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The Carpatho-Balkanides of south-eastern Europe is a double 180° curved orogenic system. It is comprised of a foreland-convex orocline, situated in the north and east and a backarc-convex orocline situated in the south and west. The southern orocline of the Carpatho-Balkanides orogen formed during the Cretaceous closure of the Alpine Tethys Ocean and collision of the Dacia mega-unit with the Moesian Platform. Following the main orogen-building processes, the Carpathians subduction and Miocene slab retreat in the West and East Carpathians have driven the formation of the backarc-convex oroclinal bending in the south and west. The orocline formed during clockwise rotation of the Dacia mega-unit and coeval docking against the Moesian indenter. This oroclinal bending was associated with a Paleocene-Eocene orogen-parallel extension that exhumed the Danubian nappes of the South Carpathians and with a large late Oligocene – middle Miocene Circum-Moesian fault system that affected the orogenic system surrounding the Moesian Platform along its southern, western and northern margins. This fault system is composed of various segments that have different and contrasting types of kinematics, which often formed coevally, indicating a large degree of strain partitioning during oroclinal bending. It includes the curved Cerna and Timok faults that cumulate up to 100 km of dextral offset, the lower offset Sokobanja-Zvonce and Rtanj-Pirot dextral strike-slip faults, associated with orogen parallel extension that controls numerous intra-montane basins and thrusting of the western Balkans units over the Moesian Platform. We have performed a field structural study in order to understand the mechanisms of deformation transfer and strain partitioning around the Moesian indenter during oroclinal bending by focusing on kinematics and geometry of large-scale faults within the Circum-Moesian fault system.Our structural analysis shows that the major strike-slip faults are composed of multi-strand geometries associated with significant strain partitioning within tens to hundreds of metres wide deformation zones. Kinematics of the Circum-Moesian fault system changes from transtensional in the north, where the formation of numerous basins is controlled by the Cerna or Timok faults, to strike-slip and transpression in the south, where transcurrent offsets are gradually transferred to thrusting in the Balkanides. The characteristic feature of the whole system is splaying of major faults to facilitate movements around the Moesian indenter. Splaying towards the east connects the Circum-Moesian fault system with deformation observed in the Getic Depression in front of the South Carpathians, while in the south-west the Sokobanja-Zvonce and Rtanj-Pirot faults splay off the Timok Fault. These two faults are connected by coeval E-W oriented normal faults that control several intra-montane basins and accommodate orogen-parallel extension. We infer that all these deformations are driven by the roll-back of the Carpathians slab that exerts a northward pull on the upper Dacia plate in the Serbian Carpathians. However, the variability in deformation styles is controlled by geometry of the Moesian indenter and the distance to Moesia, as the rotation and northward displacements increase gradually to the north and west.

This chapter describes the behaviour of faults in the laboratory. The chapter is organised from small scale to large scale experiments, introducing the reader to general and less general observations of faulting and friction, and showing how these observations are linked to faulting processes occurring in nature. The first section introduces cm-scale friction experiments on gouge materials including the concept of rate-and-state friction, i.e., how velocity affects friction in the quasi-static regime. The following section is devoted to dynamic friction, i.e., observations of friction at high velocity as well as observations of dynamic rupture. The third section discusses the evolution of discrete faults and fault zones in up to meter-scale physical analogue experiments, their dependence on material properties and their significance for the study of large-scale tectonic structures. Finally, the various microstructural features and their possible link to fault stability obtained in the quasi-static regime will be discussed.

