Phases Of Deformation Research Articles

Unravelling the tectonic phases: The impact of the South Caspian Block on Late Cenozoic deformation in the Central Alborz, Iran

Paleostress reconstruction through polyphase fault-slip data of a multi-deformed region suffered collisional tectonics can lead to detecting the stress phases. Based on earthquakes’ focal mechanisms and morphotectonic features, multiple deformation phases model has been proposed for the Alborz Mountains located in the collision zone between the Arabian (Central Iran) and Eurasian (South Caspian block) plates during the Late Cenozoic. In this study, paleostress analysis has been carried out in an area bounded by two (Kandovan and Taleghan) regional faults in the Central Alborz Mountains using fault-slip data. This analysis resulted in the identification of three main tectonic phases. The first, compressional phase is proposed to cause the inversion of the Alborz Mountains’ major initial normal faults to reverse faults during the convergence of the Arabian and Eurasian plates. The second, transpressional phase is offered as a factor for the reactivation of the hidden Alborz basement faults to form the NE-striking left-lateral strike-slip faults on the sedimentary cover. The third, transtensional phase is suggested to be responsible for the development of the NNE–SSW left-lateral transtensional faults. It is proposed that the second and third paleostress phases are affected mainly by the indentation of the South Caspian Block into the Alborz Mountains during the Late Cenozoic.

Migmatite dome as a result of multi-fold interference pattern, in the Damara Belt, Namibia

The western part of the Pan-African Damara Orogen in Namibia is located at the intersection of two highly oblique mobile belts: the coastal NNW-trending Kaoko-Gariep belts and the inland NE-trending Damara Belt. The Namibfontein-Vergenoeg (NV) domes are two, basement-cored, migmatite domes exposed in this orogenic intersection. These domes formed through the superposition of four deformation phases in the presence of melt, giving rise to syn-migmatitic multi-fold interference patterns. Early E-W shortening produced steep N–S striking S1 fabrics linked to km-scale steeply E-inclined F1 folds, likely reflecting the southern continuity of the Kaoko Belt fabrics. The superposition of NE-plunging, NNW-inclined F2 folds formed during NNW-SSE, orogen-perpendicular shortening and produced a Type 1 dome-and-basin fold interference pattern. Progressive with D2, D3 deformation caused localised m-scale folding of steep fabrics into inclined to recumbent, NW-plunging F3 folds, and local top-to-the-S or -SE thrusting. NNW-SSE shortening is correlated with the collision of the Congo and Kalahari cratons during Damara Belt formation. Finally, orogen-parallel NE-SW shortening, produced localised NE-inclined and NE-plunging F4 folds. This weaker shortening phase in the Damara Belt is enigmatic and may reflect tectonic activities further in eastern and western Gondwana. The superposition of F4 folds on F2 folds defines a Type 3 fold interference pattern that established the final 3D architecture of the NV domes. The deformation fabrics at the NV domes document three distinct regional shortening events related to large-scale tectonic switches involved in the western Gondwana Supercontinent assembly.

Geochronological and stratigraphical characterization of lower Jurassic tectonically-controlled felsic tuff ring volcanism in Northwestern Patagonia, Argentina

