Late Cretaceous basin inversion in the Kattegat – Skagerrak segment, Sorgenfrei – Tornquist Zone, Denmark, and Mesozoic – Cenozoic crustal tectonics of the eastern North Sea Basin

Ole Graversen, Department of Geosciences and Natural Resource Management,
Section for Geology, University of Copenhagen, Denmark, oleg@ign.ku.dk.

The Sorgenfrei – Tornquist Zone is a NW-SE trending, 50-100 km wide fault zone that cut off the East North Sea Block (ENSB), i.e. the Mesozoic basement of the Eastern North Sea Basin, from the Baltica Palaeozoic platform. The break was established in the Triassic, where the ENSB was established as the hangingwall block in the Kattegat area; by contrast, the Baltica platform develloped as the hangingwall block in the Fjerritslev halfgraben to the northwest (1).

In the Kattegat area, the Triassic faulting established a staircase fault block trajectory with downfaulting towards the southwest into the Danish Basin. In the Jurassic – Early Cretaceous, the Kattegat segment changed into an asymmetric, northeast dipping graben, the Kattegat Graben. In the Late Cretaceous, maximum subsidence returned to the southwest into the Danish Basin, while the Kattegat Graben was inverted during backward tilt of the graben block.

The ENSB formed the northeast flank of the Central North Sea Dome (2). The Jurassic – Cenozoic structural evolution of the ENSB was governed by the rise and fall of the Central Graben rift dome: 1) synrift rise in the Jurassic – Early Cretaceous, 2) Late Cretaceous transition phase with collapse of the Central Graben rift, 3) Cenozoic postrift subsidence (3). A model of the Mesozoic crustal tectonics associated with the ENSB illustrates the interrelationship between the evolution of the Kattegat – Skagerrak segment and the Central Graben Dome across the eastern North Sea Basin (4).

References

(1) Vejbæk, O.V. 1997: Dybe strukturer i danske sedimentære bassiner.
Geologisk Tidsskrift 4, 1-31.
(2) Ziegler, P.A. 1990: Geologcal Atlas of Western and Central Europe, Shell Internationale Petroleum Maatschappij B.V.
(3) Graversen, O. 2006: The Jurassic-Cretaceous North Sea Rift Dome and associated basin evolution. American Association of Petroleum Geologists, Search and Discovery Article #30040.
(4) Graversen, O. 2002: A structural transect between the central North Sea
Dome and the South Swedish Dome: middle Jurassic–Quaternary uplift–
subdidence reversal and exhumation across the eastern North Sea Basin.
Geological Society, London, Special Publications 196, 67-83.