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[Display omitted] • We describe tectonic processes linked to the opening and closure of an arc basin. • Ductile extensional shear zones exhumed Cadomian ophiolites. • Cadomian ophiolites exhumation culminated during the Variscan Orogeny. The Cadomian Orogeny formed as an accretionary orogen surrounding Gondwana. The structure resulting from the Cadomian Orogeny is pervasively reworked during the Paleozoic, within the frame of the Variscan Cycle. In SW Iberia (Mina Afortunada Massif), a tectonometamorphic and geochronological analysis revealed two Cadomian deformation phases. The first phase (D C1 ; 586 Ma, U-Pb dating in inherited metamorphic garnet from Mina Afortunada Gneiss) is associated with ophiolite accretion during the closure of a back-arc or intra-arc basin (Cuartel Ophiolite). A metamorphic fabric related to this phase is preserved as an internal foliation in Ediacaran (meta)sedimentary rocks. The second phase (D C2 ; 515–485 Ma) is constrained by the age of the igneous protolith of Mina Afortunada Gneiss (∼515 Ma), which is affected by a penetrative foliation formed during D C2 , and by the unconformable deposit of Ordovician sediments, which are not affected. The telescoping of metamorphic isograds during D C2 and the geometry of detachment faults associated with this phase suggest extensional tectonics as the driving mechanism for the early exhumation of the Cadomian suture zone in Mina Afortunada Massif. The superimposition of Variscan folds and shear zones onto the Cadomian structures contributed to the subsequent exhumation of the Cadomian suture zone. The analysis and reconstruction of Cadomian and Variscan structures, plus the geochronological data, allow us to correlate the Cuartel Ophiolite with the Mérida Ophiolite, being two pieces of the same, yet dismembered, Cadomian suture zone. The number of Cadomian suture zones in Gondwana does not coincide with that of Cadomian suture zone exposures. Reworked orogens such as the Cadomian could be subjected to duplication of their suture zones. Assessments regarding the Cadomian paleogeography should consider the multiplier effect of the structural overprints after ophiolite accretion. [ABSTRACT FROM AUTHOR]

Understanding the origin of Late Jurassic volcanism in southern Patagonia is crucial for unraveling the early Andean orogenic evolution. However, radiometric dating is not connected to stratigraphic analysis along the South Patagonian Andes, which obscures the real duration of the Late Jurassic magmatic activity. In this contribution, we present the results of a volcanic stratigraphy analysis, complemented by structural and petrographic data, on a thick succession of acidic volcanogenic rocks in the Laguna Verde district of southern Chile located along the south shore of General Carrera-Buenos Aires Lake. Through the recognition of igneous stratigraphy, we strategically sampled representative volcanogenic rocks that cover the entire duration of eruptive activity. By doing so, the new U–Pb zircon magmatic ages, combined with a compilation of U–Pb crystallization ages from the South Patagonian Andes, allows us to constrain the volcanic activity in the study area to a period of 8 My (~ 155–146 Ma, V3 stage) and 11 My considering age inherent errors. The field recognition of normal faults and the syn-kinematic emplacement of sub-volcanic bodies, which are inferred to conform to a ring-fault system, along with the presence of a thick succession of ignimbrites, suggest that the syn-extensional volcanic emplacement occurred in a caldera volcanic environment. This setting was responsible for the short-lived, voluminous eruptions. Furthermore, the high Th/U zircon ratios identified for the ~ 155–150 Ma period indicate the climax of extensional tectonics. The integration of these data supports the hypothesis that retreating-mode subduction played a major role in producing ignimbrite flare-ups. [ABSTRACT FROM AUTHOR]

The Banda Arc in eastern Indonesia has a complex tectonic history involving oceanic and continental subduction, arc‐continent collision and slab rollback. Among these the subduction rollback that began at 16 Ma shaped the regional tectonic configuration, causing notable upper plate extension evidenced by the Banda Sea and Weber Deep. However, the effects of subduction rollback on the lower plate remain less understood. The Aru Trough, part of subducting Australian continental margin, shows strong deformation and high seismicity, making it ideal for studying these effects. Utilizing multibeam bathymetry, seismic reflection profiles, GPS observations, seismicity and focal mechanisms, we investigate the crustal deformation, driving mechanisms and seismic risks in the Aru Trough under the background of Banda slab rollback. The Aru Trough shaped like an inverted triangle narrows from 160 to 40 km southward. It has a fast 53.8 mm/yr extensional rate at present, when combined with its maximum width suggesting a 3 Ma age. High‐angle faults (>60°) are present at its margins and interior. The trough has a high density of seismicity up to 5.9 events per 25 km2, with dominant normal and strike‐slip events, consistent with observed deformational patterns. The low seismic b‐value of 0.82 ± 0.01 suggests a high‐stress state with potential for strong earthquakes (Mw ≥ 6.5). Our findings indicate that lower plate deformation is profoundly influenced by subduction rollback, oblique arc‐continent collision and regional strike‐slip faulting. Understanding deformation in the Aru Trough is crucial for grasping the broader tectonic evolution of the Banda Arc and assessing seismic risks. Key Points: The Aru Trough is deformed by extension as evidenced by high‐angle normal faults and fast present‐day extensional rate of 53.8 mm/yrThe Aru Trough was initiated by slab rollback at 3 Ma with subsequent evolution affected by arc‐continent collision and strike‐slip faultingSeismicity in the Aru Trough shows a high density and low seismic b‐value, indicating high stress and a potential for strong earthquakes [ABSTRACT FROM AUTHOR]

This contribution explores the formation and evolution of hyper‐extended basins, associated with the early stage of core complex formation, controlled by low‐angle normal faults active at <30°. Based on a high‐resolution industrial 3D seismic reflection survey along the southern margin of the South China Sea (SCS) (Dangerous Grounds), we mapped and analyzed the 3D geometry of low‐angle normal fault systems and the related stratigraphy. Two main hyper‐extended basins were documented, filled by up to 6 km of sediments including pre‐ to post‐rift sequences. The observed normal faults on depth migrated seismic sections show an average dip angle of <30° and appear planar, characterized by continuous reflections with no clear steepening at depth and sole‐out on distinct decollement levels. Detailed fault surface mapping reveals the occurrence of km‐scale corrugations together with large wavelength undulation. The formation of these hyper‐extended basins is associated with polyphased syn‐rift infill during the development of the low‐angle normal faults. The first syn‐rift sequence appears as chaotic and discontinuous packages that has been dismembered and fragmented during the activity of low‐angle normal faults. The second syn‐rift package shows unexpected sedimentary wedges developing successively toward the footwall and the hangingwall. This geometry results from the interplay between the main low‐angle normal fault and antithetic faults defining a so‐called extensional fishtail. The deep structure of these basins shows nascent domes with limited evidence of magmatism. Eventually, these basins likely capture the earliest stage of core complex development in the proximal margin of the southern SCS. Key Points: Hyper‐extended basins in Dangerous Grounds (South China Sea) are controlled by normal faults formed and active at low‐angle (<30°)High‐resolution 3D mapping shows the formation of nascent continental core complexesAlternating syn‐rift wedges form from the interaction between low‐angle normal faults and antithetic faults, defining an extensional fishtail [ABSTRACT FROM AUTHOR]

Travertines are terrestrial carbonates that are commonly associated with fault activity in extensional and transtensional basins. The faults serve as conduits for the rising and mixing of carbonate‐enriched fluids with thermal and meteoric CO2 inputs promoting travertine precipitation at the surface. Therefore, travertine successions provide key constraint on the faulting, depositional environments, fluid flow and climate. This work focuses on the travertine succession in the Miocene Levač Basin, the marginal basin of the Morava Corridor situated at the junction of the Dinarides and the southernmost Carpathians. Detailed sedimentological, geochronological (U–Pb age, laser ablation – inductively coupled plasma – mass spectrometry) and structural analyses of the travertines are used to reconstruct the evolution of the feeding geoothermal system. Furthermore, these data were used to understand the controlling factors governing alternation of fluid flows enriched in thermally generated and meteoric CO2, and precipitation of travertines in Levač Basin, and finally to elucidate the late stage of basin evolution. Four facies associations are distinguished within the succession, i.e. travertine slope, ridge, flat, and travertine flat under the fluvial influence. The results demonstrated that travertine deposition was controlled by north‐west/south‐west and north‐east/south‐east normal fault arrays. Stable isotope data show positive δ13C values (with δ18O being negative) shifting to negative in the distal and stratigraphically younger deposits implying dilution of deep hydrothermal fluids by mixing with meteoric waters. Finally, travertine deposits yielded a new U–Pb age of ca 14 Ma indicating that the Middle Miocene extensional phase known from other intermountain basins in the Dinarides reached as far east as the Levač Basin and Morava Corridor. [ABSTRACT FROM AUTHOR]

