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Orogenic forelands host interactions between deformation and static or migrating fluids. Given their accessibility and dimensions, these areas are not only historic landmarks for structural geology, but they are also areas of prime interest for georesource exploration and geological storage, and loci of potential geohazards. Geochemical techniques applied on cements filling tectonic structures and associated trapped fluids can constrain the temperature, pressure, origin and pathways of fluids during deformation and allow the characterization of the past fluid system. In this review focused on calcite cements, we first present and critically discuss the most used geochemical techniques to appraise specific parameters of the fluid system. Second, we summarize the outcomes of selected case studies where the past fluid system was reconstructed with consideration of tectonics, either at the scale of the individual fold/thrust or at the scale of the fold-and-thrust belt. At first order, the past fluid system evolves in a similar way with respect to the considered stage of deformation, being rather closed to external fluids when deformation is bounded to mesoscale structure development, and opening to vertical flow when thrust and folds develop. In a more detailed view, it seems that the past fluid system evolves and distributes under the influence of the structural style, of the geometry of the major faults and of the lithology of the sedimentary succession. Through this review, we illustrate the concept of geochemistry-assisted structural geology through case studies where the geochemistry of calcite veins constrained subsurface geometries and structural developments in orogenic forelands. [ABSTRACT FROM AUTHOR]

For this reason, the characterization of the fluid system (origin and nature of the fluid; I T i , I P i , timing of mineral precipitation, degree of fluid-rock interaction, hydraulic structure of the fractured reservoirs) and its evolution through time remains a challenging task (Aubert I et al. i [6], [7]; Petit I et al. i [75]). The relations among fluid migration, fluid storage and rock deformation still remain to be further documented, quantified and integrated in comprehensive models of short-term and long-term fault and fracture behaviours and crustal mechanics, with implications for mineralization pattern and geothermal resources in ancient and active structurally complex, tectonic settings (e.g. Clemenzi I et al. i [24]). However, fault rocks and veins may show a variety of calcite cements, and may also be affected by fluid-rock interactions subsequent to syn-tectonic cement precipitation, for instance during rock exhumation from depth (e.g. Aubert I et al. i [8]). Fractures and faults are common structural elements of shallowly deformed rocks. [Extracted from the article]

Introduction: Intramuscular (IM) midazolam is indicated for the treatment of status epilepticus. Administration must be efficient to rapidly terminate prolonged seizures and prevent complications. The objective of this study was to compare, in terms of relative bioavailability and bioequivalence, IM midazolam injection by needle-free auto-injector, in different settings, to IM midazolam injection by a conventional syringe and needle.In this open-label, randomized, four-period crossover study, healthy adults received single doses of midazolam (10 mg) under fasting conditions. The reference treatment (conventional syringe) was administered once, on bare skin in the thigh. The tested treatment (the needle-free auto-injector ZENEO®) was administered three times: on bare skin in the thigh, on bare skin in the ventrogluteal area, and through clothing in the thigh. Repeated plasma samples were collected to obtain 36-h pharmacokinetic (PK) profiles. Primary PK parameters were area under the plasma concentration–time curve, from time zero to the last measurable time point (AUC0−t) and from time zero to infinity (AUC0–∞), and the maximum observed plasma concentration (Cmax).Forty adults were enrolled and included in the PK analysis set. In all comparisons, the 90% confidence interval (CI) of the least-squares geometric mean ratios for AUC0−t and AUC0−∞ were within the bioequivalence range of 80–125%, with low intra-individual coefficients of variation (< 20.5% for all parameters in all comparisons). Bioequivalence was also met for Cmax in all comparisons except when comparing the tested treatment through clothing versus the reference treatment, where the 90% CI lower limit was slightly outside the bioequivalence range (78.8%). With all tested treatments Cmax was slightly lower, but early mean plasma concentrations (first 10 min post-dosing) were higher when compared to the reference treatment. In general, all treatments were well tolerated, with maximum sedation 0.5–1 h post-injection.This study establishes that IM midazolam injection on bare skin in the thigh with the ZENEO® is bioequivalent to IM midazolam injection with a syringe and needle. An acceptable relative bioavailability, compatible with emergency practice, was also shown in multiple settings. Higher mean concentrations within the first 10 min with the ZENEO® device, and quicker two-step injection suggest a faster onset of action, and thereby an earlier seizure termination, thus preventing the occurrence of prolonged seizure and neurological complications.ClinicalTrials.gov identifier: NCT05026567. Registration first posted August 30, 2021, first patient enrolled May 9, 2022.Methods: Intramuscular (IM) midazolam is indicated for the treatment of status epilepticus. Administration must be efficient to rapidly terminate prolonged seizures and prevent complications. The objective of this study was to compare, in terms of relative bioavailability and bioequivalence, IM midazolam injection by needle-free auto-injector, in different settings, to IM midazolam injection by a conventional syringe and needle.In this open-label, randomized, four-period crossover study, healthy adults received single doses of midazolam (10 mg) under fasting conditions. The reference treatment (conventional syringe) was administered once, on bare skin in the thigh. The tested treatment (the needle-free auto-injector ZENEO®) was administered three times: on bare skin in the thigh, on bare skin in the ventrogluteal area, and through clothing in the thigh. Repeated plasma samples were collected to obtain 36-h pharmacokinetic (PK) profiles. Primary PK parameters were area under the plasma concentration–time curve, from time zero to the last measurable time point (AUC0−t) and from time zero to infinity (AUC0–∞), and the maximum observed plasma concentration (Cmax).Forty adults were enrolled and included in the PK analysis set. In all comparisons, the 90% confidence interval (CI) of the least-squares geometric mean ratios for AUC0−t and AUC0−∞ were within the bioequivalence range of 80–125%, with low intra-individual coefficients of variation (< 20.5% for all parameters in all comparisons). Bioequivalence was also met for Cmax in all comparisons except when comparing the tested treatment through clothing versus the reference treatment, where the 90% CI lower limit was slightly outside the bioequivalence range (78.8%). With all tested treatments Cmax was slightly lower, but early mean plasma concentrations (first 10 min post-dosing) were higher when compared to the reference treatment. In general, all treatments were well tolerated, with maximum sedation 0.5–1 h post-injection.This study establishes that IM midazolam injection on bare skin in the thigh with the ZENEO® is bioequivalent to IM midazolam injection with a syringe and needle. An acceptable relative bioavailability, compatible with emergency practice, was also shown in multiple settings. Higher mean concentrations within the first 10 min with the ZENEO® device, and quicker two-step injection suggest a faster onset of action, and thereby an earlier seizure termination, thus preventing the occurrence of prolonged seizure and neurological complications.ClinicalTrials.gov identifier: NCT05026567. Registration first posted August 30, 2021, first patient enrolled May 9, 2022.Results: Intramuscular (IM) midazolam is indicated for the treatment of status epilepticus. Administration must be efficient to rapidly terminate prolonged seizures and prevent complications. The objective of this study was to compare, in terms of relative bioavailability and bioequivalence, IM midazolam injection by needle-free auto-injector, in different settings, to IM midazolam injection by a conventional syringe and needle.In this open-label, randomized, four-period crossover study, healthy adults received single doses of midazolam (10 mg) under fasting conditions. The reference treatment (conventional syringe) was administered once, on bare skin in the thigh. The tested treatment (the needle-free auto-injector ZENEO®) was administered three times: on bare skin in the thigh, on bare skin in the ventrogluteal area, and through clothing in the thigh. Repeated plasma samples were collected to obtain 36-h pharmacokinetic (PK) profiles. Primary PK parameters were area under the plasma concentration–time curve, from time zero to the last measurable time point (AUC0−t) and from time zero to infinity (AUC0–∞), and the maximum observed plasma concentration (Cmax).Forty adults were enrolled and included in the PK analysis set. In all comparisons, the 90% confidence interval (CI) of the least-squares geometric mean ratios for AUC0−t and AUC0−∞ were within the bioequivalence range of 80–125%, with low intra-individual coefficients of variation (< 20.5% for all parameters in all comparisons). Bioequivalence was also met for Cmax in all comparisons except when comparing the tested treatment through clothing versus the reference treatment, where the 90% CI lower limit was slightly outside the bioequivalence range (78.8%). With all tested treatments Cmax was slightly lower, but early mean plasma concentrations (first 10 min post-dosing) were higher when compared to the reference treatment. In general, all treatments were well tolerated, with maximum sedation 0.5–1 h post-injection.This study establishes that IM midazolam injection on bare skin in the thigh with the ZENEO® is bioequivalent to IM midazolam injection with a syringe and needle. An acceptable relative bioavailability, compatible with emergency practice, was also shown in multiple settings. Higher mean concentrations within the first 10 min with the ZENEO® device, and quicker two-step injection suggest a faster onset of action, and thereby an earlier seizure termination, thus preventing the occurrence of prolonged seizure and neurological complications.ClinicalTrials.gov identifier: NCT05026567. Registration first posted August 30, 2021, first patient enrolled May 9, 2022.Discussion/Conclusion: Intramuscular (IM) midazolam is indicated for the treatment of status epilepticus. Administration must be efficient to rapidly terminate prolonged seizures and prevent complications. The objective of this study was to compare, in terms of relative bioavailability and bioequivalence, IM midazolam injection by needle-free auto-injector, in different settings, to IM midazolam injection by a conventional syringe and needle.In this open-label, randomized, four-period crossover study, healthy adults received single doses of midazolam (10 mg) under fasting conditions. The reference treatment (conventional syringe) was administered once, on bare skin in the thigh. The tested treatment (the needle-free auto-injector ZENEO®) was administered three times: on bare skin in the thigh, on bare skin in the ventrogluteal area, and through clothing in the thigh. Repeated plasma samples were collected to obtain 36-h pharmacokinetic (PK) profiles. Primary PK parameters were area under the plasma concentration–time curve, from time zero to the last measurable time point (AUC0−t) and from time zero to infinity (AUC0–∞), and the maximum observed plasma concentration (Cmax).Forty adults were enrolled and included in the PK analysis set. In all comparisons, the 90% confidence interval (CI) of the least-squares geometric mean ratios for AUC0−t and AUC0−∞ were within the bioequivalence range of 80–125%, with low intra-individual coefficients of variation (< 20.5% for all parameters in all comparisons). Bioequivalence was also met for Cmax in all comparisons except when comparing the tested treatment through clothing versus the reference treatment, where the 90% CI lower limit was slightly outside the bioequivalence range (78.8%). With all tested treatments Cmax was slightly lower, but early mean plasma concentrations (first 10 min post-dosing) were higher when compared to the reference treatment. In general, all treatments were well tolerated, with maximum sedation 0.5–1 h post-injection.This study establishes that IM midazolam injection on bare skin in the thigh with the ZENEO® is bioequivalent to IM midazolam injection with a syringe and needle. An acceptable relative bioavailability, compatible with emergency practice, was also shown in multiple settings. Higher mean concentrations within the first 10 min with the ZENEO® device, and quicker two-step injection suggest a faster onset of action, and thereby an earlier seizure termination, thus preventing the occurrence of prolonged seizure and neurological complications.ClinicalTrials.gov identifier: NCT05026567. Registration first posted August 30, 2021, first patient enrolled May 9, 2022.Trial Registration Information: Intramuscular (IM) midazolam is indicated for the treatment of status epilepticus. Administration must be efficient to rapidly terminate prolonged seizures and prevent complications. The objective of this study was to compare, in terms of relative bioavailability and bioequivalence, IM midazolam injection by needle-free auto-injector, in different settings, to IM midazolam injection by a conventional syringe and needle.In this open-label, randomized, four-period crossover study, healthy adults received single doses of midazolam (10 mg) under fasting conditions. The reference treatment (conventional syringe) was administered once, on bare skin in the thigh. The tested treatment (the needle-free auto-injector ZENEO®) was administered three times: on bare skin in the thigh, on bare skin in the ventrogluteal area, and through clothing in the thigh. Repeated plasma samples were collected to obtain 36-h pharmacokinetic (PK) profiles. Primary PK parameters were area under the plasma concentration–time curve, from time zero to the last measurable time point (AUC0−t) and from time zero to infinity (AUC0–∞), and the maximum observed plasma concentration (Cmax).Forty adults were enrolled and included in the PK analysis set. In all comparisons, the 90% confidence interval (CI) of the least-squares geometric mean ratios for AUC0−t and AUC0−∞ were within the bioequivalence range of 80–125%, with low intra-individual coefficients of variation (< 20.5% for all parameters in all comparisons). Bioequivalence was also met for Cmax in all comparisons except when comparing the tested treatment through clothing versus the reference treatment, where the 90% CI lower limit was slightly outside the bioequivalence range (78.8%). With all tested treatments Cmax was slightly lower, but early mean plasma concentrations (first 10 min post-dosing) were higher when compared to the reference treatment. In general, all treatments were well tolerated, with maximum sedation 0.5–1 h post-injection.This study establishes that IM midazolam injection on bare skin in the thigh with the ZENEO® is bioequivalent to IM midazolam injection with a syringe and needle. An acceptable relative bioavailability, compatible with emergency practice, was also shown in multiple settings. Higher mean concentrations within the first 10 min with the ZENEO® device, and quicker two-step injection suggest a faster onset of action, and thereby an earlier seizure termination, thus preventing the occurrence of prolonged seizure and neurological complications.ClinicalTrials.gov identifier: NCT05026567. Registration first posted August 30, 2021, first patient enrolled May 9, 2022. [ABSTRACT FROM AUTHOR]

