Control of inherited structures and mechanical heterogeneities on the internal deformation of the Dolomites Indenter, eastern Southern Alps: a multi-scale analogue modelling study

During the Cenozoic evolution of the Alps, the Adriatic plate is traditionally considered as a rigid indenter. The structure of the northernmost part of the Adriatic plate in the eastern Southern Alps of Italy and Slovenia, referred to as Dolomites Indenter (DI), however, demonstrates significant internal deformation. Mostly Miocene shortening is accommodated within a WSW-ENE striking, S-vergent fold-and-thrust belt overprinting a pre-existing platform-basin geometry related to Jurassic extension. In this contribution we present two new sets of physical analogue experiments, addressing the effect of lateral crustal heterogeneities on the internal deformation of the DI on crustal- and lithospheric scale. The upper crust of the western Trento platform (western DI) is compositionally heterogeneous linked to Permian intrusives and extrusives (i.e., Athesian Volcanic Complex). Together with inherited basement structures this lateral heterogeneity, which strengthened the platform locally, is key for understanding upper crustal deformation and surface uplift patterns associated with Miocene basin inversion. We present brittle crustal-scale analogue experiments with inversion of pre-scribed platform-basin geometries, which indicate that variations in thickness, shape, and basement structure of especially the western platform (WP) have impact on timing and uplift of the DI’s upper crust. The mentioned variations in crustal composition, lead, compared to the reference model with simple platform-basin geometry, to (i) overall fewer thrust sheets, (ii) footwall cut-offs of the frontal thrust further in the hinterland, and to (iii) longer and flatter flats of the frontal thrust. Regarding the topographic evolution, a variation in, e.g., basement structure shows strain localization at the margin of the basal plate and stronger uplift within the southern part of the WP compared to limited uplift of the northern WP, which is consistent with documented little vertical movement north of the Valsugana fault system since the Jurassic. On the scale of the lithosphere, new analogue experiments with pre-scribed platform and basin geometries in the upper crust show similar lateral variations in thrust fault orientation across transfer zones as crustal-scale analogue models (Sieberer et al., 2023). Additionally, lateral variability of ductile lower crustal thickness predicts stronger uplift in areas of thicker lower crust. Documented thickening of the lower crust in some parts of the Southern Alps close to areas of higher uplift, tentatively interpreted being Miocene in age (Jozi Najafabadi et al., 2022), might support this finding. Ultimately our crustal and lithosphere-scale modelling predictions will be validated by high resolution low-temperature thermochronological data which cover the entire Dolomites Indenter

Quantifying continental collision dynamics for Alpine-style orogens

When continents collide, the arrival of positively buoyant continental crust slows down subduction. This collision often leads to the detachment of earlier subducted oceanic lithosphere, which changes the subsequent dynamics of the orogenic system. Recent studies of continental collision infer that the remaining slab may drive convergence through slab roll-back even after detachment. Here we use two-dimensional visco-elasto-plastic thermo-mechanical models to explore the conditions for post-collisional slab steepening versus shallowing by quantifying the dynamics of continental collision for a wide range of parameters. We monitor the evolution of horizontal mantle drag beneath the overriding plate and vertical slab pull to show that these forces have similar magnitudes and interact continuously with each other. We do not observe slab rollback or steepening after slab detachment within our investigated parameter space. Instead, we observe a two-stage elastic and viscous slab rebound process lasting tens of millions of years, which is associated with slab unbending and eduction that together generate orogenic widening and trench shift towards the foreland. Our parametric studies show that the initial length of the oceanic plate and the stratified lithospheric rheology exert a key control on the orogenic evolution. When correlated with previous studies our results suggest that post-detachment slab rollback may only be possible when minor amounts of continental crust subduct. Among the wide variety of natural scenarios, our modelling applies best to the evolution of the Central European Alps. Furthermore, the mantle drag force may play a more important role in continental dynamics than previously thought. Finally, our study illustrates that dynamic analysis is a useful quantitative framework that also intuitively explains observed model kinematics

Inversion of extensional basins parallel and oblique to their boundaries: inferences from analogue models and field observations from the Dolomites Indenter, European eastern Southern Alps

