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Although most economic geology research is concentrated at the deposit or mineral-system scale for a single well-defined deposit group with a consistent metal association, there are both academic and economic advantages in considering the similar geodynamic setting of deposits having contrasting metal compositions that are traditionally considered unrelated. As an example, there are a range of mineral deposit types or systems that are spatially associated with the margins of long-lived, relatively cold, buoyant Precambrian cratons or lithosphere with thick mantle lithosphere roots. These diverse hypogene deposit groups include world-class to giant BIF-derived iron ores, Kiruna-type Fe-P deposits, anorthosite-hosted ilmenite deposits, IOCG deposits, carbonatite-associated REE-P-Nb-(Cu) ores, intrusion-hosted Ni-Cu-PGE sulfide ores, SEDEX (and MVT) Pb-Zn-Cu deposits, Zambian Copperbelt-type Cu-Co, and IOCG deposits, that provide a high proportion of the global metal inventory. Their preservation, some older than 2 Giga-years, is due to the buoyancy of the thick, cold cratonic lithosphere. Deep extensional fault systems develop on these craton margins during rifting, leading to deposition of continental-shelf sedimentary sequences that provide both suitable host rocks for mineralization and metal and sulfur-rich high-salinity fluid sources. The long-lived lithosphere margins with fluctuating stress fields enhance the Pb-Zn-Cu endowment potential of these basins by promoting syn-basinal or later gravity-driven flow of high-salinity brines. Compressional or transpressional reactivation drives syn-orogenic fluid flow to produce the Cu-Co ores of the Zambian Copperbelt, or provide the pre-ore thrust architecture of fluid seals over reactive carbonate sequences for Carlin-type gold ores. The deep faults provided preferred conduits for the emplacement of mafic-ultramafic intrusions, with Ni-Cu-PGE sulfide deposits formed within complexities in the magma plumbing systems. The magmatic–hydrothermal group of carbonatite-related REE-P-Nb-Cu, IOCG deposits, and IRGD systems, and the hydrothermal Carlin-type deposits, all formed under extensional high heat-flow tectonic regimes and derived their ore fluids, with the probable exception of Carlin-type ores, from metal- and volatile-fertilized sub-continental lithosphere below the craton margin. The orogenic gold deposits on craton margins in China were also formed during transpressional geodynamic episodes from ore fluids with a fertilized mantle lithosphere source. A detailed analysis shows that most deposit types are sited within 100 km of the margins of Archean cratons, although sediment-hosted Pb-Zn-Cu deposits, that show no obvious relationships to craton margins, require a buffer of 200 km for thick Paleoproterozoic lithospheric blocks. These features brought out in this paper can potentially aid mineral exploration in terms of initial area selection within the available search space, but precise definition of these buffer zones is difficult due to heterogeneity of constraints on the precise location of craton and thick lithosphere boundaries globally. However, the search space for this diverse group of deposits is limited to between 10 and 35% of the continental crust in different regions, within which geophysical methodologies can further constrain more prospective targets.

The Brenner normal fault bounds the Tauern Window to the west and accommodated a significant portion of the orogen-parallel extension in the Eastern Alps. Here, we use zircon (U–Th)/He, apatite fission track, and apatite (U–Th)/He dating, thermokinematic modeling, and a topographic analysis to constrain the exhumation history of the western Tauern Window in the footwall of the Brenner fault. ZHe ages from an E–W profile (parallel to the slip direction of the fault) decrease westwards from ~ 11 to ~ 8 Ma and suggest a fault-slip rate of 3.9 ± 0.9 km/Myr, whereas AFT and AHe ages show no spatial trends. ZHe and AFT ages from an elevation profile indicate apparent exhumation rates of 1.1 ± 0.7 and 1.0 ± 1.3 km/Myr, respectively, whereas the AHe ages are again spatially invariant. Most of the thermochronological ages are well predicted by a thermokinematic model with a normal fault that slips at a rate of 4.2 km/Myr between ~ 19 and ~ 9 Ma and produces 35 ± 10 km of extension. The modeling reveals that the spatially invariant AHe ages are caused by heat advection due to faulting and posttectonic thermal relaxation. The enigmatic increase of K–Ar phengite and biotite ages towards the Brenner fault is caused by heat conduction from the hot footwall to the cooler hanging wall. Topographic profiles across an N–S valley in the fault footwall indicate 1000 ± 300 m of erosion after faulting ceased, which agrees with the results of our thermokinematic model. Valley incision explains why the Brenner fault is located on the western valley shoulder and not at the valley bottom. We conclude that the ability of thermokinematic models to quantify heat transfer by rock advection and conduction is crucial for interpreting cooling ages from extensional fault systems.

To evaluate the lateral sealing mechanism of extensional fault based on the pressure difference between fault and reservoir, an integral mathematical-geological model of diagenetic time on diagenetic pressure considering the influence of diagenetic time on the diagenetic pressure and diagenetic degree of fault rock has been established to quantitatively calculate the lateral sealing ability of extensional fault. By calculating the time integral of the vertical stress and horizontal in-situ stress on the fault rock and surrounding rock, the burial depth of the surrounding rock with the same clay content and diagenesis degree as the target fault rock was worked out. In combination with the statistical correlation of clay content, burial depth and displacement pressure of rock in the study area, the displacement pressure of target fault rock was calculated quantitatively. The calculated displacement pressure was compared with that of the target reservoir to quantitatively evaluate lateral sealing state and ability of the extensional fault. The method presented in this work was used to evaluate the sealing of F1, F2 and F3 faults in No.1 structure of Nanpu Sag, and the results were compared with those from fault-reservoir displacement pressure differential methods without considering the diagenetic time and simple considering the diagenetic time. It is found that the results calculated by the integral mathematical-geological model are the closest to the actual underground situation, the errors between the hydrocarbon column height predicted by this method and the actual column height were 0–8 m only, proving that this model is more feasible and credible.

In the Western Alps, the Penninic frontal thrust (PFT) is the main crustal-scale tectonic structure of the belt. This thrust transported the high-pressure metamorphosed internal units over the non-metamorphosed European margin during the Oligocene (34–29 Ma). Following the propagation of the compression toward the European foreland, the PFT was later reactivated as an extensional detachment associated with the development of the High Durance extensional fault system (HDFS). This inversion of tectonic displacement along a major tectonic structure has been widely emphasized as an example of extensional collapse of a thickened collisional orogen. However, the inception age of the extensional inversion remains unconstrained. Here, for the first time, we provide chronological constraints on the extensional motion of an exhumed zone of the PFT by applying U–Pb dating on secondary calcites from a fault zone cataclasite. The calcite cement and veins of the cataclasite formed after the main fault slip event, at 3.6 ± 0.4–3.4 ± 0.6 Ma. Cross-cutting calcite veins featuring the last fault activity are dated at 2.6 ± 0.3–2.3 ± 0.3 Ma. δ13C and δ18O fluid signatures derived from these secondary calcites suggest fluid percolation from deep-seated reservoir at the scale of the Western Alps. Our data provide evidence that the PFT extensional reactivation initiated at least ∼ 3.5 Myr ago with a reactivation phase at ∼ 2.5 Ma. This reactivation may result from the westward propagation of the compressional deformation toward the external Alps, combined with the exhumation of external crystalline massifs. In this context, the exhumation of the dated normal faults is linked to the eastward translation of the HDFS seismogenic zone, in agreement with the present-day seismic activity.