The idea that the critical resolved shear stress is the empirical stress at which a statistically significant number of twin nucleation sites become suddenly active provides a possible elegant way to reconcile the picture of the twin-forming process with the practical existence of a critical resolved shear stress [[4]]. Recent calcite twin-based paleopiezometric studies take into account the dependence of the critical resolved shear stress on these parameters ([[6], [12]]). E-twinning is the dominant mechanism of plastic deformation of calcite at low temperature (<300 °C), and in most limestones, e-twins are, at the crystal scale, the dominant microstructures. The adoption of a single critical resolved shear stress for twinning has been challenged [[17]] because the differential stress necessary to produce twinning is dependent upon grain size [[1]] and strain (calcite hardens once twinned) [[18]]. [Extracted from the article]

Dating syntectonic sedimentary sequences is often seen as the unique way to constrain the initiation, duration, and rate of folding as well as the sequence of deformation in the shallow crust. Beyond fold growth, however, deformation mesostructures accommodate the internal strain of pre-folding strata before, during, and after strata tilting. Absolute dating of syn-folding mesostructures may help constrain the duration of fold growth in the absence of preserved growth strata. Absolute dating of mesostructures related to early-folding layer-parallel shortening and late fold tightening provides an access to the timing and duration of the entire folding event. We compile available ages from the literature and provide new U–Pb ages of calcite cements from veins and faults from four folds (Apennines, Pyrenees, Rocky Mountains). Our results not only better constrain the timing of fold growth but also reveal a contraction preceding and following folding, the duration of which might be a function of the tectonic style and regional sequence of deformation. This study paves the way for a better appraisal of folding lifetime and processes and stress evolution in folded domains. [ABSTRACT FROM AUTHOR]

Dating syntectonic sedimentary sequences is often seen as the unique way to constrain the initiation, kinematics and rate of folding and the sequence of deformation in the shallow crust. Beyond fold growth however, deformation mesostructures accommodate the internal shortening of pre-folding strata before, during and after strata tilting. Absolute dating of mesostructures developed during extension at fold hinge may help constrain the duration of fold growth in the absence of preserved growth strata, while dating of mesostructures related to layer-parallel shortening and late fold tightening provide a valuable access to the timing and duration of the entire folding event. We compile existing ages in the literature and provide new U-Pb ages of calcite cements from veins and faults from four folds (Apennines, Pyrenees, Rocky Mountains). Our results not only better constrain the timing of fold growth but also reveal a contraction preceding and following folding, the duration of which might be function of the tectonic style and regional sequence of deformation. This study paves the way for a better appraisial of folding lifetime and processes and of stress evolution in folded domains. [ABSTRACT FROM AUTHOR]

The Sheep Mountain‐Little Sheep Mountain Anticlines, Bighorn Basin (USA) formed as basement‐cored Laramide structures in the formerly undeformed foreland of the thin‐skinned Sevier orogen. We take advantage of the well‐constrained microstructural network there to reconstruct differential stress magnitudes that prevailed during both Sevier and Laramide layer‐parallel shortening (LPS), before the onset of large‐scale folding. Differential stress magnitudes determined from tectonic stylolites are compared and combined to previous stress estimates from calcite twinning paleopiezometry in the same formations. During stress loading related to LPS, differential stress magnitudes transmitted from the distant Sevier thin‐skinned orogen into the sedimentary cover of the Bighorn basin (11–43 MPa) are higher than the differential stress magnitudes accompanying the early stage of LPS related to the thick‐skinned Laramide deformation (2–19 MPa). This study illustrates that the tectonic style of an orogen affects the transmission of early orogenic stress into the stable continental interior. [ABSTRACT FROM AUTHOR]