[Display omitted] • Early-middle Paleozoic continental arc-back-arc system developed in the Central-South Tianshan. • Latest Carboniferous crustal anatexis in the South Tianshan occurred during post-orogenic extension. • Transition from accretionary orogeny to post-orogenic extension occurred at the Carboniferous-Permian boundary. Recognition of extensional events during orogenesis is critical for the reconstruction of geodynamic evolution of orogens, but is also a challenge due to multi-stage tectonic superimpositions. The South Tianshan is the southern margin of the Paleozoic Central Asian Orogenic Belt (CAOB) and a key for understanding the geodynamic evolution of the CAOB. Here we present new structural, geochronological and geochemical data for the Paleozoic sedimentary, igneous and metamorphic rocks in the Central and South Tianshan (NW China). Based on our new results and published data, we suggest that a neritic to terrestrial back-arc basin existed to the south of the Central Tianshan magmatic arc during the Early-Middle Devonian. We document a crustal anatectic event (∼304 Ma) associated with peraluminous granitic magmatism (∼305–295 Ma) in the South Tianshan. Multi-stage ductile deformation events witnessed the Paleozoic evolution from subduction-accretion to post-orogenic collapse of the Tianshan Orogen: (1) Late Devonian-Carboniferous regional top-to-the-north ductile shearing is related to the southward subduction of the South Tianshan back-arc basins; (2) late Carboniferous south-verging folds and brittle-ductile axial-plane cleavages correspond to back-thrusting resulted from the collision between Central Tianshan and Tarim; (3) latest Carboniferous ductile normal faults developed in migmatites define a dome-like structure linked with syn -anatectic exhumation of the middle crust during the post-collisional extension; and (4) regional dextral strike-slip faulting attributed to Permian lateral extrusion. Therein, two stages of crustal extension are key puzzle pieces to reconstruct the accretionary orogenic processes of the Paleozoic Tianshan. [ABSTRACT FROM AUTHOR]

Kosovo is located in a key position in the central-west part of the Balkans providing an opportunity to understand the far-field effects of distributed intracontinental deformation caused by the Aegean extension in the south and Adriatic compression in the west. It is also situated along the NE-SW trending Shkodër-Pejë transverse zone, where the Dinarides and Albanides-Hellenides orogenic belts are juxtaposed. While the instrumental seismicity of Kosovo indicates the activity of this fault zone and many others, the active faults in the country were not discussed in detail in the current literature. In this study, we analyzed both the geomorphic and structural features of major mountain front faults in western Kosovo (i.e., Pejë, Istog, Krojmir, and Prizren faults) to reveal the relative assessment of their activities and kinematic characters. Geomorphic and morphometric analyses of all the studied four different mountain fronts indicated high activity and tectonic uplift rates of over 0.5 mm/a. On the other hand, according to the collected kinematic data from the observed fault planes, the studied faults are mainly of normal character representing a dominance of NWSE- directed extension in western Kosovo, which is most probably caused by the rollback of the subducting slab in the Hellenic trench.

A dominantly NW-SE directed extensional tectonics in the Early Cretaceous significantly reworked the Late Permian-Triassic orogenic framework of the Dabie orogenic belt. The North Dabie complex (NDC) is the principal domain recording this tectonic event. However, the precise structure-kinematic architectures, particularly those observed in the ductile regime, along with the respective time scales for different extensional stages, have not been adequately established. This significantly impedes our comprehensive understanding of the extensional style and deformation history in the North Dabie complex. To better address these issues, we conducted a systematic structural study and LA-ICP-MS zircon U-Pb dating of the pre-, syn-, and post-kinematic intrusions and syn-kinematically metamorphosed high-grade gneisses/migmatites of the NDC. Our results demonstrate that the extensional deformation in the NDC may initiate at ca. 144 Ma, which is characterized by a pervasive NW-SE oriented coaxial plastic flow in the ductile regime of the middle-lower crust. A large-scale detachment processing zone subsequently started activating at ca. 140 Ma at the upper-middle level of the middle crust, and concentratedly accommodated the extensional strain by top-to-NW ductile shearing. Locally, there was uprising of sub-magmatic flow in the atatexite-diatexite from the deeper lower crust taking place in the manner of top-to-outward shearing as early as ca. 137 Ma. This composite process of extension manifests vertical strain partitioning across the ductile middle-lower crusts and progressive strain localization during the lithospheric thinning. The NW-SE orientation dominated extensional tectonics was strongly driven by the westward subduction of the Paleo-Pacific oceanic plate during the Late Mesozoic. [ABSTRACT FROM AUTHOR]

A dominantly NW-SE directed extensional tectonics in the Early Cretaceous significantly reworked the Late Permian-Triassic orogenic framework of the Dabie orogenic belt. The North Dabie complex (NDC) is the principal domain recording this tectonic event. However, the precise structure-kinematic architectures, particularly those observed in the ductile regime, along with the respective time scales for different extensional stages, have not been adequately established. This significantly impedes our comprehensive understanding of the extensional style and deformation history in the North Dabie complex. To better address these issues, we conducted a systematic structural study and LA-ICP-MS zircon U-Pb dating of the pre-, syn-, and post-kinematic intrusions and syn-kinematically metamorphosed high-grade gneisses/migmatites of the NDC. Our results demonstrate that the extensional deformation in the NDC may initiate at ca. 144 Ma, which is characterized by a pervasive NW-SE oriented coaxial plastic flow in the ductile regime of the middle-lower crust. A large-scale detachment processing zone subsequently started activating at ca. 140 Ma at the upper-middle level of the middle crust, and concentratedly accommodated the extensional strain by top-to-NW ductile shearing. Locally, there was uprising of sub-magmatic flow in the atatexite-diatexite from the deeper lower crust taking place in the manner of top-to-outward shearing as early as ca. 137 Ma. This composite process of extension manifests vertical strain partitioning across the ductile middle-lower crusts and progressive strain localization during the lithospheric thinning. The NW-SE orientation dominated extensional tectonics was strongly driven by the westward subduction of the Paleo-Pacific oceanic plate during the Late Mesozoic.

We address the possible link between the age of subducting oceanic lithosphere and growth of elevated cordilleras versus extension-dominated arc regions. Singularity exists in South America: the lowest elevated Andean segments are found in Patagonia where the active Chile Ridge enters the trench. Subduction of active ridge triggers thermal doming, crustal extension and attenuation of former cordilleras. At the Antarctica-South America connection, three active ridge subductions induced the disruption of a former continuous cordillera during the opening of Drake Passage. Active ridge subduction induces lithosphere thermal erosion and related crustal extension in the upper plate. Evolution of regions worldwide experiencing ridge subduction confirms this hypothesis. [ABSTRACT FROM AUTHOR]

Kosovo is located in a key position in the central-west part of the Balkans, providing an opportunity to understand the far-field effects of distributed intracontinental deformation caused by the Aegean extension in the south and Adriatic compression in the west. It is also situated along the NE-SW trending Shkodër-Pejë transverse zone, where the Dinarides and Albanides-Hellenides orogenic belts are juxtaposed. While the instrumental seismicity of Kosovo indicates the activity of this fault zone and many others, the active faults in the country were not discussed in detail in the current literature. In this study, we analyzed both the geomorphic and structural features of major mountain front faults in western Kosovo (i.e., Pejë, Istog, Krojmir, and Prizren faults) to reveal the relative assessment of their activities and kinematic characters. Geomorphic and morphometric analyses of all four different mountain fronts studied indicated high activity and tectonic uplift rates of over 0.5 mm/a. On the other hand, according to the collected kinematic data from the observed fault planes, the studied faults are mainly of normal character, representing a dominance of NW-SE-directed extension in western Kosovo, which is most probably caused by the rollback of the subducting slab in the Hellenic trench. [ABSTRACT FROM AUTHOR]

ABSTRACTWe present the geological map (1:10.000) of the Montecastelli Pisano area, where (i) the relationships between Neogene-Quaternary transfer and normal faults have been carefully mapped (Sheet 1), and (ii) the mantle sequence of the Ligurian Ocean has been analysed (Sheet 2). Fault analyses allowed to define: (i) NE-trending fault system (left-lateral strike- to oblique-slip faults) belonging to a transfer shear zone; and (ii) NW-trending normal to oblique-slip faults. Their evolution is framed in the extensional tectonics affecting the Northern Apennines since Early-Middle Miocene. The ophiolite complex is constituted by serpentinized spinelharzburgite with minor serpentinized dunite channels cut by gabbro dykes. A km-scale cataclastic zone cut the mantle section, locally hosting Cu-Fe mineralization. The goal of this work is to present the distribution of the main fractures affecting an area where the occurrence of ophiolite can favor the success of the CO2 reinjection project.