The extensional structure as a normal fault could be found in many places at the southern part of Java compressive tectonic regime. The research area is in the eastern part of the South Serayu Mountains. This normal fault structure is the boundary of the South Serayu Mountains at the eastern part with Kulon Progo Tertiary volcanic Mountains. In the field, these normal fault lineament zones create the Bogowonto river as a boundary of two different geological styles. The influence of this structure on the geological dynamic of the South Serayu Mountains and the Kulon Progo Mountains is important to be explained. The study was conducted by measuring and analyzing fault data and lithology that developed in the area around the two basins boundary. The distribution of the Kulon Progo volcanic rocks indicates the presence of the extensional fault structure. The volcanic facies distribution of the volcano is cut and becomes narrow in the west, while the northward is very wide. Normal fault striations analysis on the fault plane along the fault line shows the least stress trending west-northwest that has worked to create North-South normal faults. The fault-controlled by stress with the vertical main compression area. They have worked to create North Northeast-South Southwest (NNE-SSW) normal faults with westward dipping.

Investigating the timing, structural style, and development of multiphase extensional fault systems is essential for understanding rift basin evolution and for assessment of structural trap integrity. Borehole-controlled interpretation and analysis of two-dimensional and three-dimensional seismic data sets from the eastern Dampier subbasin indicate that a northeast-trending basement weakness zone was subjected to west-northwest–east-southeast oblique extension in the latest Triassic–late Middle Jurassic, resulting in systematic segmentation of the Rosemary fault system (RFS). Temporal stress change during Cretaceous north-south extension produced complex fault systems along the RFS, including (1) east-west–trending isolated faults with maximum displacement close to their center; (2) east-west–trending abutting faults, which initially nucleated as isolated faults, later abutted against the main structure, showing large displacement accruement on the composite fault; and (3) northeast-southwest–trending splay faults characterized by systematic left-stepping segmentation, with maximum displacement occurring at the point where the splay faults deviate from the main structure. In the Miocene, the RFS was locally reactivated by northwest-southeast compression in the northeastern part of the fault system, developing a compressive fault-propagation fold at the upper tip of the inverted extensional fault. This study suggests that the style of basin boundary fault reactivation depends largely on preexisting structures and temporal stress changes. The fault reactivation style is also a significant factor in influencing basin architecture, sediment distribution, fault linkage processes, and petroleum basin prospectivity.

The gravity and shape data acquired by the Dawn spacecraft during its primary mission revealed that Ceres is partially differentiated with an interior structure consistent with a volatile-rich crust, a mantle of hydrated rock and isostatically compensated topography1–3. Detailed analyses showed that the mechanically strong crust overlays a weak, fluid-bearing upper mantle4. Previous studies, however, assumed that Ceres’s crust is a uniform layer. Here, we report findings from the new high-resolution gravity data from Dawn’s second extended mission (XM2), which reveal a complex crustal structure of Ceres. In the low-altitude regions probed by the Dawn spacecraft during the XM2 phase, we observe that gravity–topography admittance progressively shifts to a lower density solution at higher degrees, implying a radial density gradient across Ceres’s crust that is consistent with decreasing porosity with depth and/or increasing content of dense phases, such as rock and salts. That gradient brings a critical new constraint on the crustal freezing history, suggesting that the salts and silicates concentrated in the liquid phase while the crust was growing. Localized spectral analysis of the new data also shows evidence for a lower crustal density in the north polar region than in the south or near the equator, supporting impact-driven porosity variations for the observed latitudinal density differences5. On the local scale, the new data show evidence for density or rheological variations within the crust, in association with lobate landslides and ejecta deposits that were inferred to be ice-rich6,7 as well as an extensional fault system8. These inferences provide geophysical context for geological features on the surface and help us advance our understanding of the evolution of an ice-rich but heat-starved body, whose evolution was in part shaped by impacts. High-resolution gravity data from Dawn’s second extended mission could probe the global and local structure of Ceres’s crust. The results show significant spatial and vertical variations of crustal density and porosity, associated with ice features and ice-related processes driven from the interior, and impacts.

It is still controversial how the high elevation of the Tibetan Plateau established after the Indian-Asian collision during the Cenozoic. The timing of Gangdese magmatic arc exhumation and uplift history would provide useful message for this disputation. We present six zircon fission-track (ZFT) data from modern river sand in the western Tibet, around the Mt. Kailas, to decipher the long-term exhumation histories of the Gangdese magmatic arc. The data suggests that all the Gangdese magmatic arc rocks experienced rapid cooling during the Eocene (∼46’35 Ma) and Oligocene (∼31’26 Ma). The movement along the north-south trending extensional fault and dextral strike-slip Karakoram fault induced the adjacent rocks exhumed at the Middle Miocene (∼15’16 Ma) and Late Miocene (∼10’11 Ma), respectively. According to the minimum and central AFT ages for each sample, the fastest exhumation rate is about 0.4 km/Ma, with average long-term exhumation rates on the order of ∼0.3 km/Ma since the Oligocene. This result supports the outward growth model for plateau forming, indicating the southern margin of the Gangdese magmatic arc attained high elevation after the Oligocene.

The occurrence of fault-related folds in extensional settings has been gaining increased recognition during the past 20 yr. Passive margins and rift basins often present intriguing structural complexities that are potential sites for the development of extensional fault–related folds. Fault-related folds are important anticlinal traps for hydrocarbon exploration, and understanding their evolution is critical for derisking the timing of trap formation and hydrocarbon generation. This study presents folds from three areas across the North West shelf (NWS) of Western Australia and aims to determine their relationship to associated extensional faults. A series of kinematic forward models are presented as well as detailed structural and stratigraphic interpretation of folding at the three locations. The models suggest each of the three examples have formed under extension that impacted the region during the Mesozoic. The modeling also highlights different characteristics of folding that are caused by fault geometry (ramp–flat) and a propagating fault tip (trishear) that can be used as diagnostic features to distinguish different fold mechanisms. Historical exploration across the NWS has targeted a relatively small number of these anticlinal traps, some of which have been successful (e.g., Marina-1 well, Petrel subbasin) and some have not (e.g., Candace-1, Sholl Island fault anticline). This paper suggests that the prospectivity of anticlinal structures should be more carefully assessed to determine whether or not they are related to extensional activity and hence likely to have formed prior to the bulk of the hydrocarbon charge. Similar structures undoubtedly exist in other basins that have experienced repeated extension.

A subset of megathrust earthquakes produce anomalously large tsunamis for their magnitude. All of these recorded ‘tsunami earthquakes’ in the past 50 years had extensional aftershocks in the upper plate. These include the two largest and most destructive earthquakes of that period, the 2004 Sumatra–Andaman and the 2011 Tohoku events. Evidence from the region of Tohoku indicates that normal fault slip in the upper plate during the earthquake may have contributed to the tsunami size. Here we present a numerical model that shows how a reduction of the dip of a subducting slab, on a timescale of millions of years, can result in an extensional fault failure above a megathrust earthquake on timescales of seconds to months. Slab dip reduction bends the upper plate so that the shallow part fails in extension when a megathrust rupture relieves compressional stress. This results in a distribution of extensional aftershocks comparable to that seen above the Tohoku megathrust. Volcanic arc migration and uplift data for Tohoku and several other tsunami earthquakes is consistent with slab dip reduction. The collection of more such data might identify other areas of tsunami hazard related to slab dip reduction. Tsunami generation by megathrust earthquakes is enhanced by extensional faulting in the upper plate when the subducting slab shallows, according to numerical modelling and observations from the Sumatra–Andaman and Tohoku earthquake–tsunami events.

The Douglas Field is located in Block 110/13b in the East Irish Sea. It was the first oilfield to be discovered and produced in the region, having been found in 1990 and brought on stream in January 1996. The field structure comprises a series of north–south-trending, tilted, extensional fault blocks. The reservoir interval is the Triassic Ormskirk Sandstone Formation comprising good quality aeolian and fluvial sandstones. The field is relatively shallow, with the top reservoir at c. 2120 ft true vertical depth subsea. The hydrocarbon is a light oil of 44°API gravity with a maximum column height of c. 400 ft. The Douglas Field contains an estimated stock tank oil in place of 248 MMbbl and was developed with 22 wells: 15 producers, six water injectors and a single sour gas and condensate disposal well. Electric submersible pumps are installed in oil producers for artificial lift and water injection was utilized from field start-up for pressure maintenance. A water-alternating-gas pilot was implemented on the field in 2017 as an enhanced oil recovery scheme. The field currently produces at a rate of c. 4000 bopd, with approximately 90% water cut. The field has produced 103 MMbbl to date, giving a current oil recovery of c. 41%.

