Meteoric water may or may not infiltrate deeply into high-relief mountain ranges. Along its subsurface circulation path, the water heats up according to the background geothermal gradient and eventually emerges at lower elevation as thermal springs. Whether such topographically-driven circulation establishes or not depends on the host rock’s permeability and/or the hydraulic head. In terms of permeability, fault zones play an important role as they can provide preferential flow paths for fluids. This is particularly the case of active fault zones along which recurring slip counteracts clogging caused by mineral precipitation often found along non-active structures. Thus, the investigation of 4D fault and fracture geometries and their kinematics is a means to understand the locations and dynamics of geothermal systems in orogenic belts. Here, we present preliminary results from the ongoing GeoTex research project, which aims at better defining the geothermal potential of the Rhône Valley, an area of rugged topography in SW Switzerland. The Rhône Valley represents a geothermally active zone within the Alpine orogen, which is characterised by numerous thermal springs, regional-scale faults and enhanced seismic activity. It is therefore a promising setting to explore further for exploitation. Based on structural data from fieldwork and quantitative remote sensing, we characterise fault geometries (i.e., spatial orientation, relationship of intersecting fault families as well as kinematics) in the vicinity of known thermal springs. Observable paleo-fluid pathways marked by veins and rock alteration are being considered as analogues for recent thermal water circulation. These circulation paths are linked to major Alpine structures in the underlying basement units, such as large-scale strike-slip faults or the axial planes of uplifting basement domes. Our results suggest spatial correlations between the locations of hydrothermal springs and the 3D structure of the host massifs. Specifically, basement–cover contacts exert geometric and lithologic control at some sites, whereas locally dilatant domains along strike-slip faults as well as intersections of fault families focus outflow at other sites. Through the above approach in combination with seismological data, we have derived conceptual models for fluid flow, which may help to predict the locations of blind active geothermal systems elsewhere in the Rhône Valley.

During rifting, blocks of upper brittle crust may rotate about a vertical axis above the ductile parts of the crust below, in particular in settings where two rift segments interact in a so-called rift-pass structure, with important implications for our understanding of rift system development. However, whether such block rotation is edge-driven (induced by deformation in the brittle crust itself), or by viscous flow in the underlying ductile crust, and what role kinematic coupling between material in the brittle and ductile crust plays remains unclear. In this study, we apply new digital volume correlation (DVC) analysis on a previously presented crustal-scale analogue model simulating the evolution of a rift-pass structure. The improvements to our new DVC workflow include data preprocessing, increased vector resolution, improved postprocessing, and deformation quantification using finite stretch and rotation tensors. This enhanced workflow allows us to quantify the kinematic coupling between the brittle and viscous model layers in much higher spatial resolution, and to determine previously unrecognized differences in deformation styles between the brittle and viscous layers. Our improved DVC analysis reveals new insights into the kinematic evolution of a rotating rift-pass block forming between two interacting rift segments. We document (1) the evolution of a rift-pass block in the brittle layer, (2) its effect on the underlying viscous model layer and, (3) the kinematic coupling between the two model layers. Laterally confined by two rift segments, the rift-pass block rotates about a vertical axis and exerts a drag force on the underlying viscous layer where rift-axis parallel viscous flow is stimulated. As a result, a brittle-ductile transitional zone forms that shows increased shear with spatial and temporal variations in the degree of kinematic brittle-viscous coupling. Our DVC analysis suggests that edge-driven rift-pass block rotation locally weakens kinematic coupling, resulting in rift-axis parallel flow in the lower crust. Hence, rotating blocks in the upper crust may induce considerable amount of lower-crustal material to flow out of a 2D plane, which must be considered when estimating crustal extension from rift-axis perpendicular cross-sections.

Exploring how normal faults evolve is important for understanding the dynamic processes underlying the initiation and evolution of rift systems. Early-stage fault growth has been largely under-explored due to resolution limitations in seismic reflection data and the lack of three-dimensional exposures in the field. Physical analogue modelling offers a unique way to visualize and analyse early-stage fault growth. Here, we present results from an innovative analogue modelling approach that allows us to resolve fault growth in 4D through the use of a medical-grade, X-ray computed tomography (CT) scanner, as well as top-view time-lapse photography and digital image correlation (DIC) analysis. We show that faults establish their vertical height at the earliest stage of deformation and laterally grow via a cyclical growth pattern, alternating between periods of rapid lengthening associated with relay-breaching and segment linkage, and periods characterised by throw accumulation. As extension continues, strain is partitioned onto increasingly fewer, optimally spaced and orientated faults, which continue to lengthen via segment linkage; faults in stress shadows, and/or with double conjugate boundaries, become inactive. It is the first time that fault lengthening and throw have been tracked in 4D with such high-fidelity and that this style of cyclical fault growth has been resolved, representing significant advances in our understanding of normal fault growth from segment-scale to network-scale, made possible only by the innovative use of X-ray CT-scanning.

