On the structural development of the salt dome province in NW Jutland, Denmark, based on seismic studies

As a result of the renewed interest in Danish salt structures the Geological Survey of Denmark (DGU) engaged the author to outline the structural development of the salt dome province in NW Jutland, which is a part of the Norwegian Danish Basin. The work comprised the interpretation of 79 seismic sections and construction and analysis of 9 two-way time maps, 13 isopach maps and 11 cross-sections (Boldreel 1983, and in preparation). In this article only three two-way time maps, four isopach maps and two cross-sections are diseussed to iIIustrate some of the most important results. Within the area investigated there are seven salt diapirs and one salt pillow. There is a marked correlation between the positions of the stationary salt diapirs and faults in the base of Zechstein, and also between the temporal development of the diapirs and the isopachs of post-Zechstein sediments. The growth of salt pillows started in the Lower Carnian (Upper Triassic). Development of salt diapirs with associated second order peripheral sinks took place asymmetrically without lateral movement of the salt structures. In contrast the one remaining salt pillow, which has not developed diapirically, has moved from its original position in the northern part of the area towards the north-west. The movement of Zechstein deposits is minimal at present thicknesses of 300-600 m and has ceased at present thicknesses of less than 300 m. This leads to the conclusion that the Zechstein sequence does not consist of pure halite.