The Penglai 7-6 (PL7-6) structure is located on the Tan-Lu fault zone, a huge fault zone in east Asia. Tectonism of the Tan-Lu fault zone produced complex structural deformation and was an important factor in petroleum accumulation. Three-dimensional seismic data were employed to document the structural geometry and evolutionary process of the PL7-6 structure, and implications for petroleum exploration in a releasing bend of a strike-slip fault system were discussed. Systematic analysis of the seismic data indicates that the main fault (the BD2 fault) of the Tan-Lu fault system slipped right-laterally during the Cenozoic. Strike-slip movement of the BD2 fault peaked during deposition of E 1-2 k to E 3 d 3 , and decreased largely in intensity during E 3 d 1-2 deposition. In the Neogene and Quaternary, the BD2 fault was reactivated. Formation of the Bodongnan low uplift is related to the connection between the Bodongnan low uplift (N) and Bodongnan low uplift (S). The Bodongnan low uplift (N) is represented by an anticline produced by strike-slip movement of the BD2 fault, and the Bodongnan low uplift (S) is represented by the relatively uplifted strata in the vicinity of an extensional fault (the BD3 fault). The PL7-6 structure developed above a releasing bend formed by the subsequent strike-slip movement of the curved BD3 fault. Orientations of the shallow faults in the PL7-6 structure are not only associated with the lower BD3 fault, but also controlled by the basement high. Unlike traditional releasing bends that are generally disadvantage to petroleum accumulation due to the lower structural elevation in the center, the releasing bend in the PL7-6 structure is favorable for petroleum accumulation because of the three reasons: (1) adjacent to generative kitchens, (2) located on a regional structural high, and (3) served by the releasing-bend-related faults acting as conduits for vertical petroleum migration.

Through the seismo-stratigraphic analysis of new highresolution seismic data acquired along the southwestern offshore of the Hyblean Plateau, this work aims to improve the knowledge about the stratigraphic and structural setting in the marine area connecting the Hyblean Plateau Foreland to the Gela-Catania Foredeep. Two main goals have motivated the acquisition of new seismic profiles along the southern coastline of Sicily, in the Marina di Ragusa offshore: (i) to obtain a better comprehension of the Cenozoic stratigraphic and structural setting of the area, with a particular attention to the characterization of the Pliocene-Holocene sedimentary deposits and their areal distribution; (ii) to identify, in the offshore area, the possible prolongation of the main structural lineaments outcropping in the hinterland (Scicli-Ragusa-Irminio Line), and verify the presence of structures, responsible for the tectonic activity affecting the area. Our model shows that an extensional fault system, characterized by a main NE-SW orientation, affects the highly deformed Oligo-Miocene, or older, substratum, originating structural highs and downfaulted sectors. These faults are inferred to record the early history of the Scicli Line and of the polyphase kinematic evolution of the N50° oriented regional fault systems. The Gessoso-Solfifera deposits (Messinian, Late Miocene) have been recognized in several sectors of the study area, showing a very peculiar seismic facies, and occupying deep erosional channels probably resting within down-faulted sectors. This feature is in good agreement with isolated onshore areas of the Hyblean Plateau (Licodia Eubea and south Vittoria villages) where the Gessoso-Solfifera deposits are associated to normal faults, thus documenting that Messinian evaporites are not restricted to compressive tectonic setting, such as the marginal sub-basins and the thrust top minibasins of the Appennine-Maghrebian belt. A peculiar seismic facies has been associated to the Trubi Fm., unconformably lying upon the older succession. The undeformed seismic units, onlapping the older substratum, has been associated to the post-Trubi-Holocene deposits, arranged into seven seismic units that reflect the youngest depositional evolution of the nearby Catania-Gela Foredeep. These deposits, generally represented by plane-parallel seismic facies, are in turn separated by an unconformity highlighted by an onlap termination of the yougermost terms upon the older. In some cases they are interrupted by gas rising from the deeper succession that reaches, at times, also the seafloor.

Detailed geological mapping of the La Cerdanya area (Canigó unit, Eastern Pyrenees) provides new data characterizing the different structural styles exhibited by Cambrian–Lower Ordovician (Jujols Group) and Upper Ordovician successions. Their unconformable contact, related to the Sardic Phase, ranges from 0° (paraconformity) to 90° (angular discordance). The Jujols Group rocks topped by the unconformity are affected by Sardic foliation-free open folds. The pre-Sardic succession, the Sardic Unconformity and the lower part of the post-Sardic succession (Rabassa Conglomerate and Cava formations) are cut and offset by several Late Ordovician NNE–SSW-trending synsedimentary extensional faults associated with hydrothermal activity, which dramatically affected the thickness of the lower part of the Upper Ordovician succession. We relate (1) the Mid-Ordovician Sardic uplift and erosion, and (2) a Mid-to Late-Ordovician upward propagating extensional fault system bounding the outline of half-grabens, subsequently infilled by alluvial deposits, to a thermal doming event (about 475– 450 Ma) that led to the uplift and stretching of the Ordovician lithosphere. Thermal doming may be caused by mafic magma underplating and responsible for the coeval calc-alkaline magmatic activity broadly developed in the Eastern Pyrenees. We discuss the similarities between the Mid-Ordovician Sardic Unconformity and other Early Paleozoic unconformities described in neighbouring areas. Finally, we suggest a geodynamic scenario in which a regional-scale thermal event was related to the opening of the Rheic Ocean that led to the drift of Avalonia from the SW European margin of Gondwana.

Low-angle normal faults (dip

The relative role of the various mechanisms responsible for the formation of isolated carbonate build-ups occurring on the seafloor along continental margins is still uncertain. The interpretation of an extensive seismic dataset in the central Vulcan Sub-basin (NW Australia) allowed to evaluate the possible role of migration and seepage of deep-sourced fluids during the initial growth of isolated carbonate build-ups. The Neogene tectonic activity along the margin generated extensional fault systems that commonly displaced the seafloor, thus apparently creating a substratum to the initiation of various carbonate build-ups during the Pleistocene. The seismic data show reflections, with enhanced amplitude respect to background values, which are associated with both isolated carbonate build-ups and normal faults. The seismic character of these reflections supports the presence of fluids that migrated within the sedimentary pile throughout the investigated area. The interpreted occurrence of methane-derived authigenic carbonates (MDAC) on the seismic surface upon which the carbonate build-ups lay suggests that seepage of hydrocarbons likely occurred at the time of their initial formation. The fluid migration appears focused in the areas above extensional faults, which breached the seals of the Mesozoic reservoirs. Combined tectonic activity and seepage are suggested to support the initial growth of the carbonate build-ups. Various smaller, buried carbonate build-ups developed contemporaneously to those on the present-day seafloor in sites that lack evidence of past hydrocarbon seepage. Their shorter life compared to those on the present-day seafloor suggests their inability to keep-up with the frequent relative sea-level variations during the Quaternary and the importance of deep-sourced fluids for the carbonate build-ups growth in the central Vulcan Sub-basin. The initiation of the numerous carbonate build-ups documented along continental margins worldwide must be explained considering the complex and dynamic interplay of all factors potentially involved, such as geological and oceanographic settings, and an active petroleum system. In particular, the migration and seepage of deep-sourced fluid can have an important role in controlling the genesis and growth of isolated carbonate build-ups.