Polyphase deformation of continental crust is analysed through physical analogue models for settings wherein platform–basin geometries at passive continental margins are subject to subsequent shortening and orogenesis. In a first stage, segmentation of the brittle and brittle–ductile models into basins and platforms is achieved by extension. Basins are partly filled with brittle material to allow for a strength difference between basin and platform realms, simulating relatively weaker, incompetent deposits of grabens surrounded by competent pre-rift basement or carbonate platform rock, respectively. In a second stage of deformation, contraction parallel and oblique (10 to 20∘) to the basin axes has been applied, leading to the inversion of basins formed earlier. The experiments show that strength contrasts across platform–basin transitions control the localisation and overall style of compressional deformation, irrespective of the nature of the basal décollement (frictional versus viscous), the rheology of the basin fill, or changing platform–basin thickness ratios. Orientations of thrust faults change laterally across inherited platform–basin transitions throughout all experiments; higher obliquity of basin inversion leads to stronger alignment of thrust curvature with the orientation of pre-existing rift axes. At individual thrust faults, variations in the strike of thrust fronts are accompanied by changes in the shortening direction during incremental phases of deformation. Reactivation of normal faults occurs in oblique basin inversion settings only, favourably at platform–basin transitions where the normal faults face the shortening direction. The amount and style of fault reactivation depend on the material used. Our experiments are relevant for natural cases such as the Dolomites Indenter of the eastern Southern Alps, underlining the importance of inherited geologic features for the subsequent shortening geometries. Field structural data from the western segment of the Belluno thrust of the Valsugana fault system support predicted variations of thrust fault orientation and a lateral change in shortening direction (from SSW to SSE along-strike) along one single fault. Based on our modelling results, we suggest that this variability of thrust fault orientation and shortening directions, controlled by inherited structures, is consistent with strain partitioning during a single phase of deformation and does not necessarily reflect different deformation phases

Analogue modelling of basin inversion: a review and future perspectives

Basin inversion involves the reversal of subsidence in a basin due to compressional tectonic forces, leading to uplift of the basin's sedimentary infill. Detailed knowledge of basin inversion is of great importance for scientific, societal, and economic reasons, spurring continued research efforts to better understand the processes involved. Analogue tectonic modelling forms a key part of these efforts, and analogue modellers have conducted numerous studies of basin inversion. In this review paper we recap the advances in our knowledge of basin inversion processes acquired through analogue modelling studies, providing an up-to-date summary of the state of analogue modelling of basin inversion. We describe the different definitions of basin inversion that are being applied by researchers, why basin inversion has been historically an important research topic and what the general mechanics involved in basin inversion are. We subsequently treat the wide range of different experimental approaches used for basin inversion modelling, with attention to the various materials, set-ups, and techniques used for model monitoring and analysing the model results. Our new systematic overviews of generalized model results reveal the diversity of these results, which depend greatly on the chosen set-up, model layering and (oblique) kinematics of inversion, and 3D along-strike structural and kinematic variations in the system. We show how analogue modelling results are in good agreement with numerical models, and how these results help researchers to better understand natural examples of basin inversion. In addition to reviewing the past efforts in the field of analogue modelling, we also shed light on future modelling challenges and identify a number of opportunities for follow-up research. These include the testing of force boundary conditions, adding geological processes such as sedimentation, transport, and erosion; applying state-of-the-art modelling and quantification techniques; and establishing best modelling practices. We also suggest expanding the scope of basin inversion modelling beyond the traditional upper crustal 'North Sea style' of inversion, which may contribute to the ongoing search for clean energy resources. It follows that basin inversion modelling can bring valuable new insights, providing a great incentive to continue our efforts in this field. We therefore hope that this review paper will form an inspiration for future analogue modelling studies of basin inversion

Extending Continental Lithosphere With Lateral Strength Variations: Effects on Deformation Localization and Margin Geometries

We investigate the development of margin geometries during extension of a continental lithosphere containing lateral strength variations. These strength variations may originate from the amalgamation of continents with different mechanical properties as was probably the case when Pangea was assembled. Our aim is to infer if localization of deformation is controlled by the boundary between two lithospheres with different mechanical properties (e.g., “weak” and “strong”) or not. We ran a series of lithosphere-scale physical analog models in which we vary the strength contrast across equally sized lithospheric domains. The models show that deformation always localizes in the relatively weaker compartment, not at the contact between the two domains because the contact is unfavorably oriented for the applied stress and does not behave as a weak, inherited discontinuity. Wide-rifts develop under coupled conditions when the weak lithosphere consists of a brittle crust, ductile crust and ductile mantle. When a brittle upper mantle layer is included in the weak segment, the rift system develops in two phases. First, a wide rift forms until the mechanically strong upper mantle develops a necking instability after which the weak lower crust and weak upper mantle become a coupled, narrow rift system. The margin geometries that result from this two-phase evolution show asymmetry in terms of crustal thickness and basin distribution. This depends heavily on the locus of failure of the strong part of the upper mantle. The models can explain asymmetric conjugate margin geometries without using weak zones to guide deformation localization

