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Oblique-slip along transform fault boundaries is often partitioned between a strike-slip system and thrust faults that accommodate contraction. However, topography along the Yakutat-North American transform (Fairweather fault), is asymmetric with low-terrain above active thrusts on the western, Yakutat side of the transform and high topography on the continental side with peaks >4500 m (Mount Fairweather: 4671 m) to the west of the Border Ranges fault, limited recorded earthquakes >M4, and no apparent reverse faults to generate the highest terrain. In this study we compile, for the first time, published U-Pb zircon, 40Ar/39Ar and K-Ar (hornblende, muscovite, and biotite) and U-Th/He and fission-track (zircon and apatite) bedrock ages (109) from 75 samples to investigate the exhumation history of the Fairweather Range region, complemented by a published detrital sample (ZFT and AFT) and 13 new 40Ar/39Ar (hornblende, biotite, and K-feldspar) ages on 9 bedrock samples from both sides of the Fairweather fault. Additionally, we examined published seismicity and geodetic data of the Fairweather region and assessed if plate paleo-vectors correlate with the cooling history of the Fairweather Range. Cooling age, seismic, and block-motion patterns indicate the Fairweather Range has been vertically extruded between the Fairweather and the Border Ranges faults as a coherent block since ca. 25 Ma. The pre-6 Ma Pacific plate motion (N30°W) aligns with the N33°W strike of the Fairweather Fault whereas a hypothetical pre-6 Ma Yakutat microplate paleo-vector of (N39°W) does not: indicating a post-6 Ma timing for Yakutat microplate counter-clockwise rotation (9°). We infer that rotation and impingement of the Yakutat microplate along the Fairweather fault at ca. 3 Ma led to the development of the Fairweather restraining bend and increased cooling rates. The resultant thickened Fairweather welt and the ∼30 km thick southeast end of the Yakutat microplate compounded double-indenter tectonics into Alaska's southeast convergent corner • The Fairweather Transform has been active since at least ca. 30 Ma. • The Fairweather transform has experienced ∼1300 kms of horizontal slip at a minimum. • The Fairweather Range block has been undergoing vertical extrusion since ca. 25 Ma. • Double-indenter tectonics likely led to a ca. 3 Ma Yakutat microplate rotation. • The Fairweather fault restraining bend may have formed at ca. 3 Ma. [ABSTRACT FROM AUTHOR]

To decipher the mechanism by which the Phanerozoic accretionary terranes collaged with the Tarim Craton, we constructed a three-dimensional (3-D) lithospheric resistivity model using magnetotelluric data and inversion with testing. The model covers the area across the northern Tarim Craton in the south and the southern Altaids in the north and shows five tectonic-related low-resistivity regions. The low resistivity in East Junggar highlights a Permian rifting zone. The southwest Tianshan low-resistivity anomalies mark asthenospheric upwellings and are related to present-day orogenesis. The intra-crustal low-resistivity area in the northern Tarim Craton could be attributed to metamorphic products from the layered underplating coeval within the Tarim large igneous event. The relatively weak low-resistivity anomalies in Central Tianshan may represent fossil suturing zones. Beneath western Junggar and Chinese North Tianshan (NTS), a large low-resistivity anomaly is continuously distributed in the upper mantle, but spatial correspondence was not shown with the overlying resistivity structure, which could be attributed to the movement of the shallow lithosphere decoupled from the lower lithospheric mantle. We argue that the Yili-Central Tianshan terrane moved northeastward to collage with the Junggar terrane, driving the Junggar terrane rotation and shallow buckling of West Junggar, which constructed the thin-skinned Chinese NTS. The closure of the South Tianshan back-arc basin, associated with southward subduction, completed the amalgamation of peripheral accretionary terranes with the Tarim Craton after the Late Permian. The present study supplies a typical example of the amalgamation of accretionary terranes with a core, thus improving the understanding of continental growth. • We constructed the 3-D resistivity model covering > 600,000 km2. • Our model shows low-resistivities are footprints for tracing lithospheric evolution. • The model supports CAOB collaged with Tarim Craton by back-arc basin subduction. • Thickening is likely a prerequisite for young terranes amalgamating with a core. [ABSTRACT FROM AUTHOR]

We have carried out a detailed paleomagnetic study of volcanic rocks (18 sites) and red beds (10 sites) from the Late-Carboniferous-Permian series of the Cadí Basin (Eastern Pyrenees). The study provides reliable Late Carboniferous-Permian paleomagnetic directions, in an area where paleomagnetic studies are scarce. The main characteristic component in both rock types shows a SSE direction with a shallow inclination and a dominant reverse polarity. The magnetic carriers, both in the volcanic rocks and the red beds, are magnetite and hematite. The main component is interpreted as a primary magnetization of Permian age in the red beds; in the Late Carboniferous volcanic rocks, the main component likely represents primary magnetization or early remagnetization. These results are consistent with the poles for the Iberian plate during the Permian and indicate an absence of regional vertical axis rotations for the Orri nappe, in whose hanging wall the Cadí Basin was transported southwards during the Pyrenean orogeny. • Magnetization in Permian red beds. • Remagnetization in volcanic rocks. • No vertical axis rotations. [ABSTRACT FROM AUTHOR]

The study of crustal structure plays a crucial role in understanding the tectonic development and seismicity of orogens. In this contribution, we analyzed the gravitational responses caused by the subsurface structure of the Tian Shan orogen using global EIGEN-6C4 gravity field data. The quality of the EIGEN-6C4 gravity data in the eastern Tian Shan area was evaluated, and we employed the wavelet multi-scale analysis method in combination with an existing P-wave velocity model to reveal the structures at different scales. The gravity Moho of the study area that best fits the seismological Moho was obtained from the filtered third-order wavelet approach component after several tests using different reference depths and density contrasts. The results reveal significant lateral discontinuities in the lower crust and upper mantle structures across the eastern and western Tian Shan orogens. The Moho beneath the western Tian Shan is about 9 km deeper compared to the eastern Tian Shan. Towards the Tarim and Junggar basins, the Moho decreases to about 45 km in depth. The analysis of the isostatic anomaly suggests that the eastern and western Tian Shan possess varying capabilities for isostatic adjustment. Furthermore, it indicates a gradual weakening of mantle upwelling in the Tian Shan orogen from west to east, implying that different stages of mantle dynamics may have occurred in the western and eastern Tian Shan. The north Tarim fault, Nikolaev-North Nalati fault, and Kazakh fault serve as channels that control magma upwelling in the Tian Shan orogen. The distribution of earthquakes differs between the eastern and western Tian Shan, with the western Tian Shan exhibiting greater gravitational potential energy. These variations between the eastern and western Tian Shan may be attributed to the clockwise rotation of the Tarim craton. • Decomposing gravity anomaly of the Tian Shan region using wavelet multi-scale method. • Gravity inversion constrained by seismic data providing an optimal Moho depth. • The Tian Shan orogen experienced different stages of mantle dynamic revealed by gravity and Vp anomalies. [ABSTRACT FROM AUTHOR]