Accurate characterization of hydrocarbon reservoirs requires a good understanding of the paleostress history of their host sedimentary basin. This study aims at reconstructing the paleoburial and paleostress history of the syn-rift Barremian TOCA Fm. in the Lower Congo basin (West African margin). Two oriented borehole cores drilled offshore Congo were investigated using stress inversion techniques applied to calcite mechanical twins to constrain paleostress orientations and magnitudes. The inversion of calcite twins was performed on a widespread early diagenetic cement (~129 to ~113 Ma) and revealed that the TOCA Fm. has undergone a complex polyphase stress history, including (1) extensional stress regimes with vertical σ 1 and horizontal σ 3 trending NE-SW and WNW-ESE (N100) associated with the rifting episode preceding the opening of the South Atlantic (130 to 112 Ma), and with mean differential stresses of ~47 MPa for (σ 1 -σ 3) and ~ 20 MPa for (σ 2 -σ 3). The early N100 extension is associated with the development of normal faults striking N-S that likely reactivated inherited basement structures. The direction of extension evolved during the Barremian into the main NE-SW extension marked by the dominant normal faults striking NW-SE. (2) Compressional and strike-slip stress regimes with horizontal σ 1 oriented ~N-S possibly related to the far-field intraplate transmission of orogenic stresses generated at the distant Africa-Eurasia plate boundary at ~67–60 Ma, and with mean differential stresses of 40 MPa for (σ 1 -σ 3) and 28 MPa for (σ 2 -σ 3). (3) Compressional and strike-slip stress regimes with horizontal σ 1 oriented ENE-WSW to ~E-W that we tentatively relate to the mid-Atlantic ridge push and prevailing since ~15 Ma onwards, associated with mean differential stresses of ~45 MPa for (σ 1 -σ 3) and ~ 18 MPa for (σ 2 -σ 3). Our results reveal that the TOCA Fm. recorded mainly far-field stress effects that could be related to interactions between the African plate and surrounding plates, and that divergent passive margins may experience a complex tectonic history including both extensional and compressional events. • Calcite twin inversion is used to reconstruct paleostress history on the West Africa passive margin. • The orientations and magnitudes of paleostresses affecting the syn -rift TOCA Fm. are characterized from two offshore cores in the Lower Congo basin. • The timing of the successive stress regimes in the TOCA Fm. is constrained. • The influence of far-field tectonic and gravitational lithospheric stresses transferred from distant plate boundaries on the post-rift history on the West Africa passive margin is demonstrated. [ABSTRACT FROM AUTHOR]

We report U-Pb absolute ages of calcite cements from a diffuse vein network documented in the Bighorn Basin (Wyoming, USA), where distinct systematic vein sets developed at the front of the thin-skinned Sevier orogen, during Laramide layer-parallel shortening, and during thick-skinned Laramide thrusting and folding. The U-Pb age distribution illustrates: (1) an outward (eastward) transmission of Sevier orogenic stress (from 89.7 ± 2.9 Ma [2σ] in the west, and from 75.3 ± 2.8 Ma in the east); and (2) an inward (westward) development of Laramide-related fracturing and folding (72 ± 3.0 Ma and 45.4 ± 1.8 Ma, respectively, in the east; 60.5 ± 4.6 Ma and 27.9 ± 1.1 Ma, respectively, in the west), which is in accordance with the known sequence of exhumation of the major Laramide basement arches. Our results also show that the stress related to Laramide compression first overprinted the stress related to Sevier compression in the sedimentary cover around major basement uplifts. This study highlights the utility of U-Pb calcite geochronology as a powerful tool for constraining complex sequences of deformation in orogenic forelands. [ABSTRACT FROM AUTHOR]

Paleopiezometry provides an access to the past stress magnitude, key to better understand the behaviour of the earth's crust over long period of time. This contribution presents a review of some paleopiezometric techniques that can be used in the diagenetic domain, in fold-and-thrust belts and sedimentary basins. Calcite twinning and stylolite roughness techniques have been selected and are presented through a critical description of their methodologies, along with approaches to further reconstruct the complete effective stress tensor. Major geological lessons learned over the past decades from published studies are summarized and discussed along with a way forward to potential breakthroughs. [ABSTRACT FROM AUTHOR]

In the Kiggavik area (Nunavut, Canada), major fault zones along, or close to, where uranium deposits are found are often associated with occurrence of thick quartz breccia (QB) bodies. These bodies formed in an early stage (~1750 Ma) of the long-lasting tectonic history of the Archean basement, and of the Proterozoic Thelon basin. The main characteristics of the QB are addressed in this study; through field work, macro and microscopic observations, cathodoluminescence microscopy, trace elements, and oxygen isotopic signatures of the quartz forming the QB. Faults formed earlier during syn- to post-orogenic rifting (1850-1750 Ma) were subsequently reactivated, and underwent cycles of cataclasis, pervasive silicification, hydraulic brecciation, and quartz recrystallization. This was synchronous with the circulation of meteoric fluids mixing with Si-rich magmatic-derived fluids at depth, and were coeval with the emplacement of the Kivalliq igneous suite at 1750 Ma. These processes led to the emplacement of up to 30 m thick QB, which behaved as a mechanically strong, transverse hydraulic barrier that localized later fracturing, and compartmentalized/channelized vertical flow of uranium-bearing fluids after the deposition of the Thelon Basin (post 1750 Ma). The development and locations of QB control the location of uranium mineralization in the Kiggavik area. [ABSTRACT FROM AUTHOR]

The inversion of calcite twin data is a powerful tool to reconstruct paleostresses sustained by carbonate rocks during their geological history. Following Etchecopar's (1984) pioneering work, this study presents a new technique for the inversion of calcite twin data that reconstructs the 5 parameters of the deviatoric stress tensors from both monophase and polyphase twin datasets. The uncertainties in the parameters of the stress tensors reconstructed by this new technique are evaluated on numerically-generated datasets. The technique not only reliably defines the 5 parameters of the deviatoric stress tensor, but also reliably separates very close superimposed stress tensors (30° of difference in maximum principal stress orientation or switch between σ 3 and σ 2 axes). The technique is further shown to be robust to sampling bias and to slight variability in the critical resolved shear stress. Due to our still incomplete knowledge of the evolution of the critical resolved shear stress with grain size, our results show that it is recommended to analyze twin data subsets of homogeneous grain size to minimize possible errors, mainly those concerning differential stress values. The methodological uncertainty in principal stress orientations is about ± 10°; it is about ± 0.1 for the stress ratio. For differential stresses, the uncertainty is lower than ± 30%. Applying the technique to vein samples within Mesozoic limestones from the Monte Nero anticline (northern Apennines, Italy) demonstrates its ability to reliably detect and separate tectonically significant paleostress orientations and magnitudes from naturally deformed polyphase samples, hence to fingerprint the regional paleostresses of interest in tectonic studies. [ABSTRACT FROM AUTHOR]

Defining the structural style of fold–thrust belts and understanding the controlling factors are necessary steps towards prediction of their long-term and short-term dynamics, including seismic hazard, and to assess their potential in terms of hydrocarbon exploration. While the thin-skinned structural style has long been a fashionable view for outer parts of orogens worldwide, a wealth of new geological and geophysical studies has pointed out that a description in terms of thick-skinned deformation is, in many cases, more appropriate. This paper aims at providing a review of what we know about basement-involved shortening in foreland fold–thrust belts on the basis of the examination of selected Cenozoic orogens. After describing how structural interpretations of fold–thrust belts have evolved through time, this paper addresses how and the extent to which basement tectonics influence their geometry and their kinematics, and emphasizes the key control exerted by lithosphere rheology, including structural and thermal inheritance, and local/regional boundary conditions on the occurrence of thick-skinned tectonics in the outer parts of orogens. [ABSTRACT FROM PUBLISHER]