Analogue modelling of basin inversion: a review and future perspectives

Basin inversion involves the reversal of subsidence in a basin due to compressional tectonic forces, leading to uplift of the basin's sedimentary infill. Detailed knowledge of basin inversion is of great importance for scientific, societal, and economic reasons, spurring continued research efforts to better understand the processes involved. Analogue tectonic modelling forms a key part of these efforts, and analogue modellers have conducted numerous studies of basin inversion. In this review paper we recap the advances in our knowledge of basin inversion processes acquired through analogue modelling studies, providing an up-to-date summary of the state of analogue modelling of basin inversion. We describe the different definitions of basin inversion that are being applied by researchers, why basin inversion has been historically an important research topic and what the general mechanics involved in basin inversion are. We subsequently treat the wide range of different experimental approaches used for basin inversion modelling, with attention to the various materials, set-ups, and techniques used for model monitoring and analysing the model results. Our new systematic overviews of generalized model results reveal the diversity of these results, which depend greatly on the chosen set-up, model layering and (oblique) kinematics of inversion, and 3D along-strike structural and kinematic variations in the system. We show how analogue modelling results are in good agreement with numerical models, and how these results help researchers to better understand natural examples of basin inversion. In addition to reviewing the past efforts in the field of analogue modelling, we also shed light on future modelling challenges and identify a number of opportunities for follow-up research. These include the testing of force boundary conditions, adding geological processes such as sedimentation, transport, and erosion; applying state-of-the-art modelling and quantification techniques; and establishing best modelling practices. We also suggest expanding the scope of basin inversion modelling beyond the traditional upper crustal "North Sea style " of inversion, which may contribute to the ongoing search for clean energy resources. It follows that basin inversion modelling can bring valuable new insights, providing a great incentive to continue our efforts in this field. We therefore hope that this review paper will form an inspiration for future analogue modelling studies of basin inversion

Integrated analysis of topography and gravity anomalies in analogue modelling: a model of relief evolution in the Iberian Peninsula

El análisis integrado de la topografía y las anomalías gravimétricas en la Península Ibérica invoca a la presencia de grandes pliegues que afectan a toda la litosfera como precursores de los relieves E-O a NE-SO que se distribuyen por el Macizo Varisco, así como a un mecanismo de engrosamiento cortical nucleado a partir de fallas Tardi-Variscas, como origen del relieve del este peninsular (Cadena Ibérica-Costero Catalana) con patrones dominantes E-O, NE-SO y NO-SE. El modo de deformación, así como el estilo, dependen tanto de las propiedades reológicas iniciales de una litosfera a otra (litosfera resistente Varisca hacia el oeste peninsular/litosfera débil y caliente resultado de la extensión Mesozoica hacia el este) como a los accidentes tectónicos pre-existentes. Presentamos una nueva metodología aplicada a la modelación análoga, basada en el estudio del espectro de las anomalías gravimétricas y la topografía que nos han permitido inferir los procesos responsables de la asimetría en el patrón del relieve intra-placa de la Península Ibérica. A su vez, nuestros resultados arrojan luz sobre los mecanismos generadores del relieve en zonas de intra-placa donde la escasez o falta de resolución de los perfiles sísmicos y geomagnéticos impide la interpretación de la parte más profunda de la litosfera como Asia Central o los Atlas del norte de ÁfricaThe integrated analysis of topography and gravity anomalies carried out in the Iberian Peninsula invokes to the presence of large-scale folds affecting the entire lithosphere. Such folds are the precursors of E-W to NE-SO reliefs distributed along the Variscan Massif, meanwhile a mechanism of crustal thickening nucleated along Late-Variscan faults can influence the topographic pattern in the eastern part of Iberia (Iberian Range-Costero Catalan Ranges) characterised by E-W, NE-SW and NWSE trends. The mechanism of deformation as well as the style depends on the initial rheological properties from one lithosphere to another (strong and cold Variscan lithosphere to the west and a relative weak and hot lithosphere affected by the Mesozoic extension to the east) and influenced by pre-existent faults. We present a new approach based on the spectral analyses of topography and gravity over the analogue modelling results that can help to infer the responsible mechanisms for the observed intra-plate relief asymmetry in Iberia. Our results enhance the study of other areas within plate interiors like Central Asia or the Atlas in northern Africa, where the lack of data or resolution from deep seismic profiles or geomagnetics may hamper the interpretation of the lithosphere in depthDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEEspaña. Plan Nacional de Investigación Científica y Desarrollo Tecnológicopu