The Pyrenees have undergone complex geodynamic evolution starting with experiencing significant tectonic events during the Variscan Orogeny, followed by the intrusion of large granitic complexes during the late Variscan stage, then the collision between the Iberian and European plates during the Alpine Orogeny, and finally, Mesozoic extension. Despite extensive studies and the application of various geophysical methods (two-dimensional seismic reflection data, gravity, and long period magnetotellurics) to investigate the Pyrenean structure, there are still fundamental questions regarding its basement and cover architecture. Specifically, the geometry at depth of significant bodies such as the Late Variscan intrusive granites and Triassic evaporitic accumulations, remains unclear. To better understand these issues, we have conducted joint magnetotelluric and gravity surveys along a 60-km-long transect, spanning the boundary between the Axial and South Pyrenean Zones. Our final geological interpretation shows that the La Maladeta batholith consists of two distinct granitic bodies related to different intrusive pulses. In addition, we identify important Triassic evaporitic accumulations at depth. This work shows the high potential of integrating two geophysical models for understanding the geological evolution of structurally complex areas. The magnetotelluric and gravity data are complementary, with each dataset providing a different resolution for investigating the basement and cover architecture of the Pyrenees. These resolutions depend on the varied petrophysical properties of the rocks involved, including water content and deformation grade. • The South-Central Pyrenees-Axial Zone boundary has been explored through a combined magnetotelluric and gravity survey. • Important accumulations of evaporites have been identified at depth in the South-Central Pyrenees. • High-resistivity features provide evidence that the La Maladeta batholith is composed of two distinct granitic bodies. • These bodies are interpreted to be associated with two distinct intrusive pulses. [ABSTRACT FROM AUTHOR]

The Armorican Massif experienced a poly-orogenic evolution, represented by the Neoproterozoic Cadomian and the Devonian-Carboniferous Variscan tectonothermal events. In the southernmost part of the Armorican Domain (or Armorica microcontinent), the St-Georges-sur-Loire Unit consists of a block-in-matrix subunit, and a turbiditic subunit in the South and North, respectively. The St-Georges-sur Loire unit is interpreted as a remnant back-arc basin formed in Silurian-Early Devonian (ca. 440–400 Ma), and was deformed during the Variscan orogeny. Most of the sedimentary and magmatic blocks enclosed in clastic matrix are olistoliths derived from an assumed southern area called the "missing domain", presently exposed as the Variscan Mauges Nappe composed of the Cadomian rocks and Early Paleozoic sedimentary cover. The "missing domain" was subducted beneath the Armorican massif during the Variscan collision. Detrital zircon age spectra from sandstones and siltstones from the olistostrome matrix reveal Neoproterozoic and Early Paleozoic age clusters, and less abundant Paleoproterozoic and Archean ages. Hf isotopic compositions of detrital zircons indicate dominantly negative ε Hf (t) values which are in agreement with a recycled continental source. Minor positive values correspond to a juvenile component that was formed during the Neoproterozoic Cadomian orogeny or Archean-Paleoproterozoic events. The Cambrian and Early Ordovician ages can be related to the pre-Variscan rifting of the Pannotia megacontinent that separated the Armorica microcontinent from Gondwana. Neoproterozoic ages imply a source of the magmatic rocks exposed in the Cadomian belt of the northern part of the Armorica microcontinent, and in the Mauges Nappe. • Detrital zircon ages spectra and their Hf isotopic composition are indicative of the predominance of populations • The analyzed zircon grains are preferentially derived from a southern source, but at northern one cannot be discarded • Most of the grains record negative Hf isotopic values indicating that crustal melting played a major role [ABSTRACT FROM AUTHOR]

An extensive early Carboniferous foreland basin (the Moravosilesian Culm Basin, MSCB) delineates the northeastern margin of the Bohemian Massif (Variscan orogenic belt). The basin overlays a complex suture between the outer Brunovistulia microplate, forming a promontory previously accreted to Laurussia, and inner Gondwana-derived units that form the remainder of the Bohemian Massif. Our structural, paleomagnetic and magnetic anisotropy data from the eastern portion of the MSCB indicate that its depositional architecture, internal fabric, and deformation by folding and faulting record a major switch from orthogonal convergence to orogen-oblique strike-slip shearing. First, the Brunovistulia microcontinent was subducted frontally towards W during ~346–335 Ma, followed by a shift of the subduction vector towards ~SSW at around 335–330 Ma. From ~330 Ma onwards, the underthrusting had ceased and the ~WNW–ESE dextral Elbe shear zone, related to the westward movement of Gondwana with respect to Laurussia, controlled deformation of this region. Displacement of the northerly Eastern Sudetes 'block' towards ~ESE produced regional ~WNW–ESE pure-shear shortening against the Brunovistulia indentor and resulted in an overall doubly-vergent structure of the MSCB. Simultaneously, the southerly Moldanubian unit was translated towards ~WNW, away from the Brunovistulian microplate, and likely contributed to an extensional regime related to orogenic collapse progressing outward from the internal domains of the Bohemian Massif. On a larger scale, we suggest that the MSCB is an illustrative example of a polykinematic foreland basin, where deposition, syn- to post-sedimentary deformation, and thus geodynamic processes changed significantly during basin evolution, starting off with microplate impingement into a continental margin reentrant and terminated by strike-slip shearing. Our data also do not support previous models for the tectonic development of the northeastern termination of the Variscan Belt, which suggested either a large-magnitude, vertical-axis oroclinal rotation of the foreland or its translation along an orogen-perpendicular strike-slip fault. • Structural, magnetic anisotropy and paleomagnetic study of a foreland basin • Late-orogenic Moravosilesian Culm Basin, northeastern Variscan belt • The deformational architecture developed in two stages • Basin records switch from frontal convergence to dextral strike-slip shearing • Shearing driven by westward movement of Gondwana with respect to Laurussia [ABSTRACT FROM AUTHOR]

