Nøvling: An unusual salt structure on the soutbern margin af the Danish Basin

The N~vling salt structure is located on the southern margin of the DanishZechstein Basin. The present study of this structure is based on a detailed gravitysurvey, reflection and refraction seismic data, and well information. Apart fromthe exploratory well NØvling-l, and a shallower well Herning-l, a number ofwells, mainly 20-30 m deep, were drilled in this general area (by the GeologicalSurvey of Denmark). Through this combined study using geological and geophysical methods it is possible to distinguish several stages in the developmentof the N~vling structure. It is shown that these stages are closely related to faulting at the base Zechstein level. The faulting, which apparently started as normalfaulting in the Triassic, triggered the first salt movements from the deeper partsof the basin to this peripheral area. The faulting was reactivated during the lateJurassic, resulting in the formation of a salt pillow. The tectonic regime changedin the post-Paleocene tertiary when transpressional movements along a prominent basement wrench fault became dominant. This ultimately resulted in theformation of a positive flower structure and the uplifting of the Saale Quatemarysurface. At shallow depths the salt became dissolved creating a topographic depression above the flower structure. The present depression was formed at thebeginning of the last late glacial time. Quatemary landforms in the N~vling areaare therefore greatly influenced by recent tectonic events.