Defining the structural style of fold-and-thrust belts is an important step for understanding the factors that control their long- and short-term dynamics, for comprehending seismic hazard associated with them, and for assessing their economic potential. While the thin-skinned model (no basement involvement) has long been the driving methodology for cross section construction and restoration of foreland fold-and-thrust belts, a wealth of new geological and geophysical studies have shown that they are often thick-skinned, that is, basement-involved. [ABSTRACT FROM PUBLISHER]

Abstract: A 3D structural model of the Po Valley basin (Northern Italy) was built by integrating the dataset available from the public domain (DEM, wells, isobath-maps, cross-sections, outcrop-trends). The model shows the complex foredeep-foreland architecture across the basin, from the Moho level to the topography while illustrating the top Basement, top Triassic, top Mesozoic and base-Pliocene surface-grid structures. The results, by model slicing and isopach-map reconstruction, suggest that the deep Moho architecture and the original tectonics of the ancient Adria-Po Valley passive continental margin are key factors in controlling the current structures type, orientation and distribution, at any of the shallowest levels across the basin. In particular, the analysis of the final 3D Mesozoic geometries against the pre and post-Alpine trends confirms the structural interference between the mutually perpendicular Triassic–Jurassic extensional structures and the Tertiary compressional ones, this being evident from the regional to the oil-field scale. Despite the model uncertainty, mainly related to its dimension versus the original non-homogeneous dataset quality and distribution, the final geo-volume offers, for the first time in the region, a continuous three-dimensional visualization of the Po Valley tectonic architecture. It provides, simultaneously, a powerful tool for the reviewing of the basin structures and the potential support to future applications for both industry and academia. [Copyright &y& Elsevier]

Abstract: Reconstructing the evolution of paleofluid (over)pressure in sedimentary basins during deformation is a challenging problem, especially when no hydrocarbon-bearing fluid inclusions are available to provide barometric constraints on the fluid system. This contribution reports the application to a natural case (the Bighorn Basin) of recent methodological advance to access fluid (over)pressure level prevailing in strata during sub-seismic fracture development. The fluid pressure evolution in the Mississippian-Permian Madison–Phosphoria limestone reservoir is tentatively reconstructed from the early Sevier Layer Parallel Shortening to the Laramide folding in two basement-cored folds: the Sheep Mountain Anticline and the Rattlesnake Mountain Anticline. Results point out that supra-hydrostatic pressure values prevail in the limestone reservoir during most of its whole Sevier–Laramide history. The comparison of the reconstructed fluid overpressure values within situ measurements in various overpressure reservoirs in other oil-producing basins highlights that the supra-hydrostatic fluid pressure gradually reaches the lithostatic value during the whole basin contraction and fold development. During most of the LPS history, however, overpressure level can be defined by a mean gradient. Among the factors that control the pressure evolution, the mechanical stratigraphy, the stress regime under which fractures developed and regional fluid flow are likely dominating in the case of the Bighorn Basin, rather than classical factors like disequilibrium compaction or fluid generation during burial. A coeval evolution between fluid overpressure and differential stress build-up is also emphasized. The approach presented in this paper also provides estimates of strata exhumation during folding. [Copyright &y& Elsevier]

Highlights: [•] Study of the hinterland part of the Balkan and Hellenic orogens. [•] New methodological approach to define heterogeneous fault-slip data by taking into account the similarities of their geometry and kinematics. [•] New tectonic scenario of the South Balkan Peninsula since the Oligocene. [•] A model using concepts like lateral extrusion, retreating and advancing plate boundaries, transpressional tectonics. [•] Study of the brittle deformation driven by late orogenic and post-orogenic processes. [ABSTRACT FROM AUTHOR]

Mechanical twins are common microstructures in deformed calcite. Calcite twins have been used for a long time as indicators of stress/strain orientations and magnitudes. Developments during the last decade point toward significant improvements of existing techniques as well as new applications of calcite twin analysis in tectonic studies. This review summarises the recent progress in the understanding of twin formation, including nucleation and growth of twins, and discusses the concept of CRSS and its dependence on several factors such as strain, temperature and grain size. Classical and recent calcite twin measurement techniques are also presented and their pros and cons are discussed. The newly proposed inversion techniques allowing for the use of calcite twins as indicators of orientations and/or magnitudes of stress and strain are summarized. Benefits for tectonic studies are illustrated through the presentation of several applications, from the scale of the individual tectonic structure to the continental scale. The classical use of calcite twin morphology (e.g., thickness) as a straightforward geothermometer is critically discussed in the light of recent observations that thick twins do not always reflect deformation temperature above 170–200 °C. This review also presents how the age of twinning events in natural rocks can be constrained while individual twins cannot be dated yet. Finally, the review addresses the recent technical and conceptual progress in calcite twinning paleopiezometry, together with the promising combination of this paleopiezometer with mechanical analysis of fractures or stylolite roughness. [ABSTRACT FROM AUTHOR]

Abstract: Based on a review of published literature and on the report of a few case studies, this paper summarizes the state of the art on paleostress determinations by fault slip data inversions, with the aim at discussing whether these techniques actually yield a quantity that has a “paleostress meaning” (i.e., ancient stress) and whether there is an adequate basis for a reliable comparison of such “paleostresses” with contemporary stresses in terms of orientations and patterns at different scales of time and space in the Earth''s crust. [Copyright &y& Elsevier]

Pre-/early folding fracture patterns were recognized in several anticlines from three structural domains in the Simply Folded Belt of the Fars arc. These fracture sets were characterized in terms of opening mode and relative chronology and used to reconstruct the main compressional trends related to the early Zagros collisional history. The palaeostress reconstructions based on these fracture sets were further refined by combination with newly collected or already available fault-slip and calcite twin data. As an alternative to previous models of rigid block rotations or regional stress rotation, we propose that the complex pattern of pre-folding fractures and the contrasting palaeostress orientations through time in the different domains investigated are related to the presence of basement faults with N–S and WNW trends, above which basement and cover were variably coupled during stress build-up and early deformation of the Arabian margin. Beyond regional implications, this study draws attention to the need to carefully consider pre-existing fractures, possibly unrelated to folding, to build more realistic conceptual fold–fracture models. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new approach to constrain paleoburial and subsequent uplift by folding in fold–thrust belts, combining differential stress estimates from mechanically-induced calcite twins with the assumption that stress in the upper crust is in frictional equilibrium. Calcite twin data were collected from pre-folding veins in late Cretaceous limestones from the Ionian zone in Albania in order to (1) determine Paleogene–Neogene stresses associated with the development of the major vein sets in the frontal anticlines of the Outer Albanides and (2) estimate paleoburial of the Cretaceous reservoir rocks during pre-folding flexural subsidence of the foreland. The first vein set (set I) trends N140 (±20) and the second set (set II) is oriented N060 (±20). Calcite twinning analysis from set I veins reveals a pre-folding N030° extension likely related to foreland flexure; a later pre-folding, NE-directed compression (LPS) is identified either from one or from both vein sets in the samples from the Saranda anticline; this NE compression is instead recorded by twinning in set II veins from the Kremenara anticline during late stage fold tightening. This NE compression well agrees with independent microtectonic data, regional transport direction and contemporary stress. The differential stress values related to this NE compression are combined with the hypothesis of crustal frictional stress equilibrium to derive first-order estimates of paleoburial of the Cretaceous limestones just before they were uplifted by folding. The ~4 km paleoburial of these limestones estimated in the Saranda anticline is consistent with independent paleoburial estimates from stratigraphy, maturity rank of organic matter, paleotemperature/paleogeothermal gradients from fluid inclusions and predictions of kinematic modelling of the Albanian foreland. Our results therefore place reliable constraints on the amount and rate of vertical uplift of these Cretaceous limestones and yield a promising methodology for better constraining paleoburial and therefore erosion and uplift in fold–thrust belts. [Copyright &y& Elsevier]

Abstract: The evolution with depth of paleo-differential stress magnitudes (mostly derived from calcite twinning paleopiezometry) in various tectonic settings is compared to the modern differential stress/depth gradients deduced from in situ measurements. Despite dispersion, both independent sets of stress data support to a first-order that the strength of the continental crust down to the brittle-ductile transition is generally controlled by frictional sliding on well-oriented pre-existing faults with frictional coefficients of 0.6–0.9 under hydrostatic fluid pressure. Some ductile mechanisms may, however, relieve stress and keep stress level beyond the frictional yield, as for instance in the detached cover of forelands. The main conclusion is that despite inherent differences, contemporary stress and paleostress data can be combined to bring useful information on the strength and mechanical behaviour of the upper continental crust over times scales of several tens of Ma. [Copyright &y& Elsevier]