It is commonly accepted that many orogens form by contractional reactivation of earlier continental rifts or rifted margins. Therefore, to better understand orogenesis, it is important to also understand how rift domains and their associated structures are incorporated into orogens. We investigate the role of rift structural inheritance during orogeny using the Western Pyrenees as a case-study. To achieve our aim, we use a kinematic forward lithosphere deformation model (RIFTER) to produce flexural isostatically compensated as well as balanced cross-sections showing the structural and stratigraphic development of both the rift and orogenic stages of the Western Pyrenees. The cross-section produced extends from the Northern to the Southern Foreland Basins and crosses the Mauléon-Arzacq Basin. Our modelling results show how rift-domains and their faults are sequentially reactivated and incorporated into the present-day Western Pyrenees architecture. Based on the results from our case-study, we identify a sequence of tectonic stages separated by critical events that record the transition between different tectonic styles by which lithosphere is deformed. The pre-orogenic extensional stage is characterized by a hyper-extended rift system that eventually led to exhumed mantle. This constitutes the pre-orogenic template. The subsequent contractional tectonics consists of two stages: (i) the inversion of the hyper-extended rift system reactivating extensional structures and (ii) the crustal shortening of the southern proximal rift domain. Results of the Western Pyrenees case-study may be used to understand the development of other Alpine-type collisional systems involving the sequential reactivation and inversion of former hyper-extended rift systems. [ABSTRACT FROM AUTHOR]

Anisotropy of magnetic susceptibility (AMS) has been shown to be a good proxy for crystallographic preferred orientation (texture). However, it is not clear in detail how different factors, e.g. modal composition and preferred orientation, define the total AMS in a rock. Black shale samples from a drill core on the Appalachian Plateau in western Pennsylvania were analyzed with respect to their microfabric as determined by texture and microstructure, and AMS. Low- and high-field AMS, which was measured at room temperature, reveals that the AMS of the samples is dominated by the para- and diamagnetic phases. Synchrotron diffraction was applied to determine the texture of all relevant mineral phases incorporated in the samples. Muscovite and chlorite pole figures show single maxima perpendicular to the foliation, reflecting dominant flattening strain. From these textures and the modal compositions, AMS models were calculated using the intrinsic magnetic anisotropy of the single crystals. The modeled and measured AMS are comparable in terms of their principal directions and shapes of the anisotropy ellipsoid for the dominantly paramagnetic samples, with the maximum susceptibility axes oriented subhorizontal to the NE-SW. Both, textures and AMS, indicate that the samples have undergone largely bedding compaction with a weak tectonic overprint linked to the Alleghenian orogeny. Our results suggest that the microfabric and the magnetic fabrics on the plateau, 200 km away from the Allegheny Front, detect the tectonic shortening. The AMS modeling demonstrates how the contribution of the intrinsic AMS of each mineral controls the AMS of the whole rock. • Good agreement between measured and modeled AMS of para- and diamagnetic black shales • Modeling of AMS from textures shows the strong dependence of anisotropy on the phyllosilicates. • Layer parallel shortening due to Alleghenian orogeny is recorded in texture and magnetic lineation. [ABSTRACT FROM AUTHOR]

The Triassic-Jurassic transition marks an important change in the basin configuration of the Greater Barents Sea. A contiguous basin with km-thick sedimentary successions changed into a partitioned basin with uplift in the west and foreland basins in the east with significant implication for the basin infill history. Our study employs a range of different high-resolution datasets from a distal part of the basin which unravels the complex pattern of differential uplift and erosion in the basin during this period. We record for the first time distinct angular unconformities between Upper Triassic strata and overlying Lower Jurassic strata within the basin, showing that large parts of it formed topographic highs. Our study links these angular unconformities to compression induced by the Novaya Zemlya Fold and Thrust Belt. A heterolithic basement below a thick sedimentary succession where the fold belt developed created a complex uplift pattern in the basin, at the same time similar to but different from typical forebulge areas. Compression caused inversion of older basement rooted faults defining platforms and graben systems throughout western parts of the Barents Sea basin, in addition to salt remobilization that resulted in differential uplift and erosion. These local zones of uplift controlled the sediment distribution pattern to the basin at a time when the most important reservoir units in the basin were deposited. This new understanding of the basin development explains hitherto enigmatic sequence boundaries that has inspired complex paleogeographic models in the past. • Compression-induced uplift of sedimentary basin • Tectonic control on distribution of reservoir rocks • Impact of Novaya Zemlya Fold and Thrust Belt • Northward continuation and late stage evolution of the Uralide orogeny • Remobilization of salt [ABSTRACT FROM AUTHOR]

The Anaximander Mountains and the Rhodes Basin at the junction of Cyprus and Hellenic arcs are one of the tectonically most complex regions in the eastern Mediterranean. Harmonically-tilted Messinian and the uppermost Messinian–Pliocene successions across the northern and eastern margins of the Rhodes Basin showed that these regions experienced dramatic subsidence exceeding ~1500–2500 ms (~1125–1875 m @ 1500 m s−1) during the upper Pliocene–Quaternary. Tilted upper Pliocene–Quaternary growth strata wedges showing apparent north-directed downlap along the northern foothills of the Anaximander Mountain suggested that this region experienced ~1000–2500 ms (~750–1125 m) concomitant uplift. The absence of faults showing extensional stratigraphic separations and the relative subsidence rates calculated using amount of tilting collectively suggest that the Rhodes Basin experienced sagging of its deeper basinal regions, which is attributable to the loading effect of the building of the Tauride Mountains modified by the vertical axis rotations of the Beydağları Block and the Island of Rhodes, and the horizontal axis rotation of the Anaximander Mountain. Messinian and uppermost Messinian–Pliocene were tectonically relatively quiet as shown by the harmonically structured and isopachous successions across the Rhodes Basin and Anaximander Mountain. This interval coincides with the paleomagnetically-determined 9° counterclockwise vertical axis rotation of the Island of Rhodes. The dramatic subsidence observed within the Rhodes Basin and the concommitant uplift of the Anaximander Mountain and its western extension occurred broadly coincident with southeast tilting of the Island of Rhodes and its associated 500–600 m subsidence between 2.5 and 1.8 Ma, the northwest tilting between 1.5 and 1.1 Ma, and the associated re-emergence of the southeastern coast. The large counterclockwise rotation of the Island of Rhodes since 0.8 Ma corresponds with the enormous subsidence observed across the northeastern sector of the Rhodes Basin, which brought the shelf-edge deltas from the near-sea level to their present-day depth of 1200–1500 m. [ABSTRACT FROM AUTHOR]