Abstract. This work investigates the influence of rheological contrasts on the nucleation and behavior of strike-slip faults. To achieve this, we have carried out a series of brittle-viscous strike-slip shear analogue models, using quartz sand and microbeads as granular materials with different internal friction and cohesion values. Particle Imaging Velocimetry (PIV) was applied to time-series of surface images to calculate incremental and cumulative strains. Understanding how strike-slip faults nucleate and interact in the heterogeneous upper crust is relevant in seismic hazard analysis and geothermal and hydrocarbon exploration. To reproduce the heterogeneity of the upper crust, three sets of experiments we performed: 1) upper layer composed either of quartz sand or microbeads; 2) upper layer with a vertical contrast i.e., quartz sand surrounded by microbeads and vice-versa; and 3) same set-up as in the previous set but changing the orientation of the vertical contrast. Our study shows that the introduction of an upper crustal vertical contrast influences the behavior and evolution of strike-slip faults. The models containing a vertical contrast were more complex and induced a compartmentalization of the model. The initial fault strike is related to the material’s properties. However, this initial strike changes when faults crosscut the materials with less internal friction angle clockwise, and anticlockwise when the contrast has higher internal friction angle. Areas containing materials with less internal friction angle take longer to localized the deformation, but they show a greater number of faults. The biggest increase in the number of synthetic and antithetic faults occurs with the introduction of vertical contrast. These results were compared with the intraplate fault systems of the NW Iberian Peninsula, focusing on the Penacova-Régua-Verin and Manteigas-Vilariça-Bragança fault systems. They are major left-lateral faults that cross-cut lithologies characterized by vertical rheological contrasts, with deformation patterns similar to those observed in our analogue models.

This study investigates how lithological changes can affect the strike-slip fault propagation patterns using analogue models. Strike-slip fault zones are long structures that may cut across pre-existing tectonic or lithological steep boundaries. How strike-slip faulting is affected by a laterally heterogeneous upper crust is crucial for understanding the evolution of regional and local fault patterns, stress reorientations, and seismic hazard. Our models undergo sinistral distributed strike-slip shear (simple shear) and have been analysed by particle image velocimetry (PIV). We use quartz sand and microbeads as brittle analogue materials over a viscous mixture to distribute the deformation through the model. The first models investigate strike-slip faulting in a homogeneous upper crust using quartz sand or microbeads only. Three further models examine how the presence of a central section which laterally differs in its properties influences strike-slip faulting. The main observations are the following: The homogeneous upper crust shows typical Mohr-Coulomb strike-slip faults, with synthetic fault strikes related to the angle of internal friction of the material used. The heterogeneous upper crust has a profound effect on synthetic fault propagation, interaction, and linkage, as well as the kinematic evolution of antithetic faults that rotate around a vertical axis. The orientation of the central section determines whether antithetic fault activity concentrates along the entire length of the central contact or not.In the first case, fault activity is segmented or the number of different faults formed is increased in distinct domains. In the second case, the properties of the central material determine fault propagation, interaction, and/or linkage across the central domain.These findings have potential implications for nature that have been seen in the NW Iberian Peninsula. In this area, the change in direction of the sinistral faults and the position of the antithetic faults can be explained due to lithological change.

<p>The inversion of rift basins is commonly associated with the reactivation of normal, basin-bounding faults or shear zones. Analogue models have shown how the reverse reactivation of these pre-existing structures facilitates the uplift of a basin’s sedimentary infill. However, few of these models examine the viscous processes occurring beneath the brittle crust, which may or may not drive basin inversion. In our study, we use lithospheric-scale analogue experiments of orthogonal extension followed by shortening to simulate rifting followed by inversion and orogenesis. Here we explore how the flow behaviours of ductile layers underneath rift basins promote or suppress basin inversion.</p> <p>In our experiments, we simulate rifting by extending a multi-layer, brittle-ductile lithosphere which floats on a fluid asthenosphere, creating a system of distributed basins. This extension is followed by shortening of the model, during which strain is accommodated by the reactivation of basin-bounding faults and folding or upwelling of the ductile layers. These experiments reveal that the rheology of the ductile lower crust and lithospheric mantle, modulated by the imposed bulk strain rate, determine: (1) how rift basins are distributed during extension and (2) whether all or only some of these basins are inverted during shortening. We interpret that this selective basin inversion is related to the superposition of crustal-scale and lithospheric-scale boudinage during the basin-forming extensional phase. Our findings demonstrate that lithospheric-scale analogue models can be a powerful tool for investigating the interaction between brittle and viscous deformation during basin inversion.</p>