Abstract: New structural data, available seismicity data together with mechanical constraints on the Eurasian continental lithosphere and reconstruction of paleostress trajectories are combined in order to re-assess and discuss the dominant deformation mode (thin-skinned vs thick-skinned) in the Western fold-and-thrust belt of the active Taiwan collision zone. Serial balanced cross-sections and computed paleostress tensors suggest that structural styles and stress trajectories at the front of the Taiwan mountain belt may vary rapidly along-strike depending on the presence of pre-orogenic Paleogene troughs in the Chinese continental margin (Taihsi and Tainan basins) that are favourably oriented to be reactivated and inverted. In localities of the western foreland, where basin inversion and thick-skinned basement-involved shortening predominate, the crustal seismic activity is important and characterized by strike-slip faulting. In these domains of the fold–thrust belt, the stress deviations with respect to the regional transport direction are also important. By contrast, in domains of significant syn-orogenic subsidence, a thin-skinned style of deformation may be prominent due to the lack of available pre-existing features. The seismic activity is limited to few major faulted boundaries such as the active Chelungpu–Sani thrust, and the stress deviations are limited. The timing of deformation at the belt front seems to be independent of the structural styles, so that frontal folds are active since probably 0.5Ma. However, in inner parts of the Western Foothills of Taiwan, where superimposed thick-skinned and thin-skinned deformation are required, out-of-sequence thrusting occurs to maintain the topographic profile. Finally, we suggest that kinematics and structural styles of the western fold–thrust belt are controlled by the mechanics of the Eurasian continental margin in agreement with a recent study. At the scale of the orogen, the limited shortening amounts across the WF and in the Central Range as well as the absence of continental HP-rocks better support a thick-skinned collision model for Taiwan. [Copyright &y& Elsevier]

Abstract: The small intestine is the major site of drug absorption. Some reports in the literature have evoked the concept of “absorption windows” in the small intestine: are there specific regions where drug absorption is significantly higher than others? To investigate this question, we used an everted gut sac method to study the permeability of drugs and markers every 3–4cm down the entire small intestine in rat. These markers were chosen to be representative of the mechanisms by which drugs cross the small intestinal mucosa: paracellular and transcellular passive diffusion, via influx transporters, and a drug (digoxin) that is effluxed from cells by P-glycoprotein (P-gp). The passive diffusion and influx transporter markers gave similar profiles with a plateau of permeability along the jejunum, and with the exception of l-Dopa, lower permeability in the ileum. Digoxin showed a linear decrease in the profile from the proximal jejunum to the ileum. Permeability in the duodenum was two to three times lower than the jejunum for all compounds. There were no narrow specific regions of high permeability and so the concept of discrete “absorption windows” along the small intestine as suggested from some pharmacokinetic studies may be related to other effects such as pH and/or solubility. [Copyright &y& Elsevier]

A structural and microtectonic analysis performed in the Liuchiu Hsu island demonstrates that its Plio-Pleistocene tectonic evolution was dominated by alternating NW–SE shortening and local radial extension caused by mud diapirism. Previous models based on seismic data considering both the formation of the Liuchiu Hsu island and the fold development in SW Taiwan as mainly driven by mud diapirism, fail to account for both the asymmetry of the west vergent thrust-related anticlines onshore and the elongated character of the ridges formed by diapir alignments offshore, which rather argue in favour of a tectonic origin. To cite this article: O. Lacombe et al., C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

Stylolites are pressure solution structures, the roughness of which yields quantitative information about the magnitude of the normal stress applied to the stylolite plane. The stress magnitude is calculated from the cross over length (L c) determined using the signal analysis of a 2D track. For a sedimentary, bedding-parallel stylolite (BPS), L c scales to the magnitude of the vertical maximum principal stress σ 1 , hence to the burial depth at the time the roughness of the stylolite froze. We present a dataset of nearly 200 BPS from Meso-Cenozoic folded carbonates across the Umbria Marche Apennine Ridge. The BPS population is used to address the discrepancies between L c values obtained by using different signal analysis methods. Assuming that in compressional settings burial-related pressure-solution more probably halts because of the switch of σ1 from a burial-related vertical attitude to a tectonic-related horizontal attitude, the vertical stress magnitudes derived from the inversion of the BPS roughness were combined to burial models at each investigated fold to reconstruct the absolute timing at which the orogenic stress started to prevail. The results indicate that the onset of horizontal compression started at ∼10 Ma and ∼8 Ma in the innermost and outermost folds, respectively, and predated fold development as indicated by the age of growth strata. These results establish Stylolite Roughness Inversion Technique as a reliable depth gauge that enables refining the timing of the onset of contraction in fold-and-thrust belts. [ABSTRACT FROM AUTHOR]

Characterizing the origin of natural fractures in organic-rich fine-grained deposits is key to constraining permeability evolution in these potential source rocks and tight reservoirs, as well as to assess the hydraulic connectivity of the fluid systems in which they develop. Differently oriented calcite-filled fractures (i.e. veins), hosted by organic-rich mudrocks of the Lower-Middle Triassic Montney-Doig unconventional resource play (Western Canada Sedimentary Basin), were sampled in sub-surface well cores from British Columbia. A multidisciplinary approach (including sedimentology, Rock-Eval pyrolysis, petrography, O–C–Sr isotope geochemistry and fluid inclusion microthermometry) was applied to host-rocks and fracture filling calcites. The results demonstrate the relevance and usefulness of such multidisciplinary studies to gather insights on: 1) the lithology-related factors controlling fracture occurrence; 2) the timing of fracture opening and the origin of the circulating paleo-fluids; 3) the openness of the fluid system through time. More specifically, host-rock facies (particularly grain size) and vertical facies changes appear to be the leading factors controlling fracture occurrence. A less relevant role was played by the occurrence of diagenetic carbonates, while TOC possibly did not control fracture occurrence. Three generations of calcite cemented fractures were identified. Vertical fractures (first generation) post-dated the onset of oil generation (Late Cretaceous). Horizontal, bedding-parallel fractures (second generation) post-dated the onset of gas generation and possibly opened close to maximum burial, corresponding to peak hydrocarbon (CH 4) generation (Late Cretaceous - Early Paleogene). Vertical fractures (third generation) post-dated the horizontal ones and opened during basin uplift (Middle to Late Paleogene). The consistent petrographic and geochemical features of all the calcite cements point to parent fluids in equilibrium with the host-rock lithologies, that possibly behaved as a closed hydraulic system during Late Cretaceous to Paleogene time; this would support the hypothesis that, at least in the portion of the basin investigated, the Montney Fm also acted as source rock of the unconventional system. • Fracture diagenesis of Montney-Doig Fms in sub-surface cores was characterized. • Lithology-related factors controlled fracture occurrence. • Timing of fracture opening and role of circulating paleo-fluids were constrained. • The succession behaved like a closed hydraulic system during Late Cretaceous - Paleogene time. [ABSTRACT FROM AUTHOR]

This special issue of Geological Magazine presents a collection of 17 papers dealing with different aspects of the Zagros orogen. Many, though not all, of these contributions were presented as part of a highly successful session devoted to the geodynamic evolution of the Zagros belt at the European Geosciences Union General Assembly 2010 in Vienna (Austria). The aim of this gathering was to assemble a broad group of Earth scientists interested in the Zagros orogen to discuss and disseminate new results and ideas efficiently. This volume presents a collection of some of the diverse research that is currently being carried out in the Zagros. We believe that these studies contribute to the understanding of the geodynamic evolution of the Zagros Mountains in particular, but in addition to orogenic processes in general. [ABSTRACT FROM AUTHOR]

