Towards resolving Cretaceous to Miocene kinematics of the Adria–Europe contact zone in reconstructions: Inferences from a structural study in a critical Dinarides area

One key element in the current debate analysing the Central Mediterranean evolution is the Cretaceous structure and kinematics of the present-day oroclinal bent contact between Adria- and Europe-derived continental units in the Dinarides, interpreted in different tectonic reconstructions as a subduction-related thrust system or a large-scale strike-slip fault zone. We provide a solution to the debate by a structural and kinematic study in a key area located in central Serbia along the Europe–Adria orogenic suture of the Sava Zone. The results demonstrate that large-scale, top-SW, in- to out-of-sequence thrusting is the dominant mechanism that deformed the observed accretionary wedge-trench sediments during the Late Cretaceous subduction of the Neotethys Ocean and the ensuing Adria–Europe collision. The subsequent Oligocene–Miocene extension of the Pannonian Basin was associated with opposite-sense rotations of different Sava Zone segments, which created the observed ~80° oroclinal bending

Towards resolving Cretaceous to Miocene kinematics of the Adria–Europe contact zone in reconstructions: Inferences from a structural study in a critical Dinarides area

One key element in the current debate analysing the Central Mediterranean evolution is the Cretaceous structure and kinematics of the present-day oroclinal bent contact between Adria- and Europe-derived continental units in the Dinarides, interpreted in different tectonic reconstructions as a subduction-related thrust system or a large-scale strike-slip fault zone. We provide a solution to the debate by a structural and kinematic study in a key area located in central Serbia along the Europe–Adria orogenic suture of the Sava Zone. The results demonstrate that large-scale, top-SW, in- to out-of-sequence thrusting is the dominant mechanism that deformed the observed accretionary wedge-trench sediments during the Late Cretaceous subduction of the Neotethys Ocean and the ensuing Adria–Europe collision. The subsequent Oligocene–Miocene extension of the Pannonian Basin was associated with opposite-sense rotations of different Sava Zone segments, which created the observed ~80° oroclinal bending

Tectonic evolution of the Vršac Mts. (NE Serbia): Inferences from field kinematic and microstructural investigations

The Vršac Mts. in NE Serbia represent the key area to investigate structural relations between the Northern Serbo-Macedonian Subunit and Supragetic Unit of the Dacia Mega-Unit. The geodynamic events during the Variscan orogeny in the Late Paleozoic colligated the two units and led to their metamorphic differentiation. The Late Cretaceous extension exhumed the medium-grade Serbo-Macedonian metamorphic rocks and structurally juxtaposed them against the low-grade metamorphosed basement of the Supragetic Unit along an E-dipping shear zone, which outcrops in the crystalline basement of the Vršac Mts. The subsequent Oligocene–Miocene extension, which led to the formation of the Pannonian Basin, overprinted the effects of earlier tectonic phases to a large extent. Hence, large segments of the Northern Serbo-Macedonian Subunit and the Supragetic Unit, including their contact, were buried beneath the Neogene deposits of the southern part of Pannonian Basin. The tectonic uplift of the Vršac Mts. occurred in middle to late Miocene times along the SW-dipping normal faults that controlled deposition in the adjacent Zagajica Depression. The Miocene extension, triggered by the retreat of Carpathian slab, exhumed the crystalline basement of the mountains, and exposed the Late Cretaceous Serbo-Macedonian/Supragetic extensional contact

The influence of back-arc extension direction on the strain partitioning associated with continental indentation: Analogue modelling and implications for the Circum-Moesian Fault System of South-Eastern Europe

