EP2 - 3D-Structural Model


Aims

In order to understand the fluid system of our Thuringian Basin case study, and in particular the coupling between near-surface and deep groundwater, detailed knowledge of the basin´s present, three-dimensional architecture is of prime importance. Apart from the geometries of aquifers and aquitards, deep-reaching faults play an important role as conduits for vertical fluid circulation. EP 2 contributes to the creation of a three-dimensional structure model of the entire basin (see also ZPK), focussing on the configuration and evolution of the fault zones. An essential innovation is the consistent use of kinematic reconstructions to constrain structural interpretations. This entails a stronger emphasis on process-oriented modeling. EP 2 also cooperates with other EPs in unraveling the basin´s evolution over different time scales. We investigate fractures and their formation on spatial scales from outcrops to entire fault systems, also taking the regional framework of the Thuringian Basin into account.

Working area

The study area of EP 2 comprises the entire Thuringian Basin as geologically defined. Many investigations are aimed at the prominent, NW-SE striking fault zones traversing the Thuringian Basin. Small-scale investigations into individual fractures and paleostress analysis from populations of small faults also include the little deformed areas between the major fault zones.

Methods

Using kinematic reconstructions throughout our work results in better constrained structure models of the Thuringian Basin. Geological cross-section interpretations are checked for consistency of bed lengths (Marshak and Woodward, 1988) and areas (Mitra and Namson, 1989) and corrected until retrodeformable, balanced cross-section (Dahlstrom, 1969) are achieved. Serial balanced sections allow us to use strain compatibility between adjacent sections as an additional constraint on the structure interpretations, and to track the evolution of structures along strike. The sets of serial sections constitute internally consistent, quantitative, nearly three-dimensional structure models. These models enable well-constrained estimates of the magnitudes of tectonic extension and shortening. With added kinematic information from paleostress analysis they are used to derive a detailed deformation history of the Thuringian Basin.

Results

EP 2 has produced some 45 balanced cross-sections traversing the main fault zones and intervening low-strain areas of the Thuringian Basin. Ten cross-sections cover the Finne fault zone, six the Schlotheim graben, four the Erfurt fault zone, nine the Ilmtal graben and 15 the long Eichenberg-Gotha-Saalfeld fault zone. With additional detailed studies of specific structural features and the paleostress results they constitute a 2.5-dimensional structural-kinematic model of the Thuringian Basin that provides a structural framework for the investigations of many other EPs. The structural basin model is a milestone on the way to an integrated geological model describing the Thuringian Basin´s evolution over geologic time, a task we will approach together with other EPs in the working group "Basin Evolution" within INFLUINS.

Team

Members of the Team EP2 you will find here.

References

Dahlstrom, C.D., 1969. Balanced cross sections. Canadian Journal of Earth Sciences 6, 747-757.
Marshak, S., Woodward, N., 1988. Introduction to Cross-Section Balancing, Basic Methods of Structural Geology.
Englewood Cliffs, New Jersey. Mitra, S., Namson, J., 1989. Equal-area balancing. American Journal of Science 289, 563-599.