Boudinage, a common feature in extended competent layers, is primarily controlled by the mechanical contrast between the layer and its surrounding host rock. Recent numerical modelling has demonstrated that the aperture of veins precipitated between the inter-boudin surfaces of adjacent segments influences both the evolving boudin geometry and the degree of segment separation. This study examines natural aplite boudins from an abandoned quarry near Spitz an der Donau (Bohemian Massif, Austria) to quantify their segment aspect ratios (A) and the normalized initial gap widths (B) of quartz veins separating the segments. The objective is to assess the influence of parameters A and B on boudin shape and segment separation, and to provide natural examples that complement previous numerical investigations. Consistent with model predictions, no statistically significant correlation was found between aspect ratio A and boudin shape. In contrast, the calculated B-values qualitatively show a strong influence on both boudin geometry and segment separation, supporting numerical results that suggest larger B-values promote more efficient separation. Additionally, small B-values favour the development of a central convex bulge on the otherwise concave inter-boudin surface, a feature documented here for the first time in natural examples. However, the findings indicate that using boudins as strain gauges to estimate background extension is challenging and yields only minimum strain values. The observed variability in initial inter-boudin gap widths within a single dyke, along with evidence of internal foliation predating segment separation, suggests that both the standard and strain reversal methods may substantially underestimate extensional strain.

Eclogite lenses are exposed within the orthogneiss-dominated core of the Orlica-& Sacute;nie & zdot;nik Dome in the Sudetes, which forms the northeastern margin of the Bohemian Massif (Variscan Belt of Central Europe). The presence of coesite inclusions in garnet and omphacite confirms that these eclogites underwent ultrahigh-pressure metamorphism. This interpretation is further supported by phase equilibria modelling, which indicates peak-pressure metamorphic conditions of 2.9-3.2 GPa and 750 degrees C-830 degrees C. The results are consistent with estimates derived from conventional geothermobarometry and Zr-in-rutile thermometry applied to rutile inclusions in garnet. Based on quartz-in-garnet elastic barometry, a maximum entrapment pressure of approximately 2.0 GPa is obtained. We interpret this discrepancy as a result of viscous relaxation of garnet at high temperature. The first stage of re-equilibration during decompression occurred at a pressure of 2.0-2.2 GPa and a temperature of 680 degrees C-770 degrees C. The observed rock associations exhibit similarities to other UHP occurrences within the Saxo-Thuringian Zone, suggesting a comparable exhumation mechanism. This likely involved initial buoyancy-driven exhumation within a subduction channel, followed by crustal-scale folding. Furthermore, the maximum pressure recorded in the eclogites may partly reflect nonlithostatic components, such as transient pressure variations arising from rheological heterogeneity between the eclogites and their host rocks.

We investigate how multilayer stack geometry and viscosity stratification influences fold shapes, focusing on the case of a competent layer embedded within a layered host subject to 60% layer-parallel shortening. First, we compare the growth rate spectra calculated with an upscaled anisotropic model and a fully discrete multilayer model. We derive a novel analytical expression for growth rates of a single layer embedded in a confined anisotropic medium. The growth rates computed for the layered host case inherently split depending on whether the low- or high viscosity host layer is in contact with the main layer. For fine host layering, their average converges to the growth rates calculated for the equivalent anisotropic host. Further, using a series of two-dimensional finite element numerical simulations, we vary the internal structure of host layering and analyse the resulting fold patterns. To isolate the influence of geometric configuration, we adjust host layer viscosities to maintain a fixed effective host anisotropy factor across the simulations. To quantify fold shapes in deforming multilayer sequences, we propose a new method that is based on reconstructing an average fold shape for each folded layer. Using the fold classification diagram of Srivastava and Lisle (2004), we obtain a robust characterization of the simulated fold geometries and analyse shape variations within each model and across studied multilayer configurations. Our results demonstrate that even for the same effective anisotropy factor, variations in host layer thicknesses produce a wide spectrum of fold shapes, emphasising the important role of host layer geometry in controlling fold development.

