Tunnel Valley Infill and Genesis: Insights from High‑Resolution 3D Seismic Data and Numerical Modelling of Subglacial Water Flow in the North Sea

Abstract:

The geological record of landforms produced beneath deglaciating ice sheets offers insights into otherwise inaccessible subglacial processes. Large subglacial channels formed by meltwater erosion of sediments (tunnel valleys) provide valuable empirical constraints for numerical ice‑sheet models; however, many aspects of tunnel valley formation, and the processes by which they are infilled, remain poorly understood. Here, we use novel high‑resolution 3D seismic reflection data to analyse the infill architecture of buried tunnel valleys in the North Sea. The spatial resolution of our seismic data (6.25 m bin size, ~3.5 m vertical resolution) represents a step change in our ability to investigate the mechanisms and rates at which tunnel valleys are formed and filled. Inside the tunnel valleys, we identify a suite of buried glacial landforms including eskers, crevasse‑squeeze ridges, glacitectonic structures and kettle holes. We use these landforms to make inferences about the processes which control tunnel valley genesis and infill. In addition, simulations of subglacial water flow beneath an ice sheet which formerly occupied the North Sea are used to investigate potential subglacial water routing pathways and the steady-state discharges which eroded the tunnel valleys, providing constraints on the timescales over which these features form.