Continental indentation is associated with deformation transfer from shortening to strike-slip faulting and is often affected by subduction related processes such as slab roll-back driven back-arc extension. We use crustal-scale analogue modelling to investigate the effects of extension direction on the strain partitioning and deformation transfer during indentation. The modelling results show that extension parallel to the strike-slip margin of the indenter creates subsidence distributed in several areas which may connect to form a large sedimentary basin behind the indenter. This transtensional basin with v-shape geometry narrows gradually towards the strike-slip margin of the indenter. In contrast, models with extension perpendicular to the strike-slip margin distributes transtensional deformation away from the indenter. Our results are in good correlation with the evolution of the Carpatho-Balkanides orocline of South-Eastern Europe, where the Circum-Moesian Fault System accommodates oroclinal bending during indentation against the Moesian Platform. In this area, the modelling explains the coeval and contrasting extensional features observed along the strike-slip margin and behind the indenter (i.e. the Getic Depression and the Morava Valley Corridor), driven by the roll-back of the Carpathian embayment and Adriatic slabs

Top-view and cross-section photographs from analogue experiments of strain partitioning during coeval indentation and back-arc extension performed in the Tectonic modelling laboratory (TecLab) at Utrecht University

This dataset contains original unaltered top-view and cross-section photographs of 4 crustal-scale analogue models. Top-view photographs were taken at a regular time interval from the beginning until the end of each experiment (for details see below). Cross-section photographs were taken at the end of each experiment. Top-view photographs were used to analyse surface deformation through time and space, while in cross-sections vertical deformation was studied. The dataset is arranged in 4 folders, each containing the data for the individual models (model1 to model4). The folder numbering corresponds to the model numbers as described in Krstekanić et al. (in prep.). Each folder contains two sub-folders named m#-cross-sections and m#-top-views where m stands for the model and # for the number of the model (i.e., the same number as the parent folder). The m#-cross-sections sub-folder contains one top-view photograph showing the locations of the cross-sections as well as the corresponding cross-section photographs. A number in each cross-section photograph is the same as the number next to the cross-section location in the top-view. The m#-top-views sub-folder contains all top-view photographs of that particular model, from its initial, undeformed state to the end of the experiment, showing the surface of the model at the moment of the photo acquisition. All photographs in this dataset are in .jpg format and their names are original generic names created by the camera software at the moment of acquisition. Detailed information about the files as well as information on how the data is processed is given in the explanatory file krstekanic-et-al-2021-data-documentation.docx. Contact person is Nemanja Krstekanić - PhD Candidate - [email protected] - https://www.uu.nl/staff/nkrstekani

Strain partitioning in a large intracontinental strike-slip system accommodating backarc-convex orocline formation: The Circum-Moesian Fault System of the Carpatho-Balkanides

The evolution of oroclines is often driven by the interplay of subduction and indentation associated with complex patterns of deformation transfer from shortening to strike-slip and extension. We study the kinematics and mechanics of indentation in an orocline with a backarc-convex geometry, the European Carpatho-Balkanides Mountains. Within this orocline, the kinematic evolution of the Serbian Carpathians segment is less understood. The results demonstrate that the overall deformation was accommodated by the Circum-Moesian Fault System surrounding the Moesian indenter, where strain was partitioned in a complex network of coeval strike-slip, thrust and normal faults. This system represents one of the largest European intracontinental strike-slip deformation zones, with a northward-increasing accumulated 140 km dextral offset along previously known and newly found faults. These strike-slip faults transfer a significant part of their offset eastwards to thrusting in the Balkanides and westwards to orogen-parallel extension and the formation of intramontane basins. The correlation with paleogeographic and geodynamic reconstructions demonstrates that the overall formation of the fault system is driven by subduction of the Carpathian embayment, resulting in laterally variable amounts of translation and rotation associated with indentation of the Moesian Platform. The onset of Carpathian slab retreat and backarc extension at 20 Ma has dramatically increased the rates of dextral deformation from ~3.5 mm/yr to ~2 cm/yr, facilitated by the pull exerted by the retreating slab. Our study demonstrates that indentation requires a strain partitioning analysis that is adapted to the specificity of deformation mechanics and is, therefore, able to quantify the observed kinematic patterns

Understanding partitioning of deformation in highly arcuate orogenic systems: Inferences from the evolution of the Serbian Carpathians

