The architecture of sedimentary basins reflects the relationship between accommodation space and sediment supply, their rates and localization being variable during basin evolution. The mechanisms ...driving the interplay between tectonics and sedimentation in extensional back‐arc basins overlying rheological weak zones inherited from an earlier orogenic evolution are less understood. A typical example is the Pannonian back‐arc basin of Central Europe. It is floored by continental lithosphere and was affected by large amounts of extension driven by the subduction rollback that took place in the Carpathians and/or Dinarides. A novel kinematic and seismic sequence stratigraphic interpretation calibrated by wells allows the quantification of the link between the formation of half grabens and coeval sedimentation in the Great Hungarian Plain part of the basin. While the lower order tectonic‐induced cycles characterize the main phases of extension in various subbasins, the higher‐order cyclicity and associated unconformities define individual moments of fault (re)activation. Our novel interpretation of a temporal and spatial migration of extension during Miocene times explains the contrasting present‐day strike of various subbasins as a result of their gradual clockwise rotation. Incorporating the observed asymmetry, in particular the associated footwall exhumation, infers that the amount of extension is much larger than previously thought. The quantitative link between tectonics and sedimentation has allowed the definition of a novel model of sedimentation in asymmetric basins that can be ported to other natural scenarios of similarly hyperextended back‐arc basins observed elsewhere.
Key Points
Coupled tectonosedimentary evolution of the Pannonian Basin
Kinematics of extension in back‐arc settings
Migration of tectonic phases
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We present a new tomographic model for P- and S-velocity anomalies beneath Europe (30°N–55°N, 5°W–40°E), extending in depth up to 700 km and constrained by inversion of data from the International ...Seismological Center (ISC) catalogue. The algorithm uses the traveltimes from events located in the study area recorded by all available worldwide stations, as well as times from teleseismic events recorded by European stations. The events from the ISC catalogue have been relocated and combined into composite events. All the traveltimes were corrected for crustal structure using the reference model EuCRUST-07. The resulting velocity anomalies show similar large-scale patterns as observed in previous studies, but have a higher resolution, which allows detection of some features in more detail. For example, it is now possible to assess the depth extension of the small slow velocity body beneath the Eifel region and Eger graben. The P and the S model show a good consistency in the uppermost 200 km below most of the European area and in some parts even in the deeper layers (e.g. beneath the Apennines and the Hellenic arc). The new model provides clear images of some principal features, which were previously detected in a limited number of studies, while the comparison between P- and S-velocity anomalies provides novel constraints to address on their nature (e.g. the gap in the Adriatic plate subducted below the central-southern Apennines). In this paper, we pay special attention to testing the reliability of the results. The random noise effect is evaluated using a test with independent inversion of two data subsets (with odd/even events). The spatial resolution is estimated using different checkerboard tests. Furthermore, we present a synthetic model with realistic patterns, which reproduces after performing forward and inverse modelling the same shape and amplitudes of the anomalies as in the case of the real data inversion. In this case, the parameters of the model can be used to assess the amplitudes of P and S anomalies that is critical for evaluation of other petrophysical parameters (temperature, density, composition, etc.) in the upper mantle.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Contractional deformation of passive continental margins may resemble early stages of induced subduction initiation. Mechanical instabilities are required to permit underthrusting of the oceanic ...plate. Therefore, the success of developing a new subduction zone will largely depend on the rheology of the mantle lithosphere. In this physical analogue modelling study, a range of mantle viscosities subject to different convergence rates serve as a proxy to simulate contraction of differently aged passive margins with the purpose of describing and quantifying passive margin deformation and mantle stability using the buoyancy number. The experiments illustrate distinct differences in geometry and length-scale of deformation as a function of lithospheric mantle strengths. The results indicate that deformation occurs at passive margins for intermediate strength lithospheric mantle and high strain rate. In contrast, low and high strength mantle lithospheres lead to dominantly intra-oceanic deformation or long wavelength buckling of the entire model, respectively. Our experiments portray an evolution in which early-stage deformation commences at the ocean-continent transition and is controlled by the ductile lower crust of the continent. In the next stage, shear localization through the formation of a decollement within the ductile passive margin crust favors underthrusting of the oceanic lithosphere, leading to a reduction of the area affected by deformation. Prior to underthrusting, the primary response of the lithosphere to compression is by folding at scaled wavelengths of 100–300 km and 500–1000 km, controlled by the strength of the mantle lithosphere.