The present-day topography in Iberia is related to geodynamic processes dealing with lithospheric-scale deformation. However, little attention has been paid to the role of inherited crustal- or lithospheric-scale structures involved in the recent observed large-scale topographic patterns. Whereas the analysis of brittle structures focuses on the evolution of Mesozoic sedimentary basins and their subsequent response to tectonic inversion, their contribution to mountain building has been underestimated. Large numbers of structures, from ductile to brittle, which affected the whole lithosphere, were developed during the evolution of the Cantabrian orocline (ca. 310-300 Ma). The contribution of these Paleozoic post-Variscan structures, together with lithospheric mantle evolution and replacement during orocline development in the Mesozoic and Cenozoic geological evolution of Iberia, remains unexplored. To explore the role of these inherited structures on the final configuration of topography during N-S Pyrenean shortening, we carried out a series of analogue experiments complemented by surface velocity field analyses. Our experiments indicate that strain was concentrated along preexisting crustal- to lithospheric-scale discontinuities, and they show several reactivation events marked by differences in the velocity vector field. Differences in fault displacement were also observed in the models depending upon preexisting fault trends. The obtained results may explain the different amount of displacement observed during the reactivation of some of the post-orocline structures in Iberia during the Cenozoic, indicating the key role of unveiled structures, which probably have accommodated most of the Alpine shortening., This work was funded by the Spanish Ministry of Science, Innovation and Universities under the project IBERCRUST (PGC2018–096534-B-100) and by Происхождение, металлогения, климатические эффекты и цикличность Крупных Изверженных Провинций (КИП; Origin, Metallogeny, Climatic Effects, and Cyclical Large Igneous Provinces; 14.Y26.31.0012; Russian Federation) to Gutiérrez-Alonso. Fruitful field discussions with M.I. Benito and P. SuárezGonzález are greatly appreciated. We are indebted to Daniel Pastor-Galán, the editor, and three anonym

A series of analogue experiments utilizing sequences of sand with interlayered silicone polymer have been performed to investigate the effects of multistage extension on rock sequences of different strength, with particular reference to the Hoop Fault Complex of the Barents Sea. It was found that the width and style of the graben systems as seen in map view depend strongly on the extension velocity. Wide areas of graben formation are promoted by fast extension, whereas narrowly constrained deep-graben structures are typical of slow extension rates. Furthermore, the decoupling strata are likely to be characterized by flow rather than by distinct detachment faults. The scaled experiments produced units of contrasting fault frequencies and styles in individual sand layers positioned between layers of silicone polymer. It was also found that the fault segments developed from different levels were related to varying extents (hard-linked, soft-linked, firm-linked, unlinked). The fault configurations and the general fault pattern obtained in the experiments is similar to that observed in natural faults where salt or unconsolidated mudstone separate sequences of sand.

Southern Ethiopia is a key region to understand the evolution of the East African rift system, since it is the area of interaction between the main Ethiopian rift (MER) and the Kenyan rift. However, geological data constraining rift evolution in this remote area are still relatively sparse. In this study the timing, distribution, and style of rifting in southern Ethiopia are constrained by new structural, geochronological, and geomorphological data. The border faults in the area are roughly parallel to preexisting basement fabrics and are progressively more oblique with respect to the regional Nubia–Somalia motion proceeding southward. Kinematic indicators along these faults are mainly dip slip, pointing to a progressive rotation of the computed direction of extension toward the south. Radiocarbon data indicate post 30 ka faulting at both western and eastern margins of the MER with limited axial deformation. Similarly, geomorphological data suggest recent fault activity along the western margins of the basins composing the Gofa Province and in the Chew Bahir basin. This supports that interaction between the MER and the Kenyan rift in southern Ethiopia occurs in a 200 km wide zone of ongoing deformation. Fault-related exhumation at ~10–12 Ma in the Gofa Province, as constrained by new apatite fission track data, occurred later than the ~20 Ma basement exhumation of the Chew Bahir basin, thus pointing to a northward propagation of the Kenyan rift-related extension in the area.

Physical analogue experiments are used to investigate the effect of plate and intra-lithospheric coupling on the efficiency of continental lithosphere subduction and the style of collision. Key parameters investigated in this study are: the degree of plate coupling, regulated by the viscosity ratio of the decoupling zone and the surrounding crust and/or mantle lithosphere; and the depth of decoupling. The experimental results show that subduction of the slab is deepest in cases with strong decoupling at the plate interface and at the level of the lower crust of the downgoing plate, with upper-plate deformation restricted to the area close to the plate contact. In these cases, the strongly asymmetric orogenic wedge is widest, consists of a series of imbricated upper-crustal slices derived from the lower plate, and lacks a retro-wedge. In contrast, a reduced strength contrast across the plate interface, at the depth of either the lithospheric mantle or the ductile crust, leads to a combination of subduction and thickening of the mantle lithosphere in both the upper and the lower plates. The degree of plate coupling determines the efficiency of subduction of continental lithosphere under conditions of collision of neutrally buoyant lithospheres, whereas the vertical position of decoupling horizons within the subducting plate controls the amount of subducted lower crust. Transfer of strain to the upper plate depends critically on (1) the degree of plate coupling, with stronger coupling leading to more deformation, and (2) the presence of decoupling horizons within the upper plate, which act as strain guides to propagate deformation into the upper plate. The experimental results explain the geometry and the sequence of deformation in subduction dominated orogens, such as the Carpathians or the Dinarides, and provide a mechanical basis for the transfer of strain to the upper plate.