The Central Andean Forearc (26°S) structure has been debated for decades. Extension, contraction, and strike-slip deformation are commonly proposed mechanisms to explain the main tectonic elements exposed in the Domeyko Cordillera, Salar de Pedernales Basin, and others partially exposed in the Coastal Cordillera and Central Depression. Although pre-Andean tectonic inheritance seems to have influenced the style and mechanisms of mountain uplift in this region, its current architecture and the way it controlled the shortening distribution during orogen evolution are highly speculative, mainly because some of the tectonic provinces in this segment consist of covered areas (e.g., the Central Depression). To address this question, we present the first balanced cross-section and pre-shortening restoration of the Andean forearc at 26°S. We integrated new field data from the Coastal and Domeyko cordilleras with well data and re-interpreted 2D seismic profiles from the Salar de Pedernales Basin to construct a regional-scale cross-section of 210 km length from the Coastal Cordillera to the current Volcanic Arc, thus showing a two-dimensional (2D tectonic model to help understand the tectonic evolution of the western Central Andes. The results indicate a pre-shortening architecture dominated by Late Permian–Jurassic half-graben structures related to continental rifting. West- and east-dipping basement-rooted normal faults controlled rift-related basins, along which kilometric-scale marine and continental syn -rift sequences accumulated. During early Andean orogenesis, the normal faults were partially inverted, and large anticlines developed at the hanging wall faults, which Upper Cretaceous progressively covered to Paleocene synorogenic units. This suggests that the initial topographic relief in the region resulted from a basin inversion. During the more advanced stages of orogenesis (mid-Cenozoic), new reverse and thrust faults (or shortcut faults) were created, which connected upward with incompetent stratigraphic units and facilitated the propagation of localized fold-and-thrust belts in the eastern Domeyko Cordillera and Salar de Pedernales basins. A minimum of 16.3 km of W-E shortening was reported; however, nearly 11 km was accommodated by the newly created thrusts, indicating that these were most relevant to mountain building. • The 2D tectonic model of the Central Andes forearc at 26°S shows present-day and pre-orogenic architectures of the western Central Andes. • The structures consisted of thick-skinned and doubly verging structures. • 16.3 km of W-E shortening was accommodated by the propagation of shortcut faults connecting the basement-involved to the thin-skinned structures. [ABSTRACT FROM AUTHOR]

The Greater East Shetland Platform and its intra-platform basins (i.e. the Dutch Bank Basin and East Orkney Basin) are examples of poorly explored areas in the UK Continental Shelf (Northern North Sea), hosting a locally thick (1–8 km) Devonian-to-Tertiary sedimentary succession that unconformably overlies the Caledonian crystalline basement. Starting from a grid of seismic reflection lines, six recently acquired profiles were selected, interpreted and depth-converted. The resulting geological cross sections were integrated with forward modelling of the observed Bouguer gravity and magnetic anomalies, and constrained by the available wellbore-derived petrophysical parameters. Our seismic interpretation and modelling suggest that the first-order contributors to the observed Bouguer gravity anomalies are related to the scattered distribution of the Mesozoic sedimentary sequences in the intra-platform basins. Furthermore, the main sources of the modelled magnetic anomalies are related to high-susceptibility (≤0.05 SI units) bodies in the crustal basement that locally correspond to zones of high reflectivity imaged in the seismic profiles. Such deep sources are interpreted as paleo-domains inherited from the pre-Devonian tectonic evolution of the study area and assembled during the Caledonian Orogeny. This may be relatable to the offshore extension of first-order pre-Devonian tectonic lineaments exposed in the Scottish Highlands and Orkney-Shetland islands. • Combined gravity and magnetic anomaly forward modelling in the Greater East Shetland Platform. • Thickness of the Mesozoic sequences significantly affects the gravity anomaly. • Deep crustal high-susceptibility geometries possibly relate with inherited Caledonian structures. [ABSTRACT FROM AUTHOR]

The relationship between parallel and oblique to the orogen faults and the magmatic evolution is key to understanding the evolution of a hot orogen, such as the Central Andes. The Andean orogenesis along the southern Central Andes, during the Neogene is characterized by regional compression and magmatic processes associated with subduction. The outcome of this dynamic interaction between plate tectonics and magmatism has generated reverse, normal and strike-slip faults, both parallel and oblique to the trench. Despite the progress made on studying these fault systems, both their relationship with the stress field and their role in magma propagation into the shallow crust are still enigmatic. In this work, geomorphological observations are coupled with kinematic and dynamic analyses, as well as with kinematic forward modeling, to reconstruct the evolution of two main faults affecting the western slope of the Puna plateau, the Barrancas Blancas fault and the Tocomar fault, during the Neogene. The obtained data reveal that, between 17 and 10 Ma, the Barrancas Blancas fault had reverse activity, while the Tocomar fault had left-lateral strike-slip movement. At 10 Ma, the area was affected by the coeval reactivation of the Volcan de Punta Negra fault and the right-lateral activity of the Tocomar fault. During the last stage, strike-slip movement along the Tocomar fault favored the rise of magma, while the hydrothermal activity evolved along the Barrancas Blancas fault. The study results reveal that the oblique-to-the-orogen faults play a role in the segmentation of the reverse parallel-to-the-trench deformation and control the position of the volcanic centers, while the parallel-to-the-orogen faults control the relief development and the evolution of hydrothermal systems. The proposed model helps in understanding how magma rises to the surface associated with movement along reverse and strike-slip faults during the thickening of the crust. • Interactions between coeval reverse and strike-slip faults. • Control of fault in the ascent and evolutions of magmas. • Reconstruction of paleo-stress vector in the forearc of central Andes. • Evidence of NW-SE strike-slip fault in the forearc of Central Andes. [ABSTRACT FROM AUTHOR]

Continent-continent collision drives crustal deformation, topographic rise and geodynamic change. Africa-Eurasia convergence accommodated in the Eastern Mediterranean involved subduction of the Neotethyan oceanic lithosphere in Anatolia. Subduction was followed by collision of continental crust of Greater Adria with Eurasia to form the Izmir-Ankara-Erzincan suture zone. Discerning the effects of this collision from pre-collisional ophiolite obduction-related orogeny of Greater Adria is notoriously difficult. Estimates on the timing of collision in Central Anatolia are based on a forearc-to-foreland basin transition along the Eurasian margin and suggest a ~60 Ma age of initial collision. Here, we assess whether this age is also representative for collision in Eastern Anatolia and across the Cenozoic Sivas Basin that straddles the Greater Adria-Europe suture. To this end we retro-deform regional block rotations in the Pontides, the Kırşehir Block and the Taurides, building a first-order regional 'block circuit' around the Sivas Basin. We show that up to ~700 km of convergence must have been accommodated across the Sivas Basin after Central Anatolian Kırşehir-Pontide collision at ~60 Ma – an order of magnitude more than estimated crustal shortening, and that wholesale lithospheric subduction must have occurred throughout much of the Cenozoic. Paleocene collision would require that this subduction consumed continental lithosphere, which is unlikely. We consequently infer that oceanic subduction continued much longer in Eastern Anatolia, perhaps well into the Miocene. We postulate that prolonged oceanic subduction and slab pull drew the Eastern Taurides north relative to the Central Taurides, leading to shortening and oroclinal bending in Central Anatolia. The diachronous demise of the Neotethys Ocean in Anatolia, as a function of its paleogeography, is thus a likely driver for the strong non-cylindricity of the Cenozoic Anatolian collisional orogen. • Continent-continent collision in Anatolia was diachronous. • After ~60 Ma, ~700 km of convergence was yet to be accommodated in Eastern Anatolia. • Convergence accommodated is an order of magnitude more than crustal shortening. • Prolonged subduction resulted from a kinked passive margin paleogeography. • Oceanic subduction in Eastern Anatolia continued longer than previously thought. [ABSTRACT FROM AUTHOR]

