The Heligoland Glacitectonic Complex in the southeastern North Sea: indicators of a pre- or early-Elsterian ice margin

Glacial landforms are abundant in the North Sea basin and are often used to reconstruct the impact and dynamics of ice sheets during the Pleistocene. Geophysical methods have allowed the mapping and structural analysis of glacial landforms at the surface and in the subsurface to estimate the position of former ice margins in the North Sea. However, the glacial history of the southeastern North Sea remains underexplored. In this study, we present a structural analysis of Late Pliocene to Late Pleistocene sediments based on a dense grid of 2D high-resolution multi-channel reflection seismic data from the German sector of the southeastern North Sea. We show that the Heligoland Glacitectonic Complex (HGC) is larger than previously assumed (700 km(2), 32x22 km) and characterized by three distinct zones of thrusting and deformation on two decollements. The kinematic restoration of seismic cross-sections and dip measurements of thrust faults demonstrate that the HGC was formed by an ice lobe advancing from the southeast. To explain the origin of the HGC, we provide alternative models for its formation during a single ice advance or two ice advances in the study area. Furthermore, we validate the early or pre-Elsterian age of the HGC based on nearby Elsterian tunnel valleys, and conclude that salt structures in the subsurface may have influenced its location.

Automated summary

Glacial landforms in the North Sea basin have been studied using geophysical methods to reconstruct ice sheet dynamics during the Pleistocene. This study focuses on the structural analysis of sediments in the southeastern North Sea, revealing a larger-than-expected Heligoland Glacitectonic Complex formed by ice advance from the southeast. The study presents alternative models for the formation of the complex and suggests a potential influence of salt structures on its location.