On the nature of the junction zone between the Vienna and Pannonian sedimentary basins

Abstract

The results of long-term (2001–2009) measurements of fractures in sedimentary rocks of the Badenian and Pannonian age within the Rust-Fertorakos Highland and adjacent areas are presented and interpreted in terms of paleostresses in the study. The Rust-Fertorakos Highland has a nearly north-south trending strike and separates the Vienna and Pannonian Basins. It is expressed not only in the topography but also in the thickness of the sedimentary cover. Faults in the basement of the Rust-Fertorakos Highland have a nearly north-south strike diagonal to the general NE-SW strike of the faults of the basement of the Vienna Basin. The data of measurements of joints made in quarries and on road slopes that were subsequently computer processed using two independent techniques indicate that, along with joint systems, which are orthogonal to the rock bedding and are of a primary lithogenetic origin, joints joining to form systems obliquely oriented to the bedding are quite common in the region. These secondary joint systems have been formed at later stages of development of already lithified rocks under the influence of tectonic paleostresses. Interpreting pairs of secondary systems as conjugated shear joints, the authors have reconstructed the orientations of the axes of the relevant tectonic paleostresses. At some observation points, the identification of conjugated shear systems has been ambiguous. In these cases, two possible solutions for the paleostress axes have been drawn. Despite some ambiguities, all of the solutions obtained have a steady tendency in terms of the orientation of the minimum compression axis T3. This axis is subhorizontal and is oriented nearly east-west with some variation. The maximum compression axis T1 and the intermediate principal stress axis T2 are normally inclined to the horizontal, and the orientation of these axes depends on the observation point.