The role of the plate boundary in a continental collisional setting is investigated by lithospheric-scale analogue models. Key variables in this study are the degree of coupling at the plate interface and along the Moho of the lower plate as well as the geometry of the plate contact. They control the onset of intra plate deformation, orogenic architecture, amount of mantle lithosphere subduction and basin development. In all experiments, deformation initiates at the plate interface by the formation of a pop-up structure. A vertical plate boundary with respect to the shortening direction results in buckling of the lithosphere, whereas experiments with an inclined plate boundary show underthrusting and foreland basin development without orogenic wedge formation. Continental collision and coinciding mantle lithosphere subduction may occur only if the lower crust of the foreland plate is weak enough promoting crust-mantle decoupling. During decoupling the weak lower crust beneath the orogen thickens significantly by ductile flow as it detaches from the down going mantle lithosphere. This lower crustal thickening effects the distribution of upper crustal deformation and topography. Subduction of weak lower crust is favored when the weak plate interface has a significant thickness (~ 15 km in nature) and a high amount of shortening is applied. Increasing coupling at the plate interface through time leads to intra plate deformation by thickening and gentle folding and influences surface uplift and subsidence above the plate interface. The transition from a mechanically decoupled plate boundary with a significant amount of mantle lithosphere subduction towards stronger plate coupling resulting in intra plate deformation and topography development can be recorded in for instance the Caucasus, the Colombian Cordillera, the Pyrenees and the Alps. Thickening of the lower crust as portrayed for the Western Alps does not demand a strong, frictional-type behavior of the lower crust, but can also be the consequence of ductile processes. © 2009 Elsevier B.V. All rights reserved.

Unlike for subaerial settings, the impact of subaqueous relay ramps on sediment dispersal is still poorly understood. A combination of analogue laboratory experiments in a sandbox with numerical flow calculations is used to simulate relay ramp topographies on rifting continental margins and to analyse the resulting turbidity current pathways and their deposits. Various scenarios are investigated, including inflow perpendicular and oblique to the relay ramp axis as well as flow constrained by an incised channel on the ramp and by a landward-directed tilt of the ramp. Without channelling, most sedimentation takes place on the basin floor because the bulk of the flow follows the steepest gradient down the fault and into the rift basin. With a channel along the relay ramp, significant flow occurs initially down the ramp axis, but channel spillover and basinward ramp tilting combine to redirect much of the sediment down the fault slope into the basin. When the relay ramp has a landward-oriented tilt, most of the current flows down the ramp and deposits its sediment load there and at the foot of the ramp. However, also here a considerable amount of the flow is shed over the hanging wall fault and into the basin, forming a secondary depocentre, while ponding redistributes thin deposits over a wider area of the basin. The quantitative dependence of these results on the specific ramp geometries remains to be investigated further but may bear great importance for refined sedimentary models in subaqueous rifted settings as well as for hydrocarbon exploration therein. © 2009 The Authors. Journal compilation © 2009 International Association of Sedimentologists.

Lithospheric-scale analogue experiments have been conducted to investigate the influence of strength heterogeneities on the distribution and mode of crustal-scale deformation, on the resulting geometry of the deformed area, and on its topographic expression. Strength heterogeneities were incorporated by varying the strength of the crust and upper mantle analogue layers and by implementing a weak plate or part-of-a-plate between two stronger ones. Three (brittle crust/ viscous crust/strong viscous upper mantle) and four (brittle crust/ viscous crust/brittle upper mantle/strong viscous upper mantle) layer models were confined by a weak silicone layer on one side in order to contain but not oppose lateral extrusion. Experimental results show that relative strength contrasts between converging plates and intervening weak plates control the location and the shape of deformation sites taken as 'collision orogens'. If the contrast is small, internal deformation of the strong plates through fore- and backthrusting occurs early in the deformation history. However, the bulk system is dominated by buckling that nucleates on the weak plate whose antiformal topography is highest; model Moho of the bordering stronger plates is deepest under these conditions. If the contrast is large, deformation remains localized within the weak plate for a larger amount of shortening and develops a root zone below a narrow deformation belt, which coincides with the locus of maximum topography. Implementing a buoyant, low-viscosity layer above the model Moho of the weak plate favours the development of asymmetric model orogens notwithstanding the initial symmetric setup. Once the asymmetry is established strain remains localized in thrust faults and ductile shear zones documenting foreland directed displacement of the model orogen. Such laterally and vertically irregular configurations have applications in continent-continent collision settings such as the Eastern Alps. First-order mechanical boundary conditions recognized from modelling to be favourable to the post early Oligocene tectonics of the Eastern Alps include: (1) subtle rather than high-strength contrasts between the Adriatic indentor and the strongly deformed region comprising Penninic and Austroalpine units to the north of it; (2) decoupling of Penninic continental upper crust from its substratum to allow for crustal-scale buckling of the Tauern Window; (3) weak mechanical behaviour of the European lower crust during collision to account for its constant thickness along the TRANSALP deep seismic transect; and (4) the direct continuation of the basal detachment underlying the fold and thrust belt in the hangingwall of the European plate with a wide ductile shear zone in the core of the orogen, which separates the European from the Adriatic plate. © The Geological Society of London 2005.