Extensional fault-related folding has been widely observed in rift systems that are characterised by basement-involved fault reactivation. On the Enderby Terrace, NW Shelf of Australia, oblique reactivation of a basement structure resulted in a depth-branched fault system that consists of six splay faults in the cover stratigraphy. Extensional fault-related folding is obvious and predominantly developed in the hangingwall of reactivated basement fault. The mechanically weak Locker Shale not only plays an important role in displacement accommodation at the basement fault tip but also exerts a strong impact on ‘flat’ development of the ‘ramp–flat–ramp’ fault, thereby controlling the location and geometry of the hangingwall anticline. The kinematic evolution of these structures can be determined based on the well-preserved stratigraphy of the hangingwall basins. Faults and folds deformation exhibits systematic lateral changes which provides clues for the kinematic evolution of the hangingwall folds, that is (i) hangingwall synclines and anticlines formed as a result of fault propagation and linkage, (ii) partial truncation of the anticline by adjacent fault segments due to lateral fault lengthening and interaction, and (iii) complete truncation of the anticline by a planar fault that results in the abandonment of the curved fault plane in the footwall. Results of this study are applicable to other extensional fault and fold systems of similar origin and provide models for partially preserved outcrop deformation and poorly imaged seismic data interpretation.

This contribution focuses on field and laboratory analyses of carbonate fault cores pertaining to high-angle extensional fault zones currently exposed in the central and southern Apennines, Italy. The fault zones studied crosscut Mesozoic platform-related carbonate rocks, strike ca. NW-SE, and dip steeply SW. They formed during the Plio-Quaternary downfaulting of the Apennine fold-and-thrust belt and were exhumed from shallow crustal levels ( < 1.5 km). The carbonate fault cores include grain-supported, matrix-supported, and cement-supported fault rocks, fluidized layers of ultracataclasites with injection veins, and main slip surfaces. Our results of microstructural, petrographic, and cathodoluminescence analyses highlight the contrasting diagenetic evolution of calcite- and dolomite-rich fault rocks. Physical compaction was common within the dolomite-rich fault rocks, whereas chemical compaction coupled with dissolution characterized the calcite-rich fault rocks. Furthermore, multiple generations of calcite cements are documented in the fault zones. The first generation consists of a microcrystalline calcite cement, which developed around survivor grains and lined intergranular pores. The second generation is made up of light-luminescent, fibrous calcite crystals, which precipitated within open fractures and around survivor grains. The third generation consists of an euhedral calcite cement that surrounded survivor grains and infilled both open fractures and intergranular pores.

Extensional faults and folds exert a fundamental control on the location, thickness and partitioning of sedimentary deposits on rift basins. The connection between the mode of extensional fault reactivation, resulting fault shape and extensional fold growth is well‐established. The impact of folding on accommodation evolution and growth package architecture, however, has received little attention; particularly the role‐played by fault‐perpendicular (transverse) folding. We study a multiphase rift basin with km‐scale fault displacements using a large high‐quality 3D seismic data set from the Fingerdjupet Subbasin in the southwestern Barents Sea. We link growth package architecture to timing and mode of fault reactivation. Dip linkage of deep and shallow fault segments resulted in ramp‐flat‐ramp fault geometry, above which fault‐parallel fault‐bend folds developed. The folds limited the accommodation near their causal faults, leading to deposition within a fault‐bend synclinal growth basin further into the hangingwall. Continued fold growth led to truncation of strata near the crest of the fault‐bend anticline before shortcut faulting bypassed the ramp‐flat‐ramp structure and ended folding. Accommodation along the fault‐parallel axis is controlled by the transverse folds, the location and size of which depends on the degree of linkage in the fault network and the accumulated displacement on causal faults. We construct transverse fold trajectories by tracing transverse fold hinges through space and time to highlight the positions of maximum and minimum accommodation and potential sediment entry points to hangingwall growth basins. The length and shape of the constructed trajectories relate to the displacement on their parent faults, duration of fault activity, timing of transverse basin infill, fault linkage and strain localization. We emphasize that the considerable wavelength, amplitudes and potential periclinal geometry of extensional folds make them viable targets for CO2 storage or hydrocarbon exploration in rift basins.

The Canning Basin is a largely unexposed and underexplored frontier basin, formed mostly in the Paleozoic. Geological knowledge of this basin is based predominantly on sparse regional “vintage” two-dimensional seismic and small three-dimensional (3-D) seismic surveys and less than 230 exploration wells. Following seismic interpretation, an integrated interpretation was completed on airborne gravity gradiometer (AGG), magnetic, seismic, well, and complementary data along the southwestern margin of the Fitzroy trough and Gregory subbasin. Seismic data were reinterpreted using AGG data to produce a better constrained geological model. A basement structure map, two intrasedimentary structure maps, and a formation distribution map were produced. The interpretation of seismic profiles, validated through 2.5-dimensional gravity gradiometer modeling, is essential to this workflow. Repeatedly reactivated west–northwest and northwest structural trends, inherited from Proterozoic orogenies, respectively delineate the Fitzroy trough and the Gregory subbasin with its northwestern structural extension into the Fitzroy trough, the Gregory subbasin trend. Subsidence occurred during two periods of extension. An asymmetric extensional system of the Fitzroy trough controlled Ordovician–Silurian deposition of the Carribuddy Group. Devonian–Carboniferous subsidence defines the Gregory subbasin trend. This Pillara extension reactivated structures in the east of the Fitzroy trough. Simultaneous activity of both extensional fault systems and growth faulting controlled the facies and thickness distribution of carbonates and clastics of the early Carboniferous Fairfield Group. The Meda and Fitzroy transpressional phases inverted faults of the Gregory subbasin trend and Fitzroy trough, producing prospects by structural interference. The improved understanding of tectono-stratigraphic relationships, including the 3-D distribution of carbonate reservoirs, benefited the planning of seismic surveys, prospect evaluation, drilling, and acreage relinquishment.

The Lower Eocene siliciclastics in the northern steep slope of the Dongying Depression, Bohai Bay Basin, are described and interpreted as subaqueous fans associated with a thick succession of lacustrine deposits. As a whole, the complicated interplay between the depositional process of these lacustrine fans and slope topography is underrepresented. An integrated study of cores, well-logs, seismic sections and seismic attribute maps have enabled the identification of three types of subaqueous fans at the root of slope, including channelized near-shore subaqueous fans, non-channelized near-shore subaqueous fans and slump turbidity fans. Channelized near-shore subaqueous fans, characterized by straight or slightly curved multi-distributary channels in N-S direction, are mainly filled with conglomerates or pebbly sandstones interbedded with mudstones. In contrast, non-channelized near-shore subaqueous fans are lobate in plane-view, lacking major channels. Slump turbidity fan typically shows an elongate shape with a single, straight-to-weakly meandering channel fronted by terminal splay. Spatial distribution and the types of these subaqueous fans varied through time along the strike of steep slope during the Eocene Es4s depositional time. Slope geomorphology from which the sediments were derived has been reconstructed. The steep slope, evolved from the joining points of extensional fault scarps, preserves numerous gullies incised downdip the whole slope. These gullies, acting as conduits for transporting sediments through the steep slope into the lacustrine basin, are downslope - oriented, ca 4 km long, ca 1 km wide and