ABSTRACT The early Jurassic syn-rift phase generated a significant set of half-grabens, calderas, and pull-apart basins along the southwestern margin of South America. In particular, the Loncon Complex, located in the western Extra-Andean region of North Patagonia (∼40°S), forms part of such structures. In the present contribution, we characterize and define the Early Jurassic extensional architecture of the Loncon Complex, constituted of a small-scale pull-apart basin associated with polygenetic volcanism, based on outcrop-scale kinematic data from strike-slip faults, and stratigraphic analysis. Lithofacies analysis, texture, componentry, and structural data allow us to distinguish four stages during the evolution of the Complex; the three early stages are followed by a deformational phase, and crowned by a limited felsic monogenetic volcano; stages consist of a) A continental alluvial to fluvial sedimentation related with an early pull-apart basin phase; b) local phreatomagmatic explosions with syn-eruptive sedimentation periods of a medium life cycle (~104-105 years), b) effusive andesitic stage generated by strike-slip transtension, resulting in partial deformation and development of a local unconformity, and c) a final short-term silicic tuff ring volcano construction (days to months’ time span). The measured faulting pattern is synchronous with the Loncon Complex’s sedimentation and volcanism. Kinematic data allow us to characterize the Loncon Complex evolution under NNE-NNW minimum horizontal stress (SHmin). This local NNE-oriented extension is interpreted as a consequence of a regional process, in a similar way to the report for the Neuquén Basin and the surrounding region in Patagonia. New U-Pb data indicate the onset of volcanism began in the Sinemurian (193.08 ± 1.13 Ma) also supporting an equivalent timing with the vicinity half-grabens areas of the North Patagonia region and the Neuquén Basin (Figure S1a). The process that occurred during the Sinemurian, and probably during the Pliensbachian, affected the entire back-arc basin developed along the southwestern border of Gondwana.

Structure-controlled mineralization resulted from Paleoproterozoic orogenesis in the Dahenglu Cu-Co deposit, NE China

Paleoproterozoic orogenic-related (or orogenic-like) ore deposits play a significant role in the metal and non-metal metallogenic systems in the North China Craton. This study focuses on detailed field structural of the Dahenglu Cu-Co deposit to reveal relationship between structural controls and enrichment process of cobalt (Co)-bearing hydrothermal fluids in the metasedimentary rock. In the context of Paleoproterozoic orogenesis, at least three phases of deformation were identified within the ore-bearing country rocks: an early DPl-1, the peak-orogenic deformation phase called DPl-2 and a final exhumation stage of deformation designated as DPl-3. Through meticulous structural analysis, microscopic examination of drilling cores, and the application of the TESCAN Integrated Mineral Analyzer, we have discerned that thrust faults, operating at both outcrop-scale and microscale, function as substantial conduits for the migration of ore-forming hydrothermal fluids. Additionally, fractures within thrust faults, the core of folds, and the high strain micro-scale shear zone between overturned folds provided ideal spaces for the precipitate of Co-bearing hydrothermal fluid. Based on the regional geological correlations, the second phase of deformation (DPl-2) is characterized by S2 foliation, crenulation cleavage, and thrust fault, which played a crucial role in the enrichment of cobalt in minerals such as siegenite and pyrite. This cobalt enrichment is attributed to the peak-orogenic stage, DPl-2, which likely occurred between 1.95 and 1.90 Ga. The ore-forming geodynamic was associated with Paleoproterozoic orogenesis, characterized by intense deformation and metamorphism. This conclusion aligns with cobalt enrichment observed in the Paleoproterozoic Trans North China orogen in the central North China Craton and the Paleoproterozoic Peräpohja belt in northern Finland. The structures generated by significant tectonic events, such as Paleoproterozoic orogenesis, represent key controlling factors of Co-rich ore deposits.

The Boumaadine Fe–Mn–Pb–Cu (± Au) ore deposit (Jbel Skindis, eastern High Atlas, Morocco): New insights from geological, hydrothermal alteration and geochemical investigations