Analyses of active and past normal fault behaviour in extensional settings provide key insights into regional-scale tectonic processes driven by plate boundary forces. To better understand past tectonic environments in the Tāmaki Makaurau-Auckland region of northern Aotearoa-New Zealand, we examine normal faults with Miocene to Quaternary movements dissecting the Early Miocene Waitematā Group. Structural data were collected from coastal outcrops, including fault geometry and kinematics, and reveal a dominant NE-trending strike direction, indicating NW-SE extension. Faults dissecting coeval and younger Waitākere Group rocks west of the study site exhibit the same NE-striking fabric, and thus may represent the westward continuation of Waitematā Group extensional structures. Furthermore, a NE-trending normal fault fabric is present within the adjacent Taranaki Basin, suggesting that the observed extension in the Waitematā Group was widespread over northern Aotearoa, with some extension still occurring today in southern parts of the Taranaki Basin. We propose that many of the observed normal faults in the Waitematā Group represent the northern portion of the Taranaki Basin fault system, with the Taranaki faults likely representing the younger continuation of the extension recorded in the Waitematā Basin, resulting from the migration of back-arc extension due to roll-back of the Hikurangi subduction margin. [ABSTRACT FROM AUTHOR]

The Columbrets Basin is the largest Mesozoic rift basin of the Valencia Trough in the Western Mediterranean. The analysis of a seismic‐reflection survey makes it possible to reconstruct the tectonic fabric underlying the sedimentary basin, including the structure of the top of the lower crust and the Moho. It is proposed that the ductile deformation of the mid‐lower crust was the main mechanism controlling the basin geometry, with the radial flow of mid‐lower crust coeval with the reactivation of two large‐offset SW‐dipping normal faults, inherited from the precursor Permian–Triassic rifting. Mid‐lower crustal necking occurred below the major depocenters, immediately before hyperextension. Our results provide new insight into the formation of circular‐shaped basins and the evolution of depth‐dependent extensional processes during rifting. [ABSTRACT FROM AUTHOR]

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The NE‐dipping Anghiari normal fault, bounding to the west the Sansepolcro basin in the Upper Tiber Valley (northern Apennines), is thought to be a synthetic splay of the Altotiberina low‐angle normal fault (LANF), an active ENE‐dipping extensional detachment whose seismogenic behavior is debated. In order to assess the Anghiari fault capability to break the surface during strong earthquakes and be the source of historical earthquakes, we acquired high resolution topographic data, performed field survey and geophysical investigations (Seismic reflection, Ground Penetrating Radar, Electrical Resistivity Tomography) and dug three paleoseismological trenches across different fault sections of the Anghiari fault. The acquired data reveal for the first time the Late Pleistocene to historical activity of the Anghiari fault, constraining the age of seven paleo‐earthquakes over the last 25 ka, the youngest of which is comparable with one of the poorly constrained historical earthquakes of the Sansepolcro basin. The yielded slip rate is >0.2 mm/yr averaged over the last 25 ka and the recurrence interval is about 2,500–3,200 years. An analysis of the anisotropy of the magnetic susceptibility performed in one of the paleoseismological trenches revealed an extensional stress field, continuously acting during the sedimentation of the entire trenched stratigraphy. Our results confirm the ability of the Anghiari fault to generate surface faulting earthquakes. In addition, if the Anghiari fault does sole at depth into the Altotiberina low‐angle normal fault, this LANF could also be seismogenic and generate M > 6. Plain Language Summary: We analyzed the capability of the Anghiari fault (Upper Tiber Valley, Northern Apennines of Italy) to reach and break the topographic surface during a strong earthquake. This fault may links to the Altotiberina low‐angle normal fault (ATF), a detachment fault accompanied by a system of synthetic splays whose seismogenic behavior is still debated because of a lack of seismological and paleoseismological data. Thanks to geological, morphological, and geophysical analyses, four sites have been selected for paleoseismological investigation. The paleoseismological data revealed the seismic history of the Anghiari fault, assessing its capability to recurrently break the surface during strong earthquakes. In addition, an analysis of the anisotropy of the magnetic susceptibility performed in one of the paleoseismological trenches indicates that the stress field has been extensional, acting continuously during the sedimentation of the entire trenched stratigraphy. Our results suggest that the AF is capable to break the surface during strong earthquakes. This has potential implications for the seismogenic behavior of the ATF low‐angle normal fault, as the strong earthquakes (M > 6) may nucleate on the low‐angle fault plane if the AF is soling at depth into that detachment. Key Points: Revealed the Late Pleistocene—Holocene slip history of the Anghiari fault, considered a synthetic splay of a low‐angle normal faultThe capability of the Anghiari fault to rupture the surface during M > 6 earthquakes has been ascertainedThe results have potential implications for the activity and seismogenic behavior of a continental low‐angle normal faults [ABSTRACT FROM AUTHOR]

Many works in the last decades underline the role of evaporites, not just as a conditioning factor but as the engine for subsidence and eventually basin inversion. The western Mediterranean alpine ranges are being investigated in this regard because of the presence of discontinuous units of Permian to Triassic evaporites, deposited in the western Tethys basins. This work presents a thorough analysis of two particular structures (Cañada Vellida and Miravete anticlines) in the intraplate Maestrazgo basin (eastern Iberian Chain, Spain) in which evidence to support their reinterpretation as salt‐driven structures have been recently reported. Our analysis includes (i) a comprehensive stratigraphic and structural study of the folds along their entire trace, (ii) the compilation of thickness and distribution of evaporite–bearing and supraevaporite units, paying special attention to changes in the thickness of units in relation to anticlines, and (iii) the study of fault patterns, sometimes in relation to the mechanical stratigraphy. All three aspects are also documented and discussed on a regional scale. The new data and interpretations reported here reinforce the extensional origin of the Late Jurassic–Early Cretaceous basins, and the role of regional extensional tectonics as the responsible for the development of first‐order syn‐sedimentary normal fault zones driving the formation and evolution of sub‐basins. These basins were subsequently inverted and deformed, including the formation of complex, box‐geometry anticlines that, in their turn, controlled deposition in Cenozoic basins. The review of the arguments that support the alternative of salt tectonics for the origin of such anticlines has allowed us to delve into the sedimentary and tectonic evolution of the inverted extensional basins and to propose a specific model for the development of these faulted anticlines. The role of salt levels and other interlayered detachments in the structuring of sedimentary basins and their inversion is also pondered. The observations in the eastern Iberian Chain reported here have implications to assess ongoing reinterpretations in terms of salt tectonics in other alpine basins and ranges of the western Mediterranean. [ABSTRACT FROM AUTHOR]

Morphometric studies coupled with geophysical investigations from petroliferous basins provide valuable information about tectonics of the regions. We deduce six morphologic parameters from the River Cauvery's designated (sub)watersheds and perform dendrogram clustering analysis. The main channels of the (sub)watersheds showcase steeper gradient and meandering nature with less concavity. On the other hand, the distributaries portray lesser gradient and straight nature with greater concavity. From the offshore region of the Cauvery basin, we perform gravity modeling. The results show variations in gravity values from low to high, −150 to 50 mGal probably because of the basement ridge-depression features. This anomaly orientation indicates the extension of the sub-basin in the region. A strong NE-SW gravity trend possibly suggests a high-density plug at crustal-level. The low gravity values near the Vedaranyam region indicate low-density rocks within the basement. Places of high gravity anomaly show a decrease in bathymetry depth and vice versa. This indicates isostatic compensation of the Moho geometry, possibly due to crustal thinning in the offshore areas. Isostatic regional gravity fields are manifested by Moho relief and can have implications on the lithospheric mechanical strengths. Bathymetric studies indicate multi-directional slopes. Relatively flat areas can indicate depocenters. E-W trending lineaments mapped on the Precambrian basement from a portion of the study area is presumably a manifestation of Cauvery Shear zone, which also persists in the offshore region. • Cauvery basin in onshore region analyzed morphometrically • Main channels of (sub)watersheds & distributaries display contrasting linear parameters • Effect of gravity on uncompensated bathymetry topographic height (depth) is attempted • Isostasy analyzed using Airy-Heiskanen model in which local isostatic compensation of surface topography was compensated at Moho [ABSTRACT FROM AUTHOR]