Abstract. Basin inversion is commonly attributed to the reverse reactivation of basin-bounding normal faults. This association implies that basin uplift and inversion-related structures are mainly controlled by the frictional behaviour of pre-existing faults and associated damage zones. In this study, we use lithospheric-scale analogue experiments of orthogonal extension followed by shortening to explore how the flow behaviour of ductile layers underneath rift basins promote or suppress basin inversion. Our experiments show that the rheology of the ductile lower crust and lithospheric mantle, modulated by the imposed bulk strain rate, determine (1) basin distribution in a wide rift setting and (2) strain accommodation by fault reactivation and basin uplift during subsequent shortening. When the ductile layers deform uniformly during extension (i.e. stretching) and shortening (i.e. thickening), all of the basins are inverted. When deformation in the ductile layers is localised during extension (i.e. necking) and shortening (i.e. folding), only some basins – which are evenly spaced apart – are inverted. We interpret the latter as selective basin inversion, which may be related to the superposition of crustal-scale and lithospheric-scale boudinage during the previous basin-forming extensional phase and/or folding of the ductile layers during shortening.

Basin inversion is a process that takes place when a sedimentary basin is subjected to compressional stresses resulting in the reactivation of pre-existing faults and/or the localization of deformation along new reverse faults. The Araripe Basin (NE Brazil) is an example of a Cretaceous intracontinental aborted rift, with its sedimentary infill found at ca. 1000 m altitude, 500 m above the host basement. Post-rift basin inversion has been proposed by previous authors as the cause of this topographic high, but how inversion affected this basin remains a matter of debate, with the following two end-member scenarios: reactivation of pre-existing normal faults leading to local uplift or regional uplift and differential erosion. Neither end-member fully explains the observations from seismic and field data. In this study, we, therefore, conducted analogue models to explore how basin inversion in the Araripe Basin could have taken place. We present two series of crustal-scale brittle–viscous experiments: (i) extension followed by compression without sedimentation, with a variation in divergence and convergence directions (orthogonal or 45∘ oblique); and (ii) extension with syn-rift sedimentation followed by compression, with the same variation in rifting and inversion directions. We found that orthogonal rifting without sedimentation forms throughgoing graben boundary faults, whereas oblique rifting initially creates en échelon faults that eventually link up, creating large graben boundary faults. Rift basins with syn-rift sedimentation evolved in a similar fashion; however, sedimentary loading resulted in increased subsidence. During both oblique and orthogonal inversion, most shortening was accommodated along new low-angle reverse faults. Significant intra-graben fault reactivation occurred in all models without syn-rift sedimentation. By contrast, orthogonal inversion of models with syn-rift sedimentation did not reactivate rift faults, whereas only a minor reactivation of rift faults took place during oblique inversion since the sediments strengthened the otherwise weakened basin, thus acting as a buffer during convergence. Based on our modelling results, we propose an alternative scenario for the evolution of the Araripe Basin, involving oblique inversion and the development of low-angle reverse faults, which better fits observations from seismic lines and field data from the region.

Continental rifts evolve by linkage and interaction of adjacent individual segments. As rift segments propagate, they can cause notable re-orientation of the local stress field so that stress orientations deviate from the regional trend. In return, this stress re-orientation can feed back on progressive deformation and may ultimately deflect propagating rift segments in an unexpected way. Here, we employ numerical and analog experiments of continental rifting to investigate the interaction between stress re-orientation and segment linkage. Both model types employ crustal-scale two-layer setups wherein pre-existing linear heterogeneities are introduced by mechanical weak seeds. We test various seed configurations to investigate the effect of (i) two competing rift segments that propagate unilaterally, (ii) linkage of two opposingly propagating rift segments, and (iii) the combination of these configurations on stress re-orientation and rift linkage. Both the analog and numerical models show counterintuitive rift deflection of two sub-parallel propagating rift segments competing for linkage with an opposingly propagating segment. The deflection pattern can be explained by means of stress analysis in numerical experiments wherein stress re-orientation occurs locally and propagates across the model domain as rift segments propagate. Major stress re-orientations may occur locally, which means that faults and rift segment trends do not necessarily align perpendicularly to far-field extension directions. Our results show that strain localization and stress re-orientation are closely linked, mutually influence each other, and may be an important factor for rift deflection among competing rift segments as observed in nature.