Petrographic, structural and geochemical analysis combined with SEM and XRD were performed on the Boumaadine Fe–Mn–Pb–Cu (±Au) mineralization of Jbel Skindis in the eastern High Atlas, (Morocco). The results indicate a polyphasic process of mineralization, which produced orebodies with distinct features and different chemical conditions formation. The earliest mineralization formed replacement and disseminated Fe–Mn–Pb orebodies under oxidizing conditions, with a mineral assemblage composed of coronadite, plumboferrite, cesarolite, specularite and calcite, in association with a large-scale hydrothermal alteration consisting essentially of Fe–Mn minerals, i.e., ferroan dolomite, hematite, jacobsite and limonite. The second event was formed under reducing conditions that generate some veins filled mainly by sulfides (galena, with minor pyrite and chalcopyrite), in addition of calcite and dolomite.The mineralization is hosted in Lower Liassic dolostones and is linked to the structural evolution of the study area. Fractures related to the displacement of the Boumaadine fault seem to control the disposition and the localization of the alteration and the mineralization: (i) the Fe–Mn–Pb oxides are related to a NE-SW conjugate fault system generated during the first phase of deformation, with a horizontal principal stress striking NNW-SSE, and (ii) the sulfide mineralization occurs mainly as filling conjugate fractures of two preferentially directions striking N80–90 and N150-165 with a slight dip (15–40°) to the NE. These latter were caused by a dextral movement along the Boumaadine fault, generated during the late phase of deformation with a NW-SE bearing horizontal principal stress.The deep-seated Boumaadine fault has acted as pathways for the rising fluids, and supports the origin of lead and other metals from the Paleozoic basement. The Triassic evaporitic sequence along the Boumaadine fault has also contributed to the chemical composition of the fluid, and represents the potential source of both the salinity and sulfur. The oxide-sulfide mineralogical assemblage and its associated alteration emphasize a polyphasic hydrothermal activity with distinct physicochemical conditions; an iron-manganese rich, and highly oxidizing brine is considered to be responsible for the Fe–Mn alteration and for the deposit of the oxide assemblage. Furthermore, a mixing of the oxidizing fluid with a meteoric reducing fluid could have resulted in the sulfide-rich ore.

SAR interferometry on full scatterers: Mapping ground deformation with ultra-high density from space

Spaceborne time series SAR interferometry (TS-InSAR) technology has been widely applied in ground deformation monitoring. The current popular TS-InSAR are carried out mainly on permanent scatterers (PS) or distributed scaterrers (DS), which can map the ground deformation on sparse targets with high or moderate coherence. However, high-precision and high-density deformation monitoring is always restricted by atmospheric artifacts and surface decorrelation, especially over nonurban areas. Here we show that the ground deformation can be precisely mapped with high density by spaceborne InSAR technique. We proposed a full scatterers InSAR (FS-InSAR) methodology, which can significantly improve the quality of the interferograms by applying a dual-scale temporal low-pass filter (DTLF) to separate both atmospheric and noisy phases from deformation phases, without external atmospheric data. Simulation experiments were conducted to determine the small-scale and large-scale window sizes and evaluate the effectiveness of DTLF. Then we applied the FS-InSAR method to the Tianjin-Tangshan region, China using Sentinel-1 data, assessed the regenerated differential low-frequency phases, and validated the results with leveling measurements and groundwater depth data. What's more, detailed ground deformation was retrieved over the Tangshan mining area with an unprecedented density of 98.55%. Our results demonstrate that the FS-InSAR strategy contrasts sharply with the previous PS-InSAR or DS-InSAR methods by simultaneously solving the two bottleneck problems of atmospheric artifacts and decorrelation in most cases except for water bodies or dense vegetations such as rainforest, thereby it is of great importance for future monitoring and understanding the ground deformation to prevent and control geological disasters.

Insights into the Subduction of the Ligure-Piemontese Oceanic Basin: New Constraints from the Metamorphism in the Internal Ligurian Units (Northern Apennines, Italy)

In the Northern Apennines, the Internal Ligurian Units are considered deformed and metamorphosed fragments of the Ligure-Piemontese oceanic basin. In this paper, we report on the temperature and pressure conditions of the metamorphic peak for four Internal Ligurian Units, estimated using different geothermometers and geobarometers based on the white mica and chlorite compositions. These minerals were formed during the D1 deformation phase in the pre-Oligocene. The results indicate that the Portello and Gottero units are both characterized by metamorphic conditions pertaining to low blueschists facies, while the Colli-Tavarone and Bracco-Val Graveglia Units show a lower metamorphic imprint that produces assemblages of prehnite-pumpellyite facies. The estimated geothermal gradient for the metamorphic peak achieved by the analyzed Internal Ligurian Units during the D1 phase is 7–15 °C/Km, which is indicative of deformation in a subduction setting. Under these conditions, the D1 phase developed in these units as a result of underplating at the base of the accretionary wedge during the closure of the Ligure-Piemontese basin. These data indicate a close geodynamic correlation among the Internal Ligurian Units and the ophiolite-bearing units of the Alps.