We present the geological map (1:10.000) of the Montecastelli Pisano area, where (i) the relationships between Neogene-Quaternary transfer and normal faults have been carefully mapped (Sheet 1), and (ii) the mantle sequence of the Ligurian Ocean has been analysed (Sheet 2). Fault analyses allowed to define: (i) NE-trending fault system (left-lateral strike- to oblique-slip faults) belonging to a transfer shear zone; and (ii) NW-trending normal to oblique-slip faults. Their evolution is framed in the extensional tectonics affecting the Northern Apennines since Early-Middle Miocene. The ophiolite complex is constituted by serpentinized spinelharzburgite with minor serpentinized dunite channels cut by gabbro dykes. A km-scale cataclastic zone cut the mantle section, locally hosting Cu-Fe mineralization. The goal of this work is to present the distribution of the main fractures affecting an area where the occurrence of ophiolite can favor the success of the CO2 reinjection project. [ABSTRACT FROM AUTHOR]

Upwelling mantle plumes often instigate extensional stress within the continental crust of Earth. When stress exceeds crustal strength, extensional structures develop, reducing the effective stress and trigger magmatic processes at the crust–mantle boundary. However, such processes and their relationship to the formation of many surface structures remain poorly characterized on Mars. We identified a series of extensional structures in the southern highlands of Mars which collectively resemble continental rift zones on Earth. We further characterized these extensional structures and their surrounding region (area of ~1.8 M km2) by determining the surface mineralogy and bulk regional geochemistry of the terrain. In turn, this constrains their formation and yields a framework for their comparison with extensional structures on Earth. These terrains are notable for olivine and high-Ca pyroxene with a high abundance of potassium and calcium akin to alkali basalts. In the case of Mars, this Earth-like proto-plate tectonic scenario may be related to the plume-induced crustal stretching and considering their distribution and temporal relationship with the Hellas basin, we conclude that the plume is impact-induced. Overall, the findings of this work support the presence of mantle plume activity in the Noachian, as suggested by thermal evolution models of Mars. [ABSTRACT FROM AUTHOR]

Geothermal systems in terrains affected by polyphase deformation have reservoirs with a 3D geometry that is always difficult to predict. In this paper we describe a fossil exhumed geothermal system exposed in eastern Elba Island that developed in a polyphase folded and faulted setting, which can help us to understand how geothermal fluids circulate in geological bodies with inherited structures. Geothermal circulation at Elba allowed the deposition of Fe-ore deposits (haematite/magnetite and pyrite) and altered rock volumes, which represent tracers of the palaeo-fluid flow. Normal and oblique-slip faults dissected a polyphase folded metasiliciclastic succession and produced a secondary permeability in the range of 5 × 10−13 to 5 × 10−16 m2. From the permeable fault zones acting as feeder conduits, geothermal fluids permeated the hydraulically connected metasiliciclastic rock bodies previously deformed by two generations of folds. Geothermal fluids followed the already defined geometry, thus giving rise to apparent folded mineralized levels. Fluid migration into the metasiliciclastic rocks was possible due to their chemical aggression, which favoured the dissolution and reprecipitation of quartz, and Fe-oxide and sulphide deposition. Renewed fluids maintained their chemical properties (pH value and temperature, mostly). This conclusion provides inputs for reconstructing geothermal conceptual models and evaluating the geothermal potentiality of exploitable areas developing in similar geological settings. [ABSTRACT FROM AUTHOR]

Fault barriers are key structures for studying seismic hazard in regions of intense brittle deformation. The interaction between fault sets affects their seismogenic behavior, if some of them act as barriers. The Granada Basin, in the Betic Cordillera, is a region affected by shallow brittle deformation, as it was the scenario for the recent Granada 2021 seismic sequence. This seismicity presented a swarm behavior at the beginning of the sequence, followed by mainshock‐aftershock features. Geological and gravity data presented here reveal that the basement is affected by two sets of NW‐SE and NE‐SW normal faults and intensely deformed by vertical NW‐SE joints. Improved relocation of the Granada 2021 seismicity reveals a confined chimney‐shape seismicity caused by the activity of a 2 km long NW‐SE normal fault segment. The confinement of the sequence is associated with the NE‐SW fault set acting as a barrier that restricts the rupture area, limiting the maximum magnitude, and favoring the recurrence of events with smaller magnitude. The chimney‐shape of the seismic sequence suggests that the deformation is propagated vertically to the surface, facilitated by preexisting fractures. The shallow extensional deformation during the uplift of the central Betic Cordillera drove the activity of the local structures obliquely to the regional extensional trends, as evidenced by the seismic sequence. This multidisciplinary study improves the knowledge on the origin of the Granada Basin and underlies the important role of preexisting fractures on fault segmentation and seismic propagation, decreasing the seismic potential of this area. Key Points: The Granada 2021 seismicity is related to the activity of a 2 km NW‐SE normal fault segment bounded by oblique faults acting as barriersThe confined seismic activity extended vertically due to preexisting intense brittle deformation of the basementThe seismic barriers responsible for a swarm evolving to mainshock‐aftershock behavior decreased the seismic potential by some extent [ABSTRACT FROM AUTHOR]

The late Eocene to earliest Miocene volcanic arc of the Southern Central Andes (33–40°S) and North Patagonian Andes (40–44°S) exhibits distinctive features that shed light on the dynamics of subduction-related volcanic activity in extensional tectonic settings. This period is particularly significant in the Andes, as it records the opening of forearc, intra-arc, and retroarc extensional basins, accompanied by high-volume volcanism, preceding the middle-late Miocene final major uplift phase of the Andes. This extensional event occurred in two phases, associated with changes in the geometry and dynamics of the subduction system: from oblique convergence at low rates during the late Eocene-early Oligocene to an orthogonal convergence at high rates during the late Oligocene-early Miocene. This study presents a compilation of field, petrographic, geochemical, and isotopic data from volcanic sequences in the North Patagonian Andes and the Southern Central Andes, aiming to analyze petrogenetic processes at different stages of arc evolution. During the late Eocene to early Oligocene, subduction-related volcanism occurred in a wide area from 100 to 300 km from the trench. In this period, magmatic arc rocks exhibit intermediate composition and a relatively homogeneous geochemical signature, transitional between tholeiitic and calc-alkaline series, with a marked subduction-related signature. These magmas originated from depleted mantle sources with high slab-derived fluid and sediment contributions and limited crustal interactions. In contrast, the late Oligocene to earliest Miocene volcanic activity, at the peak of the extensional regime, displays significant geochemical differences along the Andes. In the Southern Central Andes (33–40°S), volcanism displays compositions similar to those of the previous stage with varying influence from the subducting slab. In some sectors, magmas register the climax of the extensional conditions, whereas the youngest volcanic rocks towards the north (33–34°S) present evidence of the onset of contractional tectonics, demonstrated by the increased interaction of the magmas with a progressively thickened crust. In the North Patagonian Andes (40–44°S), subaerial and subaqueous arc-related lava flows are interbedded with marine deposits, indicating a rapid subsidence regime. These rocks exhibit geochemical features transitional from arc to E-MORB and even OIB compositions, which suggest a genesis primarily dominated by decompression melting of a heterogeneous mantle source. Above all, the contrasting nature of late Eocene-early Miocene arc products in the Southern Central and Patagonian Andes highlights that no single process can explain the changes in composition, distribution, and evolution of arc magmatism; rather, it is a combination of factors, including variations in subduction zone configuration and mantle dynamics and composition. • Mid-Cenozoic Andean volcanic arc developed in an extensional setting (32–44°S). • We identified two stages with distinct geological and geochemical features. • Late Eocene-early Oligocene magmas stem from depleted arc-related sources. • Late Oligocene-early Miocene volcanism shows contrasting features along the Andes. • Upper plate extension, slab rollback, and mantle-convection controlled arc evolution. [ABSTRACT FROM AUTHOR]