We apply the stylolite roughness inversion technique on sedimentary, bedding-parallel stylolites hosted in the Paleozoic carbonates of the Bighorn and Madison formations cropping out in the Bighorn Basin, Wyoming, USA. The inversion technique applied to bedding-parallel stylolites allows determination of the absolute magnitude of the vertical stress experienced at the time dissolution stops along the pressure-solution planes. At the basin scale, reconstructed vertical stress magnitudes range from 19 ± 2 MPa to 35 ± 4 MPa in the Bighorn Fm, and from 12 ± 2 MPa to 37 ± 4 MPa in the Madison Fm. Once converted into depth and compared with up-to-date basin models of burial and contractional history, the dataset highlights that bedding-parallel stylolites accommodated compaction from ca. 220 Ma until ca. 90 Ma, i.e. until stress build-up related to the Sevier contraction made the maximum horizontal principal stress high enough to overcome the vertical principal stress. This study is key to illustrate how stylolites can be used to consistently access paleoburial and to unravel both stress evolution and timing in foreland settings, and indicates that pressure-solution remains active throughout the carbonate deposition history. • Bedding parallel stylolites are used to reconstruct past vertical stress history in a contractional basin. • Long-term burial history is unravelled with no assumption on the past geothermal gradient. • Bedding-parallel stylolites are active until the horizontal stress magnitude overcomes the vertical stress magnitude. [ABSTRACT FROM AUTHOR]

Stylolites are rough dissolution surfaces commonly found in carbonates, characterized by peaks oriented parallel to the maximum principal stress active at the time the dissolution occurred. The development of the Stylolite Roughness Inversion Technique (SRIT) applied to sedimentary bedding-parallel stylolites (BPS) provides an access to the magnitude of the vertical maximum principal stress experienced by the host carbonates, and thus to their maximum paleo-burial depth. A recent study of a BPS population hosted in poorly tectonized Middle Jurassic carbonates of the Paris basin sub-surface (France) unravelled that stylolite morphology controls the maximum vertical stress at which the stylolite was still active. That led to possibly reconstruct the burial history of strata from a BPS population regardless of the fluid pressure and temperature. However, the reliable use of BPS to better constrain the burial depth in tectonized contexts where unroofing by erosion likely occurred such as fold-and-thrust belt was not tested.This study reports a critical comparison of the results of SRIT applied to BPS stylolite populations in various fold-and-thrust belts: a first population hosted in deformed Paleozoic carbonates of the Bighorn basin in the Laramide fold-and-thrust belt (Wyoming, USA); a second population hosted in deformed Jurassic carbonates of the Umbria-Marche fold-and-thrust belt (Apennines, Italy); and a third population hosted in Jurassic carbonates of the Bearnaise Chains (Pyrenees, France). Results highlight how a population of BPS can record intermediate to maximum burial depths, as long as the maximum principal stress remains vertical, i.e., until it switches to horizontal in response to tectonic stress build-up. Especially suture and sharp peak BPS are better suited to estimate the maximum depth at which the principal maximum stress switch from vertical to horizontal, whereas seismogram pinning BPS record preferentially intermediate depths, providing new insights into possibly complex burial history, including tectonic burial by thrust sheets. [ABSTRACT FROM AUTHOR]

Stylolites that develop commonly in carbonates are stress-related pressure solution features of which roughness signal can be used as a paleopiezometer. While sedimentary stylolites records the depth of burial reached by strata as long as the maximum principal stress remains vertical, tectonic stylolites records the absolute horizontal stress magnitudes during the contraction phase they formed. This contribution reports the paleopiezometric inversion of the roughness of bedding-parallel and systematic tectonic stylolites to reconstruct the long-term stress magnitude history that prevailed from strata burial to early Laramide layer-parallel shortening in the Paleozoic carbonates of the Bighorn basin, Wyoming, USA. Our quantitative stress estimates are combined with the results of earlier microstructural, paleostress and thermochronological studies to refine the scenario of stress evolution in both the western part (Rattlesnake Mountain) and the eastern part (Sheep Mountain, Little Sheep Mountain Anticlines, Bighorn Mountains) of the basin. Tectonic stylolite paleopiezometry yields differential stress magnitudes in the range 15-50 MPa for the ~E-W directed Sevier layer-parallel shortening and in the range 3-27 MPa for the NE-directed early Laramide layer-parallel shortening. This results therefore unravels a systematic difference in the level of differential stress sustained by sedimentary cover rocks, with unexpected higher magnitude during thin-skinned Sevier shortening than during thick-skinned Laramide shortening. When integrated with U-Pb absolute ages of calcite veins kinematically related to these two stages of layer-parallel shortening, our results illustrate how distinctively deformation propagates and stress build-up occurs in thin-skinned and thick-skinned tectonics, and how the tectonic style affects the magnitude of the orogenic stress transmitted towards the continental interior. [ABSTRACT FROM AUTHOR]

We report the results of a multiproxy study that combines structural analysis of a fracture–stylolite network and isotopic characterization of calcite vein cements and/or fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the regional fluid systems and pathways that were present during the main stages of contraction in the Tuscan Nappe and Umbria–Marche Apennine Ridge (northern Apennines). We reconstruct four steps of deformation at the scale of the belt: burial-related stylolitization, Apenninic-related layer-parallel shortening with a contraction trending NE–SW, local extension related to folding, and late-stage fold tightening under a contraction still striking NE–SW. We combine the paleopiezometric inversion of the roughness of sedimentary stylolites – that constrains the range of burial depth of strata prior to layer-parallel shortening – with burial models and U–Pb absolute dating of fault coatings in order to determine the timing of development of mesostructures. In the western part of the ridge, layer-parallel shortening started in Langhian time (∼15 Ma), and then folding started at Tortonian time (∼8 Ma); late-stage fold tightening started by the early Pliocene (∼5 Ma) and likely lasted until recent/modern extension occurred (∼3 Ma onward). The textural and geochemical (δ18O , δ13C , Δ47CO2 and 87Sr/86Sr) study of calcite vein cements and fault coatings reveals that most of the fluids involved in the belt during deformation either are local or flowed laterally from the same reservoir. However, the western edge of the ridge recorded pulses of eastward migration of hydrothermal fluids (>140 ∘ C), driven by the tectonic contraction and by the difference in structural style of the subsurface between the eastern Tuscan Nappe and the Umbria–Marche Apennine Ridge. [ABSTRACT FROM AUTHOR]

We report the results of a multi-proxy study that combines structural analysis of fracture-stylolite network and isotopic characterization of calcite vein cements/fault coating. Together with new paleopiezometric and radiometric constraints on burial evolution and deformation timing, these results provide a first-order picture of the regional fluid pathways network during the main stages of contraction in the Tuscan Nappe and Umbria Marche arcuate ridge (Northern Apennines). We reconstruct four continuous steps of deformation at the scale of the belt: burial that developed sedimentary stylolites, Apenninic-related layer parallel shortening with a contraction striking NE-SW, local extension related to folding, then a late stage of fold tightening under a contraction still striking NE-SW. In order to assess the timing and burial depth of strata at all stages, we combine a paleopiezometric tool based on inversion of the roughness of sedimentary stylolites that constrains the range of burial depth of strata prior to layer-parallel shortening, with burial models and U-Pb absolute dating of fault coatings. In the western part of the ridge, layer-parallel shortening started in Serravalian time (~ 12 Ma), then folding started at Tortonian time (~ 8 Ma), late stage fold tightening started in early Zanclean (~ 5 Ma) and likely lasted until recent/modern extension occurred (~ 3 Ma onward). This timing provides important constraints on the temperature that expectedly prevailed in the studied strata through its history. The textural and geochemical (δ18O, δ13C, Δ47CO2 and 87Sr/86Sr) study of calcite vein cements and fault coatings reveals that most of the fluids involved in the belt during deformation are local, or flowed laterally from the same reservoir. However, the western edge of the ridge recorded pulses of eastward squeegee-type migration of hydrothermal fluids (> 140 °C), that can be related to the difference in structural style of the subsurface between the eastern Tuscan Nappe and the Umbria Marche Ridge. [ABSTRACT FROM AUTHOR]

E -twinning is a common plastic deformation mechanism in calcite deformed at low temperature. Strain rate, temperature and confining pressure have negligible effects on twinning activation which is mainly dependent on differential stress. The critical resolved shear stress (CRSS) required for twinning activation is dependent on grain size and strain hardening. This CRSS value may obey the Hall–Petch relation, but due to sparse experimental data its actual evolution with grain size and strain still remains a matter of debate. In order to provide additional constraints on twinning activation and development, new mechanical tests were carried out at room temperature on unconfined single crystals of calcite, with different sizes and crystallographic orientations. Uniaxial deformation was performed at a controlled displacement rate, while the sample surface was monitored using optical microscopy and a high-resolution CCD (charge-coupled device) camera. The retrieved macroscopic stress–strain behavior of the crystals was correlated with the surface observations of the deformation process. Results show (1) the onset of crystal plasticity with the activation of the first isolated mechanical twins during the strain hardening stage, and (2) the densification and thickening of twin lamellae during the steady-state flow stress stage. Such thickening of twin lamellae at room temperature emphasizes that calcite twin morphology is not controlled solely by temperature. The different values for the CRSS obtained for the activation of isolated twins and for the onset of twin densification and thickening raises questions regarding the appropriate value to be considered when using calcite twin data for stress inversion purposes. [ABSTRACT FROM AUTHOR]

