3D microstructural architecture of deformed glacigenic sediments associated with large‐scale glacitectonism, Jasmund Peninsula (NE Rügen), Germany

Abstract

The Wissower Bach Syncline on the Jasmund Peninsula (NE Germany) has been examined to understand the complicated glacitectonic environment in the southern Baltic Sea region, comprising folds and thrust faults from the Weichselian Pleniglacial. Soft-sediment thin sections from a SW-dipping thrust fault at the southwestern limb of the syncline between Cretaceous chalk (hangingwall) and Pleistocene deposits (footwall) were analysed using micromorphology and microstructural mapping. Within the diamicton bounding the fault, three different clast microfabrics were distinguished: an older, but dominant S1 fabric; a second S2 foliation orientated perpendicular to S1; and a younger subvertical S3 fabric. These fabrics developed during large-scale folding and thrusting, subsequent fabric rotation adjacent to the thrust fault accompanied by dewatering of the diamicton and extension; the latter implying late-stage reactivation and gravitational relaxation at the southwestern limb of the syncline as the ice retreated. The combination of a 3D microstructural model and the macroscale information has led to the development of a detailed model for the evolution of the Wissower Bach Syncline during glacitectonism and the localised reactivation of the associated thrusts in response to ice retreat. Moreover, this methodology provides a robust dataset on which to interpret the structural evolution of glacitectonic complexes.

Blieschow on Jasmund – geomorphology and glacigenic landforms: keys to understanding the deformation chronology of Jasmund

“…The Jasmund peninsula is situated in the NE of Germany's largest island, the isle of Rügen. It is a major example of large-scale glacitectonic folding and thrusting (Groth, 2003;Müller and Obst, 2006;Ludwig, 2011;Gehrmann et al, 2017). The structural framework shows a glacitectonic complex, which was probably formed after the Last Glacial Maximum (MIS 2) in response to a readvance of the Scandinavian Ice Sheet (SIS) during the Pomeranian phase (W2, 17.6 ka BP) (Müller and Obst, 2006;Litt et al, 2007;Gehrmann and Harding, 2018).…”

“…The lakes are potential karst phenomena, kettle holes, or both (e.g. Paulson, 2001;Groth, 2003). The effect of these depressions is especially noticeable at the boundary between the southern and the northern ridge set and at the area SE of the highest elevation, Piekberg (160.9 m a.s.l.…”

“…2). Groth (2003) proposed a complex segmentation of the tectonic complex into five structural units, which are assigned to four developmental phases (Fig. 2).…”

The Quaternary geology of the North Sea basin

“…A microscale approach to the analysis of glacially deformed sediments and bedrock is provided by the paper by Gehrmann et al (2017). These authors examine the complex microscale deformation fabrics developed with a prominent thrust fault deforming the south-western limb of the Wissower Bach Syncline on the Jasmund Peninsula on the Baltic coast of north-east Germany (5 on Fig.…”

Micromorphology of diamicton affected by iceberg-keel scouring, Scoresby Sund, East Greenland

“…7-9), including human-made materials such as concrete and mortar (Menzies et al, 2010;van der Meer and Menzies, 2011 -and references within), is undeniable. In addition, quantification of microstructures (Carr and Goddard, 2008;Menzies and Whiteman, 2009;Patel, 2011;van der Meer and Menzies, 2011;Linch and van der Meer, 2013;Neudorf et al, 2013;Lea and Palmer, 2014;Narloch et al, 2015) and new methods in 'microstructural mapping' (Phillips et al, 2011;Gehrmann et al, 2016), are developing with promising results. Finally, in combination with thin sections, 3D microtomography studies of microstructures (Kilfeather and van der Meer, 2008;Tarplee et al, 2011;Bendle et al, 2015;Groves, in prep) and development of the Metripol microscope system to automatically measure and record birefringence (Linch and van der Meer, 2013;Hiemstra and Carr, in prep) should be even more rewarding.…”