Abstract. Basin inversion is a process that takes place when a sedimentary basin is subjected to compressional stresses and may result in the reactivation of pre-existing faults and/or the localization of deformation along new reverse faults. The Araripe Basin (NE Brazil) is an example of a Cretaceous intracontinental aborted rift with its sedimentary infill found at ca. 1000 m altitude in the present day. Post-rift basin inversion is proposed as the cause of this topographic high, however how inversion mechanisms affected this basin is a matter of debate with two end member scenarios: reactivation of pre-existing normal faults leading to local uplift, or regional tectonic uplift. In this study, we conducted analogue models of basin inversion to test these scenarios. We present two series of crustal-scale brittle-viscous experiments: i) extension followed by compression without sedimentation, with a variation of rifting and inversion directions (orthogonal or 45° oblique) and ii) extension and compression with syn-rift sedimentation, with the same variation in rifting and inversion directions. We used a seed representing a structural weakness that was applied at the base of the brittle layer to localize deformation along the model axis. We found that orthogonal rifting without sedimentation forms through-going border faults, whereas oblique rifting creates initial en-echelon faults that eventually link up creating large border faults. Rift basins with syn-rift sedimentation evolved in a similar fashion, however sedimentary loading increased subsidence. During inversion, most deformation is accommodated along new low angle reverse faults. Within that framework, significant intra-graben fault reactivation occurred in models without sedimentation. By contrast, syn-rift sedimentation caused only minor reactivation of rift faults in oblique inversion since the sediments acted as a buffer during compression; no rift fault reactivation occurred in orthogonal compression situations. Comparing the existing scenarios for inversion in the Araripe Basin with our model results and field data show that these scenarios do not fully explain the natural example. Therefore, we propose an alternative scenario based on our models, involving oblique compression and the development of low angle reverse faults, which better explains inversion in the Araripe Basin.

Continental rifts typically result from regional horizontal stretching of the lithosphere and in modelling studies, such rifts are typically assumed to be the result of orthogonal or oblique extension. However, in nature often V-shape rift geometries occur indicating an underlying rotational component that results in a divergence velocity gradient along plate boundaries. Consequently, the geometric, kinematic, and dynamic rift evolution in such rotational settings may significantly differ from those of orthogonal or oblique rifts. Here, we present new findings from an analogue modelling study using a crustal-scale model series with a rotational opening component to investigate the effect of such a rift-axis parallel divergence velocity gradient on fault growth and rift propagation towards the rotation axis. We use a simplified two-layer system simulating an upper brittle and a lower ductile crust with an imposed initial mechanically weak zone on top of the viscous layer to ensure localized rifting. The experimental monitoring by means of a stereoscopic camera setup and X-Ray computed tomography (XRCT) enables a detailed and quantitative investigation of near-surface rift evolution and internal deformation, respectively. With the combination of 3D surface topography, 3D displacement fields, and XRCT, we gain a comprehensive understanding of deformation evolution in analogue models of rotational rifting. Our modelling results depict a novel characterization of normal fault growth under rotational extension and a rift evolution which is described by (1) rift propagation in two consecutive stages: A first stage showing bidirectional fault growth due to segment linkage with high rift propagation rates, and a second stage during which rift propagation occurs by unidirectional fault growth towards the rotation axis with linearly decreasing growth rates at decreasing distance to the rotation axis, (2) strain partitioning between competing conjugate normal faults with fault activity switching repeatedly from one segment of a normal fault to a segment on the oppositely dipping normal fault, and (3) active faulting migrating from the rift boundary faults inwards to intra-rift normal faults. Our quantitative, spatiotemporal fault growth analysis reveals a characteristic segmentation of all deformation features listed above. The conclusion that the gradual decrease of the divergence velocity towards the rotation axis causes segmented deformation propagation is key and can help to understand natural examples of rotational rift settings such as the Taupo Rift Zone in New Zealand.