The paleostress history and associated deformation mechanisms affecting passive margins are seldom studied, as access to offshore parts is rather limited. We analyze an offshore wellbore core of the Albian, post-rift carbonates of the Sendji Fm which directly overlies the salt of the Aptian Loeme Fm in the Lower Congo Basin. Paleopiezometry based on stylolite roughness inversion (SRIT) and calcite twin inversion (CSIT) was combined with fracture analysis, U–Pb geochronology of calcite cement and burial modeling to unravel the orientations and magnitudes of horizontal and vertical stresses affecting the Sendji Fm over time, with a focus on the impact of salt tectonics on stress records. The results of SRIT on bedding-parallel stylolites constrain the range of depths over which the Sendji Fm strata deformed under a vertical principal stress σ1 to 650–2800 m (median ∼1300 m). Once projected onto the burial model derived from TemisFlow™ software, the range of depths converts to a period of pressure solution activity, from 101 to 15 Ma. Calcite twin measurements within the early diagenetic cement (U–Pb age = 101 ± 1 Ma) reveal three main types of stress regimes: (1) extensional stress regimes with σ3 trending ∼ N–S and ∼E-W associated with local, thin-skinned salt tectonics (101–80 Ma), (2) strike-slip stress regimes with σ1 trending ∼ NW-SE to NNE-SSW and a compressional stress regime with σ1 trending NNW-SSE, reflecting possible intraplate stress transfer from the distant Africa-Eurasia plate boundary (67–60 Ma); (3) a strike-slip and a compressional stress regime with σ1 trending E-W likely related to the mid-Atlantic ridge push possibly combined with effects of variations in elevation and density of the lithosphere and sedimentary flexural loading (15 Ma to present). The paleostress sequence suggests that the sedimentary cover was decoupled from the crust during salt tectonics and then recoupled from the late Cretaceous onwards. • The paleostresses affecting deep carbonates are characterized by studying an offshore core in the west African passive margin. • The timing of the successive stress regimes in the Sendji Fm is constrained. • Local gravitational stress from salt tectonics and far-field tectonic stress from plate boundaries influenced the margin. • The potential of a multi-proxy approach is established. [ABSTRACT FROM AUTHOR]

E-twinning is a common plastic deformation mechanism in calcite deformed at low temperature. Strain rate, temperature and confining pressure have negligible effects on twinning activation that is mainly dependent on differential stress. The critical resolved shear stress (CRSS) required for twinning activation is dependent on grain size and strain hardening. This CRSS value may obey the Hall-Petch relation, but due to sparse experimental data its actual evolution with grain size and strain still remains a matter of debate. In order to provide additional constraints on twinning activation and development, new mechanical tests were carried out at room temperature on unconfined single crystals of calcite, with different sizes and crystallographic orientations. Uniaxial deformation was performed at controlled displacement rate, meanwhile the sample surface was monitored using optical microscopy and high resolution CCD camera. The retrieved macroscopic stress-strain behavior of the crystals was correlated with the surface observations of the deformation process. Results show (1) the onset of crystal plasticity with the activation of the first isolated mechanical twins during the strain hardening stage, and (2) the densification and thickening of twin lamellae during the steady state flow stress stage. Such thickening of twin lamellae at room temperature emphasizes that calcite twin morphology is not only controlled by temperature. The different values for the CRSS obtained for the activation of isolated twins and for the onset of twin densification and thickening questions the appropriate value to be considered when using calcite twin data for stress inversion purposes. [ABSTRACT FROM AUTHOR]

Uranium mineralization in the Kiggavik area, on the eastern border of the Thelon basin (Nunavut, Canada), hosts significant uranium resources within the basement and its understanding is critical to comprehending the genesis of unconformity-related deposits’ structural controls and therefore exploration of these types of deposits in this prospective district. This article deciphers the complex multiphase fracture network associated with uranium mineralization of the most recently discovered, basement-hosted prospect in the Kiggavik area, named Contact. The Contact prospect is located along the Andrew Lake Fault (ALF), a major NE-SW fault corridor in the area. This study combines field work, drillcore logging, sampling, and macro- to micro- petro-structural analyses. Key results from this study highlight that the NE-trending ALF, along with the ENE-trending Thelon (TF) and Judge Sissons (JSF) faults, formed early during intracratonic rifting and deposition of the Baker Lake and Wharton groups (ca. 1850–1750 Ma) in response to the Thelon and Trans-Hudsonian orogeny. The ALF was affected by a strong silicification-brecciation event that likely developed at ca. 1750 Ma, and partitioned later deformation and fluid circulation. In the Contact prospect, the ALF was reactivated multiple times and mineralized in three stages with distinctive secondary fracture patterns, alteration, and mineralization types. Ten fracture stages have been identified at the Contact prospect, f1–f10. The first stage of mineralization, coeval with f5, is related to fluids of unconstrained origin that circulated through E-W faults in the area that locally re-activated quartz veins of the brecciation event at the intersection with the ALF. Mineralization at this stage is polymetallic and associated with weak clay alteration. The second stage of uranium mineralization occurred coeval with transtensional reactivation of the NE-SW trending ALF (f6c) and in relation to circulation of oxidizing basinal brines within the fault zone. Mineralization at this stage is monometallic and associated with illite and sudoite alteration. Later reactivation of the inherited fracture network (f8) led to strong illitization and bleaching of the host rock, with local reworking of the ore body. Finally, reactivation of the fracture network during f9 and 10 lead to circulation of meteoric fluids that remobilized mineralization in a third stage of uranium re-concentration along redox fronts, with strong illitization and bleaching of the host rock. Unlike the classic unconformity-related uranium deposits in the Athabasca Basin where clay alteration halos occur around the ore bodies related to mineralizing processes, in the Contact prospect the strongest clay alteration event (f8) postdates both main stages of mineralization. Along with uranium remobilization, the basement-hosted Contact prospect is likely a relict of what was once a larger deposit. [ABSTRACT FROM AUTHOR]

The timing of porosity destruction in reservoir rock is key for hydrocarbon exploration. This study constrains the porosity destruction of the syn-rift Barremian (130-125 Ma) TOCA Fm. from one drill core located in the Lower Congo basin (West African passive margin). We apply an unprecedented multi-proxy approach to reconstruct the absolute timing of mechanical compaction, pressure-solution and cementation as well as their relative contribution to porosity destruction. LA-ICP-MS U–Pb geochronology combined with petrological observations suggest that the main interstitial diagenetic cement C1 filling the porosity of the packstones and dated 127.4 ± 2.2 to 119.4 ± 6.4 Ma predates pressure-solution. The quantification of the cement distribution by image analysis indicates that C1 clogged ∼30% of the initial porosity before the strata were buried at 400 m. We assume that the early cementation limited the effect of mechanical compaction on porosity reduction which is estimated to ∼2% in the first 100 m of burial. In contrast, a first order estimate of the chemical compaction-reprecipitation can account for up to ∼6% of the initial porosity destruction, as estimated by the inversion of sedimentary stylolite roughness. This technique also documents that the burial-related pressure-solution in the TOCA Fm. occurred in the 550–1750 m burial depth range corresponding to a time spanning from 117 to 95 Ma considering the burial-time model of the TOCA Fm. Our study reveals that the initial porosity of carbonates was reduced down to its current value of 4–8% within the first 35 Ma of its burial history, reaching ∼10% after only 10 Ma, i.e. in the first 400–500 m of burial. This case study indicates that the fate of reservoir properties in bioclastic carbonate formations such as the TOCA Fm. may be largely controlled by early, very shallow diagenetic processes rather than subsequent deep-burial mesogenetic reactions. • The diagenesis of the tight, deeply buried Cretaceous lacustrine TOCA carbonates is characterized from the study of an offshore core in the Lower Congo basin. • The timing and amount of porosity destruction of the TOCA Fm. Are constrained. • The stylolite abundance and depth of stylolite activity in the TOCA Fm. Are controlled by texture. • The impact of early cementation on the reservoir properties of bioclastic carbonates is demonstrated. • The potential of a multi-proxy approach combining U–Pb geochronology of cements, burial modelling and inversion of the roughness of sedimentary stylolites is established. [ABSTRACT FROM AUTHOR]

