Geodynamical Models of the Rotation and Extension of Alcapa and Tisza Blocks in the Pannonian Basin of Central Europe (original) (raw)

Kinematics of Deformable Blocks: Application to the Opening of the Tyrrhenian Basin and the Formation of the Apennine Chain

Geosciences

We describe the opening of back-arc basins and the associated formation of accretionary wedges through the application of techniques of deformable plate kinematics. These methods have proven to be suitable to describe complex tectonic processes, such as those that are observed along the Africa–Europe collision belt. In the central Mediterranean area, these processes result from the passive subduction of the lithosphere belonging to the Alpine Tethys and Ionian Ocean. In particular, we focus on the opening of the Tyrrhenian basin and the contemporary formation of the Apennine chain. We divide the area of the Apennine Chain and the Tyrrhenian basin into deformable polygons that are identified on the basis of sets of extensional structures that are coherent with unique Euler pole grids. The boundaries between these polygons coincide with large tectonic lineaments that characterize the Tyrrhenian–Apennine area. The tectonic style along these structures reflects the variability of relati...

Hercynian-thrust related shear zones and deformation of the Varied Group on the contact of granulites/Southern Moldanubian, Bohemian Massif/

Geologische Rundschau, 1986

Drei Deformationsphasen der variszischen tektonischen Entwicklung sind in der Bunten Gruppe des siidlichen Moldanubikums des B6hmischen Massivs enthalten. Die Deformation ist mit der yon NW nach SE orientierten Uberschiebung von grogen Krusteneinheiten mit Granuliten verbunden. Die Entstehung yon jiingeren N-S und NW-SE verlaufenden Scherzonen kann auf die Uberschiebungsbewegung bezogen werden. Die Strukturentwicklung beginnt mit F1 isoklinalen Falten, die wahrscheinlich den nichtmetamorphisierten Sedimenten aufgepr~igt wurden. W~ihrend der Abschlugphase der Formung wurden sie stark gepl~ittet und es entstand die B1 Boudinage. Die Aplitg~inge, Migmatitisation der Paragneisse und Metamorphose der Gesteine sind gleichzeitig. Die D2 Deformationsphase wurde dutch einfache Scherung der Einheit hervorgerufen und es entstanden Falten verschiedenen tektonischen Stils in der Umgebung starrer Einschliisse und die Blattverschiebung an der Grenze yon Granulit und Bunter Gruppe. Die F1 und F2 Falten liegen parallel zur Streckungslineation und Uberschiebungsrichtung ab. Die j/ingste Deformation ist charakterisiert durch eine spektakul~ire Boudinage und Falmng der senkrecht stehenden FI~ichen.

Deformations in Transform Faults with Rotating Crustal Blocks

Pure and Applied Geophysics, 2006

A continuum model of deformation of a transform fault is considered. The fault interior is modelled as a part of a plate fragmented into a large number of angular blocks. The blocks are not joined together by any binder, but are rather held together due to external compression such that they can, in principle, rotate independently. Significant numbers of blocks involved in the deformation process permit a continuum description of the deformation, which in view of the possibility of independent rotations, necessitates the application of the Cosserat theory. The crucial point in the described model is the interconnection between the rotations and the normal stresses associated with the angular shape of the blocks: the rotating blocks 'elbow' one another. Furthermore, elbowing produces compressive stresses independent of the direction of rotations. Consequently, the constitutive equations become non-linear involving absolute values of the components of the curvature tensor. The paper analyses a simple shear of a fault under constraining compression acting in the direction normal to the fault. An infinite layer subjected to opposite displacements and zero rotations at the edges is considered. It is shown that block rotations can lead to complex deformation patterns. There exists a displacement threshold proportional to the pressure: for imposed displacements below the threshold, the deformation pattern coincides with the conventional one as predicted for a classical elastic isotropic layer with uniform displacement gradient in the absence of block rotations. When the imposed displacement exceeds the threshold value, boundary zones of nonuniform rotations, displacement gradients and dilatation emerge. It is interesting to note that these features, which could be mistaken for indicators of non-elastic or localisation processes, occur in a situation where only elastic processes are acting at the scale of blocks and no friction or other energy dissipation processes take place.