Under modern oxidising Earth surface conditions, dehydrated subducted slabs show Mo isotope compositions as low as 898/95Mo = -1.5 degrees/00, compared to the depleted mantle 898/95Mo = -0.2 degrees/00. Such light Mo isotope compositions reflect the redox-dependent aqueous mobility of isotopically heavy Mo associated with slab dehydra-tion. Here we analysed basaltic glasses from the South-Mid Atlantic Ridge, whose parental melts are influenced by the enriched Discovery and Shona mantle plumes. We report increasingly higher 898/95Mo of up to -0.1 degrees/00 from the most depleted sam-ples towards those tapping more enriched mantle sources. 898/95Mo values correlate with radiogenic Sr and Nd isotopes, which indicates the recycling of Proterozoic sedi-ments with a Mo isotopic composition that was not affected by subduction-related, oxic dehydration. We propose that the Mo isotope signatures were retained during subduction and reflect anoxic conditions during deep sea sedimentation in the mid-Proterozoic. Finally, Mo isotope fractionation between different terrestrial reservoirs likely depends on the slab redox budget, and therefore on the timing of subduction with regard to Earth's surface oxygenation.

Significant Mo mobility and isotope (δ98/95Mo) fractionation is induced during prograde metamorphism at present-day subduction zones. Depending on the redox conditions during early subduction and accompanied slab dehydration, isotopically heavy Mo is released towards the overlying mantle wedge, leaving behind a depleted, and isotopically light subducted slab. This isotopically light Mo signature has been detected in slab-melt influenced volcanic rocks and potentially will be traceable in ocean-island basalts, if their geochemical signatures are affected by previously subducted lithologies (i.e. slab and overlying sediments). Thus, the isotope composition of mantle plume-influenced volcanic rocks might reveal the nature of subducted and re-incorporated lithologies and possibly redox conditions during subduction. In this study, we present new Mo isotope data for South-Mid Atlantic Ridge basalts that partly interacted with the enriched Discovery and Shona mantle plumes. Isotopically heavier Mo isotope ratios (δ98/95Mo > ambient depleted mantle) are observed in samples tapping a more enriched mantle source. Furthermore, δ98/95Mo correlates with radiogenic isotopes (Sr, Nd, Hf) indicating recycling of a Proterozoic sedimentary components with a Mo isotopic composition that was not modified during and before subduction by Mo mobility under oxidising conditions. Rather, the new Mo isotope data supports and expands on previous stable Se and S isotope evidence that suggests the incorporation of subducted anoxic Proterozoic deep-sea sediments into the mantle of the South-Mid Atlantic Ridge basalts.

Continental rifts are the expression of regional horizontal stretching and are in modelling studies often assumed to be the result of orthogonal or oblique extension. However, naturally occurring V-shaped rift geometries infer an underlying rotational component, resulting in a divergence velocity gradient. Here we use such analogue models of rifting in rotational settings to investigate and quantify the effect of such a divergence velocity gradient on normal fault growth and rift propagation towards a rotation pole. Particularly, we apply different divergence velocities and use different brittle-ductile ratios to simulate different crustal configurations and analyse its effect on rift propagation and surface deformation. Surface deformation is captured using stereoscopic 3D Digital Image Correlation, which allows for quantifying topographic evolution and surface displacement including vertical displacement. In combination with X-Ray computed tomography, we gain insights into the three-dimensional structures in our two-layer models. Based on our models, we present a novel characterisation of normal fault growth under rotational extension which is described by 1) an early stage of bidirectional stepwise growth in length by fault linkage with pulses of high growth rates followed by a longer and continuous stage of unidirectional linear fault growth; 2) segmented rifting activity which promotes strain partitioning among competing conjugate faults and 3) along-strike segmented migration of active faulting from boundary faults inwards to intra-rift faults allowing different fault generations to be simultaneously active over the entire rift length. For models with higher divergence velocities, inward migration is delayed but other first-order observations are similar to models with lower divergence velocities. Our quantitative analysis provides insights on spatiotemporal fault growth and rift propagation in analogue models of rotational rifting. Although natural rifts present complex systems, our models may contribute to a better understanding of natural rift evolution with a rotational component.