Steep limestone plateaus of the Northern Calcareous Alps rise abruptly above deeply incised valleys, yet despite their sharp relief, they rarely experience large-scale slope failures. To understand why these massifs remain remarkably stable, we investigated five alpine karst plateaus: Göll, Untersberg, Hagengebirge, Tennengebirge, and Totes Gebirge, using a combination of speleothem geochronology, structural mapping, limit equilibrium analysis and elastic stress modelling. Cave archives reveal a long-lived history of episodic gravitational deformation spanning the last 550 ka. Individual slip events remained small (<40 cm) and did not evolve into continuous rupture surfaces, even though the region experienced repeated glaciations and intermittent tectonic reactivation along the Königssee–Lammertal–Traunsee and Lammertal fault systems. Both stress modelling and structural data show that near-surface deformation is governed mostly by gravitational loading and steep topography, whereas far-field tectonic stresses prevail in the deeper parts of the massifs, with the greatest disturbances in the ridges and edge of the plateaus. Limit equilibrium analyses further demonstrate that the thick-bedded, high-cohesion Dachstein limestones remain stable under dry static conditions, with slip reactivation requiring transient triggers such as seismic loading. Together, these results highlight the stabilizing role of cohesive limestone, the limited persistence of discontinuities, and efficient karst drainage. Even under strong climatic and tectonic perturbations, deep-seated slope deformation in these massifs remained limited in magnitude. This provides new insight into the mechanical resilience of Alpine karst plateaus and constrains the long-term behaviour of carbonate slopes subjected to combined geodynamic and climatic forcing.

The Snieznik eclogites experienced peak ultrahigh-pressure (UHP) metamorphism in around ~770°C at ~3.2 GPa followed by isothermal decompression and amphibolite-facies retrogression during Variscan Orogeny. The well-preserved peak metamorphic assemblage of these UHP eclogites comprises garnet + omphacite + kyanite + phengite + rutile + coesite. The mineral assemblage connected with the isothermal decompression episode is present in the form of diopside-amphibole-plagioclase symplectites that are locally disintegrating the main foliation. Here, we investigate plagioclase rims developed around kyanite at the interface with quartz and diopside-plagioclase symplectite. They are present only around kyanite occurring in the vicinity of zones developed during the isothermal decompression event. In some parts, the plagioclase rims are locally replaced by the diopside-plagioclase symplectite. The monomineralic plagioclase rims, having max. 20 µm radial thickness, are polycrystalline. They consist of individual plagioclase grains (each 2-15 µm in diameter) with different crystallographic orientations. The rims as a whole exhibit zoning with the highest Ca content observed at the contact with the kyanite grains. The measured CaO content increases from ~2% near quartz and diopside-plagioclase symplectite to ~6% at the kyanite boundary. In this contribution we investigate the chemical and mechanical effects, that might have contributed to the preservation of the observed zoning and the microstructural heterogeneity of the rims.

Due to the presence of low-viscosity rock-salt, evaporite sequences show a remarkable susceptibility to deformation across diverse geological settings. These sequences often exhibit intercalations of rock-salt with siliciclastic rocks, anhydrite, and sometimes various bittern salts like carnallite and bischofite. Their distinct layering serves as invaluable markers, facilitating a comprehensive analysis of internal salt deformation. The extensive deformation of the evaporites often gives rise to complex internal architectures within the salt body, characterized by commonly observed fold structures. The geometries of these structures are highly sensitive to the mechanical properties of the layers, thus offering profound insights into rock-salt rheology. Unravelling the rheological behaviour of rock-salt holds significant implications, particularly in salt mining, salt cavern operation, and advancing our understanding of salt tectonics. In this project, we focus on specific outcrops within salt mines located in Romania, Austria, and Poland, where prominently exposed fold structures offer unique field laboratories. These sites hold significant potential for deciphering the mechanical behaviour of rocks during their long-term deformation. In our study, we combined field observations, detailed mapping and microstructural analysis of various single and multilayer folds complemented by numerical models of fold evolution. In our numerical simulations, we use the Carreau model for rock-salt, which captures two primary deformation mechanisms: pressure solution and dislocation creep. The mechanisms correspondingly result in the linear (Newtonian) and non-linear (power-law) rheological regimes, influenced by rock grain size and differential stress. Varying the rock-salt grain size enabled us to analyse fold evolution in both regimes as well as in the transitional domain. By systematically comparing our numerical analysis with field observations, we refine our understanding of the mechanical properties of evaporites, contributing to advancements in the study of rock deformation.