Highly curved orogens often demonstrate a complex poly-phase tectonic evolution and significant strain partitioning. While the oroclinal bending towards the outer arc is understood to be often driven by rapid slab roll-back, processes driving such bending towards the back-arc domain are less understood. The Serbian segment of the larger, highly bended Carpathians–Balkanides Mountains is one key example where we studied the kinematics of nappe stacking and the mechanics of oroclinal bending by the means of a field kinematic study correlated with available information in adjacent orogenic segments. Although not apparent in the large-scale structure of the Serbian Carpathians, our results demonstrate a poly-phase evolution, where the late Early Cretaceous nappe stacking was followed by Oligocene–middle Miocene ~40° of clockwise rotations. The superposition of Dinarides extension with the oroclinal bending in the Carpathians created overlapping stages of orogen-perpendicular extension and dextral strike-slip coupled with orogen-parallel extension, driven by the 100 km cumulated offset of the Cerna and Timok Faults. Extension was associated with the formation of Oligocene–Miocene basins, providing critical timing constraints for our kinematic study. These deformations were followed by the late Miocene E-ward thrusting of the Upper Getic sub-unit, which was driven by a transfer of deformation in the orocline and around the Moesian Platform during the last stages of Carpathians collision. These results show that the mechanics of oroclinal bending is associated with the activation of strike-slip faults and strain partitioning by bi-modal extension, enhanced by the overlap between different geodynamic processes

Analogue modelling of strain partitioning along a curved strike-slip fault system during backarc-convex orocline formation: Implications for the Cerna-Timok fault system of the Carpatho-Balkanides

Large-scale strike-slip faults are associated with significant strain partitioning in releasing/restraining bends and often display map-view curvatures ending in horse-tail geometries. Such faults are commonly associated with indentation tectonics, where shortening in front of indenters is transferred laterally to transpression, strike-slip and the formation of transtensional/extensional basins. We investigate how these structurally distinct domains are kinematically linked by the means of a crustal-scale analogue modelling approach where a deformable crust is moved against a stable and rigid indenter. The modelling demonstrates that the geometry of the indenter is the major controlling parameter driving strain partitioning and deformation transfer from thrusting and transpression to strike-slip and transtension, whereas the rotation of the mobile plate controls the opening of triangular shaped transtensional basins. Flow of the ductile crust leads to the distribution of deformation over a wider area, facilitating strike-slip splaying into transtension/extension behind the indenter. Our results show a very good correlation with the Moesian indentation in the Carpatho-Balkanides system of South-Eastern Europe, where strain is partitioned around the dextral Cerna and Timok strike-slip faults and transferred to thrusting in the Balkanides part of the Moesian indenter and to transtension/extension in the neighbouring South Carpathians

The influence of back-arc extension direction on the strain partitioning associated with continental indentation: Analogue modelling and implications for the Circum-Moesian Fault System of South-Eastern Europe

Continental indentation is associated with deformation transfer from shortening to strike-slip faulting and is often affected by subduction related processes such as slab roll-back driven back-arc extension. We use crustal-scale analogue modelling to investigate the effects of extension direction on the strain partitioning and deformation transfer during indentation. The modelling results show that extension parallel to the strike-slip margin of the indenter creates subsidence distributed in several areas which may connect to form a large sedimentary basin behind the indenter. This transtensional basin with v-shape geometry narrows gradually towards the strike-slip margin of the indenter. In contrast, models with extension perpendicular to the strike-slip margin distributes transtensional deformation away from the indenter. Our results are in good correlation with the evolution of the Carpatho-Balkanides orocline of South-Eastern Europe, where the Circum-Moesian Fault System accommodates oroclinal bending during indentation against the Moesian Platform. In this area, the modelling explains the coeval and contrasting extensional features observed along the strike-slip margin and behind the indenter (i.e. the Getic Depression and the Morava Valley Corridor), driven by the roll-back of the Carpathian embayment and Adriatic slabs