The San Dimas district is a world-class silver-gold low-sulfidation epithermal deposit located in the central part of the Sierra Madre Occidental of Mexico, within the eastern part of the Gulf of California extensional province. Previous works assumed a single period of mineralization between ∼38.5 and 31.9 Ma, which is at odds with the existence of vein systems with two different orientations and Ag/Au ratios. We present a re-evaluation of this district based on new zircon U/Pb and apatite fission-track ages as well as petrographic and field observations of mineralization styles. Our study also includes two new prospective areas of Causita and Mala Noche located to the south of the main district. Within the Lower Volcanic Complex, we identify a Late Cretaceous volcanic succession (∼77 to 69 Ma) correlative with the Tarahumara formation from southern Sonora and coeval with the San Ignacio batholith exposed to the west. This volcanic succession hosts Au-rich mineralized sub-volcanic felsic bodies yielding slightly younger ages and is covered by Paleocene intermediate lavas with hypabyssal intrusions with ages around 48 Ma. A voluminous intrusive suite (Piaxtla batholith and associated dike swarms) was emplaced in the region between ∼49 and 44 Ma. Early extensional basins were filled by a continental sedimentary sequence (Palmas formation), which yielded U/Pb age peaks at 66 and 56 Ma from detrital zircons and a maximum depositional age of ∼43 Ma. The last magmatic activity, as in the rest of the Sierra Madre Occidental, consists of silicic ignimbrites and less basaltic lava flows clustered in two pulses of ∼31.5–29 Ma and 24–20 Ma. NNW–SSE extensional fault systems expose the mineralization and tilted all the succession prior to the emplacement of a ∼24 Ma ignimbrite package. This late Oligocene extension, associated to the early stage of the Gulf of California rift, is confirmed by apatite fission-track dating of samples from the Piaxtla batholith, which consistently indicate an episode of cooling at 25–23 Ma followed by a second episode at ∼12.5 Ma. Our absolute ages and geologic mapping allow to infer that an older, WSW–ENE trending normal fault system with up to 1 km of displacement must exist between the San Dimas district and the Causita area to the south. This fault system, currently buried beneath Oligocene–Miocene ignimbrites, may have controlled the intrusion of the Piaxtla batholith and played a crucial role in the preservation of large vein systems of San Dimas in a tectonic depression setting. The main epithermal mineralization is associated with two kinds of structures: Ag/Au veins with WSW–ENE to E–W orientation and Au/Ag veins with NNW–SSE to N–S orientation. The dominant Ag/Au veins slightly post-date the Piaxtla intrusive suite and partly recycled older felsic intrusion with porphyry mineralization. The NNW–SSE to N–S Au/Ag veins are most probably associated with the Oligocene silicic volcanism.

Sinkiang Hami Redstone Copper in China is a super-large volcanic hydrothermal deposit formed as a result of multi-stage secondary tectonic activity in the Hercynian period of tectonic movement. In this work, we have studied the effect of the geomechanical nature on the structure of faults stretched in different directions and have studied the age of Hercynian U-Pb detrital rock in trenches by SHRIMP zircon dating. Our studies have shown that there were strong tectonic plate movements 286-218 million years ago, and a main mineralization stage in the period 285-270 million years ago. Our results showed four developmental fault zones with different properties in the Redstone copper: the first stage is represented by nearly EW and NWW, extensional fault zones in the Upper Carboniferous period, with which formation of the ore structure is associated; the second stage is represented by a nearly SN fault zone formed at the boundary between the Upper Carboniferous and the Lower Permian periods, in which mineralization occurred; the third stage is represented by a NE and NEE fault zone in the Upper Permian period; and the fourth stage is represented by NE faults in the Lower Triassic period, which are mainly broken ore structures. Study of the tectonic stresses showed the presence of the following stresses: NNE tension, nearly EW tension, a pair of sinistral SN horizontal shears and a pair of NNE horizontal shears, a pair of dextral SN horizontal shears and EW tension.

The integration of field geology and high-resolution seismological data allowed us to reconstruct the 3D Fault Model of the sources which gave rise to the 2010–2014 Pollino seismic sequence. The model is constrained at the surface by structural geological data which provide the true attitude of the single faults and their cross-cut relationships. At depth, the fault geometry was obtained using the distributions of selected high-quality relocated hypocenters. Relocations were carried out through a non-linear Bayloc algorithm, followed by the double-difference relative location method HypoDD, applied to a 3D P-wave velocity model. Geological and seismological data converge in describing an asymmetric active extensional fault system characterized by an E to NNE-dipping low-angle detachment, with its high-angle synthetic splays, and SW- to WSW-dipping, high-angle antithetic faults. The cluster of hypocenters and the peculiar time-space evolution of the seismic activity highlight that two sub-parallel WSW-dipping seismogenic sources, namely the Rotonda-Campotenese and Morano-Piano di Ruggio faults activated during the seismic crisis. By applying to the activated structures the appropriate earthquake-scaling relationships, based on fault length and fault area, we infer that the maximum expected magnitudes calculated using the fault area are the more reliable. We estimated Mw = 6.4 for the Rotonda-Campotenese and Mw = 6.2 for the Morano-Piano di Ruggio deducing that both the faults did not release their seismic potential during the 2010–2014 seismic sequence. The size of the activated patches, reconstructed by projecting on the 3D seismogenic fault planes the early aftershocks of the seismicity clusters, are consistent with the observed magnitude of the associate strongest events. Finally, we point out that the western segment of the Pollino Fault, despite not being presently active, acts as a barrier to the southern propagation of the Rotonda-Campotenese and Morano-Piano di Ruggio faults, limiting their dimensions and seismogenic potential.

The Papuan Fold and Thrust Belt (PFTB) in Papua New Guinea is actively forming within a complex tectonic setting at the boundary of the obliquely converging Australian and Pacific plates. The tectonic setting and inaccessibility of the PFTB make it one of the least well-understood fold and thrust belts on Earth. On February 25, 2018, a Mw 7.5 earthquake occurred within the PFTB, triggering an aftershock sequence which included five events ≥Mw 6. In this study, we combine seismological, GPS and remote sensing observations to investigate the spatiotemporal distribution of crustal deformation during these events. All earthquakes ≥Mw 6 were related to reverse offset on northeast-dipping fault planes and five out of the six, including the mainshock, were associated with midcrustal focal depths (∼15–30 km). During the sequence, the PFTB underwent up to 1.2 m of uplift and ground deformation occurred over 7,500 km2. Combining these observations with our geological knowledge of this convergent margin highlights the primary control of the northern Australian passive margin on PFTB structural style. We propose that the earthquake sequence was related to tectonic inversion on a hidden extensional fault system beneath the PFTB and lateral variations along this fault zone had significant influence on the complex distribution of ground deformation. It follows that this fault system has had an important control on the evolution of variable structural styles within the PFTB. This study highlights the complexity that can characterize the evolution and structural style of fold and thrust belts.

This study analyzes geomorphic landforms and drainage patterns to assess the neotectonic activity of the NW-SE oriented Vigodi Fault (VF). The VF lies in the western flank of the Kutch Basin, which shows typical wrench geometry. The fault zone comprises, a complex zone of compressional and extensional fault segments, collectively form the Vigodi–Gugriana–Khirasra fault complex. The fault zone encompasses various neotectonic landforms such as terraces underlain with bedrock (strath) on the upthrown block and fill sediments on the downthrown block, fault scarps, warped Quaternary sediments, and slot canyons within Quaternary sediments, river knickpoints, and deflected rivers. The presence of strike- and dip-parallel slickensides within the VF zone indicates oblique slip motion of the fault. Furthermore, we extracted conventional morphometric parameters from the river network and calculated the river gradient length anomaly (GLA) to determine the variability of fault activity across the strike of VF. The observed values of GLA correspond to the long-term uplift and subsidence associated with the VF. The results of our geomorphic and morphometric analyses show that the area is neotectonically active. The combined observations made from the present investigation can be used to estimate the seismic hazard and mitigation planning of the study area.