The Mesozoic tectono-thermal evolution of eastern South China plays an important role in forming the abundant magmatic rocks and associated giant polymetallic deposits. The middle-late Mesozoic granitoids in Mufushan and adjacent regions (e.g., Lianyunshan, Wangxiang, Taohuahsan, etc.) represent the western front of the southeast China magmatic province. However, the tectonic regimes and petrogenesis of the magmatic rocks are still elusive. Here, we report zircon U Pb ages, geochemistry, and Sr-Nd-Hf-Pb isotopic data for the granitic rocks in the Mufushan region, in combination with data available from the literatures, to discriminate the middle-late Mesozoic tectono–magmatic history of the Mufushan complex in north-central South China Block. New zircon U Pb dating suggests that the Mufushan two-mica monzogranites were emplaced at 149–144 Ma, a short time after the 153–151 Ma granodiorites. These late Jurassic felsic magmas share broad similarities in geochemical-isotopic characteristics, with significant enrichment in LREEs and LILEs (e.g., Ba, Rb, Th, and K), depletion in some HFSEs (e.g., Nb, Ta, Ti, and P) and positive Pb anomalies, similar to those of arc-type rocks. The common existence of Neoproterozoic zircons within the magmatic rocks indicates a certain amount of ancient material involved in the genesis of the magma. The two-mica monzogranites have ε Hf (t) values ranging from −13.4 to +3.5, overlapping with those of the granodiorites (−11.3 to +6.6), but both are lower than contemporaneous diorites (−2.4 to +0.59), suggesting a greater incorporation of enriched materials into the source for the granitoids. The two-mica monzogranites and granodiorites have ε Nd (t) values ranging from −7.9 to −8.8 and − 10 to −7.9, with corresponding two-stage Nd model ages of 1.7–1.6 Ga and 1.6 Ga, respectively, falling within their two-stage Hf model ages of 2.0–1.4 Ga and 1.8–1.4 Ga, respectively. Compared with the geochemical and isotopic compositions of the coeval magmatic rocks in eastern South China, we favor that the late Jurassic Mufushan granodiorites evolved from variable mixing and differentiation of the diorites and granitoids, accompanied by a continuous magma assimilation. The presence of late Jurassic highly fractionated granites suggests an extensive magma differentiation in eastern South China and the well-developed early Cretaceous A-type granites in eastern South China reflect a dominant extensional tectonic regime induced by slab roll-back of the Izanagi plate. The involvement of subduction-related melts facilitated the underplating of mantle-derived magma and crustal heating, triggering intensive partial melting of the lithosphere and magma enrichment, as well as the polymetallic deposits in eastern South China. [Display omitted] • The late Jurassic granitic rocks in Mufushan were derived from a common source. • Neoproterozoic crustal materials were involved in middle-late Mesozoic magmatism. • Mesozoic magmas were subjected to significant modification by slab-derived components. • The slab-roll back of the oceanic Plate beneath ESCB likely began by the middle Jurassic. [ABSTRACT FROM AUTHOR]

Magmatic continental rifts often constitute nascent plate boundaries, yet long‐term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time‐averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM‐X science digital elevation model to evaluate fault‐scarp geometries and determine fault throws across the volcano‐tectonic axis of the inner graben of the NKR. Along rift‐perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new 40Ar/39Ar radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time‐averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long‐term extension rate based on mid‐Pleistocene to recent brittle deformation has minimum values of 1.0–1.6 mm yr−1, locally with values up to 2.0 mm yr−1. A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20‐km‐wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano‐tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR. Plain Language Summary: When two of the world's tectonic plates slowly move apart, a rift valley forms, which will form a divergent plate boundary. After millions of years of spreading, such a rift valley can become an ocean basin, but at first, the valley is still part of the continent, and the landscape has steep steps and volcanoes. The Kenya Rift in East Africa is such an opening plate boundary in its early form. However, it is difficult to find out how fast the opening has been on long timescales. With the help of a digital elevation model and a specialized computer code, we measure the heights of the topographic steps inside the Northern Kenya Rift valley. We also took rock samples to determine the age of the volcanoes and their lava flows. These two pieces of information can be put together: We calculate an average speed of the extension of the Northern Kenya Rift. We found out that during the last half million years, the Kenya Rift has opened at least about 1.6 mm each year. This movement happens mostly in the center of the rift valley. The flanks of the Kenya Rift valley are currently not affected. Key Points: In the inner graben of the Northern Kenya Rift valley, normal fault scarp heights have been mapped using the 12‐m‐resolution TanDEM‐X DEMThe minimum long‐term extension rate at this plate boundary is between 1.0 and 1.6 mm yr−1 since the middle PleistoceneExtension is focused in the volcano‐tectonic axis of the rift while older border faults show virtually no activity in the last 0.5 m.y [ABSTRACT FROM AUTHOR]

The Late Mesozoic tectono-thermal evolution and geodynamic setting of the Great Xing'an Range (GXR), particularly in the south margin, are still ambiguous. In this study, we present original low-temperature thermochronological data of six granitoid samples collected from Maanzi pluton in the south margin of the GXR. The apatite and zircon (U-Th)/He ages vary of 70.8 ± 4.3–119.0 ± 7.0 Ma and 120.0 ± 7.1–146.7 ± 8.7 Ma, respectively. Further numerical inverse modeling results reveal that the granitoid plutons experienced a rapid cooling and exhumation stage during Early Cretaceous with a rate of ∼5.0–6.0 °C/Ma and ∼0.14–0.17 mm/yr, respectively, including the western minor pluton emplaced during Early Permian and the major pluton crystallized in latest Jurassic, corresponding to the extensional tectonics in NE China. The rapid exhumation processes in the south margin of the GXR during the Early Cretaceous could be related to both the rollback of Paleo-Pacific oceanic plate and the collapse of thickened crust in the Mongol-Okhotsk Orogen. [ABSTRACT FROM AUTHOR]

Abstract Magmatic continental rifts often constitute nascent plate boundaries, yet long‐term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time‐averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM‐X science digital elevation model to evaluate fault‐scarp geometries and determine fault throws across the volcano‐tectonic axis of the inner graben of the NKR. Along rift‐perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new 40Ar/39Ar radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time‐averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long‐term extension rate based on mid‐Pleistocene to recent brittle deformation has minimum values of 1.0–1.6 mm yr−1, locally with values up to 2.0 mm yr−1. A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20‐km‐wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano‐tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR.

In the Main Ethiopian Rift (East Africa) a complex tectonic history preceded Tertiary rifting creating pre-existing discontinuities that influenced extension-related deformation. Therefore, this area offers the opportunity to analyze the control exerted by pre-existing structures on continental rifting at different scales. In this paper we present an overview of such an influence. We show that at a large scale (up to ∼800–1,000 km) rift localization has been controlled by a lithospheric-scale inherited heterogeneity corresponding to a Precambrian suture zone, separating two different lithospheric domains beneath the plateaus surrounding the rift. The inherited rheological differences between these two lithospheric domains, as well as the presence of pre-existing lithospheric-scale transversal structures, largely controlled the along-axis segmentation and symmetry/asymmetry of different, ∼80–100 km-long rift segments. Inherited transversal structures also controlled the development of off-axis volcano tectonic activity in the plateaus surrounding the rift. At a more local scale (

Oceanic transform faults (OTFs) are an inherent part of seafloor spreading and plate tectonics, whereas the process controlling their morphology remains enigmatic. Here, we systematically quantify variations in transform morphology and their dependence on spreading rate and age‐offset, based on a compilation of shipborne bathymetric data from 94 OTFs at ultraslow‐ to intermediate‐spreading ridges. In general, the length, width and depth of OTFs scale systematically better with age‐offset rather than spreading rate. This observation supports recent geodynamic models proposing that cross‐transform extension scaling with age‐offset, is a key process of transform dynamics. On the global scale, OTFs with larger age‐offsets tend to have longer, wider, and deeper valleys. However, at small age‐offsets (<5 Myr), scatters in the depth and width of OTFs increase, indicating that small age‐offset OTFs with weak lithospheric strength are easily affected by secondary tectonic processes. Plain Language Summary: In the past 5 decades, studies on oceanic transform faults (OTFs) have revealed significant complexity in their morphology, which calls for detailed quantitative analysis to study the processes controlling the morphology of OTFs. Using the most complete and advanced compilation of bathymetric data from ultraslow‐ to intermediate‐spreading ridges, we parameterized the morphological characteristics of OTFs and extracted length, width and depth for each transform fault from the compiled bathymetric data. Moreover, correlations between these morphological parameters and related tectonic factors (e.g., spreading rate, age‐offset) were investigated in this study. We find that correlations between morphological features and spreading rate are rather weak. Comparison of correlations suggests that age‐offset scales better with the morphological parameters, along with scatters mostly at small age‐offsets, indicating small‐age‐offset OTFs are unstable due to their weak lithospheric strength. Our observation evidences extensional tectonics at OTFs. Key Points: We compiled multibeam bathymetric data of 94 oceanic transform faults (OTFs) to quantify their morphological characteristicsMorphology of OTFs is dominated by age‐offset rather than spreading rateTransform valleys get systematically deeper and wider with increasing age‐offset, implying extensional tectonics at OTFs [ABSTRACT FROM AUTHOR]

Upwelling mantle plumes often instigate extensional stress within the continental crust of Earth. When stress exceeds crustal strength, extensional structures develop, reducing the effective stress and trigger magmatic processes at the crust–mantle boundary. However, such processes and their relationship to the formation of many surface structures remain poorly characterized on Mars. We identified a series of extensional structures in the southern highlands of Mars which collectively resemble continental rift zones on Earth. We further characterized these extensional structures and their surrounding region (area of ~1.8 M km2) by determining the surface mineralogy and bulk regional geochemistry of the terrain. In turn, this constrains their formation and yields a framework for their comparison with extensional structures on Earth. These terrains are notable for olivine and high-Ca pyroxene with a high abundance of potassium and calcium akin to alkali basalts. In the case of Mars, this Earth-like proto-plate tectonic scenario may be related to the plume-induced crustal stretching and considering their distribution and temporal relationship with the Hellas basin, we conclude that the plume is impact-induced. Overall, the findings of this work support the presence of mantle plume activity in the Noachian, as suggested by thermal evolution models of Mars.

