In salt‐detached fold‐and‐thrust belts, contractional modification of salt structures may include decapitation by thrusting, but examples are not well known in the subsurface and undocumented in outcrop. Here we present a surface exposure of an intrasalt, sub‐horizontal shear zone at the boundary between the Tarcău and Subcarpathian nappes in the Romanian Eastern Carpathians. The Mânzălești diapir forms the largest rock salt outcrop in Europe, with unique salt‐karst geomorphology. Numerous wells show that the outcrop is above deep‐seated salt of a precursor salt‐cored anticline or passive diapir whose base is at >3,500 m. Multiscale observations using UAV‐based digital outcrop models, fieldwork, and microstructure analysis show that the outcrop is characterized by sub‐horizontal foliation with isoclinal folds, unlike the subvertical fabric of most Romanian diapirs. The halite is rich in clastic inclusions, with a power‐law size distribution caused by tectonic reworking of originally impure salt. Microstructures show that the halite matrix is strongly deformed by dislocation creep, forming subgrains and dynamically recrystallized grains around large porphyroclasts with piezometry indicating relatively high differential stress of around 4 MPa, at pressures sufficient to suppress dilatancy. The observations are best explained by sub‐horizontal shear generated by an overriding nappe, overprinting an original coarse‐grained salt fabric during decapitation of the salt body.

The Inner Moray Firth Basin (IMFB) forms the western arm of the North Sea trilete rift system that initiated mainly during the Late Jurassic–Early Cretaceous with the widespread development of major NE–SW-trending dip-slip growth faults. The IMFB is superimposed over the southern part of the older Devonian Orcadian Basin. The potential influence of older rift-related faults on the kinematics of later Mesozoic basin opening has received little attention, partly owing to the poor resolution of offshore seismic reflection data at depth. New field observations augmented by drone photography and photogrammetry, coupled with U–Pb geochronology, have been used to explore the kinematic history of faulting in onshore exposures along the southern IMFB margin. Dip-slip north–south- to NNE–SSW-striking Devonian growth faults are recognized that have undergone later dextral reactivation during NNW–SSE extension. The U–Pb calcite dating of a sample from the synkinematic calcite veins associated with this later episode shows that the age of fault reactivation is 130.99 ± 4.60 Ma (Hauterivian). The recognition of dextral-oblique Early Cretaceous reactivation of faults related to the underlying and older Orcadian Basin highlights the importance of structural inheritance in controlling basin- to sub-basin-scale architectures and how this influences the kinematics of IMFB rifting. Supplementary material: Analytical protocols and analysed sample details are available at https://doi.org/10.6084/m9.figshare.c.5635432

The separation and characterisation of different deformation events in superimposed basins can be challenging due to the effects of overprinting and/or fault reactivation, combined with a lack of detailed geological or geophysical data. This paper shows how an onshore study can be enhanced using a targeted interpretation of contiguous structures offshore imaged by seismic reflection data. Two deformation events, including evidence of fault reactivation, are recognised and associated with the onshore part of the Lossiemouth Fault Zone (LFZ), southern‐central Inner Moray Firth Basin. The basin is thought to record a history of Permian to Cenozoic deformation, but it is difficult to conclusively define the age of faulting and fault reactivation. However, structures in onshore outcrops of Permo–Triassic strata show no evidence of fault growth, and new interpretation of seismic reflection profiles in the offshore area reveals that Permo–Triassic fills are widely characterised by subsidence and passive infill of post‐Variscan palaeotopography. We propose that sequences of reactivated faulting observed onshore and offshore can be correlated and can be shown in the latter domain to be Early Jurassic–Late Cretaceous, followed by localised Cenozoic reactivation. The workflow used here can be applied to characterise deformation events in other superimposed rift basins with contiguous onshore (surface)—offshore (subsurface) expressions.

