Structural analysis of the Rubjerg Knude Glaciotectonic Complex, Vendsyssel, Northern Denmark

• Main Author: Pedersen, Stig A. Schack
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Survey of Denmark and Greenland 2005
• Subjects: Northern Jylland; Denmark; Weichselian; glacial geology; glaciotectonics; thin-skinned thrust faulting; balanced cross-section; thrust-fault dynamics; imbricate duplexes mud diapirs; piggyback basins; Geology; QE1-996.5; Geophysics. Cosmic physics; QC801-809; Arctic; Jylland; Rubjerg Knude; Ice Sheet; Geological Survey of Denmark and Greenland Bulletin; Knude
• Online Access: https://doaj.org/article/54dcedf1a73c4fedba503d4542de7693

The Rubjerg Knude Glaciotectonic Complex is a thin-skinned thrust-fault complex that was formed during the advance of the Scandinavian Ice Sheet (30 000 – 26 000 B.P.); it is well exposed in a 6 km long coastal profile bordering the North Sea in northern Denmark. Theglaciotectonic thrust-fault deformation revealed by this cliff section has been subjected to detailed structural analysis based on photogrammetric measurement and construction of a balanced cross-section. Thirteen sections are differentiated, characterising the distal to proximal structural development of the complex. The deformation affected three stratigraphic units: the Middle Weichselian arctic marine Stortorn Formation, the mainly glaciolacustrine Lønstrup Klint Formation and the dominantly fluvial Rubjerg Knude Formation; these three formations are formally defined herein, together with the Skærumhede Group which includes the Stortorn and Lønstrup Klint Formations. The Rubjerg Knude Formation was deposited on a regional unconformity that caps the Lønstrup Klint Formation and separates pre-tectonic deposits below from syntectonic deposits above.In the distal part of the complex, the thrust-fault architecture is characterised by thin flatlying thrust sheets displaced over the footwall flat of the foreland for a distance of more than 500 m. Towards the proximal part of the complex, the dip of the thrust faults increases, and over long stretches they are over-steepened to an upright position. The lowest décollement zone is about 40 m below sea level in the proximal part of the system, and shows a systematicstep-wise change to higher levels in a distal (southwards) direction. The structural elements are ramps and flats related to hanging-wall and footwall positions. Above upper ramp-hinges,hanging-wall anticlines developed; footwall synclines are typically related to growth-fault sedimentation in syntectonic piggyback basins, represented by the Rubjerg Knude Formation. Blocks and slump-sheets constituting parts of the Lønstrup Klint Formation were ...