Pre‐existing crustal structures are known to influence rifting, but the factors controlling their influence remain poorly understood. We present results of digital image correlation that allows for the surface strain analysis of a series of analog rifting experiments designed to test the influence of the size, orientation, depth, and geometry of pre‐existing crustal weak zones on strain localization and partitioning. We apply distributed basal extension to crustal‐scale models consisting of a silicone weak zone embedded in a quartz sand layer. We vary the size and orientation (α‐angle) of the weak zone with respect to the extension direction, reduce the thickness of the sand layer to simulate a shallow weak zone, and vary the geometry of the weak zone. Our results show that at higher α‐angle (≥60°) both small‐scale and large‐scale weak zones localize strain into graben‐bounding (oblique‐) normal faults. At lower α‐angle (≤45°), small‐scale weak zones do not localize strain effectively, unless they are shallow. In most models, we observe diffuse, second‐order strike‐slip intra‐graben structures, which are conjugate and antithetic under orthogonal and oblique extension, respectively. Generally, the observed spectrum of rift faulting styles (from discrete fault planes to diffuse fault zones, from normal to oblique and strike‐slip) highlights the sensitivity of rift architecture to the orientation, size, depth, and geometry of pre‐existing weak zones. Our generic models are comparable to observations from many natural rift systems like the North Sea and East Africa, and thus have implications for understanding the role of structural inheritance in rift basins. Key Points: The interplay between the orientation, size, depth, and geometry of inherited weak zone dictates their influence on rifting styleOblique normal‐slip and strike‐slip displacements are important strain accommodating mechanisms during oblique riftingUnder oblique extension, intra‐graben faults that are orthogonal to the extension direction, initiate as strike‐slip Riedel shears [ABSTRACT FROM AUTHOR]

The formation of large, economic borate deposits requires a boron-rich source, the means of transporting and concentrating the boron in a restricted environment, and mechanisms for the preservation of the deposit. There are several Miocene basins in western Turkey containing world-class borate reserves, with mineralization present as stratabound deposits in volcano-sedimentary successions. Although it is well-documented that the conditions required to form and preserve large borate deposits are most common in post-collisional tectonic settings (of which western Anatolia is a prime example), recent advances in the understanding of extensional tectonics and volcanism in this region, make it possible to gain fresh insights into their formation. Here, we suggest that formation of one of the largest borate deposits in the world was intimately related to the recently recognized Kırka-Phrigian caldera that lies in the northernmost part of the Miocene Eskişehir–Afyon volcanic field. Following caldera collapse, the basin filled with lacustrine sediments and volcaniclastic deposits with the boron mineralization concentrated in two main sub-basins: Sarıkaya and Göcenoluk. The close spatial and temporal relationship between borate deposition and the vast Early Miocene ignimbrite deposits that surround the caldera (and contain high levels of elements associated with mineralization) strongly suggest that the ignimbrites were the major source of boron. The boron was transported by geothermal fluids and post-volcanic gases that vented into warm water at the base of the caldera-paleolake system and was then concentrated during cycles of sedimentation and evaporation, with most of the mineralization concentrated along a N-S striking fault system. [ABSTRACT FROM AUTHOR]

The craton is a long-lived stable geologic unit on the Earth's surface. However, since the Mesozoic, the North China Craton (NCC) experienced large-scale lithospheric removal, the fundamental change of physical and chemical characteristics of the lithospheric mantle, widely distributed crustal deformation, and extensive magmatism. This complex evolution contrary to other cratons is called the NCC destruction. Widespread magmatism in the eastern NCC is an important response to the lithospheric removal at depth and crustal deformation on the surface. The plutons emplace under a tectonic context and therefore record the information of the tectonics; especially, the anisotropy magnetic susceptibility (AMS) pattern of the pluton was acquired with the influence of regional stress. In the past fifteen years, about 22 plutons intruding during the different periods from the Late Triassic to the late stage of the Early Cretaceous have been studied with AMS. The emplacement mechanisms of plutons and the contemporary tectonic setting were discussed to constrain their relationship with the NCC destruction in different stages of magmatism. As a result, the Late Triassic, Early Jurassic, and Late Jurassic plutons exhibit consistent N(E)-S(W) trending magnetic lineations. The early stage of Early Cretaceous plutons display NW-SE trending magnetic lineations, while the late stage of Early Cretaceous plutons show magnetic lineations with various orientations. Combined with previous studies, it is concluded that the emplacements of the plutons intruding in these three stages were controlled by weak N(E)-S(W) trending extension, regional NW-SE trending extension, and weak extension in the shallow crustal level, respectively. The transformation of regional extension from the N(E)-S(W) to the NW-SE direction was accompanied by a strain-increasing tendency. The extensional tectonics in the eastern NCC was interpreted to represent the interaction between Mongol-Okhotsk belt, Paleo-Pacific plate, and eastern Eurasian continent. [ABSTRACT FROM AUTHOR]

We provide a thorough review of the literature on peraluminous magmatism of Late Neoproterozoic and Early Palaeozoic (mostly Late Cambrian-Middle Ordovician) age cropping out in many places around the world (SW South Africa, NE Patagonia, NW Argentina, Colombia, SE Mexico and Guatemala, the European Variscan Massifs and from Turkey to northern Burma through Tibet). Petrographically, these volcanic and plutonic rocks contain K-feldspar phenocrysts and sometimes smaller bluish-quartz phenocrysts in a glassy/fine-grained (volcanic/subvolcanic) or medium- to coarse-grained (plutonic) matrix of quartz, plagioclase, K-feldspar and biotite, with other Al-bearing phases such as muscovite and garnet as minor phases. Notably, amphibole is conspicuously absent. Geochemically, these dacitic (tonalitic) to rhyolitic (granitic) rocks are silica-rich, peraluminous and with a strongly crustal Sr-Nd isotopic signature, pointing to S-type magmatism, but they also show characteristics of I-type subduction (a trace element signature typical of continental-arc magmatism) and A-type (enrichment in Ga) magmatism. A prominent geochemical feature is a marked depletion in Sr, resulting in low to very low Sr/Y ratios (usually <5). This, together with flat HREE slopes, suggests melting at low pressures. The arc signature is inherited from their crustal sources, which may comprise an old crustal basement and sediments derived from Pan-African and from Andean-type orogenic belts. Coeval, volumetrically minor mafic rocks are also common in many outcrops and are part of a bimodal sequence. Researchers have mostly attributed this magmatism to extensional tectonics in a back-arc setting, where the upwelling of the asthenospheric mantle triggered the high-temperature-low-pressure partial melting of a largely metasedimentary (upper continental) crust with little or no contribution from the mantle. In a reconstruction of Early Palaeozoic Gondwana, all outcrops are situated in peri-Gondwanan terranes, implying that they are related to (and the consequence of) rifting processes that led to the opening or aborted opening of several oceans (Rheic, proto-Tethys), reflecting a common evolution of the margin of Gondwana during the Cambrian and Ordovician. Given the similarities in petrography and geochemistry (major and trace elements and Sr-Nd isotopes) and the very large volume, several silicic Large Igneous Provinces have been proposed for some sectors, and the possibility that the entire magmatism comprises a single LIP is evaluated. Although correlations of this magmatism in different regions have been established previously, to our knowledge, this is the first study to integrate detailed petrographic, geochemical and geochronological data from all outcrops and to conclude that the peraluminous porphyritic magmatism reviewed here is the main magmatic expression of extension in the peri-Gondwanan area during the Early Palaeozoic. [Display omitted] • A belt of mostly peraluminous rocks developed in Early Palaeozoic peri-Gondwana. • The magmatism exhibits S-type features with hints of I- and A-type characteristics. • The most striking geochemical feature of the magmatism is the very low Sr/Y ratio. • The peraluminous belt formed due to extensional tectonics in a back-arc region. • Early Palaeozoic peri-Gondwana underwent back-arc extension after Gondwanan assembly. [ABSTRACT FROM AUTHOR]

