roskosch et al., in press) imply that the faults were active between 16-13 ka. Independent numerical simulations of the deglaciation seismicity also point to the probability of seismic events with a thrust mechanism in the study area between 15.5-12.3 ka. Numerous soft sediment deformation structures in the Pleniglacial alluvial-aeolian sediments imply that these Lateglacial movements on the Osning Thrust caused earthquakes with a significant magnitude (Brandes et al., 2012; Brandes & Winsemann in review). The observed soft-sediment deformation structures cover a wide range of different types and can be grouped into six main categories, a) ball and pillow structures, b) flame structures, c) dish structures, d) flower- to antler-like dewatering structures, e) dykes and sills, and f) sand volcanoes. Especially sand volcanoes and clastic dykes are characteristic for seismic events indicating explosive water escape. In the autumn of 1612, an earthquake took place in this area that caused distinct damage (Vogt & Grünthal, 1994).

 

The Lateglacial seismicity and the 17th century earthquake activity point to repeated movements along the Osning Thrust. This is a novelty in northern Germany and sheds new light on the seismicity of the area. The distribution of soft sediment deformation structures, together with the location of the 1612 earthquake, implies that seismic activity is concentrated in the Oerlinghausen area, SE of Bielefeld.

 

 

References

 

Brandes, C., Winsemann, J., Roskosch, J, Meinsen, J., Tanner, D.C., Frechen, M., Steffen, H. & Wu, P. (2012): Activity of the Osning thrust during the Lateglacial: ice-sheet and lithosphere interactions. Quaternary Science Reviews, 38, 49-62.

Brandes, C. & Winsemann, J. (in review): Soft sediment deformation structures in NW Germany caused by Lateglacial seismicity.

Roskosch, J., Tsukamoto, S., Meinsen, J., Frechen, M. & Winsemann, J. (in press): Luminescence dating of an Upper Pleistocene alluvial fan and aeolian sand-sheet complex: The Senne in the Münsterland Embayment, NW Germany. Quaternary Geochronology.

Vogt, J. & Grünthal, G. (1994): Die Erdbebenfolge vom Herbst 1612 im Raum Bielefeld. Geowissenschaften 12, 236-240.



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Letzte Änderung 13.07.2012