The presented study is a part of a broader project, which includes field as well as numerical investigations into the evolution of tectonic structures within fold-and-thrust belts, with a particular focus on the development of fault-related structures in layered rocks. The existing models for deformation in fold-and-thrusts belts predominantly adopt a kinematic approach, wherein layering is considered as passive. The kinematic approach neglects rheological effects such as mechanical anisotropy, which plays an important role in layered rocks commonly found within fold-and-thrusts belts. To explore the role of mechanical anisotropy we have analysed folding and thrusting in the central Northern Calcareous Alps (NCA), which comprise the Permo-Mesozoic sediments of the Upper Austroalpine unit. The NCA represents a fold and thrust belt, in which folds are formed by processes along overthrusts (e.g. fault-bend folds or fault-propagation folds), but out-of-syncline overthrusts are also present. The tectonic evolution of NCA is strongly influenced by sedimentary facies. Nappes in the NCA were imbricated during Jurassic and Cretaceous thrusting. Our research has focused on the Scythian (Lower Triassic) mixed clastic-carbonate sediments of the Werfen Fm, located to the SW of Hallstatt at the base of the fold-and-thrust system, as well as on the Upper Jurassic limestones of the Oberalm Fm located SE of Bad Ischl that are deformed syndepositionally into thrusts and folds forming the shallowest part of the fold-and-thrust belt during the Jurassic deformation stage. During fieldwork, documentation was gathered through the acquisition of orientation measurements of tectonic structures: folded bedding, faults with slickensides, fold axes, cleavage, joints, etc. Photographic documentation of tectonic structures was undertaken to produce georeferenced photogrammetric models. Digital outcrop models in the form of georeferenced textured polygon meshes, which allow the integration of spatial data with the results of detailed geological mapping, were created. All field observations, including outcrop images and measurements, were integrated in a 3D environment, which facilitated the collection of additional data from the digital models. Sequential restoration and kinematic forward modelling of structures performed in Move software confirm the limitations inherent with kinematic modelling to represent real-world strain patterns. Hybrid modes of kinematic models provide more acceptable results and prove that rheological contrasts within the sedimentary pile exert a strong control in the distribution of folding and faulting. These observations made at the meter-scale, relate to structures that represent a scale of strain normally not represented in regional-scale (kilometer-scale) cross-sections and dealt with as ‘internal strain’. Our observations imply that strain distribution within sedimentary units can be strongly anisotropic and its distribution should be contemplated when performing kinematic modelling of regional-scale structures.

