Do deep geological structures influence shallow Quaternary erosional patterns in the North Sea?

Tunnel valley formation and orientation are primarily controlled by the hydraulic gradient beneath large ice sheets. However, recent onshore studies from Denmark have motivated the hypothesis that deep fault systems may also influence the position and orientation of shallow erosional features like tunnel valleys. Onshore, this hypothesis has been supported by observed similarities in the overall orientation and spatial trends of deep fault systems and shallow erosional features. These correlations have been attributed to reactivation of the faults due to loading and unloading by large ice sheets as well as subtle variations in sediment strength caused by the deep structural features.

Importantly, these onshore studies are based on interpretations of transient electromagnetic data and sparse 2D reflection seismic data. Offshore where reflection seismic data is almost exclusively applied, the onshore methods cannot be applied directly, leaving the question of deep–shallow correlations largely unexplored.

In order to test this hypothesis further, we have gathered previously mapped tunnel valleys and deep geological structures offshore, combined with new interpretations from various reflection seismic data sets and analyzed the orientation and position of the tunnel valleys on both regional and local scale using a geostatistical approach specifically developed for this study. This approach allows us to distinguish between local and regional-scale correlations, which can support the hypothesis offshore while also be applied onshore. The large-scale analysis can also highlight other trends within the extensive suite of buried tunnel valleys in the North Sea, including the influence of salt structures, multiple tunnel valley generations and past ice sheet dynamics.