Rift-basins are the shallow effects of lithosphere-scale extensional processes often producing polyphase faulting. Their sedimentary evolution depends on the mutual interplay between tectonics, climate, and eustasy. Estimating the role of each factor is generally a challenging issue. This paper is focused on the tectono-sedimentary evolution of the Neogene Siena-Radicofani Basin, a polyphase structural depression located in the inner Northern Apennines. Since Miocene, this basin developed after prolonged extensional tectonics, first as a bowl-shaped structural depression, later reorganized into a half-graben structure due to the activation of high-angle normal faults in the Zanclean. At that time the basin contained coeval continental and marine settings controlled by the normal faulting that caused the development of local coarse-grained depositional systems. These were investigated to: (i) discriminate between the influences of tectonics and climate on sedimentation patterns, and (ii) provide detailed time constraints on fault activity. The analysed successions were deposited in an interval between 5.08 and 4.52 Ma, when a climate-induced highstand phase occurred throughout the Mediterranean. However, evidence of local relative sea-level drops is registered in the sedimentary record, often associated with increased accommodation space and sediment supply. Such base-level fluctuations are not connected to climate changes, suggesting that the faults generally control sedimentation along the basin margins. [ABSTRACT FROM AUTHOR]

Isotopic and thermochronological data were recently obtained from the footwall of the Büyük Menderes detachment ranges from 29.0 ± 1.9 Ma (ZFT) to 1.6 ± 0.2 Ma (Ap U - Th / He), and they can be grouped in three different time intervals. These results are well explained by the Alaşehir type-rolling hinge mechanism, which suggests active rotated initial normal fault during successive normal fault development of the graben formation. This paper suggests that the Alaşehir type-rolling hinge mechanism is applicable to the Büyük Menderes graben by using field observations, published isotopic / thermochronological and subsurface data. It also contributes to the long-lasting discussion about the activation problem on the low-angle normal faults. [ABSTRACT FROM AUTHOR]

The Anisian depositional history in the Western Tethys realm provides the possibility to study the stepwise opening of the Neo-Tethys, and is well preserved in the sedimentary record of the Northern Calcareous Alps. Whereas the depositional characteristic in the Early (to early Middle) Anisian is characterized by shallow-water carbonates, formed in a semi-restricted environment, the situation changed in the Middle Anisian. A rapid increase of subsidence resulted in an abrupt deepening event with deposition of deeper-water limestones, in some cases even with chert nodules, sometimes with resedimented shallow-water debris intercalated in radiolaria-filament wackestones, or with clayey or marly intercalations. This abrupt deepening, termed the Annaberg Event, is followed by a shallow-water carbonate evolution. The deeper-water limestones can be dated by conodonts and shallow-water organisms like calcareous algae or foraminifera from the resedimented intercalations as Late Bithynian to Early Pelsonian. In contrast to the Early Anisian microbial carbonates, formed under semi-restricted conditions, the Middle Anisian (Pelsonian) shallow-water carbonates were formed under fully marine influence and a diverse fauna and flora was, therefore, able to counterbalance the rapid subsidence by increasing carbonate production. During Middle Anisian times, the newly tectonically created accommodation space became rapidly filled by shallow-water carbonates. At the end of the Middle Anisian (Late Pelsonian), the final break-up of the Neo-Tethys led to a rapid decrease of carbonate production and widespread deposition of deep-marine and condensed limestones. This drowning event (Reifling Event) was accompanied by the formation of a horst-and-graben morphology, dated by conodonts and ammonoids as late Middle Anisian from overlying condensed limestones. In contrast to the well-known drowning event in the late Middle Anisian, precursor events to the final oceanic break-up of the Neo-Tethys have not yet been described, but play an important role in the reconstruction of the opening history of the Neo-Tethys. This knowledge gap is filled by the analysis of exactly datable sedimentary successions in the central Northern Calcareous Alps. [ABSTRACT FROM AUTHOR]

The Eastern Galicia Magnetic Anomaly is the best studied anomaly of the Central Iberian Arc. This is due to its location, on the Lugo‐Sanabria gneiss dome, and to the fact that its source rocks crop out in the Xistral Tectonic Window. Multiple studies of this anomaly have been carried out, but still, new results keep on shedding light on its understanding. This paper presents the first results on rock magnetic analyses, natural remanent magnetization, anisotropy of the magnetic susceptibility, X‐ray diffraction, and stable isotopes geochemistry carried out on the source rocks of this anomaly. Results suggest that magnetization responds to the increase in oxygen fugacity underwent by rocks affected by late Variscan (330‐300 Ma) extensional tectonics. Extensional detachments were the pathways that allowed the entrance of fluids that led to syntectonic crystallization of magnetite and hematite in metasediments and inhomogeneous S‐Type granitoids derived from their partial melting. Accordingly, magnetization is not linked to lithologies, but to extensional structures developed in the late Carboniferous/earliest Permian, during the Kiaman reverse superchron. Systematic reverse magnetic remanence exhibited by hematite‐bearing samples confirms the age of the magnetization and adds complexity to the interpretation of the anomaly. Understanding the EGMA contributes to the interpretation of other anomalies existing in the CIA, also located on thermal domes. The observed extension‐related magnetization probably affected most of the NW Iberian Massif, thus hindering the study of previous tectonics by paleomagnetic techniques. This work aims to provide new hints to interpret magnetic anomalies located in extensional tectonic contexts worldwide. Plain Language Summary: This paper presents a further step in the understanding of the Eastern Galicia Magnetic Anomaly (Iberian Massif), the biggest and most studied magnetic anomaly in Spain. Understanding the source and age of magnetization of this anomaly is key to understand the age of the Central Iberian Arc as it allows (1) to infer the origin of other anomalies found in the internal zone of the Central Iberian Arc and (2) shed more light on the age of the arc itself. Previous papers on this matter are: Ayarza et al. (2007) and Martínez Catalán et al. (2018), https://doi.org/10.1029/2017tc004887. Both represent the evolution on the investigations carried out in this area after the papers by Aller et al. (1994), https://doi.org/10.1016/0040‐1951(94)90255‐0 and that of de Poulpiquet (2012). The MS submitted now includes new AMS, rock magnetism, NRM, field work, and geochemistry studies of the area and proves the role that late Variscan orogenic extension has played in magnetization. Key Points: NRM of the EGMA exhibits a component of inverse polarity coherent with the characteristics of the Kiaman superchronSynkinematic S‐Type granitoids of the Lugo‐Sanabria dome are heterogeneously but highly magneticLate Variscan extension produced the magnetization of EGMA and other areas at the core of the Central Iberian Arc during the Kiaman superchron [ABSTRACT FROM AUTHOR]

Kishtwar region of Jammu and Kashmir, India has been investigated to identify the traces of active faults preserved in the topography of the area. The objectives were achieved by geomorphic mapping with the help of satellite imageries (Cartosat-1 with 2.5 m resolution), detailed geological field investigations, shallow sub-surface geophysical mapping and the optical luminescence dating. Active tectonic landforms mapped in this study include Kishtwar rhombohedral basin, fault scarps, drainage offset, deformed recent sediments, uplifted lacustrine sediments and faulted river terraces. The evidence of active extensional topography reported here is from the compressional tectonic regime of NW Himalaya and is represented by the ~ 10 km long and 2–3 km wide Quaternary basin, interpreted as a tectonic graben. The basin is vaulted by normal faults, where master fault and the antithetic fault show continuous and en echelon behaviour respectively. The presence of normal fault system bounding the basin/graben, lead to hypothesize that the releasing bend of Kishtwar strike-slip fault is responsible for their origin. Detailed field investigation along these faults led to highlight their active nature and future prospects for palaeoseismic investigations. The active nature of these faults is supported by dip-slip movement, fault scarp, fault rupture and displacement in the Holocene and recent sediments. The spatial distribution of these features has been confirmed with the help of Ground Penetrating Radar (GPR) survey. Optically Stimulated Luminescence (OSL) dating of the deformed units demonstrate that the displacement along the Kishtwar fault has occurred between 16.35 ± 2.13 to 13.14 ± 0.91 ka and 13.14 ± 0.91 to 7.89 ± 0.71 ka. [ABSTRACT FROM AUTHOR]