Distributed deformation and block rotation in three dimensions

Journal of Geophysical Research, 1991

The focus of this paper is to understand distributed deformation, in particular the relationship between fault slip and rotation of faults and blocks in a three dimensional stress field. Regions of distributed deformation, such as Southern California, are organized in complex arrays of contemporaneously active block-faulted domains. We believe that the present day orientation of faults in many domains is due to the contemporaneous slip and rotation of the faults and of the blocks they bound. Traditional friction models cannot explain active unfavorably oriented faults and do not consider how faults become unfavorably oriented. To solve this problem, we propose a three dimensional block rotation model that tracks the orientation of blocks and their bounding faults during rotation. Mechanically, we consider Coulomb criteria for rock fracture as an upper bound, and slippage on a frictional surface as a lower bound. The key parmeter in our model is the value of q5 --(a2 -a3)/(al -a3). Principal stress directions are assumed irrotational through time. This model predicts up to 750 of vertical axis rotation along a single set of faults. During rotation, fault slip may change, sometimes dramatically, giving rise to mixed vertical as well as horizontal axis of rotation of blocks and faults. For very unfavorably oriented faults the model predicts rotations about a vertical axis in both the normal and reverse stress regimes, and about a horizontal axis in the strike-slip stress regime. Therefore paleomagnetically inferred rotations may not always be directly related back to a specific stress regime. Combining frictional constraints of the block rotation model with paleomagnetic, structural and geological data, we show how only one set of faults, preexisting and rotating in an irrotational strike-slip stress field, can account for the three major phases of deformation observed in the Western Transverse Range domain, Southern California: preexisting north-northeast faults were reactivated as normal faults, rotated and became strike-slip, and subsequent rotations of faults resulted in their present east-west high angle reverse orientation. This example demonstrates that it is not necessary to invoke complex regional and local changes in the stress regime or erratic changes in plate motion to account for alternate periods of compression and extension. 1. CRUSTAL DEFORMATION BY BLOCK ROTATION 1.1. The Problem Deformation at plate boundaries is commonly distributed across a wide zone characterized by domains of faults [Freund, 1970, 1971; Carlunkel, 1974; Luyendyk et al., 1980; Ron et al., 1984; and others]. Throughgoing faults, such as the San Andreas and Gatlock faults in southern California (Figure 1), often mark domain boundaries. Within each domain faults form a set having similar orientations and fault slips. Adjacent fault sets may have different orientations and may have different fault slips as well.

Mechanics of basin inversion: Finite element modelling of the Pannonian Basin System

Tectonophysics, 2009

This finite element modelling study addresses the contraction of rheologically layered and laterally heterogeneous lithosphere representative for the Pannonian Basin and its surroundings. The time interval and strain rate adopted in the experiments reflect the Pliocene-Quaternary inversion of the basin. Several sets of fully coupled elastoviscoplastic thermo-mechanical, plane strain 2D models explore the evolution of buckling, and stress/strain changes across the lithosphere. The viscous rheology of the asthenosphere allows for a detailed simulation of isostatic rebound during deformation. The numerical models predict the successive development of surface undulations, caused by crustal and/or lithosphere folding, at three different characteristic wavelengths. Among these, the longest wavelength folds occur systematically at the rim of the basin as marginal bulges, while the short wavelength folds overprint the earlier folds and are observed at a later stage during compression. The thermo-mechanical evolution of the lithosphere in response to progressive horizontal contraction is described in terms of a characteristic delay of the changes in the stress regime and a reduction of elastic strain in the strong crustal layers. The models predict a change in stress state along the flanks of the basin, caused by the development of weak basin lithosphere in their vicinity. Comparing the modelling results with tectonic features of the Pannonian Basin has resulted in the identification of three different stages in the Pliocene-Quaternary basin inversion of the Pannonian-Carpathian system.

Rheology predictions across the western Carpathians, Bohemian massif, and the Pannonian basin: Implications for tectonic scenarios

Tectonics, 1999

On the basis of extrapolation of failure criteria, lithology, and temperature models, we predict the rheology of the lithosphere for several sections through the Carpathians and surrounding regions. Our models show significant lateral variations in rheology for the different tectonic units, with important implications for the tectonic evolution. The rheologically strong lithosphere of the Polish Platform area contrasts with the weak lithosphere of the Pannonian basin, indicating that the arcuate shape of the Carpathian orogen is primarily caused by an inherited curvature of an ancient embayment in the foreland, with the Pannonian units passively filling the space. The Polish Platform and the Moesian Platform exhibit a similar rheological anisotropy caused by NW-SE trending weakness zones paralleling the Tomquist -Teisseyre zone. This anisotropy was the main controlling factor on the behavior of the lithosphere in this area since Cadomian times, as documented by the geological evolution of the Sudety Mountains and the Mesozoic Polish Trough, including the Late Cretaceous Alpine inversion and the Neogene development of the Carpathian foreland. This rheological anisotropy appears to have a major controlling impact on the development of at least the eastern part of the European lithosphere. Rheology predictions for the Bohemian massif support the idea that the rigid lithosphere of the Bohemian massif governed the bending of the Alpine-Carpathian transition zone, expressed in the large-scale wrench movements opening the Vienna basin. In the foreland area, detachment levels are predicted for upper and lower crustal levels, leading to a decoupling of crustal and •ubcrustal flexure in most areas. Comparison with basin formation models indicates that our predictions for effective elastic thickness (EET) are similar to those derived from flexural models for the foreland area. Also, EET predictions from extensional basin models in the Pannonian region yield values close to our findings.