Deformation-dependent gel surface topography due to the elastocapillary and osmocapillary effects.

Actively tuning surface topography is crucial for the design of smart surfaces with stimuli-responsive friction, wetting, and adhesion properties. This paper studies how elastocapillary deformation and osmocapillary phase separation can lead to rich deformation-dependent surface topography in polymeric gels. In a purely elastic material, stretching always flattens the surface due to the Poisson effect. We show that stretching can roughen the surface due to the elastocapillary and osmocapillary effects. The roughening can be tuned by the gel stiffness, the gel osmotic pressure, the deformation mode, and the initial amplitude of surface roughness. The rich deformation-dependent behavior of gel surface topography points to a new direction in designing smart surfaces.

Neogene evolution of the margin adjacent to the La Plata River Delta (Pelotas Basin): Sedimentary pathways and the origins of the Rio Grande Cone

AbstractContinental margins that exhibit high terrigenous input are generally located near deltas that are capable of transporting large quantities of sediments into the basin. However, in rare cases, high terrigenous sedimentation occurs in regions deprived of major riverine systems where the sedimentary pathway is enigmatic. One such case is the Neogene of the Pelotas Basin of Brazil and Uruguay, adjacent to the La Plata River mouth. Since the Miocene, anomalous sedimentation formed a giant progradational wedge, the Rio Grande Cone, one of the largest submarine fan‐like features on Earth. To understand the Neogene evolution of the margin and the origins of the Rio Grande Cone, here we present a seismic‐stratigraphic framework based on well‐logs and 2D seismic data. Three depositional environments are identified: (1) on the shelf, upper Miocene to Pliocene fluvial channels delivered sand deposits on the mud‐dominated shelf; (2) on the slope, sediment instability resulted in structural deformation and multiple phases of mass transport deposition and (3) on the lower slope and basin floor, large contourite drifts formed by sediment reworking. We classify the Rio Grande Cone as a megaslide complex, due to its depositional and structural setting. Local deltaic systems were active on the shelf in the Neogene, but the limited size of their paleo‐drainage systems in comparison to the volume of sedimentation in the margin suggests that an additional sedimentary pathway existed. In this sense, the demise of an epicontinental sea over the La Plata Basin during the Neogene likely enabled the input of large volumes of fine sediments into the margin, via the La Plata plume water. We suggest that the desiccation of this epicontinental sea and the intensification of ocean currents since the middle Miocene explains the anomalous Neogene terrigenous influx into the SW Atlantic margin.

Experimental study on the strain energy evolution mechanism of thick and hard sandstone roof in Xinjiang Mining Area

For understanding the mechanical performance and strain energy evolution mechanism of thick hard roof sandstone samples, a sequence of uniaxial compression trials with acoustic emission (AE) monitoring were carried out. The results indicate: (1) The stress-strain curve of the thick hard roof sandstone specimens exhibits distinct stage characteristics. Based on the evolvement of instantaneous axial stiffness, it is separated into Fracture Closure Phase, Elastic Deformation Phase, Steady Fracture Expansion Phase, Unsteady Fracture Expansion Phase, and Post-Peak Phase. (2) The AE energy and cumulative count curves of the thick hard roof sandstone specimens also exhibit significant stage characteristics and can be mutually corroborated with the stage division of the stress-strain curve. (3) Based on the energy conservation principle, the evolution of strain energy density in the thick hard roof sandstone specimens under uniaxial compression loading was analyzed, and plastic strain energy increment was employed to study the stage characteristics of strain energy dissipation. (4) A damage constitutive model for the thick hard roof sandstone specimens was constructed, considering the characteristics of strain energy dissipation. This model effectively describes the stress-strain relationship among the samples, which undergo strain hardening, strain softening, and sudden destruction.