We investigated the salt deposits found within the Altaussee salt mine, which represent the Permian to Triassic evaporitic Haselgebirge Formation situated in the Northern Calcerous Alps (Austria). The extensive deformation of the evaporite sequence spanning from the Middle Triassic to Neogene periods led to the formation of a tectonic mélange. The sediments commonly comprise fragments of anhydrite, polyhalite, sandstone and limestone embedded in the halite-rich matrix. The dimensions of these blocks can exceed 10 meters in diameter, while the bulk volume of halite content in these layers is ranging from approximately 30 to 65 volume percent. Our investigation focuses on the internal structure within the evaporite sequence. In particular, we examine various outcrops in caverns, galleries, and corridors that illustrate the role of block shape and size on the deformation pattern. Particularly noteworthy are findings from a large, well-exposed salt cavern ceiling covering approximately 4000 square meters. Utilizing tailored photogrammetric approach, image post processing techniques and using lidar data as reference, we generated detailed ortophoto map of 1000 square meters of cavern ceiling with resolution of 1 mm/pixel. This reveals intricate patterns around rigid blocks and their interactions at different scales. Fine layering within the rock salt allowed to illustrate spectacular structures that developed around the rigid blocks and also interaction between the blocks. Significantly, observations of layer deflection beneath blocks hint at potential block-sinking dynamics, offering valuable insights into the complex geological processes at play.

Giant polygonal anhydrite ridges with diameters of 2-4 km have been identified in the NE margin of the Southern Permian Basin in Poland. The primary ridges reach heights of 80-120 m, and secondary ridges, <40 m in height, subdivide them into smaller cells similar to 1 km in diameter. The ridges were up to similar to 40% higher before the alteration of gypsum to anhydrite. Both seismic and gravity surveys indicate the presence of similar structures over an area of thousands of square kilometers. Two alternative hypotheses, gypsum diapirism and free water convection, are proposed to explain their formation.

The Śnieżnik Massif forms the eastern part of the Orlica-Śnieżnik Dome (OSD), located in the north-eastern part of the European Variscan Belt. The OSD, which exposes the root zone of the Variscan Orogen, comprises mostly orthogneisses containing small bodies of ultra-high pressure (UHP) eclogites. Previous studies on the metamorphic conditions recorded by these eclogites yielded inconsistent results. Some authors suggest that they were metamorphosed in conditions of ~1.9-2.2 GPa and ~700-750 °C 1. Others, however, argue that the eclogites experienced nearly-UHP peak metamorphic conditions of ~2.6-3.0 GPa and 800-930 °C.2This study provides the first evidence of UHP metamorphic episode recorded in eclogites from the OSD, as coesite inclusions were discovered in garnet and omphacite grains. This finding is consistent with our results obtained using Grt-Cpx-Ky-Ph-Coe/Qtz geothermobarometry and phase equilibria modelling, which both indicated conditions of peak metamorphism of ~2.8 – 3.2 GPa and ~830-870 °C, partially overlapping the coesite stability field.We also applied quartz-in-garnet elastic barometry to provide additional constraints on the pressure conditions of metamorphism. About 60 inclusions of quartz were identified using Raman spectroscopy. The residual pressure calculated from the spectral shifts of 464 cm-1 characteristic quartz Raman band reaches a maximum of ~0.73 GPa. This corresponds to the entrapment pressure of ~2.1 GPa, calculated based on the elastic solution for an isotropic spherical inclusion. This estimation contradicts the results coming from methods based on equilibrium thermodynamics. Moreover, such low peak pressure would not explain the presence of the observed coesite inclusions. We hypothesize that the discrepancy might be related to viscous relaxation of garnet host grains under such high peak metamorphic temperatures. References[1] Štípská, P. et al. The juxtaposition of eclogite and mid-crustal rocks in the Orlica-Śnieżnik Dome, Bohemian Massif. J. Metamorph. Geol. 30, 213–234 (2012).[2] Majka, J. et al. Integrating X-ray mapping and microtomography of garnet with thermobarometry to define the P-T evolution of the (near) UHP Międzygórze eclogite, Sudetes, SW Poland. J. Metamorph. Geol. 37, 97–112 (2019).