Seismic mapping of subsurface faults is hampered by factors such as seismic resolution, velocity control for depth conversion and human bias. Here, we explore the challenges and pitfalls related to interpreting normal faults by comparing objective and subjective uncertainties. A panel of 20 interpreters, with different geoscientific backgrounds, interpreted faults in modern conventional (dominant frequency 40 Hz) and high-resolution P-Cable (dominant frequency 150 Hz) 3D seismic data from the Hoop area, SW Barents Sea. The interpretations created by the test-panel were sorted into 10 scenarios characterized by different fault geometries. These scenarios were explored with 2(3)D point-spread function based convolution seismic modelling to investigate the potential of seismic data to image detailed fault architectures. The results reveal that: (1) Statistical analysis shows considerable variations between manually picked faults. (2) Identifying the location of fault tips is challenging and smaller antithetic faults are rarely recognizable. (3) Uncertainties arise from masking of closely spaced fault segments even where displacement values are large, showing distorted reflection signatures of apparent extensional fault tip monoclines. The distortion is larger for conventional versus high-resolution data. (4) In the conventional and high-resolution seismic data the vertical resolution of closely spaced reflections and small offset faults is 20 m and 5 m, respectively. (5) The utilisation of high-resolution seismic data, combined with seismic modelling, add confidence to interpretation of conventional seismic data in the same area. We conclude that subsurface fault mapping with seismic data requires insight in objective uncertainties associated with the data. Automatic machine-learning fault interpretation is void of subjective bias but still hampered by objective limitations. Further, a risking workflow requires acknowledgement of uncertainties that are transferred to seismic based fault analysis techniques such as juxtaposition analysis, quantitative fault seal analysis, and fault stability analysis. publishedVersion

The permeability structure of a fault zone is strongly dependent on the occurrence of meso-scale fracture patterns within the damage zone. Here, structural analyses of Virtual Outcrop Models (VOM) integrated with Discrete Fracture Network (DFN) modelling are used to constrain the relationship between meso-scale fracture patterns and the bulk permeability of a regional-scale fault zone. The Goddo Fault Zone (GFZ, Bomlo – Norway) is a long-lived extensional fault zone cutting across a granodioritic body developed during the long-lasting rifting of the North Sea. Fracture geometrical characteristics and the spatial variation of fracture intensity derived from VOM structural analysis were adopted as input for stochastic DFN models representing selected portions of the GFZ to constrain the variability of the structural permeability tensor K related to the mesoscopic fracture pattern. The intensity of fault-related fracture set(s), and the associated structural permeability computed with DFN models, likely exhibits a decreasing power-law trend within the damage zone with increasing distance from the fault cores. The orientation of the maximum K tensor component is controlled by the intersection direction of the dominant fracture sets. These results highlight the fundamental role of mesoscopic fracture patterns in controlling the bulk petrophysical properties of large fault zones.

Raised paleoshorelines were detected in the eastern margin of the Campania Plain, which is one of the largest coastal basins in the Tyrrhenian back-arc basin system associated with the Neogene to Quaternary Apennine orogen. The paleoshoreline remnants crop out at variable elevations at several sites, including quarry cuts, which provide excellent 3D exposures of the coastal landforms and deposits, the associated continental sediments and faults dissecting those landforms and deposits. Based on the integration of geomorphological, stratigraphic, micropaleontological and facies analyses with structural data, we reconstructed shoreline development in response to erosional/depositional processes governed by relative sea level change in the framework of coeval extensional tectonics. Most of the paleoshoreline remnants are assigned to three displaced marine terraces that, based on new U-series dating, are related to the late part of the Middle Pleistocene. The faults offsetting the marine terraces (namely, E-W striking normal faults and NNW striking transfer faults) are interpreted as part of a single, segmented extensional fault system controlled by roughly N-S to NNW-SSE horizontal extension. The identified extensional system, being consistent with the regional structure imaged by seismic data, represents the first field evidence of the tectonics controlling the formation of the Campania Plain basin. Our results, providing new direct evidence that effectively complements the large amount of existing subsurface datasets, allow for a significant step forward in the understanding of the tectonic and sedimentary processes governing the Quaternary development of the Tyrrhenian back-arc basin margin.

During the last decades, central Italy has been struck by severe seismic sequences. Some authors have suggested that inherited thrust faults may have played an important role in controlling the recent-to active extensional deformation in the area, particularly during the 2016 Central Italy seismic sequence. To explore this hypothesis, we performed an analogue modelling study that addressed the structural evolution of a composite, heterogeneous multilayer affected by polyphase deformation. The overall three-dimensional geometry resulting from the modelling consists of a flat-ramp extensional fault system, with flats being localised along the weaker stratigraphic units, and ramps locally reactivating the pre-existing thrust ramps at depth. At shallower levels, deformation can localize at newly-formed short-cut faults depending on the geometry of deeper structures. The experimental results provide further support to the hypothesis of a link between Quaternary normal faults and inherited thrust faults during the 2016 seismic sequences. Specifically, analogue modelling results suggest that the Quaternary fault pattern may be controlled by the interaction between the active stress field and the pre-existing compressional structures. This scenario bears significant implications regarding the empirical relationship between the geometry of surface faulting and the magnitude of earthquakes, with considerable repercussions on seismic risk assessment.

The Devonian Orcadian Basin in Scotland hosts extensional fault systems assumed to be related to the initial formation of the basin, with only limited post-Devonian inversion and reactivation. However, a recent detailed structural study across Caithness, underpinned by published Re–Os geochronology, shows that three phases of deformation are present. North–south- and NW–SE-trending Group 1 faults are related to Devonian ENE–WSW transtension associated with sinistral shear along the Great Glen Fault during the formation of the Orcadian Basin. Metre- to kilometre-scale north–south-trending Group 2 folds and thrusts are developed close to earlier sub-basin-bounding faults and reflect late Carboniferous–early Permian east–west inversion associated with dextral reactivation of the Great Glen Fault. The dominant Group 3 structures are dextral oblique NE–SW-trending and sinistral east–west-trending faults with widespread syndeformational carbonate mineralization (± pyrite and bitumen) and are dated using Re–Os geochronology as Permian (c. 267 Ma). Regional Permian NW–SE extension related to the development of the offshore West Orkney Basin was superimposed over pre-existing fault networks, leading to local oblique reactivation of Group 1 faults in complex localized zones of transtensional folding, faulting and inversion. The structural complexity in surface outcrops onshore therefore reflects both the local reactivation of pre-existing faults and the superimposition of obliquely oriented rifting episodes during basin development in the adjacent offshore areas. Supplementary material: Stereographic projections of compiled structural data from individual fieldwork localities are available at https://doi.org/10.6084/m9.figshare.c.5115228

Low-grade mylonitic shear zones are commonly characterized by strain partitioning, with alternating low strain protomylonite and high strain mylonite and ultramylonite, where the shearing is most significant. In this paper the capo Castello shear zone is analyzed. It has developed along the contact between continental quartzo-feldspathic, in the footwall, and oceanic ophiolitic units, in the hangingwall. The shear zone shows, mostly within the serpentinites, a heterogeneous strain localization, characterized by an alternation of mylonites and ultramylonites, without a continuous strain gradient moving from the protolith (i.e., the undeformed host rock) to the main tectonic contact between the two units. The significance of this mylonitic shear zone is examined in terms of the dominant deformation mechanisms, and its regional tectonic frame. The combination of the ultramafic protolith metamorphic processes and infiltration of derived fluids caused strain softening by syntectonic metamorphic reactions and dissolution&ndash, precipitation processes, leading to the final formation of low strength mineral phases. It is concluded that the strain localization, is mainly controlled by the rock-fluid interactions within the ophiolitic level of the Capo Castello shear zone. Regarding the regional setting, this shear zone can be considered as an analogue of the initial stage of the post-collisional extensional fault, of which mature stage is visible along the Zuccale fault zone, a regional structure affecting eastern Elba Island.