Bi-directional extensional control of the Berane Basin formation, northern Montenegro

The Berane Basin is a Miocene, northeast-southwest oriented intramountain basin of the Dinarides, overlying the pre-neotectonic basement of the Drina-Ivanjica unit, the East Bosnian-Durmitor unit and the Western Vardar Zone. The structural evolution and the tectonic regimes that controlled the formation of the Berane Basin are not fully understood. In this paper, we conducted field kinematic analysis by applying fault-slip inversion to derive paleostress regimes and study the deformation phases that led to the formation of the Berane Basin. Observed deformation is related to the latest Oligocene-Miocene extension in two directions, perpendicular and parallel to the Dinarides orogen. Such bi-directional extension resulted in a complex fault pattern where, among observed normal, oblique and strike-slip faults, those with oblique-normal slip dominate. The observed faults likely form a system of mutually overprinting half-grabens, mainly driven by orogen-parallel extension associated with the large-scale regional Skadar-Pec Fault, while orogen-perpendicular extension has subordinate effects on the Berane Basin formation.

Salt tectonics evolution in the Provençal Basin, Western Mediterranean Sea

The Messinian Salt Giant in the Provençal Basin represents a good example to study salt tectonics: salt deposition occurred throughout the basin well after basin opening, with a tectonic context stable since ∼16 Ma, in a closed system. Also, the youth of salt tectonics has led to less mature structures and an evolutionary history that is easier to decipher than in older salt-bearing margins. We conducted an analysis of the chronology of salt deformation, from its deposition to the present-day, thanks to the basin-wide correlation of the Late Miocene and Pliocene-Pleistocene stratigraphic markers. The large seismic dataset provided detailed analysis of the causes and timing of salt deformation at a regional level. The salt tectonics started relatively early, during the Messinian Upper Unit (UU) deposition (phase 1) in the deepest part of the basin. From the Pliocene to the present-day, salt movement is divided into two more main phases (phases 2 and 3), the first of small intensity, occurred during the Pliocene and the second, more intense, during the Pleistocene. The geometric relationship between salt tectonics and crustal nature domains has revealed, regardless of the timing deformation phases, a more rapid and intense salt deformation above the proto-oceanic crust domain than in the continental or transitional crust domain. This observation, remaining unexplained, emphasizes the role of the influence of crustal nature, associated thermal regime and fluid circulation system on salt tectonics.

Sedimentology and chronostratigraphy of the Apt Basin, Southeastern France: lacustrine response to late Paleogene cooling and regional rifting

The Apt Basin, sub-basin of the wider Manosque Basin of southeastern France, contains deposits of Eocene-Oligocene lake systems that were part of a broader network of evaporative lakes and lagoons spread across the European Cenozoic rift system. The onset and mechanisms of subsidence in the rift system, the interconnectivity of these lakes, and their response to the transition into the Oligocene icehouse are poorly understood. This study aims to clarify these points by examining the stratigraphy and depositional environments in the Apt Basin. We correlate and date Eocene to lowermost Oligocene geological units using a basin-wide facies model combined with sedimentological and geochronological approaches. We show the existence of three lacustrine phases, each separated by complete lake drying events: (1) an Ypresian (?) − Lutetian lake-marsh system dominated by palustrine carbonates; (2) a Bartonian (?) − Priabonian siliciclastic fluvio-deltaic and saline lake system; and (3) a lower Rupelian saline carbonate lake system. The presence of a lake system during the Ypresian (?) − Lutetian suggests an onset of basin subsidence before most other basins of the rift system in southeastern France, and is associated with the late Pyrenean deformation phase. The initiation of the second lacustrine phase marks the beginning of E-W extension and the formation of the Apt Basin as an individual horst & graben system. Based on facies distribution, we demonstrate the hydrological isolation of the Apt Basin from other basins and the improbability of any marine connection during the first two phases. This isolation is less certain for the third phase. We show a close synchronicity between the second lake drying event and the Eocene-Oligocene Transition. The third lacustrine phase, dominated by carbonate production and low siliciclastic input, is interpreted as reflecting a long-term decrease in surface runoff associated with the fall into the Oligocene icehouse.