Key in understanding the geodynamics governing subduction and orogeny is reconstructing the paleogeography of 'Greater India', the Indian plate lithosphere that subducted since Tethyan Himalayan continental collision with Asia. Here, we discuss this reconstruction from paleogeographic, kinematic, and geodynamic perspectives and isolate the evolution scenario that is consistent with all three. We follow recent constraints advocating a ~58 Ma initial collision and update a previous kinematic restoration of intra-Asian shortening with a recently proposed model that reconciles long-debated large and small estimates of Indochina extrusion. Our new reconstruction is tested against paleomagnetic data, and against seismic tomographic constraints on paleo-subduction zone locations. The resulting restoration shows ~1000–1200 km of post-collisional intra-Asian shortening, leaving a 2600–3400 km wide Greater India. From a paleogeographic, sediment provenance perspective, Eocene sediments in the Lesser Himalaya and on undeformed India may be derived from Tibet, suggesting that all Greater Indian lithosphere was continental, but may alternatively be sourced from the contemporaneous western Indian orogen unrelated to India-Asia collision. A quantitative kinematic, paleomagnetic perspective prefers major Cretaceous extension and a 'Greater India Basin' opening within Greater India, but data uncertainty may speculatively allow for minimal extension. Finally, from a geodynamic perspective, assuming a fully continental Greater India would require that subduction rates close to 20 cm/yr was driven by a down-going lithosphere-crust assemblage more buoyant than the mantle, which seems physically improbable. We conclude that the Greater India Basin scenario is the only sustainable one from all three perspectives. We infer that old pre-collisional lithosphere rapidly entered the lower mantle sustaining high subduction rates, whilst post-collisional continental and young Greater India basin lithosphere did not, inciting the rapid India-Asia convergence deceleration ~8 Myr after collision. Subsequent absolute northward slab migration and overturning caused flat slab subduction, Tibetan shortening, arc migration and arc volume decrease. Unlabelled Image • Following 58 Ma India-Asia collision, Asia shortening 1000-1200 km and 2600-3400 km of (Greater) India subducted • Combined paleogeographic, kinematic, and geodynamic constraints strongly suggest a Greater India Basin scenario • Post-58 Ma upper mantle slab buckling induced flat slab subduction causing India-Asia slowdown and Tibetan shortening [ABSTRACT FROM AUTHOR]

Abstract The effects of initial rift inversion over the geometry of a far-foreland intracratonic fold-and-thrust belt are investigated. A total of 25 seismic reflection lines and stratigraphic data from 9 wells are used in association to digital elevation and field geological data, to investigate the geometric relationship between shallow thrust development and initial positive inversion of buried rift faults in a cratonic environment, where inversion tectonics is not common. The study case is conducted in the meeting region of the opposed-verging Brasília and Araçuaí foreland fold-and-thrust Neoproterozoic belts, located in central Brazil, formed in the first stages of West Gondwana amalgamation. Seismic reflection sections are used to map buried paleorift faults and trust ramps. The best 5 sections are also interpreted in detail in terms of fold and thrust geometry and their relationship to the inverted rifts is analyzed. They show high correlation between shallow fold-and-thrust geometry and the shortening of synrift strata, caused by rift inversion. Results indicate that initial positive rift fault reactivation exerts a determinant control over the locus of thrust ramp nucleation, by causing syn-rift strata to overfold and drape fold. The passive folding propagates upwards forming gentle folds in the décollement plane, where thrust ramps tend to nucleate. Back-thrust-forethrust pairs tend to form over elevated horsts, where higher topographic plateaus are preserved. Multiple thrusting and lower relief occur over buried rifts with multiple inverted faults. Strata over non-rifted basement remain practically unaffected by thrusting and folding. Moreover, the development of thrust salients and recesses are demonstrated to be conditioned by the morphology of buried rifts. The study also contributes with a more precise mapping of the buried rift system and thrust system in the area, and brings new insights about the structural evolution of the Brasiliano-Pan Africano orogeny affecting the São Francisco craton basement and covers. Highlights • Initial paleorift inversion detected in intracratonic setting. • Thrust ramps nucleate where paleorift inversion folds décollement. • Strain channeling within paleorift results in thrust curvature. • Thrust-related breccia occurs under thrust-ramp, on thrust terminations. • Paleorift initial inversion influences geomorphological evolution. [ABSTRACT FROM AUTHOR]

Abstract A possible Mesozoic-Cenozoic trajectory for the North American craton is outlined from latitude changes of the craton derived from a revised apparent polar wander path, and from westward movement of the craton based on the assumption that Africa has been the least mobile continent geographically since the latest Paleozoic. During each of five time intervals that span 220 million years, the craton trajectory had a different vector. Each vector appears to be reflected in the Canadian Cordillera by the dominant style and orientation of structures formed during that interval. For much of the past ~ 220 million years, the ~meridionally-oriented western margin of the Pangea-Laurasia-North America Plate has been the site of arc magmatism where weak arc/back arc lithosphere, sandwiched between strong ocean-floor and craton lithospheres at times coupled across convergent or transform plate boundaries, focused and recorded strain. When the craton apparently moved due westward, between ~180–160 Ma and ~120–60 Ma, the dominant structures formed then record orogen-normal compression and were accompanied by orogeny. Structures formed during the earlier episode are mainly in the eastern and interior Cordillera and their formation shortly followed or coincided with accretion of most terranes to the craton margin. In the later episode, compressional structures span the entire Cordillera, which emerged as a tectonic and physiographic entity. Before and between these intervals, when the craton apparently moved mostly northwestward, mainly geological and paleomagnetic considerations indicate some terranes moved southward (sinistrally) relative to the craton. After ~60 Ma, southwestward movement of the craton was concurrent with large northward (dextral) strike-slip faults that disrupted the newly-established ancestral Cordillera. The coincidence between the age of structures that record dominant orogen-normal compression at times when the craton apparently moved due westward, and orogen-parallel displacements when the craton had either northward or southward components of motion, suggests the craton, acting as a "Continental Bulldozer", was the primary driver of Cordilleran deformation and orogenesis. Highlights • A Mesozoic-Cenozoic trajectory for the North American craton is proposed. • Periods of due westward motion correlate with main phases of Cordilleran orogeny. • This was due to increased coupling of the craton and subducting ocean lithosphere. • Terrane accretion long recognized as a fundamental process in Cordilleran orogeny. • However, movement of the craton was the principal control on Cordilleran orogenesis. [ABSTRACT FROM AUTHOR]