The lower parts of warm, thick continental crust can flow in a ductile fashion to accommodate thinning of the upper brittle crust during extension. Naturally occurring continental rifts with a rift‐axis parallel deformation gradient imply an underlying rotational component. In such settings, rift‐parallel crustal flow transports material perpendicular to the direction of rifting. We use analog experiments to investigate rotational rifting and coeval crustal flow. To test the effect of rift‐axis parallel flow on rift evolution, we use different gravitational loads resulting in a range of horizontal pressure gradient magnitudes which drive horizontal lower‐crustal flow. The use of (three dimensional) 3D Digital Volume Correlation techniques on X‐ray CT data combined with 3D Digital Image Correlation techniques applied to topographic stereo images provides detailed insights on the contemporaneous evolution of ductile flow patterns and brittle rift structures, respectively. Our results depict a complex flow field in the ductile lower crust during rotational rifting with: (a) extension‐parallel horizontal inward flow and vertical upward flow that compensates thinning of the brittle upper crustal layer; (b) rift‐axis parallel lateral flow, that compensates greater amounts of thinning further away from the rotation axis; and (c) different degrees of mechanical coupling between the brittle and viscous layers that change during rift propagation. Our analog experiments provide insights into ductile lower crustal flow patterns during rift evolution. The results emphasize the three dimensionality of rifting, which is an important effect that should be considered when estimating the amount of crustal extension from two dimensional (2D) cross sections.

White mica has been widely used to date microstructures and tectonic events in faults, shear-zones and folds because of its suitability for radiogenic dating. However, complex (i) microstructural evolution, (ii) individual chemical evolution of the K-bearing phases, (iii) mixing of ‘detrital grains’ with newly formed and/or recrystallized or chemically reset grains as well as (iv) volume diffusion may result in apparent K-Ar ages. Here, specimens from a prograde sediment sequence of the exhumed fossil European Alpine accretionary wedge were used to investigate resetting processes of white mica by the type and intensity of deformation as well as peak metamorphic conditions. We combine the K-Ar system with mass and mineral quantities from grain size fractions to calculate the amount of recrystallized white mica in each grain size fraction along the metamorphic gradient. Increasing recrystallization with increasing metamorphic grade is related to thermally activated pressure solution and dissolution-precipitation creep, as seen by the formation of a spaced cleavage of recrystallized phyllosilicates documented through Synchrotron X-ray Fluorescence Microscopy and Scanning Electron Microscope imaging techniques. Increasing recrystallization by dissolution-precipitation processes induces chemical resetting of the isotopic system, resulting in a prograde decrease of apparent K-Ar ages. We demonstrate that Ar volume diffusion does not play a significant role for the low-temperature samples, promoting recrystallization as the important physico-chemical process for age resetting. However, white mica chemistry reveals that no simple relation between isotopic resetting and grain size exists along the prograde path. Reliable age information can therefore only be obtained in the case of (nearly) complete resetting, which accounts only for the smallest grain size fraction at the highest metamorphic temperature. These findings could shed new light on accurate dating of mica-rich fault rocks, where the time constraints depend not only on the temperature, but also on the amount and type of deformation.

Here we present new results and findings from an analogue modelling series using an extension gradient to simulate continental rifting in rotational settings. We study the effect of a pressure-gradient driven, rift-axis parallel lower crustal flow on rift propagation. The dynamically scaled two-layer models represent a brittle upper and a ductile lower crust. To simulate different crustal set-ups, we use variable ductile/brittle ratios RDB, where increasing values indicate a hotter crust with the brittle-ductile transition at relatively shallower depth. An additional package of sand on one part of the model simulates tectonic loading to provoke a pressure-gradient driven lower crustal flow. Several factors play a role in dynamic rift propagation such as extension rates, fault evolution and the interplay of vertical motions at the surface as well as model-internal rift-axis parallel horizontal flow. We combine surface and internal deformation analysis using stereoscopic Digital Image Correlation and Digital Volume Correlation applied on surface stereo images and XRCT images, respectively to obtain the fully quantified model deformation. Our results show that rift propagation occurs in two consecutive stages: (i) bidirectional step-wise growth in fault length by linkage and (ii) unidirectional linear fault growth. Strain partitioning of bulk extension causes episodic alternative fault growth on conjugate rift margin faults. Over time, fault activity abandons rift boundary faults and migrates inward creating intra-rift faults. This process occurs segment-wise along the rift axis, where different fault generations are simultaneously active. We quantify increasing lower crustal flow parallel to the rift axis with increasing RDB as the result of tectonic loading. In return, such lower crustal flow causes vertical and horizontal motions at the surface expressed by dynamic topography and deformation features. These results give insights into deformation processes of rifting and highlight the important role of extension gradients on fault growth and strain partitioning in segmented rotational rift systems. Rift-axis parallel lower crustal flow in rotational rift settings may be of relevance when dealing with restorations of 2D crustal seismic sections across rifts.