Seismic interpretation and structural restoration of the Heligoland glaciotectonic thrust-fault complex: Implications for multiple deformation during (pre-)Elsterian to Warthian ice advances into the southern North Sea Basin

• Main Authors: Winsemann, Jutta, Koopmann, Hannes, Tanner, David C., Lutz, Rüdiger, Lang, Jörg, Brandes, Christian, Gaedicke, Christoph
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amsterdam [u.a.] : Elsevier 2020
• Subjects: Glaciotectonics; North Sea; Pre-Elsterian ice-margin; Retrodeformation; Tunnel valley; Warthian ice-margin; 550; Ice; permafrost
• Online Access: https://oa.tib.eu/renate/handle/123456789/7743; https://doi.org/10.34657/6790

Despite a long history of research, the locations of former ice-margins in the North Sea Basin are still uncertain. In this study, we present new palaeogeographic reconstructions of (pre-) Elsterian and Warthian ice-margins in the southeastern North Sea Basin, which were previously unknown. The reconstructions are based on the integration of palaeo-ice flow data derived from glaciotectonic thrusts, tunnel valleys and mega-scale glacial lineations. We focus on a huge glaciotectonic thrust complex located about 10 km north of Heligoland and 50 km west of the North Frisian coast of Schleswig-Holstein (Northern Germany). Multi-channel high-resolution 2D seismic reflection data show a thrust-fault complex in the upper 300 ms TWT (ca. 240 m) of seismic data. This thrust-fault complex consists of mainly Neogene delta sediments, covers an area of 350 km2, and forms part of a large belt of glaciotectonic complexes that stretches from offshore Denmark via northern Germany to Poland. The deformation front of the Heligoland glaciotectonic complex trends approximately NNE-SSW. The total length of the glaciotectonic thrust complex is approximately 15 km. The thrust faults share a common detachment surface, located at a depth of 250–300 ms (TWT) (200–240 m) below sea level. The detachment surface most probably formed at a pronounced rheological boundary between Upper Miocene fine-grained pro-delta deposits and coarser-grained delta-front deposits, although we cannot rule out that deep permafrost in the glacier foreland played a role for the location of this detachment surface. Restored cross-sections reveal the shortening of the complex along the detachment to have been on average 23% (ranging from ca. 16%–50%). The determined ice movement direction from east-southeast to southeast suggests deformation by an ice advance from the Baltic region. The chronospatial relationship of the thrust-fault complex and adjacent northwest-southeast to northeast-southwest trending Elsterian tunnel valleys implies a pre-Elsterian (MIS 16?) age ...