The tectonic evolution of a collisional hinterland sourcing the Ha?eg Basin, a Late Cretaceous syn-orogenic sedimentary basin in the South Carpathians (Romania), is revealed through fission track thermochronology of detrital apatite and zircon grains. This basin formed on the upper plate (Getic unit) in response to Late Cretaceous collision with the lower plate (Danubian unit), an allochtonous continental block of the Moesian Platform, upon closure of a narrow oceanic basin (Severin Basin). The fission track results suggest that Turonian to lower Maastrichtian sediments of the Ha?eg Basin have been dominantly derived from pre-Late Cretaceous sources. The age components they contain relate to pre-Cretaceous tectonothermal events such as the Variscan orogenic cycle, Jurassic rifting and Severin Basin formation, and to Early Cretaceous compressional tectonics. These results are compatible with the tectonic evolution of the upper plate that is identified as the primary source. From the onset of sedimentation (late Albian) until the early Campanian the Ha?eg Basin resembles a piggy-back basin formed on the upper plate concomitant with underthrusting and internal stacking of the lower plate. In contrast, important tectonic subsidence during the late Campanian and early Maastrichtian reflects a shift to extensional tectonics causing the unroofing of the collision zone and the exhumation of lower plate rocks back to the surface. Our fission track data place important constraints on the timing of lower plate erosion that must have commenced during the late Maastrichtian, as documented by the completely reset Late Cretaceous age component within upper Maastrichtian sediments (Sinpetru Formation). Late Maastrichtian uplift of the basin and the formation of positive relief at the site of the collision zone is an expression of continuous convergence. The mismatch between the amount of denudation and the amount of sediments trapped in the Ha?eg Basin underlines the importance of concomitant extensional unroofing.

A key feature of Late Cretaceous tectonics throughout the Alpine-Carpathian-Pannonian (ALCAPA) region is the synchronous formation of sedimentary basins (Gosau basins) and exhumation of metamorphic domes. Initial subsidence, spatially varying in time (Cenomanian-Santonian), within Gosau-type basins is associated with the development of a fluvial-lacustrine to shallow marine environment and the deposition of conglomerates, sandstones, coal-bearing marls and rudist limestones were deposited. The progressive deepening of the marine basins is documented by a second subsidence pulse during the Campanian-Early Maastrichtian leading to the establishment of an open marine environment. Gosau basins on top of the Northern Calcareous Alps and equivalent nappes of the Western Carpathians which were located at or close to the northern to northwestern active margin of the Austroalpine realm (external basins) locally subsided below the CCD. In contrast a distinctly shallower water environment prevailed in Gosau basins in central areas of the actively evolving Alpine-Carpathian mountain chain (internal basins). Deposition of flysch-type deposits is common for the deep-water facies. Subsidence analysis of internal Gosau basins were performed and their mutual relationship to coevally exhuming metamorphic domes, documented by a number of geochronologic data, is emphasised. A compilation of these data revealed a diachronic evolution of the ALCAPA region. Major vertical movements post-dating nappe imbrication and metamorphism started first in the Tisza-Dacia related orogenic compartments (East-, South Carpathians and Apuseni Mts.) as early as Late Aptian, whereas exhumation and subsequent cooling of metamorphic crust in the East Alpine-West Carpathian domain occurs from the Cenomanian onward. This characteristic basement-basin relationship suggests a strong coupling between lithospheric and surface processes, largely controlled by the rheology of the orogenic system. Formation of internal Gosau basins is seen in context with collapse of thickened and gravitationally unstable continental crust.