•Analogue models are used to infer favourable mechanical conditions for subduction initiation at passive continental margins.•Strength of the ductile lithospheric mantle is key for creating instabilities.•Ductile continental crust is important for focusing deformation at the base of the margin during underthrusting.•Prior to underthrusting, folding at passive margin is the primary response to compression.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The intraplate deformation of Iberia during the Cenozoic produced a series of ranges and deformation belts with a wide variety of structural trends. The Spanish‐Portuguese Central System is the most ...prominent feature crossing over the whole of central Iberia. It is a large thick‐skinned crustal pop‐up with NE‐SW to E‐W thrusts. However, the 500‐km‐long left‐lateral strike‐slip Messejana‐Plasencia fault, also NE‐SW oriented, bends these thrusts to produce NE‐SW local paleostresses close to the fault, which seems to be consistent with a common deformational arrangement. This is also supported by the similar sedimentary infilling characteristics found in the surrounding Cenozoic basins. The moment of the maximum intraplate deformation is registered at the same time in all these basins during the upper Priabonian‐lower Chattian. As there are two possible sources for the intraplate compressive stresses, the Pyrenean (N‐S shortening) orogen to the north and the Betic (NW‐SE shortening) orogen to the south, neither can simply explain both simultaneous movements (NE‐SW strike‐slip and NE‐SW thrusting). The deduced age of the main deformation indicates a Pyrenean origin. In contrast, the concept of strain partitioning between the two types of faults gives as a result an overall north trending compression. Existing data do not support crustal detachment from the Betics neither from the Pyrenees but are consistent with a crustal uplift related to lithospheric folding. The subsequent Betic‐related stress field only slightly reworked previously Pyrenean‐related structures, except for the Portuguese sector, where tectonic activity occurred mainly in the Upper Miocene.
Key Points
The Spanish‐Portuguese Central System (SPCS) is a 2,500‐m‐high Cenozoic intraplate crustal pop‐up, with a length of 700 km and a throw of 5 km, with no evidence for tectonic inversion
The SPCS is northwardly connected to the Pyrenean Orogen. The maximum compression was recorded during the Upper Priabonian to Lower Chattian, with an Upper Tortonian‐Gelasian (Betic) rejuvenation
The presence of the large NE‐SW subvertical Messejana‐Plasencia Jurassic dyke conditioned a strike‐slip displacement in the Messejana‐Plasencia (MP) Fault that was compensated throughout thrusts with the same trend by strain partitioning
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A series of analogue experiments simulating intra-continental subduction contemporaneous with lateral extrusion of the upper plate are performed to study the interference between these two processes ...at crustal levels and in the lithospheric mantle. The models demonstrate that intra-continental subduction and coeval lateral extrusion of the upper plate are compatible processes leading to similar deformation structures within the extruding region as compared to the classical setup, lithosphere-scale indentation. Strong coupling across the subduction boundary allows for the transfer of stresses to the upper plate, where strain regimes are characterized by crustal thickening near a confined margin and dominated by lateral displacement of material near a weak lateral confinement. The strain regimes propagate laterally during ongoing convergence creating an area of overlap characterized by transpression. When subduction is oblique to the convergence direction, the upper plate is less deformed and as a consequence the amount of lateral extrusion decreases. In addition, strain is partitioned along the oblique plate boundary resulting in less subduction in expense of right lateral displacement close to the weak lateral confinement. Both oblique and orthogonal subduction models have a strong resemblance to lateral extrusion tectonics of the Eastern Alps (Europe), where subduction of the adjacent Adriatic plate beneath the Eastern Alps is debated. Our results imply that subduction of Adria is a valid mechanisms to induce extrusion-type deformation within the Eastern Alps lithosphere. Furthermore, our findings suggest that the Oligocene to Late Miocene structural evolution of the Eastern Alps reflects a phase of oblique subduction followed by a later stage of orthogonal subduction conform a Miocene shift in the plate motion of Adria. Oblique subduction also provides a viable mechanism to explain the rapid decrease in slab length of the Adriatic plate beneath the Eastern Alps towards the Pannonian Basin.
