TY - JOUR

T1 - Seismic interpretation and structural restoration of the Heligoland glaciotectonic thrust-fault complex

T2 - Implications for multiple deformation during (pre-)Elsterian to Warthian ice advances into the southern North Sea Basin

AU - Winsemann, Jutta

AU - Koopmann, Hannes

AU - Tanner, David C.

AU - Lutz, Rüdiger

AU - Lang, Jörg

AU - Brandes, Christian

AU - Gaedicke, Christoph

N1 - Funding Information: The research presented in this paper was part of the Diploma Thesis of Hannes Koopmann carried out at the Federal Institute for Geosciences and Natural Resources (BGR) and Leibniz Universität Hannover. We thank crew members and participants of cruises BGR03, BGR04 and HE242, especially the party chiefs H. Kudraβ, S. Neben, L. Reinhardt and M. Wiedicke. We further thank reviewers, J. Lee and R. Waller as well as editor C. O'Cofaigh for insightful comments, which helped to improve this manuscript. F.S. Busschers, A. Grube, P. Sandersen and H.-J. Stephan are thanked for discussion. The authors acknowledge the use of the MOVE Software Suite granted by Petroleum Experts Limited, which we used to restore the cross-sections.

PY - 2020/1/1

Y1 - 2020/1/1

N2 - 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 of the glaciotectonic complex. However, the age of these Elsterian tunnel valleys is poorly constrained and the glaciotectonic complex of Heligoland may also have been formed during an early Elsterian ice advance into the southeastern North Sea Basin. The glaciotectonic complex underwent further shortening and the Elsterian tunnel-valley fills that were incised into the glaciotectonic complex were partly deformed during the Saalian Drenthe and Warthe (1) ice advances.

AB - 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 of the glaciotectonic complex. However, the age of these Elsterian tunnel valleys is poorly constrained and the glaciotectonic complex of Heligoland may also have been formed during an early Elsterian ice advance into the southeastern North Sea Basin. The glaciotectonic complex underwent further shortening and the Elsterian tunnel-valley fills that were incised into the glaciotectonic complex were partly deformed during the Saalian Drenthe and Warthe (1) ice advances.

KW - Glaciotectonics

KW - North Sea

KW - Pre-Elsterian ice-margin

KW - Retrodeformation

KW - Tunnel valley

KW - Warthian ice-margin

UR - http://www.scopus.com/inward/record.url?scp=85075153836&partnerID=8YFLogxK

U2 - 10.1016/j.quascirev.2019.106068

DO - 10.1016/j.quascirev.2019.106068

M3 - Article

AN - SCOPUS:85075153836

VL - 227

JO - Quaternary Science Reviews

JF - Quaternary Science Reviews

SN - 0277-3791

M1 - 106068

ER -