As the world's largest archipelagic country in Earth's most active tectonic region, Indonesia faces a substantial earthquake and tsunami threat. Understanding this threat is a challenge because of the complex tectonic environment, the paucity of observed data and the limited historical record. Here we combine information from recent studies of the geology of Indonesia's Banda Sea with Global Positioning System observations of crustal motion and an analysis of historical large earthquakes and tsunamis there. We show that past destructive earthquakes were not caused by the supposed megathrust of the Banda outer arc as previously thought but are due to a vast submarine normal fault system recently discovered along the Banda inner arc. Instead of being generated by coseismic seafloor displacement, we find the tsunamis were more likely caused by earthquake-triggered submarine slumping along the fault's massive scarp, the Weber Deep. This would make the Banda detachment representative not only as a modern analogue for terranes hyper-extended by slab rollback but also for the generation of earthquakes and tsunamis by a submarine extensional fault system. Our findings suggest that low-angle normal faults in the Banda Sea generate large earthquakes, which in turn can generate tsunamis due to earthquake-triggered slumping. Low-angle normal faults in the Banda Sea have caused large earthquakes that indirectly generated tsunamis due to earthquake-triggered submarine slumping, according to an analysis of historical earthquake and tsunami events and GPS observations.

Coupled fluid characterization and absolute dating of fracture networks may provide insights into the understanding of critical stages of evolution of a growing orogen. As a result of the collision between the European and Apulian plates, the Alps have experienced several evolutionary stages comprising continental subduction, nappe stacking, thick- to thin-skin tectonics in relation with the frontal propagation of a fold and thrust belt, and extensional reactivation of the major Penninic Frontal Thrust (PFT). Current evolution of the orogen (Tricart et al., 2001, 2007 and Sue et al., 2007) shows an ongoing extensional seismic activity along PFT while borders of the orogenic system remain in compression. The transition from compression to extension along the PFT remains unconstrained.This study aims to constrain the time of the PFT inversion and provide a characterization of the tectonic structures through time during the formation of upper Durance normal fault system. For this, we applied several novel dating techniques (in-situ U-Pb calcite and (U-Th)/He hematite dating techniques). In addition, we determined the geochemical signature of the fluids trapped (calcite crystallization) deformation by δ13C and δ18O stable isotope analysis of calcites to constrain the fluid reservoirs, and thus the size of the involved tectonic structures. Stable isotopes show that the fluids associated with the early extensive structures bear isotopic signatures close to those of their host rocks, indicating a fluid at equilibrium and thus a close system in agreement with the small (mm-cm) size of mostly ductile structures. In a second stage, connection of veins and fractures lead to major fault formation (metric to kilometric scale structures) show isotopic signatures in agreement with ascending metamorphic fluids, featuring an open system along the PFT.U-Pb dating on calcite was successful on several samples despite high common lead concentrations. Two fault gouge samples associated with kilometric scale faults gave ages between 3.5 Ma and 2.5 Ma. These structures are a signature of the paleoseismic activity wich occured some 2.5-3.5 Ma ago when the wall domain of PFT was few km depth. Moreover, (U-Th)/He hematite dating was used on slickensides of the same fault system. Preliminary ages of 2.5, 1.5 and 15 Ma were obtained. The 15 Ma age is interpreted as a minimum age inversion of the PFT, while other ages overlap with the U-Pb calcite ages. This multidisciplinary inverstigation in the Western Alps helps to constrain the exhumation history of the paleo-seismogenic zone related to the inversion of the PFT.

On the basis of strike-slip fault scale in the Qaidam Basin, the authors hold that the strike-slip fault can be graded into basin-scale, zone-scale, trap-scale and microscope-scale, the complicated strike-slip fault and relevant tectonic combination are related to tectonic movement and evolution, the authors make an analysis of the evolution age in this area, and pointed out that the strike-slip fault is extensional fault depression basin in Early Himalayan movement, reversal fault in Middle Himalayan movement and compressional strike-slip fault in Late Himalayan movement. Corresponding to the tectonic movements, three kinds of strike-slip fault (extensional faulted depression, depression and compressional strike-slip) were formed with different mechanical characteristics. Finally, the paper discusses how strike-slip fault impact trap formation, oil and gas transmission, and reservoir, and how such impacts are related to hydrocarbon accumulation, research on strike-slip fault play an important role in accumulation forming process, controlling the hydrocarbon accumulation, oil and gas distribution patterns.

The Plio-Pleistocene Calvello-Anzi Basin (CAB) represents a synorogenic shallow marine to alluvial succession deposited during the late phase of the Apennine Orogenic event. While the stratigraphy and sedimentary cycles are well known, the precise role and timing of the tectonic phases affecting this area are unclear. In this paper we report the major findings from a study aimed at unraveling the signatures of the Plio-Quaternary tectonic events affecting the CAB and this portion of the Southern Apennines by using a field integrated approach characterized by facies analysis, structural surveying, and basin architecture. The CAB is located in the axial portion of the Southern Apennine chain and has a roughly E-W orientation which is at a high angle with respect the main NW-SE striking regional tectonic structures controlling the foreland-directed migration of the compression. In the study area, an approximately 1,200-meter-thick package of Zanclean (early-middle Pliocene) to Santernian (middle Pleistocene) shelf, shallow marine, and alluvial deposits accumulated during the late stages of the Apennine orogenic evolution. Within the CAB deposits we recognize two main depositional motifs which roughly correspond to previously established regional cycles that are genetically linked to two corresponding tectonic phases of the Southern Apennine chain. Our results reveal how these two main tectonic phases played a primary role in controlling the depositional architecture, facies, depocenter distribution, and the basin shape throughout the CAB's lifespan. In the proposed model, during the first depositional stage (Zanclean), the CAB formed as a wedge-top basin, controlled by the subsurface propagation of NW-SE-trending thrusts related to the main NE-SW directed shortening of the Apennines. This stage is recorded in the basal units of the CAB infill by progressive unconformities, the development of syn-tectonic shallow marine sedimentary wedges along a high gradient tectonically controlled depositional surface, and a marked SE migration of the main depocenter. During the second depositional stage (upper Piacenzian to Santernian), the CAB was controlled by a series of roughly E-W-trending normal faults which crosscut the preexisting compressional structural fabric. Syndepositional activity along these faults played a direct role in creating an E-W oriented tectonic depression and controlling the accommodation space for the upper portion of the CAB infill. This second stage is marked by two points of evidence. The first point is revealed by a southwestward migration of the CAB depocenter driven by ~90-degree rotation from a roughly NW-SE elongated pattern to roughly elongated W-E transverse to the Pliocene regional structural fabric. This depocenter drift also coincides with an abrupt change in depositional regime from shallow marine to continental sedimentation. The second and most important point of evidence is the presence of several basin-bounding extensional fault zones which cut the lower Pliocene basin-fill units. We relate these features to the middle upper Pleistocene transition to along-strike extension, widely reported in the Southern Apennines, which is related to the overall extensional regime that is acting on the chain also at present. Data from this study provide additional insight into the evolution of the Southern Apennine chain, the formation of the Plio-Pleistocene CAB, and the debated role of Quaternary tectonics on the basin's development during the post-collision orogenic phases. Given the proximity of the study area with several oil fields and considering that hydrocarbon traps in Southern Apennines are Plio-Quaternary in age, the constraints provided on the timing and the style of the regional deformation may improve the definitions of hydrocarbon traps in the buried Apulian platform.

Inversion structures are now recognized in most orogenic belts and in many other tectonic settings. Identification of inversion structures has been facilitated by classic geometric concepts that illustrated initial extensional fault geometry and its subsequent compressional reactivation as essential components of an inversion structure and by recent improvements in seismic imaging. However, many inversion structures in the outer parts of orogenic belts have been misinterpreted as either thin-skinned thrusts or strike-slip structures in outer fold-thrust belts and extensional basins, respectively. Furthermore, there remains some confusion about definition and usage of the term ‘inversion’, perhaps compounded by the fact that a wider range of geometric variations and associated deformation processes that meet the criteria for inversion are now recognized, compared to those illustrated in original discussions of several decades ago. This review focuses on: criteria for inversion structures, geometric signatures, different structural responses to inversion, tectonic settings for inversion and the time interval between extension and compression. A series of cross sections of inversion structures from a variety of tectonic settings are used to provide a reference catalogue of examples of inversion structures that cover the broad range of structural geometries that can be developed.