•Upper plate lateral extrusion coeval with intra-continental subduction.•Extrusion occurs on the scale of the lithosphere.•Oblique convergence can explain laterally varying lengths of the Adriatic slab.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Back‐arc basin evolution is driven by processes active at the main subduction zone typically assuming the transition from an extensional back‐arc, during the retreat of a mature slab, to a ...contractional basin, during high‐strain collisional processes. Such a transition is observed in the Black Sea, where the accurate quantification of shortening effects is hampered by the kinematically unclear geometries of Cenozoic inversion. By means of seismic profiles interpretation, quantified deformation features and associated syn‐tectonic geometries on the Romanian offshore, this study demonstrates that uplifted areas, observed by exploration studies, form a coherent thick‐skinned thrust system with N‐ward vergence. Thrusting inverted an existing geometry made up by successive grabens that were inherited from the Cretaceous extensional evolution. The shortening started during late Eocene times and gradually affected all areas of the Western Black Sea Basin during Oligocene and Miocene times, deformation being coherently correlated across its western margin. The mechanism of this generalized inversion is the transmission of stresses during the collision recorded in the Pontides‐Balkanides system. Syn‐tectonic sedimentation in the Western Black Sea demonstrates that this process was continuous and took place through the onset of gradual shortening migrating northward. Although the total amount of shortening is roughly constant in an E‐W direction, individual thrusts have variable offsets, deformation being transferred between structures located at distance across the strike of the system. The Black Sea example demonstrates that the vergence and offset of thrusts can change rapidly along the strike of such a compressional back‐arc system. This generates apparently contrasting geometries that accommodate the same orogenic shortening.
Key Points
Kinematics and mechanics of back‐arc basin inversion
W Black Sea evolution, from Cretaceous opening to L Eocene‐M Miocene inversion
Far field transmission of continental collision stresses into the back‐arc basin
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Thermo-tectonic age and inherited structure exert the main controls on the bulk strength of the lithosphere in intraplate settings. Mechanical decoupling within the lithosphere strongly affects the ...interaction between deep Earth and surface processes. Thermo-mechanical models demonstrate the particular importance of the rheological stratification of the lithosphere in the preservation of ancient cratonic blocks, in the surface expression of plume- and mantle lithosphere interactions and their impact on the “dynamic” topography in general. The same is true for the effect of large-scale lithospheric folding on intraplate basin formation and associated differential vertical motions. Initiation of continental lithosphere subduction, crucial for linking orogenic deformation to intraplate deformation, appears to be facilitated by plume–lithosphere interactions. We present a discussion of these aspects, focusing on better process- understanding of continental deformation, in the context of a number of well-documented cases of intraplate deformation.
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► Preservation of cratons is conditioned by strong mantle lithosphere. ► Initiation of continental subduction can be promoted by plume activity. ► Plume–lithosphere interactions can enhance folding and vice versa.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Large-scale intraplate deformation of the crust and the lithosphere in Central Asia as a result of the indentation of India has been extensively documented. In contrast, the impact of continental ...collision between Arabia and Eurasia on lithosphere tectonics in front of the main suture zone, has received much less attention. The resulting Neogene shortening and uplift of the external Zagros, Alborz, Kopeh Dagh and Caucasus Mountain belts in Iran and surrounding areas is characterised by a simultaneous onset of major topography growth at ca. 5Ma. At the same time, subsidence accelerated in the adjacent Caspian, Turan and Amu Darya basins. We present evidence for interference of lithospheric folding patterns induced by the Arabian and Indian collision with Eurasia. Wavelengths and spatial patterns are inferred from satellite-derived topography and gravity models. The observed interference of the patterns of folding appears to be primarily the result of spatial orientation of the two indenters, differences in their convergence velocities and the thermo-mechanical structure of the lithosphere west and east of the Kugitang–Tunka Line.