Separating and Unwrapping of Residual Topographical and Time-Series Deformation Phases in PS-InSAR Based on Zero-Temporal Baseline Combination and Time-Domain Differentiation

Separating and Unwrapping of Residual Topographical and Time-Series Deformation Phases in PS-InSAR Based on Zero-Temporal Baseline Combination and Time-Domain Differentiation

Structural Architectures of Precambrian Metamorphites in and Around Rongmil –Rongjeng Area, East Garo Hills Districts Meghalaya

The present work elucidates the Precambrian metamorphites in and around Rongmil-Rongjeng area in the light of their polydeformational episodes that witness four pfases of deformation showing multiple interference patterns in the ductlile to brittle fields. Field as well as microstructural study reveals that all the pre existing depositional fabrics have been affected by BD1, the first phase of deformation under progressive metamorphic phase leading to the formation of most dominant, highly penetrative schistose and gneissose fabrics of rocks of amphibolites facies. The second phase of deformation, BD2 forming NW-SE trending up and down facing folds of probable plane non cylindrical nature, was responsible for layer parallel shortening (buckling) of the mechanically active BS0 and BS1 fabrics in the NW-SE longitudinal compressive tectonics. The third phase folds, BF3 refolded the earlier set of folds into non –plane non cylindrical nature and occur as non coaxial, open warp type gently plunging with near vertical axial plane striking NW-SE direction. BD4, the fourth phase deformation is considered as brittle phase and represents the joints, fractures and fault structures.

Deformation–Induced Mechanical Synthesis of U and Fe

The phase composition of metallic α-U and Fe after mechanical synthesis in conditions of severe (mega) plastic deformation at room temperature using rotational Bridgman anvils was studied using Mössbauer spectroscopy, scanning and transmission electron microscopy. It was shown that mechanical synthesis results in U6Fe and UFe2 intermetallic formation with a precursor represented by UFe2(D) and UFe3(D) defective phases and a defective dispersed mechanical mixture of iron and uranium. Low-level annealing at 300 °C results in the ordering of the defective phases and transition of a dispersed mechanical mixture of iron and uranium into U6Fe and UFe2 intermetallics. The diffusion mechanism of intermetallic formation in conditions of cold deformation of iron and uranium mixture was established, and the high deformation and thermal phase stability of intermetallics U6Fe and UFe2 was shown.

Deformation Pattern of Well-Preserved High-Pressure Rocks (SE Syros, Cyclades)

New, detailed geological/structural mapping and field-based structural analysis were carried out to investigate the deformation pattern of well-preserved high-pressure rocks of the Blueschist Unit exposed in SE Syros (Cyclades, Greece). Geological mapping revealed the occurrence of extensive alternations between different rock groups, as well as interfingering patterns in map-scale that are possibly the result of folding. The earlier ductile deformation phase recognized in the mapped area is associated with the development of a penetrative foliation, which was formed at eclogite/blueschist-facies conditions under peak metamorphism. The subsequent main deformation phase occurred under blueschist facies conditions synchronous with the early stages of exhumation of the high-pressure rocks. This phase is mainly associated with the formation of WNW-trending folds and a pervasive axial planar foliation linked with ESE-directed shearing. The main deformation ceased under blueschist-facies conditions, and exhumation of the rocks to greenschist-facies conditions took place under very weak and localized deformation. Greenschist retrogression observed in the southwestern part of the mapped area seems to be controlled by fluids, rather than by intense deformation and formation of major syn-greenschist shear zones.

Insights into orientation-dependent plasticity deformation of HfNbTaTiZr refractory high entropy alloy: An atomistic investigation

HfNbTaTiZr refractory high entropy alloy has emerged as a prospective structural material suitable for high-temperature applications owing to its remarkable combination of high strength, good tensile ductility and excellent high-temperature properties. However, the insufficient understanding of the mechanical responses of this refractory high entropy alloy has hindered the improvement of performance in alloy design and potential for engineering applications. Therefore, the orientation-dependent tensile behaviors of HfNbTaTiZr refractory high entropy alloy are investigated from nanoscale using molecular dynamics simulations. The simulation results show that the mechanical responses under uniaxial tension are strongly correlated to the crystallographic orientation with respect to the loading direction, and the highest Young's modulus and yield strength are achieved along [111] direction. In addition, the deformation twinning and phase transformations are charactered. The tensile behavior oriented along [001] direction is dominated by the BCC-FCC phase transformation, while that oriented along [110] or [111] direction by the BCC-HCP phase transformation. The results reveal the critical role of tensile direction in generating specific crystalline microstructures under high-strain-rate loading conditions, which can enlighten new design strategy in engineering refractory high entropy alloys with specific orientations for extreme environments.

