Tunnel valleys have long fascinated the geoscientists by their scale and the consequent intensity of the sedimentary processes necessary to their formation. The filling of tunnel valleys in the southern and eastern North Sea is mainly made of clinoforms prograding north.
A new sedimentological model has been developed to comply with new observation on the 3D architecture of the valleys and their infills. The model states that the incision and the filling of the valleys are separate in times and from distinct processes. The infill is interpreted as proglacial for the newly observed southdipping clinoforms and postglacial for the northdipping clinoforms onlapping the later. The northdipping clinoforms are interpreted to be formed within a large deltaic system associated with the RhineMeuse river(s). The delta was probably infilling a lake containing 100's of m overdeeps (the underfilled tunnel valleys).
The presence of clinoforms 5080 m above the valley shoulders indicates the potential depth of the lake. The lake geometry was certainly controlled by the lithospheric flexure depression and forebulge due to ice sheet loading, during or after ice sheet recession. The lake levels might have been very variable and difficult to tie to what we see today in the topography.
This system of competition between one of the biggest river of Europe facing ice sheets and their proglacial depositional system generates a very intricate stratigraphy. We intend to solve part of the problem by numerically reconstructing the local landscape with the ice sheet and its isostatic depression. This allows to locate potential depocenters and lake thresholds/spillways to better understand the river migration and the position of the lacustrine systems. The Elsterian topography remained so far quite elusive since we show that the orientation of the slopes and the altitudes were drastically different between glacial maximums and interglacial times.