Block rotation by strike-slip faulting: Structural and paleomagnetic evidence

Journal of Geophysical Research: Solid Earth, 1984

Geometric analysis shows that motion of sets of strike-slip faults should cause block rotation; otherwise the distorted fault domain would not fit with its surrounding. The sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults, all of which can be obtained from structural data. The predictions of the geometric model can then be independently tested by paleomagnetic measurements. The model was tested in northern Israel. Structural data reveal several domains of contemporaneous right-and leftlateral strike-slip faults. Paleomagnetic measurements show that in a domain of NNW trending left-lateral faults, blocks rotated 23.3o+8.2 ø clockwise, and in a domain of rightlateral faults, blocks rotated 22.4o+9.0 ø anticlockwise. These results are in agreement with the prediction of the geometric analysis of the structure. The combined results of the heterogenous deformation of the area resembles a pure shear which allows N-S extension by about 1.3. In other domains, rotations of 34.6ø+9.1 ø and 53.1ø+11.0 ø were found. In their original orientation the left-and right-lateral faults intersected at angles of 60o-70 ø , enclosing the principal axis of shortening, in accordance with theories of brittle failure. As a result of block rotations, this angle is now larger and may reach 110 ø. The results demonstrate large block rotations, in different senses, in domains of strikeslip faults. The independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model. Northern Israel is considered to be a good model for this efficient mechanism of intraplate deformation, which is expected to occur in similar tectonic settings elsewhere. each of the faults within a domain must be related to the rotation of the blocks, and (2) the faults themselves must also rotate because they are the boundaries of the blocks (Figure 1). This idea was applied to several areas of strikeslip tectonics in eastern Iran [Freund, 1970a],

Strain localization due to structural in-homogeneities in the Central European Basin System

International Journal of Earth Sciences, 2008

The large-scale crustal deformations observed in the Central European Basin System (CEBS) are the result of the interplay between several controlling factors, among which lateral rheological heterogeneities play a key role. We present a finite-element integral thin sheet model of stress and strain distribution within the CEBS. Unlike many previous models, this study is based on thermo-mechanical data to quantify the impact of lateral contrasts on the tectonic deformation. Elasto-plastic material behaviour is used for both the mantle and the crust, and the effects of the sedimentary fill are also investigated. The consistency of model results is ensured through comparisons with observed data. The results resemble the present-day dynamics and kinematics when: (1) a weak granite-like lower crust below the Elbe Fault System is modelled in contrast to a stronger lower crust in the area extending north of the Elbe Line throughout the Baltic region; and (2) a transition domain in the upper mantle is considered between the shallow mantle of the Variscan domain and the deep mantle beneath the East European Craton (EEC), extending from the Elbe Line in the south till the Tornquist Zone. The strain localizations observed along these structural contrasts strongly enhance the dominant role played by large structural domains in stiffening the propagation of tectonic deformation and in controlling the basin formation and the evolution in the CEBS.

Block model versus thermomechanical model: new insights on the present-day regional deformation in the surroundings of the Calabrian Arc

Geological Society, London, Special Publications, 2010

A finite-element thermomechanical model is used to analyse present-day crustal deformation in the surroundings of the Calabrian Arc. The major structural complexities of the Tyrrhenian area are taken into account, along with the rheological properties of the rocks resulting from a thermal analysis. A comparison between the results obtained from a model composed of three wide rheologically uniform blocks and those obtained from the thermomechanical model allows us to better constrain the geophysical assumptions and shed light on the roles of the different active mechanisms acting in the Tyrrhenian. Our comparative analysis enlightens the crucial role played by lateral rheological heterogeneities when deformation is analysed at short wavelengths of a few hundred kilometres of the Tyrrhenian, driving the observed diffuse SW–NE extension within the regional context of active Africa–Eurasia convergence. Furthermore, a χ2 analysis based on comparisons with GPS data confirms the hypothesis...