The Strzegom – Sobótka Massif has been subject of brittle tectonics studies for more than a century. Due to an ongoing extensive mining activity, numerous good exposures occur in a relatively small area, especially in the western part of the massif. A pioneering tectonic model of jointing in granite was established by Cloos (1922) for the study area, in which the NW-SE striking joint set is the dominant one (Q) and the perpendicular set (S), striking NE-SW, is longitudinal to mineral fabric. Also, there are two sets of the so-called diagonal joints, which are supposedly younger and strike N-S and W-E.The effects of field work conducted in 20 quarries in the Strzegom – Sobótka Massiff are presented in the form of a tectonic map. In addition to direct measurements in the field, photogrammetric models were produced using aerial photographs to allow structural analysis within hardly accessible walls. For inaccessible quarries joint orientations were extracted using orthophoto maps. Several examples of fault related structures were identified and documented during field work in the studied granite quarries. Faults with slickensides and kinematic indicators were scarce but paleostress analyses were conducted whenever possible.We discuss our field measurements of joint and fault orientations in relation to different petrographic types of granites and their lateral extent to address the effects of petrographic differentiation on the evolution of brittle tectonic structures in granites. We compare our new measurements to the results of previous tectonic studies of the Strzegom – Sobótka Massiff and paleostress analyses conducted for several other parts of the Sudetes. We also discuss our new results in terms of the Alpine reactivation of the Sudetes Mountains.

&lt;p&gt;Flow perturbation can deflect the layering of the host rock around slip surfaces in shear zones resulting in the development of flanking structures. The details of flanking structure geometry can provide important clues about shear sense, flow kinematics, and finite strain, although not without ambiguities. The developing structures share similarities to fault-related folds that play an important role in sedimentary basins.&lt;/p&gt; &lt;p&gt;Mechanical anisotropy has been shown to have a major influence on both the slip rate and flow perturbation. Willis (1964) derived an analytical solution for an elliptical inclusion embedded in a homogeneous anisotropic elastic matrix subject to a uniform load in the far field. The solution can be reduced to the case of an incompressible viscous medium and an arbitrarily oriented inviscid slit (slip line). The reduced solution, which is exact for the initial state of homogeneous planar anisotropy, provides useful insights into the initial stages of deformation and it can be used to approximately study finite strain deformation of a power-law host. However, anisotropic fluids such as ductilely deforming foliated rocks keep a &amp;#8216;memory&amp;#8217; of deformation due to their evolving microstructure, which affects the flow field. In this study, I will use different numerical modeling techniques to examine the impact of host layering on the perturbing flow and structure development around a slip surface in shear zone.&lt;/p&gt;

The Kamieniec Metamorphic Belt belongs to the Variscan Belt of Europe as the NE part of the Bohemian Massif. It comprises a supracrustal succession dominated by micaschists that has not been yet recognized as a high‐ P , low‐ T ( HP – LT ) metamorphic unit. Our work demonstrates the significance of metapelites in the study of HP metamorphism of the NE part of the Bohemian Massif. To reconstruct the P–T history of the Kamieniec Metamorphic Belt, we have investigated three samples using independent geothermobarometric techniques including phase diagram modelling, Si 4+ content in white mica and quartz‐in‐garnet elastic barometry. Two samples contain mineral assemblages bearing a record of HP metamorphism followed by an LP event. The oldest assemblage is mostly preserved in the first generation of garnet and it comprises phengitic white mica and rutile. In one of the investigated samples, we also recognized chloritoid and inferred pseudomorphs after lawsonite composed of quartz, clinozoisite associated with margarite. The third of the investigated samples is strongly retrogressed and only contains the relics of phengitic white mica. All three samples contain a younger mineral assemblage comprising white mica with low Si 4+ content and ilmenite. Mineral equilibria modelling indicates the P–T conditions of the HP event culminated at ~15.5–18 kbar and ~470–570℃, while the LP episode occurred at ~5–7 kbar and ~530–570℃. The Raman shift measured in quartz inclusions in garnet in samples with a well‐preserved record of the HP stage points to their entrapment at pressures between 11 and 16 kbar. The quartz inclusions within the strongly retrogressed micaschist sample exhibit Raman shifts corresponding to the LP episode at ~5–8 kbar. Discrepant results obtained for one of the samples are discussed in detail. Our investigations show that the supracrustal succession of the Kamieniec Metamorphic Belt contains a record of HP–LT metamorphism typical for subduction systems. A recently established tectonic model for the crystalline complexes exposed in the Bohemian Massif suggests that they were formed via the collision of the Saxothuringian, Teplá–Barrandian, and Brunovistulian domains. Therefore, we interpret the Kamieniec Metamorphic Belt as representing fragments of the Saxothuringian crust that experienced cold extrusion from below the Teplá–Barrandian domain in front of the rigid Brunovistulian indenter.