[1] We present an analysis of the distribution, timing, and characteristics of the volcano-tectonic activity on the western margin of the Southern Main Ethiopian Rift in the Soddo area (latitudes between ~7°10'N and ~6°30'N). The margin is characterized by the presence of numerous normal faults, with limited vertical offset and often sigmoidal in shape, which accommodate a gentle transition from the rift floor to the Ethiopian plateau. New radiocarbon dating indicates post-30 ka fault activity, pointing to a significant Late Pleistocene-Holocene tectonic activity of the Soddo margin. Comparison of the fault architecture with analog models suggests that deformation has been controlled by a sub-E-W (roughly N100°E) extension direction, resulting in an oblique extension with respect to the roughly NE-SW-trending rift. This well accords with inversion of fault slip data collected on faults with Pleistocene-Holocene activity and is also in good agreement with recent GPS data from the Southern Main Ethiopian Rift. Our data support a close correlation between the recent volcanic activity and deformation in the study area, with eruptive vents located along the recent border faults; the axial tectono-magmatic activity is subordinate in the area. These findings support a transition from axial tectono-magmatic deformation in the Northern Main Ethiopian Rift to marginal deformation in the Central and Southern Main Ethiopian Rift, in turn indicating an along-axis, north to south decrease in rift maturity.

[1] We calculate the present-day lithospheric strength of the Eastern Alps along the new reflection seismic profile TRANSALP to examine vertical and lateral strength variations and their implications on neotectonic activity of the Eastern Alps. The large-scale geometry of the Eastern Alps and the spatial distribution of upper, and lower crustal layers, and the lithospheric mantle is constrained by the deep seismic line. Two rheological models, coupled to a kinematic thermal model that accounts for the thermal evolution of the Eastern Alps for the last 30 Myr, are investigated for the present-day lithospheric configuration in the Eastern Alps. Models with strong (Model A) and weak (Model B) crustal rheologies predict the European and the Adriatic plates to be stronger than the central zone of the orogen comprising the region between the Inntal Fault and the Periadriatic Fault. Model A is characterized by a brittle-ductile boundary between 14 and 9 km depth and strong coupling of the mechanically strong lower crust to the upper mantle, whereas Model B suggests the presence of a thick decoupling zone between the upper crust and the upper mantle and a shallower brittle-ductile boundary (7–10 km). Of these end-member scenarios, Model A is in better agreement with neotectonic data including seismicity down to the upper-lower crust boundary within the Adriatic plate, uplift of the central zone of the Eastern Alps and the Southern Alps, and eastward escape of fault-bound blocks. Such deformation pattern is best explained by lateral extrusion upon north-south compression supporting a strong-weak-strong configuration of tectonic units along the TRANSALP line.

The following changes made by the authors during the “uncorrected proof” state of the manuscript have not been taken into account bythe editorial staff of EPSL:1. The research highlights related to this publication are:● Analogue models were employed for studying the continental lithosphere response to shortening under laterally varying strength andcoupling conditions.● Decoupling along plate boundaries favours subduction-type processes and the formation of triangular shaped mountain topography.● Coupling favours deformation by buckling regardless of the initial geometry of weak zones in the lithosphere.● Plateaus and land-locked sedimentary basins at high elevations may form upon the presence of weak zones at mid-crustal levels.● Collision zones evolve from decoupled to coupled systems as the degree of orogenic wedge-foreland plate coupling increases throughtime.2. The in text citation to Cloetingh et al. (2005) relates to:Cloetingh, S. A. P. L., Ziegler, P.A., Beekman, F., Andriessen, P. A. M., Matenco, L., Bada, G., Garcia-Castellanos, D., Hardebol, N., Dezes, P.,Sokoutis, D. (2005). “Lithospheric memory, state of stress and rheology: neotectonic controls on Europe's intraplate continental topography.”Quat. Sci. Rev.3. The in text citation to Iaffaldano and Bunge (2008) relates to:Iaffaldano G., Bunge, H. P. (2008).“Strong plate coupling along the Nazca-South America convergent margin.” Geology 36(6): 443–446.In the above quoted publication the arrowheads in Fig. 6 had disappeared. The correct version of Fig. 6 is shown below.