Quantitative strain analysis of strike-slip displacements across the Arne-Elin trend, the Danish Central Graben

A method is presented for unravelling the displacement history across transpressionand transtension zones recognized on seismic sections as flower structures. Themethod has been applied to the Arne-Elin trend in the northern part of the DanishCentral Graben. The results suggest sinistral movement with alternatingtranspression and transtension along strike during the Early Cretaceous, and dextral transpressive movement during the Late Cretaceous and Paleogene. However, there is considerable variation in displacement along strike of the zone during the individual periods. The variation in displacement along the strike of theArne-Elin trend is accommodated by displacement along the fault systems in theadjoining areas. The displacement along fault systems in the adjoining areas wassinistral during the Early Cretaceous and dextral during the post-Early Cretaceous, similar to the movement along the Arne-Elin trend during the two periods.The analysis gives a detailed picture of the movements along the general structural trend and emphasizes the differences between the two periods. One of themost marked differences is that the fault system separating the Gertrud Graben,the Feda Graben and the Heno Plateau becomes locked during the Late Cretaceous/Paleogene while the Arne-Elin trend is strongly inverted.Observations show that the major inversion structures are often underlain byZechstein salt. Contemporaneous normal faulting (local extension), however, tookplace without involvement of salt. The onset of inversion of previously generatedstructures therefore depended not only on changes in the regional stress system,but also seems to be controlled by the rheology of the rocks involved.