Abstract Lower crustal flow zones occur in large and hot orogens and rifts, where they occur in association with large areas possessing high gravitational potential energy (GPE) and low lower crust viscosity. Lower crustal flow zones are also known from regions where neither the rheological nor GPE conditions are sufficiently well developed for widespread flow to occur. For these examples, the conditions required to form crustal flow zones are less well defined. One such case occurs within the ca. 600–530 Ma Petermann Orogeny in central Australia. This work investigates the conditions under which this flow zone developed, considering differences with the adjacent regions where flow is not observed. A transect of crustal structure in the central Petermann Orogen is developed that takes into account geological and geophysical data, including time-constrained pressure and temperature estimates for the Petermann Orogeny. The deformation of this region is reconstructed, showing that lower crustal flow was driven by high amplitude crustal-scale folding. The folding extruded the lower crust towards the foreland, causing crustal thickening and buoyant uplift of the orogenic core. Channelized lower crustal flow is not known from either the eastern or western parts of the orogen, and a comparison with these regions suggests three main conditions are required: Firstly, the lower crust must be sufficiently hot and volatile-rich to allow melt-weakening. Secondly, crustal rheology must allow ductile deformation of the mid to lower crust without high-strength layers. Finally, a high degree of lateral confinement is required to form pressure-gradients capable of driving flow. These three conditions were met only in the central Petermann Orogen, and not in the east or the west. This example of a lower crustal flow zone illustrates the combined influence of thermal, rheological and kinematic threshold conditions on the initiation and development of channelized lower crustal flow in orogens. Highlights • Boundary conditions are examined for an example of channelized lower crustal flow. • Thermal and rheological conditions are near the threshold for flow to occur. • Crustal-scale folding of a warm crust (T moho ≈ 800 °C) is the driver of flow. • Kinematic conditions must also be met for channelized flow to occur. [ABSTRACT FROM AUTHOR]

Abstract This paper reviews the geology of the Late Ordovician - Silurian Caledonian Moine Thrust zone in the Loch Eriboll region, NW Scotland. We present new detailed mapping and balanced/restored cross-sections to examine its structural evolution. This thrust zone comprises four major thrust slices, carried by the Moine, Lochan Riabhach, Arnaboll and Sole thrusts. Ductile mylonites were derived from lithologies in both the hangingwall (Moine schists) and the footwall (Lewisian basement gneisses, Cambrian quartzites, Ordovician dolomites) of the Moine Thrust. The mylonites are bounded by the Lochan Riabhach thrust below and the Moine thrust above. The Arnaboll thrust sheet comprises Lewisian basement gneisses and Cambrian-Ordovician sedimentary rocks over the Sole Thrust sheet, which exposes a spectacular imbricate sequence of Cambrian-Ordovician sedimentary rocks. Although thrusts sequentially propagated in-sequence from higher (Moine) to lower (Sole) thrusts with time, there is evidence for minor out-of-sequence thrusting and breakback thrusting. Thrusts evolve from deep ductile shears where strain is concentrated along mylonite zones up into the brittle field where they become discrete planar thrust faults. The Early Silurian Scandian metamorphism (~435–415 Ma) is related to a Himalayan style structure with SSE-directed subduction and WNW directed extrusion of a migmatitic core, which we liken to channel flow. We suggest that two major crustal-scale thrusts that extend down into the upper mantle imaged on seismic profiles across the foreland, the Outer Isles and Flannan thrusts, are unrelated spatially or temporally to the Moine thrust sequence. Highlights • We present new detailed mapping, together with cross-, lateral-, and restored-sections from the northern Moine Thrust zone • Restoration shows that the intensely deformed Sole Thrust Sheet experienced c. 60% shortening at Loch Eriboll • We place this mapping in its regional context and review the structural evolution of the northern Moine Thrust Zone • We review orogen wide data from the Moine Thrust hinterland and compare with Himalayan tectonic architecture [ABSTRACT FROM AUTHOR]

Abstract Due to uncertainty of single-method interpretation we applied 2-D integrated lithospheric modelling along three CELEBRATION 2000 profiles CEL01, CEL04 and CEL05. Modelling of the lithospheric thermal structure is based on the joint interpretation of gravity, geoid, topography and surface heat flow data with temperature-dependent density. The models for each profile were constrained by seismic modelling results of the large-scale international project CELEBRATION 2000. The results indicate large variations of the lithosphere thickness from the old and cold East European Craton (~200 km) and the Trans European suture zone via the Western Carpathian orogeny to the young and hot Pannonian Basin (~90 km). Important differences in the lithospheric thickness were also found along-strike of the Western Carpathian orogeny and the Trans-European Suture Zone. The western part of the Western Carpathians is characterized by weak thickening of the lithosphere (only about 145 km), while their eastern segment presents strong lithospheric thickening (~190 km). The Małopolska unit in southern Poland has a lithospheric thickness of about 130 km. Thickest lithosphere (220 km) is observed around the junction of the Carpathian Foredeep and the East-European Craton. The crustal thickness follows generally the course of the lithosphere-asthenosphere boundary. The results suggest different geodynamic evolution of the collision of the ALCAPA microplate with the European platform on the one hand and the East-European Craton on the other hand. It is suggested that the tectonic evolution of this very complex area consisting of different tectonic units has changed in time and space. Highlights • Three lithospheric thermal and density sections from the East-European craton to the Pannonian Basin are presented • Constraints through potential fields, topography, heat flow and CELEBRATION-2000 crustal seismic models • Modifications of seismic models are necessary in southern Poland (Mid-Polish Trough and Małopolska Unit) • Lithosphere thickness under the Western Carpathians increases from W to E indicating laterally varying convergence styles [ABSTRACT FROM AUTHOR]