Prediction of rock loading stages using average infrared radiation temperature under shear and uniaxial loading

Accurately predicting geologically rock loading phases under varying water levels is crucial to prevent rock engineering operations from severe geological hazards. Acoustic emission (AE) traditionally determines these phases, but machinery in rock projects can disrupt AE sensors, leading to imprecise data and potential accidents. To address this, our study tested a novel approaches using AE, Average Infrared Radiation Temperature (AIRT), Critical Slow Down Theory (CSDT), and Convolutional Neural Networks (CNNs) to predict rock loading phases accurately under different water conditions. The research findings are: (1) AE analysis divides the stress–strain curve into four phases: crack closure, elastic deformation, and stable and unstable crack propagations. Each phase exhibits distinct characteristics in terms of AE signal behavior. (2) AIRT analysis reveals specific patterns during different loading phases. The AIRT and cumulative AIRT have distinct trends in different phases. (3) The AIRT sequence's fractal dimension shows distinct trends during loading phases: it initially rises during the elastic phase and then declines. Fractal dimensions for crack closure, elastic deformation, and stable crack propagation increase, while that for unstable crack propagation decreases with water content. 4) The stress–strain curve phases were successfully predicted by using AIRT and CSDT, demonstrating a strong correlation with actual stress levels. Notably, this marks the first-time prediction of phases through non-destructive tests (IR and CSDT), where CSDT fluctuations at each stage can serve as early indicators of rock failure.5) The proposed CNNR model achieves high accuracy (98%) in predicting different phases of the stress curve using AIRT. It particularly performs well in the elastic deformation and stable crack propagation phases, with only a few instances of false negative predictions. The model shows promising potential for effective and safe geological projects, especially under varying water conditions. The findings contribute to the understanding of rock behavior and offer insights for the design of safer and more efficient rock engineering projects.

New insight on the structural architecture of northern Tunisia with a multidisciplinary approach: Association of Miocene piggy-back basin and active Plio-quaternary out-of-sequence thrusts

In order to better understand the intricate structural architecture of northern Tunisia, we use a multidisciplinary approach that includes field observations, geomorphic, sedimentological, and gravity data across this area. We offer a model of progressive thrusting in which four deformation phases occurred in the context of plate convergence (i) Uplift of the Jebel Ichkeul Triassic succession via a NE-trending thrust fault during the Eocene; (ii) Advance of Numidian thrust sheets during the late Oligocene-Middle Miocene, causing the formation of the Lake Ichkeul/Jalta as being piggy-back basin; (iii) Initial out-of-sequence thrusting during the Late Miocene, resulting in the formation of the Sejnane and El Mejel basins with syntectonic Pliocene infill; and (iv) Subsequent out-of-sequence thrusting during the Early Pleistocene, leading to the formation of the Oued (River) Zyatine basin with a syntectonic Quaternary deposits. We used the gravity data analysis to mark the thicknesses of syntectonic deposits and their bounding thrust faults. The kinematic analysis indicates the occurrence of progressive multiphase out-of-sequence thrusting events with thrusts verging to the southeast. The combination of climate and mechanical fractures induced gradually long-term damage and changed the original landscape of the evidenced out-of-sequence thrusts. Furthermore, the existence of local normal faults in the backlimbs and reverse faults in the forelimbs, together with the drainage network type, earthquakes, the slope erosion, and the aggraditional terrace system, implies a gradual landscape evolution of thrust topography. This physical evolution occurred following an active tectonics across the exhibited out-of-sequence thrusting since the Pliocene.