A Giant Paraglacial Paleo-Landslide on the Flank of a Danish Tunnel Valley

Description

Few scientific studies have documented Danish landslides and giant paleo-landslides remain virtually unexplored (Svennevig et al., 2020). Here we present a pilot study detailing the possible giant landslide ‘Nørre Vilstrup’ within the Vejle valley (Vejle Ådal) in eastern Jutland, Denmark. The Vejle valley is a tunnel valley incised into a subglacial plateau, with elevations of 80 – 100 m. The area was last glaciated during the Late Weichselian (~25-11.7 ka BP).
Based on 0.4 m LiDAR data, the lobate landform at Nørre Vilstrup exhibits morphological characteristics indicative of a paleo-landslide. The feature has an area of ~7.4 km2, measuring ~3 x ~2.3 km and protruding 0.5 km north into the valley. The lobate form contains twelve east–west-oriented linear features, spaced ~120 m apart and with ~7 m of relief, which are absent from the surrounding terrain. Within the proximal (southern) end of the lobate feature, there is a bowl-shaped depression with an area of 1.48 km2 and elevation ranging between 31-52 m. To the east and west of the depression, ~27.7 m deep gullies define the southern margin of the lobate landform. It appears to deform the valley fill forming convex accumulation stands that slope back toward the lobate body. Existing airborne Transient Electromagnetic data (SkyTEM: Sørensen et al., 2004) were used to interpret the subsurface conductivity. Co-interpretation of SkyTEM and borehole information indicates the presence of Paleocene clay and Miocene sand layers below Quaternary deposits within Nørre Vilstrup that align with the east-west linear surface fabric.
The internal structure indicates that overpressured Pleistocene clay intruded through sandy deposits via diapirism, likely forming a caldera-like depression at the landslide’s proximal end during the event. Subsequent runout to the valley floor could have modified gullies as seen on the eastern flank of the landslide.
The timing of the paleo-landslide is uncertain, but the presence of overpressured clays suggests that failure occurred soon after glacial ice retreat. Evidence of diapirism points to a sudden failure. The deformed valley fill forming stands at the distal end may represent the slide's toe or result from a “bulldozing” effect, where the valley fill was abruptly pushed outward and upward. These interpretations suggest a high-energy, catastrophic event rather than gradual deformation.
Future work will use new tTEM, resistivity surveys, and boreholes to refine stratigraphy and test the role of mud diapirism. We also aim to better constrain the landslide age from overlying deposits and reworking.

Period	14 Jan 2026
Event title	Nordic Geologic Winter Meeting
Event type	Conference
Location	Turku, FinlandShow on map
Degree of Recognition	International