Abstract In the Iberian Variscan Belt, polyphasic deformation has been recognized as comprising an early phase of crustal thickening, followed by an intermediate phase of crustal extension and doming, and a later phase of shortening. The Évora Massif is a gneiss dome of the westernmost domains of the Ossa-Morena Zone (SW Iberia), which provides a remarkable insight into the late Paleozoic deep crustal structure of the Variscan continental crust of northern Gondwana. In this study, we bring new structural and geochronological U-Pb data for the northern hanging-wall of the Évora Massif. We describe the existence of low-dipping D 2 extensional shear zones associated with Buchan-type metamorphism (M 2); this enables three tectono-metamorphic units to be distinguished: the Lower Gneiss Unit, the Intermediate Schist Unit, and the Upper Slate Unit. D 2 -M 2 structures experienced subhorizontal shortening (D 3) and were transposed by low-plunging folding, thrusting and strike-slip faulting. Zircon grains extracted from Pavia quartz-feldspathic gneiss of the Lower Gneiss Unit yielded a crystallization age of ca. 521 Ma (Cambrian Stage 2–3), which establishes a correlation with tectono-metamorphic units of the footwall and southern hanging-wall of the Évora Massif. U-Pb zircon dating of Divôr foliated quartz-diorite (339 ± 7 Ma), Malarranha weakly foliated biotite-rich granite (322 ± 3 Ma), and undeformed porphyritic granite of the Pavia pluton (314 ± 4 Ma) constrain the timing of emplacement of granitic magmas synchronously with doming. Carboniferous magmatism initiated with doming (ME 1 - ca. 343–335 Ma), continued through D 2 -M 2 (ME 2 - ca. 328–319 Ma), and lasted until the waning stage of crustal extension (ME 3 - ca. 317–313 Ma). The Évora Massif gneiss dome probably formed as result of the combined effect of gravitational collapse of the thickened crust and buoyancy-driven gravitational instability developed in the partially molten continental crust influenced by the transfer of heat from rising mantle-derived (i.e. dioritic-gabbroic) magmas rocks found in the footwall of the Évora Massif. Graphical abstract Unlabelled Image Highlights • Structure of the northern hanging-wall of Évora Gneiss Dome is revealed. • Interplay of Variscan compressional and extensional events in the Ossa Morena Zone • Viséan-Bashkirian HT-LP metamorphism, calc-alkaline magmatism and synorogenic extension • U-Pb SHRIMP geochronology of Lower Paleozoic felsic rocks and regional correlation • Geochronology of granitic rocks constrains tectonic events in the Évora Massif. [ABSTRACT FROM AUTHOR]

Abstract In this paper we present a series of thermo-mechanical experiments on continent-continent collision zones to investigate the role of lateral strength contrasts in terms of collision dynamics and orogen geometries. Our results show that differences in crustal rheology, may lead to a variety of different patterns of deformation and crustal geometries. Upper plate indentation forms a sequence of foreland propagating thrust units made of brittle upper crust on the lower plate. The strong deformation of the lower plate stands in stark contrast to the undeformed upper plate. In contrast, subduction of strong lithosphere beneath a weak upper plate forms a complex pattern of deformation. Deformation initiates on the lower plate and forms an antiformal stack made of brittle upper crust, before it indents the upper plate. Hence, deformation is present on both, the lower and upper plate, despite differences in initial strength. The outcome of this study has direct implications to natural collision zones, where differences in strength between the upper and lower plate exist. For example, along strike variability of upper vs. lower plate shortening in the Alps are likely to be controlled by contrasts in crustal strength. Furthermore, we suggest that the antiformal stack in the axial zone of the Pyrenees might indicate a strong lower plate at the onset of collision. Our results may therefore provide important constraints for the rheological state of continents during collision. Graphical abstract Image 1 Highlights • We study influences of crustal strength contrasts on continent-continent collision. • Crustal deformation always migrates from the stronger into the weaker plate with time. • Large-scale mountain geometries are controlled by crustal strength variations. [ABSTRACT FROM AUTHOR]

Abstract In the Tien Shan belt, Cenozoic to active deformation is guided by structures and rheological contrasts partly inherited from the Paleozoic Variscan orogeny and reactivated by the India-Asia collision. Cenozoic deformation net estimates are constrained by lithospheric scale geological cross-sections, which rely on reconstructions of the Paleozoic Central Asian Orogenic Belt (CAOB). However, several geodynamic scenarii have been proposed for its formation including a south or a north dipping subduction, which are still debated due to lack of constraints. Here, we designed numerical experiments to test different hypotheses about the initial geometry and the effective rheology of the paleo-sutures and especially the one located between the Tien Shan and the Tarim basin, where most Cenozoic deformation localizes. The different geometries of Paleozoic structures are used as input variables in the thermo-mechanical models, which are then run forward in time. After a finite amount of shortening, the structures that develop self-consistently out of the proposed heterogeneities are then compared to the current Cenozoic finite and active deformations. We find that a crustal south-dipping suture zone lying on a resistant lithospheric mantle best explains the localization of the deformation, the current geometry of the structures and the Moho depth variations. Using the model results, we propose a mechanically consistent depth-interpolated crustal cross-section of the Kyrgyz Tien Shan, which incorporates both geological and geophysical data. Graphical abstract Image 2 Highlights • Combination of numerical modelling, geological and geophysical data to constrain crustal structure of the Kyrgyz Tien Shan • Numerical modelling designed to test hypothesis and influence of pre-Cenozoic structure • Crustal inherited structures control the strain localization in the Kyrgyz Tien Shan. • Crustal cross-section of the Tien Shan [ABSTRACT FROM AUTHOR]

Abstract The Maures-Tanneron Massif (MTM), together with Corsica and Sardinia, represent the Southeastern branch of the huge European Variscan belt. A continuous evolution from continental collision to exhumation is described from ca. 350 Ma to ca. 320 Ma, based on an extended compilation of available geological and geochronological data. This geological compilation is complemented with thermo-mechanical modelling that tests the conditions under which deep-seated HP units can melt and exhume massively during continued convergence. We simulate in two-dimensions the development of gravitational instabilities in a partially melting crust, depending on rheological layering and heat sources, and accounting for temperature dependent elasto-visco-plastic rheologies. In order to reproduce PT exhumation patterns in the MTM, over the appropriate time-scale (> 20 My) and spatial extent (> 100 km), a best fit was obtained with a convergence rate of 0.5 cm/yr and moderate diffusive surface processes. The contribution of radiogenic heating in the pre-stacked felsic crustal units is crucial. A lateral alternation with mafic units is also required in order to prevent lateral spreading of the orogen. A low viscosity partially molten crust (1020 Pa·s, thus rather felsic) accompanies crustal exhumation in a decoupled mode from the deeper mantle. A shallow asthenosphere below the orogen (LAB at ~ 70 km depth, e.g. shallow slab break-off) produces too warm and sudden exhumation as opposed to a competent mantle lithosphere (120 km depth LAB) that restrains it. The MTM witnesses the typical competition between far-field plate convergence and internal body forces, and our study pleads for a progressive evolution of transpression towards perpendicular extension from ca. 320 Ma. Highlights • A geological synthesis is combined with thermo-mechanical models to interpret exhumation of the South European Variscan Belt, • The orogenic root exhumed diapirically over > 100 km² during convergence at ~ 0.5 cm/yr for > 20 My, • A bulk viscosity of 10^20 Pa.s appropriately simulates the formation and rise of partially molten mush at these scales. • Alternation of felsic crustal units against a mafic buttress is necessary to model the observations, • Structures and dynamics show a continuous transition from continental collision to perpendicular extension. [ABSTRACT FROM AUTHOR]