Like many rift basins worldwide, the Inner Moray Firth Basin (IMFB) is bounded by major reactivated fault zones, including the Helmsdale Fault and the Great Glen Fault (GGF). The Jurassic successions exposed onshore close to these faults at Helmsdale and Shandwick preserve folding, calcite veining and minor faulting consistent with sinistral (Helmsdale Fault) and dextral (GGF) transtensional movements. This deformation has been widely attributed to Cenozoic post-rift fault reactivation. Onshore fieldwork and U–Pb calcite geochronology of five vein samples associated with transtensional movements along the Helmsdale Fault and a splay of the GGF show that faulting occurred during the Early Cretaceous ( c. 128–115 Ma, Barremian–Aptian), while the Helmsdale Fault preserves evidence for earlier Late Jurassic sinistral movements ( c. 159 Ma, Oxfordian). This demonstrates that both basin-bounding faults were substantially reactivated during the episodic NW–SE-directed Mesozoic rifting that formed the IMFB. Although there is good evidence for Cenozoic reactivation of the GGF offshore, the extent of such deformation along the north coast of the IMFB remains uncertain. Our findings illustrate the importance of oblique-slip reactivation processes in shaping the evolution of continental rift basins given that this deformation style may not be immediately obvious in interpretations of offshore seismic reflection data. Supplementary Material: Appendix A – orthomosaic model obtained from unmanned aerial vehicle (UAV) photography of the Helmsdale locality (GeoTiff format); Appendix B – orthomosaic model obtained from UAV photography of the Shandwick locality (GeoTiff format); Appendix C – geochronology data; and Appendix D – additional thin section microphotographs of sample HD1 showing repeated cycles of syntaxial grain growth are available at https://doi.org/10.6084/m9.figshare.c.6708518

Salt, pivotal in societal evolution and vital in scientific and economic domains, notably in chemical and hydrocarbon industries, gains relevance amid the climate crisis. As the shift from fossil fuels to sustainable energy sources becomes imperative, salt deposits can advance the energy transition, notably by large-scale hydrogen storage in solution-mined caverns. Other promising applications include carbon capture utilization and storage, and geothermal energy. Due to its potential role in energy transition and the required novel geotechnical solutions, research focusing on salt's contribution remains an emerging field. The Transylvanian Basin (Romania), provides opportunities for comprehensive multiscale observations, including surface and subsurface data, offering insights into salt deformation. While studies on salt tectonics in the basin exist, it is generally understudied and the focus on energy transition applications is sparse. This paper aims to review the current state of salt tectonics in the Transylvanian Basin, emphasizing internal deformation complexities, impurity distributions and potential implications for energy transition industries. By shedding light on this significant yet underexplored aspect, this work seeks to stimulate further research interest and prompt comprehensive investigations into salt-related energy transition applications.

Constraining the age of formation and repeated movements along fault arrays in superimposed rift basins helps us to better unravel the kinematic history as well as the role of inherited structures in basin evolution. The Inner Moray Firth Basin (IMFB, western North Sea) overlies rocks of the Caledonian basement, the pre-existing Devonian–Carboniferous Orcadian Basin, and a regionally developed Permo–Triassic North Sea basin system. IMFB rifting occurred mainly in the Upper Jurassic–Lower Cretaceous. The rift basin then experienced further regional tilting, uplift and fault reactivation during the Cenozoic. The Devonian successions exposed onshore along the northwestern coast of IMFB and the southeastern onshore exposures of the Orcadian Basin at Sarclet preserve a variety of fault orientations and structures. Their timing and relationship to the structural development of the wider Orcadian and IMFB are poorly understood. In this study, drone airborne optical images are used to create high-resolution 3D digital outcrops. Analyses of these images are then coupled with detailed field observations and U-Pb geochronology of syn-faulting mineralised veins in order to constrain the orientations and absolute timing of fault populations and decipher the kinematic history of the area. In addition, the findings help to better identify deformation structures associated with earlier basin-forming events. This holistic approach helped identify and characterise multiple deformation events, including the Late Carboniferous inversion of Devonian rifting structures, Permian minor fracturing, Late Jurassic–Early Cretaceous rifting and Cenozoic reactivation and local inversion. We were also able to isolate characteristic structures, fault kinematics, fault rock developments and associated mineralisation types related to these events