Three-dimensional retro-modelling of transpression on a linked fault system: the Upper Cretaceous deformation on the western border of the Bohemian Massif, Germany

David C. Tanner1, Jan H. Behrmann1, Onno Oncken2 and Klaus Weber3

1 Geologisches Institut, Universtität Freiburg, Albertstraße 23b, D-7104 Freiburg, Germany.

2 GeoForschungsZentrum, Telegrafenberg A17, D-14473 Potsdam, Germany.

3 IDGL, Universität Göttingen, Goldschmidtstrasse 3, D-37077 Göttingen, Germany.
 

 Contents:

 Abstract 
 Introduction 
 Geological background 
     Surface structure of the modelled area 
     Geologic information from the KTB borehole 
     Geophysical interpretation 
         Seismic information 
             Gravity and magnetic anomaly modelling 
     Other geological information 
         Sedimentary record of the Mesozoic basin adjacent to the 
         ZEV 
             The record of Mesozoic and Cenozoic crustal movements 
             Paleomagnetic vectors 
The Upper Cretaceous deformation event 		    Retro-modelling in three dimensions 
     Aim of the modelling  
     Known and projected elements required for  
     modelling  
     Deformation kinematics and parameters  
 Results 
 Discussion of the results 
     Tectonic thickening and uplift of the ZEV  
     Implications for the pre-Upper Cretaceous ZEV 
     geometry  
 Conclusions 
 Acknowledgements 
 References 
 

Abstract

The Zone of Erbendorf/Vohenstrauß (ZEV) on the western margin of the Bohemian Massif was deformed by an Upper Cretaceous intra-plate deformation event. Dextral transpression was caused by the reactivation of pre-existing structures. Using the extensive geological and geophysical database available, we constructed a three-dimensional virtual model of the ZEV. The model was deformed in reverse, to remove the effects of the Upper Cretaceous event. This involved moving the hanging wall (the ZEV) in a sinistral transtensive sense northwards above a composite active fault surface composed of two steep faults, perpendicular to another in strike, and a detachment intersecting both faults at 9.5 km depth. Hanging-wall deformation was accommodated by antithetic inclined shear. Seven kilometres heave of the hanging wall fulfilled the geological constraints. Calculated uplifts range from 2-6 km. Deformation is mostly only contained within the ZEV. The hanging-wall deformation above a linked fault system was highly complex, causing rollover above one fault and drag-folding above the other. The most important control on the vertical movement and deformation of the hanging wall was a 30 degree change in the strike of one of the coupled faults.