We aim to describe flow patterns that develop in the mechanically stratified evaporite sequence during the basement-involved deformation. We use numerical methods and examine various initial setups, where different lithological profiles of the sequence and vertical offsets along the fault are tested. To better illustrate the impact of layering, we compare our results with the models containing no internal stratification. The results clearly show that the mechanical stratification can have a great impact on the flow pattern initiating heterogeneous deformation within the sequence.

We present a study on the dependence of the frictional properties of a fault rock on its degree of damage. The purpose is therefore to gain insight into frictional sliding, the governing force that controls earthquake nucleation, propagation and arrest. The focus on this topic is to try to find a reason for the experimental evidence that the friction coefficient seems to be almost independent on lithology. A possible explanation to investigate through the numerical modelling could be that the frictional properties of a realistic fault rock depend mostly on the concentration of micro- to macroscopic cracks and/or of lamellar phyllosilicates in the host rock, rather than on the composition of its bulk materials. The formalism of the Linear Elastic Fracture Mechanics (LEFM) can quantitatively reproduce the stresses and the strains on the interface propagating frictional rupture. The purpose is to use a Finite Element Method (FEM) numerical code in order to simulate the plane strain elastic deformation of a two-dimensional medium crossed by elliptical fractures and weak anisotropic inclusions. The analysis of the distribution and orientation of the stresses resulting from the interaction of a system of randomly oriented elliptical fractures under different loading conditions could provide information on the onset and propagation of frictional ruptures, such as real contact area reduction, slip velocity, number and length of global sliding precursors. The magnitude and orientation of the principal stresses around the tips of elliptical voids are crucial for the understanding of fracture coalescence and frictional reactivation of shear cracks in an elastic rock, which in turn is one of the main factors that govern the seismic cycle of natural faults.

Flanking structures are deflections of an existing planar fabric (e.g., foliation) alongside a cross-cutting element (e.g., a vein) that can develop in a wide range of rock types and glacier ice. Nearly all published examples of flanking structures are interpreted to have formed either under simple shear or transpressional general shear, although theoretically they should also form under transtensional general shear. This paper describes the geometry and development of transtensional flanking structures in glacial ice of the Pasterze, Austria's largest alpine valley glacier. The cross-cutting elements are a few metres long and are interpreted as fractures that rotate into the shear flow and consequently accommodate anti- and synthetic offset, forming a- and s-type flanking folds. However, shear bands, with co-shearing cross-cutting elements inclined against the shear flow, are absent. The geometries of the mapped structures are successfully reproduced with a semi-analytical modified Eshelby solution for a frictionless cross-cutting element embedded in a linear viscous medium deforming under a remote transtensional sub-simple shear. The geometry of the mapped flanking folds, the absence of shear bands, the spatial variation of cross-cutting element orientations and the geometry of the glacier's splaying crevasses are consistent with two-dimensional transtensional sub-simple shear caused by down-glacier valley widening.

