Mesozoic basin inversion governed by crustal extension in the Bornholm area, Sorgenfrei-Tornquist Zone, Denmark

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Mesozoic basin inversion governed by crustal extension in the Bornholm area, Sorgenfrei-Tornquist Zone, Denmark
Ole Graversen, Department of Geosciences and Natural Resource Management, Section for Geology, University of Copenhagen,

Basin inversion describes the deformation of asymmetric grabens characterized by folding and thrusting, i.e. horizontal shortening, associated with uplift of the sedimentary graben fill above regional (1). The compressive stress field has been interpreted in a plate tectonic concept as a result of continent-continent collision that established a compressive stress field in the orogenic foreland (2, 3).

However, structural analysis of basin inversion in the Sorgenfrei – Tornquist Zone illustrates, that basin inversion was the result of superposition of asymmetric extensional fault basins dipping in opposite directions. The evolution of the graben basins, took place during successive extensional tectonic regimes separated by stillstand intervals. During subsidence of the superposed, extensional basin, the primary basin was tilted backward, and the basin was inverted during local compression between the primary footwall blocks.
The Mesozoic fault block pattern of the Bornholm area illustrates, that the NW-SE trending Sorgenfrei – Tornquist Zone was extended in two directions: The main extension was in a NE-SW direction across the strike of the fault zone, and a secondary NW-SE extension along the fault zone trend.

Based on the changing graben activity, the Mesozoic has been divided into Triassic, Jurassic – Early Cretaceous and Late Cretaceous extensional tectonic regimes. Graben subsidence started in the Triassic, and basin inversion was active in the Jurassic – Early Cretaceous and again in the Late Cretaceous (4, 5). The tectonic regimes were separated by turnover intervals characterized by only minor tectonic activity in the late Late Triassic and the early Late Cretaceous.

(1) Ziegler, P.A. 1987: Compressional intra-plate deformations in the Alpine foreland – an introduction. Tectonophysics 137, 1-5.
(2) Ziegler, P.A. 1987: Late Cretaceous and Cenozoic intra-plate compressional deformations in the Alpine foreland – a geodynamic model. Tectonophysics 137, 389-420.(3) Kley, J. & Voigt, T. 2008: Late Cretaceous intraplate thrusting in central Europe: Effect of Africa-Iberia-Europe convergence, not Alpine collision. Geology 36, 839-842.
(4) Graversen, O. 2004: Upper Triassic–Lower Cretaceous seismic sequence stratigraphy and basin tectonics at Bornholm, Denmark, Tornquist Zone, NW Europe. Marine and Petroleum Geology 21, 579–612.(5) Graversen, O. 2004: Upper Triassic – Cretaceous stratigraphy and structural inversion offshore SW Bornholm, Tornquist Zone, Denmark. Bulletin of the Geological Society of Denmark 51, 111–136.
Original languageEnglish
Publication date2018
Number of pages2
Publication statusPublished - 2018
Event33rd Nordic Geological Winter Meeting - Danmarks Tekniske Universitet, Lyngby, Denmark
Duration: 10 Jan 201812 Jan 2018
Conference number: 33


Conference33rd Nordic Geological Winter Meeting
LocationDanmarks Tekniske Universitet

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