Regional-scale faults typically experience complex, long-lasting histories, commonly recording evidence of multiple reactivation events. Therefore, they contain multiscalar structural domains characterised by varying microstructures, mineralogical compositions and kinematics. These domains result from differential strain partitioning during the recorded faulting stages, and, as a result, can preserve the isotopic and kinematic signature of the different slip periods. Their detailed structural analysis integrated with K-Ar dating of the fault rock assemblage can help to identify these commonly tightly juxtaposed, although not coeval, domains, which we refer herein to as “Brittle Structural Facies” (BSF). BSF analysis is pivotal (i) to understand the structural heterogeneity of fault zones, (ii) the diachronic formation of geometrically and kinematically complex fault cores and (iii) to reconstruct faults' evolution in time and through space. Following this approach, this study relies on meso- and microstructural analysis, chemical characterisation and K-Ar dating to unravel the evolution of the Lærdal-Gjende Fault (LGF, southwestern Norway). The LGF is a multiply reactivated top-to-the-NW extensional fault with a 1 m thick poorly consolidated core. We recognised, sampled and characterised five BSF: I) Indurated dark reddish gouge, (II) Poorly consolidated cataclasite, (III) Weakly foliated greenish gouge, (IV) Clay-rich gouge and (V) A few mm-thick clay smear decorating the principal slip surface. Samples were separated into five grain size fractions (from

The main purpose of this paper is to evaluate the structural styles of Miano and Kadanwari Fields, located in the Central Indus Basin, Sindh province, Pakistan. Discovered in 1989 and 1993, Kadanwari and Miano Fields are located on the Pano Aqil graben and Kadanwari High, in between two extensive NW-SE-oriented regional highs, i.e., Jacobabad-Khairpur and Mari-Kandhkot High. The Central Indus Basin is an extensional basin exhibiting normal faulting. Fourteen seismic lines were interpreted to understand the presence, trend, and development of the fault system in the Central Indus Basin along with the assessment of the Petroleum system based on the analysis of seismic reflection data and well logs across the Cretaceous clastic reservoirs. The tectonics of Miano and Kadanwari Fields has been interpreted with the presence of normal faults, strike-slip faults, and inverted structures leading to ambiguities about the structural framework of the area. However, with this detailed study, an extensional fault system has been interpreted in the Cretaceous and lower Tertiary sections over a detachment in the incompetent Sembar Formation. In Miano Field, the faults are dominantly recognized to have NNW-SSE trend due to NW-SE-oriented extension related to northward drift of Indian Plate from Madagascar. Resultantly tilted fault blocks of half grabens geometry have developed in the area depicting bookshelf geometry of an extensional system Wrench fault system is found to be absent with exception of a probable strike-slip fault in the Kadanwari Field. The fields are interpreted to have significant recoverable reserves of 1662 (bcf) equivalents to 280 (mmboe) in tilted fault blocks having an average displacement of about 50 m.

A detailed tectono-stratigraphic analysis of the Mesozoic through Present-day structures and sedimentary sequences has been carried-out on a very large merged 3-D seismic survey that covers the great part of the central Exmouth Plateau, northern Carnarvon Basin, NW Shelf of Australia. Four main megasequences bounded by regional unconformities have been delineated. They are; (1) Megasequence-I - Early-Late Triassic pre-extension, (2) Megasequence-II - Latest Triassic (Rhaetian)-earliest Late Jurassic (Oxfordian) syn-extension; (3) Megasequence-III - Late Jurassic-Early Cretaceous post-extension; and (4) Megasequence-IV - Early Cretaceous-Present-day passive margin strata. Three populations of extensional faults and a previously unrecognised compressional phase of folding have been identified. The main Mesozoic (Rhaetian-Oxfordian) WNW-directed extension produced domino-style planar extensional faults (Fault System 1) with two principle fault sets; (i) large N–S to NNE-SSW-trending, west-dipping faults and (ii) smaller-scale, largely antithetic east-dipping faults. The large faults are possibly reactivated pre-existing deeper and older faults (possibly related to listric growth faults of the large Lower-to Mid-Triassic Mungaroo delta) as well as completely new faults developed in the upper part of the Triassic Mungaroo Formation. Synclinal hangingwall basins of this system are strongly segmented and underfilled with little ( Fault System 1 was reactivated during the Early Cretaceous-Neogene post-extension stage and strongly influenced the development of the segmented NNE-SSW-trending Fault System 2 in the Cenozoic strata (). Two stacked polygonal non-tectonic fault tiers (Fault System 3) separated by little deformed stratigraphy occur within the Berriasian to Pliocene post-extension sequences. In the early post-extension phase, Late Jurassic to Early Cretaceous NNE-SSW-directed minor contraction event produced broad WNW-ESE-striking folds in the Triassic-Early Cretaceous strata. This study documents the development of the extensional fault systems and proposes new 4-D tectono-stratigraphic evolutionary models for the central Exmouth Plateau. The results of this study have wider implications for the tectono-stratigraphy of the northern Carnarvon Basin and future exploration.

The Sarduiyeh area in the central part of the Kerman Porphyry Copper Belt (KPCB), SE Iran, contains numerous Cu deposits and prospects. This area is bound by E-W trending major faults, which show the northern and southern borders of fault duplex. Minor faults (first, second or third orders) were identified in three trends of NW, N-S and NE. Analysis of the fault kinematics data revealed an extensional fault duplex pattern for this area. In this fault zone, Cu deposits are associated with faults that have a special trend. This proposed kinematic model for evolution of Sarduiyeh extensional fault duplex emphasizes that the main Cu deposits in the Sarduiyeh area are located within the dilatational zones related to NW-SE trending normal faults. In this study, the spatial pattern analysis conducted by Fry, Fractal, Fracture density and buffer zones methods support the conceptual model of district-scale mechanism of structural controls on final emplacement of Cu deposits. This investigation of Sarduiyeh Cu mineralization revealed that the NW-SE trending faults are effective in localization of Cu mineralization in the central part of KPCB.

The widespread extensional deformation that took place during Jurassic to Cretaceous times in Western Europe and the North Atlantic margin resulted in the formation of several rift systems. Some of the resulting basins associated with these rifts show broad synclines detached on pre- or syn-kinematic Permian or Triassic salts, and are filled by thick sedimentary successions. The development of these salt-detached ramp-syncline basins has been associated to the extensional motion of ramp/flat extensional sub-salt faults. The shape and kinematics of such faults have usually been established using the architecture of syn-kinematic units and by assuming complete coupling of the hanging wall rocks. Therefore, there are fault interpretations that do not consider the role played by the deep salt layers, which clearly act as an effective detachment, decoupling sub- and supra-salt deformations. Moreover, the complexity of these scenarios further increases due to some of these basins, which, during latest Cretaceous and Cenozoic times, were partially inverted and were often incorporated into fold-and-thrust belts. Based on analog models and using the Mesozoic Columbrets Basin (Western Mediterranean) as a case study, the aim of this research is: to decipher the influence of the ramp/flat extensional fault during the syncline development and the interaction with a pre-kinematic salt; and to infer how salt-detached ramp-syncline basins are subsequently inverted. To achieve this goal we carried out an experimental program consisting of eight different sandbox models. Our results show that the main structure formed at the end of the extension is a salt-detached ramp-syncline and that its geometry not only depends on the dip and length of the fault panels, but also on the fault displacement and salt thickness. The inversion of these salt-detached ramp-synclines resulted in a major thick-skinned fault-bend anticline with minor thin-skinned contractional structures.