Earthquakes at lower crustal depths are common during continental collision. However, the coseismic weakening mechanisms required to propagate an earthquake at high pressures are poorly understood. Transient high-pressure fluids or melts have been proposed as a viable mechanism, but verifying this requires direct in situ measurement of fluid or melt overpressure along fault planes that have hosted dynamic ruptures. Here, we report direct measurement of highly overpressurized frictional melts along a seismic fault surface. Using Raman spectroscopy, we identified high-pressure quartz inclusions sealed in dendritic garnets that grew from frictional melts formed by lower crustal earthquakes in the Bergen Arcs, Western Norway. Melt pressure was estimated to be 1.8–2.3 GPa on the basis of an elastic model for the quartz-in-garnet system. This is ~0.5 GPa higher than the pressure recorded by the surrounding pseudotachylyte matrix and wall rocks. The recorded melt pressure could not arise solely from the volume expansion of melting, and we propose that it was generated when melt pressure approached the maximum principal stress in a system subject to high differential stress. The associated palaeostress field demonstrates that a strong lower crust accommodated up to 1 GPa differential stress during the compressive stage of the Caledonian orogeny.

Raman elastic thermobarometry has recently been applied in many petrological studies to recover the pressure and temperature (P–T) conditions of mineral inclusion entrapment. Existing modelling methods in petrology either adopt an assumption of a spherical, isotropic inclusion embedded in an isotropic, infinite host or use numerical techniques such as the finite-element method to simulate the residual stress and strain state preserved in the non-spherical anisotropic inclusions. Here, we use the Eshelby solution to develop an analytical framework for calculating the residual stress and strain state of an elastically anisotropic, ellipsoidal inclusion in an infinite, isotropic host. The analytical solution is applicable to any class of inclusion symmetry and an arbitrary inclusion aspect ratio. Explicit expressions are derived for some symmetry classes, including tetragonal, hexagonal, and trigonal. The effect of changing the aspect ratio on residual stress is investigated, including quartz, zircon, rutile, apatite, and diamond inclusions in garnet host. Quartz is demonstrated to be the least affected, while rutile is the most affected. For prolate quartz inclusion (c axis longer than a axis), the effect of varying the aspect ratio on Raman shift is demonstrated to be insignificant. When c/a=5, only ca. 0.3 cm−1 wavenumber variation is induced as compared to the spherical inclusion shape. For oblate quartz inclusions, the effect is more significant, when c/a=0.5, ca. 0.8 cm−1 wavenumber variation for the 464 cm−1 band is induced compared to the reference spherical inclusion case. We also show that it is possible to fit an effective ellipsoid to obtain a proxy for the averaged residual stress or strain within a faceted inclusion. The difference between the volumetrically averaged stress of a faceted inclusion and the analytically calculated stress from the best-fitted effective ellipsoid is calculated to obtain the root-mean-square deviation (RMSD) for quartz, zircon, rutile, apatite, and diamond inclusions in garnet host. Based on the results of 500 randomly generated (a wide range of aspect ratio and random crystallographic orientation) faceted inclusions, we show that the volumetrically averaged stress serves as an excellent stress measure and the associated RMSD is less than 2 %, except for diamond, which has a systematically higher RMSD (ca. 8 %). This expands the applicability of the analytical solution for any arbitrary inclusion shape in practical Raman measurements.

SUMMARYKnowledge about the stress state in sedimentary basins gives insight into geodynamics of a given region, natural fracture development and is important in design of underground engineering operations, such as hydraulic fracturing. As the direct stress measurements are expensive, usually very limited amount of data is available, and the stress state assessment bases on theoretical models. In this work, we review the commonly used stress prediction models. We focus especially on the ones which take into account material viscoelasticity, and stress transfer between layers characterized by different mechanical properties. We extend the stress-driven elastic model to material viscoelasticity, and we apply it to predict stress changes during last glacial cycle in the Baltic basin, northern Poland. We conclude that neglecting material viscoelasticity in creeping rocks like shales or rock salt may lead to erroneous stress prediction, and that coupling of the layers induces stress transfer among layers, and together with stress relaxation in ductile layers may result in significant stress amplification in strong (elastic) layers. Finally, we emphasize the crucial role of initial stress assessment.