Understanding the development of foreland-foredeep systems and the influence exerted by pre-existing structures on their evolution is an important step for defining the key factors that control long-term basin and lithosphere dynamics, comprehending the associated seismic hazard and assessing their economic potential in the domain of hydrocarbon exploration. The Po Valley is a rather unique foreland basin for two major reasons: a) it developed intermittently at the front of two different mountain chains, the Northern Apennines and the Southern Alps, progressively converging one towards the other; b) the inherited structures, mainly derived from the Mesozoic extensional tectonics, are oriented at high angle to the advancing belts. The coexistence of these two factors and their various implications make the Po Valley basin a complex case study that deserves attention. Taking advantage of the recent building of a 3D structural model across the region, we reconstructed the possible geometry and migration pattern of the Tertiary basins that developed at the front of the Northern Apennines and the Southern Alps, as part of the Po Valley tectonic evolution. In addition, a number of sections sliced from the 3D model across selected domains have then been used to restore the present-day structural units to their pre-compressional setting, while highlighting the key stages of their geological history. Results from the model analysis show that the Mesozoic extension-related tectonics and the associated carbonate facies geometry and distribution localized and constrained the Alpine structures inside/around the basin. Their control on the Cenozoic deformation and sedimentation is evident during the Paleogene and the Miocene whereas it becomes more subtle during the Plio-Pleistocene when lithospheric-scale mechanisms need to be invoked. Notwithstanding the model uncertainties and its explicit regional significance, our results may be taken as reference for any foreland-foredeep setting worldwide, especially in complex systems where tectono-sedimentary inhomogeneity is spatially and temporally dominant. [ABSTRACT FROM AUTHOR]

The Po Valley (Northern Italy) is a composite foreland–foredeep basin caught in between the Southern Alps and Northern Apennine mountain belts. By integrating the 3D structural model of the region with the public earthquake dataset, the seismo-tectonics of the basin is shown at different scales of observation. The three-dimensional geo-volume is used to review the seismicity around the region and validate the structure–earthquake association for such a complex tectonic framework. Despite the overall uncertainty due to the original data distribution-quality as well as the crustal scale model dimension, the direct correlation between structures and seismicity a) confirms the Po Valley region as an active tectonic system and b) allows the whole structural architecture to be revised by a unique three-dimensional perspective and approach. This study also indicates that 3D methodology is a powerful tool for better understanding of highly complex seismo-tectonic situations at both regional and local scales. [ABSTRACT FROM AUTHOR]

Maroteaux – Lamy syndrome (mucopolysaccharidosis type VI, MPS VI) is a lysosomal storage disease resulting from insufficient enzymatic activity for degradation of the specific glycosaminoglycans (GAG) chondroitin sulphate (CS) and dermatan sulphate (DS). Among the most pronounced MPS VI clinical manifestations caused by cellular accumulation of excess CS and DS are eye disorders, in particular those that affect the cornea. Ocular manifestations are not treated by the current standard of care, enzyme replacement therapy (ERT), leaving patients with a significant unmet need. Using in vitro and in vivo models, we previously demonstrated the potential of the β-D-xyloside, odiparcil, as an oral GAG clearance therapy for MPS VI. Here, we characterized the eye phenotypes in MPS VI arylsulfatase B deficient mice (Arsb − ) and studied the effects of odiparcil treatment in early and established disease models. Severe levels of opacification and GAG accumulation were detected in the eyes of MPS VI Arsb − mice. Histological examination of MPS VI Arsb − eyes showed an aggregate of corneal phenotypes, including reduction in the corneal epithelium thickness and number of epithelial cell layers, and morphological malformations in the stroma. In addition, colloidal iron staining showed specifically GAG accumulation in the cornea. Orally administered odiparcil markedly reduced GAG accumulation in the eyes of MPS VI Arsb − mice in both disease models and restored the corneal morphology (epithelial layers and stromal structure). In the early disease model of MPS VI, odiparcil partially reduced corneal opacity area, but did not affect opacity area in the established model. Analysis of GAG types accumulating in the MPS VI Arsb − eyes demonstrated major contribution of DS and CS, with some increase in heparan sulphate (HS) as well and all were reduced with odiparcil treatment. Taken together, we further reveal the potential of odiparcil to be an effective therapy for eye phenotypes associated with MPS VI disease. [ABSTRACT FROM AUTHOR]

Stable isotope measurements (O, C, Sr), microthermometry and salinity measurements of fluid inclusions from different fracture populations in several anticlines of the Sevier-Laramide Bighorn basin (Wyoming, USA) were used to unravel the palaeohydrological evolution. New data on the microstructural setting were used to complement previous studies and refine the fracture sequence at basin scale. The latter provides the framework and timing of fluid migration events across the basin during the Sevier and Laramide orogenic phases. Since the Sevier tectonic loading of the foreland basin until its later involvement into the Laramide thick-skinned orogeny, three main fracture sets (out of seven) were found to have efficiently enhanced the hydraulic permeability of the sedimentary cover rocks. These pulses of fluid are attested by calcite crystals precipitated in veins from hydrothermal ( T > 120 °C) radiogenic fluids derived from Cretaceous meteoric fluids that interacted with the Precambrian basement rocks. Between these events, vein calcite precipitated from formational fluids at chemical and thermal equilibrium with surrounding environment. At basin scale, the earliest hydrothermal pulse is documented in the western part of the basin during forebulge flexuring and the second one is documented in basement-cored folds during folding. In addition to this East/West diachronic opening of the cover rocks to hydrothermal pulses probably controlled by the tectonic style, a decrease in 87/86Sr values from West to East suggests a crustal-scale partially squeegee-type eastward fluid migration in both basement and cover rocks since the early phase of the Sevier contraction. The interpretation of palaeofluid system at basin scale also implies that joints developed under an extensional stress regime are better vertical drains than joints developed under strike-slip regime and enabled migration of basement-derived hydrothermal fluids. [ABSTRACT FROM AUTHOR]

Abstract: During collision, continental margins are shortened along with the inversion inherited syn-rift basins. In this contribution, we explore the internal deformation of pre-orogenic basins during their inversion in the external Western Alps. New structural and microstructural data allow us to provide a new kinematic scenario for the shortening of two inherited basins in the Oisans External Crystalline Massif. Two cleavages and three vein sets are documented by field observations in the sedimentary cover metamorphosed in the greenschist facies. Their spatial and temporal development is strongly dependent on the structural style that is controlled by the initial basin geometry. In the basement, shear zones accommodate the shortening while the cover is disharmonically folded. We present a new approach for the restoration of cross-sections where ductile deformation prevailed, thus for which classical methods do not apply. Both length conservation for basement top and area conservation for the sedimentary cover, as well as fixed hinge kinematics for the cover folds, are assumed. Such restoration is discussed in the light of cover strain ellipsoid quantification based on field data analysis. We apply this approach to the Morcles nappe and propose a new restored geometry, which is further compared to the Oisans section. [Copyright &y& Elsevier]

A number of field observations suggest that sliding on fault planes may occur at very shallow dip in the brittle field. The existence of active low angle normal faults is much debated because (1) the classical theory of fault mechanics implies that faults are locked when the dip is less than 30° and (2) shallow dipping fault planes do not produce large earthquakes ( M > 5.5). To reconcile observations and theory, we propose a new model for fault reactivation by introducing an elasto-plastic frictional fault gouge as an alternative to the classical dislocation models with frictional properties. Contrary to the classical model which implies that the dilation angle equals the friction angle , our model accounts for and permits in the fault gouge as deduced from laboratory and field observations. Whilst the predicted locking angles differ in most cases by less than 10° from the classical model, a significant amount of plastic strain (strain occurring in elasto-plastic regime) is predicted to occur on badly oriented faults prior to locking in a strain-hardening regime. We describe four modes of reactivation which include complete/partial reactivation with/without tensile failure in the surrounding medium. This paper presents analytical solutions to separate those four different modes as well as numerically computed estimates of the amount of plastic strain accumulated before locking. We conclude that plastic strain on badly oriented faults is favoured by compaction of the fault gouge and that those faults are probably aseismic because this strain always occurs in a hardening regime. [ABSTRACT FROM AUTHOR]