► We examine the interference of lithospheric folding patterns in west Central Asia. ► Spatial patterns are inferred from satellite-derived topography and gravity models. ► The observed interference is induced by Arabian and Indian collision with Eurasia.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Iberian microcontinent stands out because of its intense Alpine intraplate deformation. This is reflected in a large number of Cenozoic basins of very different sizes. Most of the contacts ...between topographic highs and basins are thrust or strike-slip faults. All these basins seem to have undergone a common sedimentary evolution, comprising four stages: initiation of sedimentation, intense syn-tectonic infilling, change from endorheic to exorheic drainage, and accelerated erosion related to fluvial incision. This simple evolutionary model shows a migration from East to West, in which basins are still tectonically active at the Atlantic margin of Iberia. This common evolution is also found in a series of geometrical characteristics, such as the ratio
r of length of strike-slip fault and length of thrust fault, that are very similar in both types of basin border settings. Thrust-related basins are mainly associated with segmented pop-downs, whereas the main basins have the characteristics of open-ramp basins. Strike-slip related basins are mostly transpressive structures, although small pull-apart basins are usual along the Vilariça and Messejana faults. For basin areas larger than 100–1000
km
2, a constant
r value of 0.6 is found (including the Ebro, Duero, Madrid, Lower Tagus and Badajoz basins). Within the Iberian microcontinent, the total amount of Cenozoic contractional deformation was distributed between strike-slip and thrust faults with an
r ratio close to 0.6. However, for small basins this parameter seems to depend on the type of fault, range or deformation belt (pure strike-slip, transtension, transpression, and pop-up) independently of its local tectonic development.
► In this study we analyze the Cenozoic tectonic evolution of more than 64 Iberian foreland basins. ► Most of the contacts between topographic highs and basins are thrust or strike-slip faults. ► All these basins seem to have undergone a common sedimentary evolution, comprising four stages: initiation of sedimentation, intense syn-tectonic infilling, change from endorheic to exorheic drainage, and accelerated erosion related to fluvial incision. ► For basin areas larger than 100–1000 km2, a constant r value of 0.6 is found. ► For small basins this parameter seems to depend on the type of fault, range or deformation belt (pure strike-slip, transtension, transpression, and pop-up) independently of its local tectonic development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In contractional (subduction/collisional) settings, convergence is accommodated by the formation of thin- and thick-skinned thrust and fold belts. The transmission of such deformation over larger ...distances into orogenic foreland areas is influenced by the inherited rheological characteristics of continental lithosphere. Lateral rheological variations parallel to the strike of continental foreland areas creates contrasting geometries and sequences of deformation that interact during orogenic build-up. We investigate the far-field transmission of strain within a continental lithosphere characterized by a laterally variable rheology through physical analogue modelling. Rheological weak crustal zones were introduced at distance from an advancing backstop to study the progressive along strike linkage and interference of structures during contraction. The results reveal that rheologically weak crustal zones localise far-field contractional deformation. When the size of weak zones, by means of their horizontal extend to depth ratio, is large, deformation localises at the boundaries of the weak zone where they lead to the formation of large-offset faults. Subsequently the faults migrate along-strike into areas that are rheologically stronger. When the size of the weak zone is reduced, a large-scale contractional step-over forms in orogenic forelands, where rheologically contrasting domains transmit out-of-sequence deformation by a gradual migration of thrust offsets and fold amplitudes along their strike. These results show that crustal scale orogenic step-overs do not always reflect variations in the geometry of the plate boundary (indenter) or along-strike gradients in shortening rates. Such features may also form in response to variations in rheology, as the ones created by inherited extensional basins situated at large distances from plate boundaries in the orogenic foreland.
•Crustal weak zone(−s) localise strain at far distance from the indenter.•Contractional step over might reveal the presence of crustal weak zone.•Crustal deformation at weak zone will be associated with lithospheric folding.•The symmetry of lithosphere fold can reveal the lithosphere strength.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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