A transition from supradetachment to rift basin signature is recorded in the ~1,500 m thick succession of continental to shallow marine conglomerates, mixed carbonate‐siliciclastic shallow marine sediments and carbonate ramp deposits preserved in the Bandar Jissah Basin, located southeast of Muscat in the Sultanate of Oman. During deposition, isostatically‐driven uplift rotated the underlying Banurama Detachment and basin fill ~45° before both were cut by the steep Wadi Kabir Fault as the basin progressed to a rift‐style bathymetry that controlled sedimentary facies belts and growth packages. The upper Paleocene to lower Eocene Jafnayn Formation was deposited in a supradetachment basin controlled by the Banurama Detachment. Alluvial fan conglomerates sourced from the Semail Ophiolite and the Saih Hatat window overlie the ophiolitic substrate and display sedimentary transport directions parallel to tectonic transport in the Banurama Detachment. The continental strata grade into braidplain, mouth bar, shoreface and carbonate ramp deposits. Subsequent detachment‐related folding of the basin during deposition of the Eocene Rusayl and lower Seeb formations marks the early transition towards a rift‐style basin setting. The folding, which caused drainage diversion and is affiliated with sedimentary growth packages, coincided with uplift‐isostasy as the Banurama Detachment was abandoned and the steeper Marina, Yiti Beach and Wadi Kabir faults were activated. The upper Seeb Formation records the late transition to rift‐style basin phase, with fault‐controlled sedimentary growth packages and facies distributions. A predominance of carbonates over siliciclastic sediments resulted from increasing near‐fault accommodation, complemented by reduced sedimentary input from upland catchments. Hence, facies distributions in the Bandar Jissah Basin reflect the progression from detachment to rift‐style tectonics, adding to the understanding of post‐orogenic extensional basin systems. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of a new approach based on sandbox models to the understanding of the tectonic evolution of the Volta Redonda Basin, southeastern Brazil. Those models were designed to replicate the overlapping process of two of the four superimposed tectonic events identified in the Volta Redonda Basin: the first one, a rifting event with NW-SE extension direction that created the basin, and the subsequent E-W sinistral transcurrent tectonics. The boundary conditions for the models were set from the geological premises described in previous works, which resulted in the current conceptual geological models of the study area. The sandbox models were composed of alternating layers of colored sand, deposited on two pieces of acetate or cardboard sheets, which acted as pre-existing basement structures. Once completed, the models were cut and photographed to allow observation and interpretation of the resulting internal structures. Moreover, the interpretations maintain similarities with adopted conceptual models and permit conclusions about structures previously identified in other works. Finally, the consequent structural framework exposes the effects of structural reactivation and Basin geometry changes due to the superposition of deformational events and matches with the general structural aspects identified in field studies.

Many oases (wet interdunes) are sedimentary systems characterized by high-frequency water-level oscillations, marked changes in salinity and intense biological activity at their margins. They are considered to be one of the most challenging environments on Earth for ecosystem development. These dynamic, depositional settings are usually unfavourable for fossilization and subsequent preservation of vegetal remains. This paper describes bryophyte (liverwort) assemblages occurring in three successive horizons interpreted to represent (i) recurrent early successional phases of biological soil crust colonization of wet interdune margins or (ii) exceptional preservation of floating or riparian liverworts in oasis pond waters associated with a progressive fall of the interdune water level. The record of in situ colonization surfaces characterized by delicate (e.g. lignin-free) three-dimensional structures represents an exceptional type of preservation herein associated with a rapid variation in phreatic interdune water level and the subsequent establishment of anoxic and reducing conditions. The occurrence of exceptionally preserved liverwort colonies coincides with the sedimentary record of, at least, three seismite levels in the oasis. Data gathered from the site suggests that the water table of the oasis was controlled by a combination of (i) a positive creation of accommodation space due to subsidence associated with movement on syn-sedimentary extensional faults, and (ii) the rise and fall of the oasis water table controlled by the oscillations of the groundwater system due to orbital changes which appear to drive the variability of the climate system. Rising groundwater levels flooded the oasis soil crusts and lead to the exceptional recurrent preservation of liverwort colonies at the oasis margins. Alternatively, considering the hypothesis of floating or riparian liverworts in the oasis pond waters, the fall in the level of the oasis water table placed the floating liverworts in contact with the oasis bottom sediments. This fall in the level of the oasis water table could indicate a cessation of accommodation space by syn-sedimentary extensional faults and/or a regional lowering of the groundwater system level associated with drought periods. Preliminary results indicate that oasis lamination between liverwort colonies records decadal and sub-decadal cyclicity, related with 11-year Schwabe sunspot and sub-decadal NAO cyclicities, conferring for every sedimentary cycle between liverwort colonies a duration of approximately 200 years, that otherwise matches the expected recurrence period for the De Vries cycle of solar activity. Image 1 • First report of recurrent bryophyte colonization surfaces in oases deposits. • Quick rises of Oasis water table led to the bryophytes preservation. • Solar modulation on oasis sedimentation defined 11 year Schwabe sunspot. • Solar modulation on oasis sedimentation defined sub-decadal NAO cyclicities. • Record of solar activity De Vries cycles between liverwort colonies. [ABSTRACT FROM AUTHOR]

East Antarctica remains one of the few continental regions on Earth where an understanding of the origin and causal processes responsible for topographic relief is largely missing. Low‐temperature thermochronology studies of exposed Precambrian basement revealed discrete episodes of cooling and denudation during the Paleozoic–Mesozoic; however, the significance of these thermal events and their relationship to topography across the continental interior remains unclear. Here we use zircon and apatite (U‐Th)/He thermochronology to resolve the low‐temperature thermal evolution of a poorly exposed section of East Antarctic basement in the Bunger Hills region and gain insights into the chronology and style of landscape evolution across East Antarctica. Thermal history modeling results indicate that Precambrian basement in the Bunger Hills region experienced a distinct cooling episode during the Late Paleozoic–Triassic, which we relate to ~2–4 km of regional exhumation associated with intracontinental rifting, followed by a second episode of localized cooling and ≤1 km exhumation during the Late Jurassic–Cretaceous separation of India from East Gondwana. These findings, combined with existing thermochronological and tectonic evidence, support a continent‐scale denudation event associated with uplift and exhumation of large sections of Precambrian basement during Late Paleozoic–Triassic Pangea‐wide intracontinental extension. By contrast, continental extension associated with the Jurassic–Cretaceous breakup of East Gondwana resulted in significant denudation only locally in regions west of the Bunger Hills. We propose that the combined effects of these Paleozoic–Mesozoic tectonic events had a profound impact on the topography across the East Antarctic interior and influenced the long‐term landscape evolution of East Antarctica. Key Points: First low‐temperature thermochronology (LTT) study of the Bunger Hills basement in East AntarcticaLTT data record widespread cooling and exhumation of East Antarctic basement associated with Pangea‐wide extensionLarge‐scale topographic framework established during intracontinental extension has influenced long‐term landscape evolution of East Antarctica [ABSTRACT FROM AUTHOR]

This paper presents the results of a new approach based on sandbox models to the understanding of the tectonic evolution of the Volta Redonda Basin, southeastern Brazil. Those models were designed to replicate the overlapping process of two of the four superimposed tectonic events identified in the Volta Redonda Basin: the first one, a rifting event with NW-SE extension direction that created the basin, and the subsequent E-W sinistral transcurrent tectonics. The boundary conditions for the models were set from the geological premises described in previous works, which resulted in the current conceptual geological models of the study area. The sandbox models were composed of alternating layers of colored sand, deposited on two pieces of acetate or cardboard sheets, which acted as pre-existing basement structures. Once completed, the models were cut and photographed to allow observation and interpretation of the resulting internal structures. Moreover, the interpretations maintain similarities with adopted conceptual models and permit conclusions about structures previously identified in other works. Finally, the consequent structural framework exposes the effects of structural reactivation and Basin geometry changes due to the superposition of deformational events and matches with the general structural aspects identified in field studies. [ABSTRACT FROM AUTHOR]

The Ulukışla Basin is one of the most important late Cretaceous-Cenozoic basins in central Anatolia. The basin is surrounded by the Bolkar Mountains of Tauride Platform in the south, the Niğde Massif of Central Anatolian Crystalline Complex to the north, and the Ecemiş Fault Zone and Aladağ Mountains in the east. The fact that time interval proposed for the formation of Ulukışla Basin is quite wide and more than one tectonic regime prevailed in the region, have led to various suggestions concerning the evolution of the basin. While the suggestions majorly examine the character of the basin during the late Cretaceous-early Cenozoic, the number of detailed studies on the status of the basin in the late Cenozoic is limited. In this study, we focused on the less-studied late Cenozoic evolution to differentiate the tectonic phases that controlled the development of Ulukışla Basin through structural data, and elaborate the responses of sedimentation and paleogeography during this period through detailed facies analyses. Our findings indicate that the Ulukışla Basin, which started to develop as a supradetachment basin in the late Cretaceous, has continued its extensional development progressively during its Cenozoic history. While the relatively well-studied early Cenozoic sequences represent a marine environment that was rapidly changed shallow- to deep-sea environment and then gained a shallow character by the middle Eocene, sedimentary features and fossil contents of the late Cenozoic units characterize deposition started in a paralic environment changing into a terrestrial environment rapidly, as a result of isolation by the uplifting of surrounding topographies while the basin continues its development under an extensional tectonic regime. However, the extensional basin history surceased in post-middle Eocene and post-middle Miocene, probably caused by the closing processes of the different branches of Neotethys Ocean. [ABSTRACT FROM AUTHOR]