Results, problems and future tasks of palaeostress and fault-slip analyses in the Pannonian Basin: the Hungarian contribution

Abstract

In the Pannonian Basin fault-slip analysis and palaeostress determinations started in 1982–1984 by the work of Françoise Bergerat, Jacques Geyssant and Claude Lepvrier. After F. Bergerat introduced some Hungarian researchers to field and laboratory techniques, fault-slip analysis expanded into the Pannonian Basin in Hungary and in some adjacent areas, and is still going on. This paper reviews the results achieved during this ~35 year time span from a historical perspective, by the compilation of the determined Cenozoic stress fields, their temporal boundaries, and uncertainties. The model for the evolution of the stress field became more complicated, and more and more details in the deformation history were realised, both in the Alcapa and Tisza–Dacia units of the Pannonian Basin. The integration of palaeomagnetic and stress data indicated that some changes in stress axes (and in fault orientation) are due to vertical-axis block rotation, and are not real rotation of the external stress field itself. With the development of new approaches, like tilt test, combination of surface and subsurface fault data, radiometric age determination of deformed rocks, fine separation of fracture sets can be achieved and the multiple recurrences of stress fields with identical principal axes were demonstrated. The refined methods permitted the demonstration of basin-wide inhomogeneity of the stress field for some phases. However, the precise timing, the number of phases, separation of events with similar stress axes, and the variability of the maximal stress axes of a given stress field remain the major questions to be solved in the future. Rheological conditions of the deforming media and physical parameters of the fracturing will be the other future steps in research, to be achieved by studies of deformation bands, fluid inclusions, isotopes, in order to better understand the connection of deformation, subsidence, diagenesis, and fluid flow.

Revealing the Mineralogical and Petrographic Signs of Fluid-Related Processes in the Kelebia Basement Area (Szeged Basin, S Hungary): A Case Study of Alpine Prograde Metamorphism in a Permo-Triassic Succession

“…On the other hand, the appearance of the deformational microstructures (e.g., disjunctive foliation, tectonically deformed quartz, and twin morphology of carbonate minerals; Figures 8 and 10) unequivocally indicates that the Permo-Triassic sequence was subject to tectonic stress before the Early Miocene uplift and erosion which later stage corresponds to an exhumed position close to the coeval surface (Figure 11). Within the ACD system, undoubtedly, the most significant orogenic events are related to the thrusting and nappe stacking during the Cretaceous [4][5][6][7][8][9][10][11][12]. Very likely, these tectonic processes favored the prograde reaction series of phyllosilicates (~300 °C temperature for the peak metamorphism), instead of burial depth.…”

“…The European Alpine-Carpathian-Dinaride (ACD) orogenic belt was the focus of several relevant projects that resulted in advanced concepts for the tectonometamorphic and thermal evolution of the region (e.g., [1][2][3][4][5][6][7][8][9][10]). Furthermore, correlational studies led to improved versions of the tectonic map of the ACD orogenic system [11][12][13][14][15][16][17].…”

Complex deformation history of the Keszthely Hills, Transdanubian Range, Hungary

“…This model implies that the preexisting normal faults and the breached relay ramps connecting them promote the formation of oblique and lateral ramps in the KH. It is also possible that such oblique inversion of a segmented graben system resulted in the development of a heterogeneous stress field, whose stress trajectory can show important variations (Fodor, 2019). The NW-SW shortening could have occurred on these inverted relay ramps (Héja et al, 2022).…”

“…5d). No direct timing is available for this stress field, but the relative chronology, the analogy from other parts of the TR (Márton and Fodor, 2003;Fodor, 2019), and the parallelism of the surface faults to graben-bounding main normal faults of the surrounding Zala and Danube basins (Tari, 1994;Csontos, 1995;Fodor et al, 2013aFodor et al, , 2021, suggest Miocene timing. In fact, in the neighboring Zala Basin this stress field marks the major syn-rift faulting and related subsidence (Csontos, 1995;Fodor et al, 1999Fodor et al, , 2013aFodor et al, , 2021Nyíri et al, 2021).…”

“…In addition, Sztanó et al (2010) found N-S-trending normal faults in the Billege gravel pit in the Tapolca Graben: these structures also belong to this phase. This stress field is widely documented throughout the entire Pannonian Basin (Fodor et al, 1999;Fodor, 2010Fodor, , 2019 and was considered as one important phase of the rifting process (Csontos et al, 1991;Fodor et al, 1999;Sasvári et al, 2007;Bodor, 2011;Sipos-Benkő et al, 2014;Petrik et al, 2016) and corresponds to the regional D10 phase of Fodor (2008Fodor ( , 2010. We adopted the classification of Fodor et al (2021), that this extension locally represents the main syn-rift phase of this part of the PB.…”