Scientific technical report
Description / Table of Contents:
The Central European Basin System (CEBS) is a complex intracontinental system of sedimentary basins that have evolved through several geodynamic phases since Late Carboniferous times. The basin system is framed by the Tornquist Zone in the north and the Elbe Fault System in the south. The main structural configuration of the basin system is well established due to decades of scientific research and intense industrial exploration for mineral resources. The scope of this PhD thesis is to assess which paleostress fields controlled the evolution of the basin system. The present thesis introduces the "Stress Inversion via Simulation" (SVS) as a new strategy for estimating paleostress states. For a set of striated fault planes with known sense of slip (fault-slip data), this stepwise technique identifies the corresponding "reduced stress tensor" comprising (1) the directions of the principal stress axes with sigma1?sigma2?sigma3 and (2) the ratio of principal stress differences, R=(sigma2-sigma3)/(sigma1-sigma3). For heterogeneous fault-slip data, SVS separates the different corresponding "reduced stress tensors". Any estimated stress tensor thereby fulfils both the criterion of low misfit angles and the criterion of high shear-to-normal-stress ratios for the associated fault-slip data. The base for the present study is provided by fault-slip data gathered from outcrops in the Elbe Fault System area (906 fault-slip data) and in the Oslo Graben area north of the Tornquist Zone (2191 data). 77 paleostress tensors have been estimated for the Elbe Fault System area and 194 tensors for the Oslo Graben area. These locally estimated stress states can be related to a small number of regionally traceable paleostress fields. The paleostress fields that have demonstrably controlled the Oslo Graben area include (1) a Caledonian compressional stress field with a horizontal NW-SE-directed sigma1, (2) a Permo-Carboniferous tensional stress field with a horizontal WNW-ESE-directed sigma3 (rifting phase) and (3) a (post?-)Permian wrench regime with a roughly N-S-directed sigma1. Thus, the Oslo Graben area probably remained widely unaffected by any major tectonic activity during much of the Mesozoic and Cenozoic. The regional stress fields reconstructed for the Elbe Fault System area comprise a compressional and a younger wrench regime both with a horizontal N S- to NE-SW-directed sigma1 and both related to the Late Cretaceous/Early Tertiary phase of basin inversion. Stress fields (wrench and tensional) that post-dated the inversion phase are much weaker, while signs of any pre-inversion stress fields have not been detected at all. While the Late Cretaceous/Early Tertiary phase of inversion widely overprinted traces of earlier deformation across the Elbe Fault System area, it had minor if not no effects on the Oslo Graben area. The respective strain localisation in particular zones of crustal weakness of the CEBS is one of the major aspects of the present study.
Type of Medium:
149 S. : Ill., graph. Darst.
Scientific technical report / Deutsches GeoForschungsZentrum GFZ 09/06
Zugl.: Berlin, Freie Univ., Diss., 2009