Abstract Mechanisms of Precambrian orogeny and their contribution to the origin of ultrahigh temperature granulites, granite-greenstone terranes and net crustal growth remain debatable. Here, we use 2D numerical models with 150 °C higher mantle temperatures compared to present day conditions to investigate physical and petrological controls of Precambrian orogeny during forced continental plates convergence. Numerical experiments show that convergence between two relatively thin blocks of continental lithosphere with fertile mantle creates a short-lived cold collisional belt that later becomes absorbed by a long-lived thick and flat ultra-hot accretionary orogen with Moho temperatures of 700–1100 °C. The orogen underlain by hot partially molten depleted asthenospheric mantle spreads with plate tectonic rates towards the incoming lithospheric block. The accretionary orogeny is driven by delamination of incoming lithospheric mantle with attached mafic lower crust and invasion of the hot partially molten asthenospheric wedge under the accreted crust. A very fast convective cell forms atop the subducting slab, in which hot asthenospheric mantle rises against the motion of the slab and transports heat towards the moving orogenic front. Juvenile crustal growth during the orogeny is accompanied by net crustal loss due to the lower crust subduction. Stability of an ultra-hot orogeny is critically dependent on the presence of relatively thin and warm continental lithosphere with thin crust and dense fertile mantle roots subjected to plate convergence. Increased thickness of the continental crust and subcontinental lithospheric mantle, pronounced buoyancy of the lithospheric roots, and decreased mantle and continental Moho temperature favor colder and more collision-like orogenic styles with thick crust, reduced magmatic activity, lowered metamorphic temperatures, and decreased degree of crustal modification. Our numerical modeling results thus indicate that different types of orogens (cold, mixed-hot and ultra-hot) could be created at the same time in the Early Earth, depending on compositional and thermal structures of interacting continental blocks. Highlights • Contrasting types of orogeny could be created at the same time in the Early Earth. • Ultra-hot accretionary orogeny (UHO) is produced by convergence of fertile lithosphere. • Juvenile crustal growth during UHO is accompanied by net crustal loss. • UHO spreads laterally with plate tectonic rates towards the incoming lithospheric block. • The modeled orogeny explains core characteristics of granite-greenstone terranes. [ABSTRACT FROM AUTHOR]

Abstract Detrital ages constrain the timing of deposition, along-strike paleo-geographic variations and the nature of erosional sources in sedimentary basins and can be used to constrain the transition between orogenic cycles. The Connecticut Valley-Gaspé (CVG) trough is a major Upper Ordovician-to-Devonian sedimentary basin that extends for >1000 km in the Northern Appalachians and was deposited during the Salinic and Acadian orogeneses. In Quebec and northern New England, the CVG trough is host to the Gaspé Belt and correlative units of the Connecticut Valley sequence (CVS). In southern Quebec, the Gaspé belt sedimentation occurred during late Silurian-to-Early Devonian crustal extension related to the Salinic orogeny. This study reports detrital U/Pb zircon and 40Ar/39Ar muscovite ages from the Ayers Cliff and Compton formations, Quebec and the correlatives Waits River and Gile Mountain formations, Vermont. Detrital zircon ages suggest that proximal early Silurian-to-Devonian erosional sources were submerged during sedimentation, which is consistent with an extension-related marine transgression marked by the Ayers Cliff and Waits River formations. The lack of Ediacaran zircons in the Ayers Cliff Formation contrasts with the Waits River Formation, suggesting that the nature of erosional sources varied during deposition of the lowermost part of the basin. Stratigraphically higher Compton and Gile Mountain formations have similar detrital zircon provenance suggesting homogenization of detrital contributions. This is attributed to the encroachment of Avalonian terranes and ongoing erosion, probably during uplift of Laurentia and Avalonian terranes leading to foreland basin development and deposition of the uppermost part of the Compton and Gile Mountain formations which yielded youngest mean ages of ca. 413 Ma and ca. 401 Ma, respectively. Low-grade metamorphic conditions allow the preservation of detrital 40Ar/39Ar muscovite ages which highlight the contribution of erosional sources that experienced Grenvillian, Taconian and Salinic metamorphism. Highlights • Transition of orogenic cycles reflected by timing of deposition, along-strike paleo-geographic variations and nature of erosional sources of syn-orogenic basin. • Implication of approaching Avalonian terranes in the transition from Salinic to Acadian orogenic cycles • Maximum age of deposition of the Gaspé Belt and Connecticut Valley sequence is c. 413 Ma and c. 401 Ma, respectively. • Sources having experienced Grenvillian, Taconian and Salinic metamorphism contributed to the Gaspé Belt sedimentation. • U Pb cristallisation age of the Averill Pluton is 367.8 ± 0.3 Ma [ABSTRACT FROM AUTHOR]

Abstract The Yukon Tanana (YTT) and Slide Mountain terranes (SMT) of the Cordillera in Canada and Alaska were interpreted in terms of opening and closing of a Late Devonian-Permian Japan Sea-style backarc basin behind a continental arc built upon YTT, which rifted from Laurentia during the Famennian-early Mississippian. Formation of Famennian transitional oceanic lithosphere supports rifting, but a combination of existing and new data on the setting and age of SMT ophiolites do not support the Japan Sea model. The studied Clinton Creek and Midnight Dome complexes represent suprasubduction zone ophiolites formed at ca. 265 Ma, consistent with analyses of other SMT ophiolites. Ultramafic rocks dominate most ophiolites. They lack sheeted dikes and contain relatively minor volumes of mafic plutonic and volcanic rocks, suggesting they formed in oceanic core complexes characterised by slow spreading and low magma productivity. The Permian ophiolites formed during or immediately after eclogite formation in YTT, coeval with or immediately preceding emplacement of orogenic peridotites into YTT due to hyperextension. Several tectonic scenarios are discussed. We propose that YTT is a composite terrane comprising a continental block and an oceanic arc-backarc complex with the latter obducted onto the former during the middle Permian-early Triassic Klondike orogeny. Obduction may have come from the west or east, but east-directed obduction is most consistent with geological constraints. Obduction was followed by initiation of west-dipping subduction east of the composite YTT; slab roll back causing extension in the composite upper plate, leading to exhumation of orogenic peridotites. Tectonic relationships show many analogies to the collision between Australia and the New Britain arc, in which collision in the Huon Peninsula of New Guinea is contemporaneous with extension in Australian crust in the adjacent Woodlark basin. Syn-orogenic Permian Klondike calc-alkaline magmatism is attributed to extension in a Woodlark basin-like setting rather than a representing a continental arc. Highlights • Permian Slide Mountain terrane (SMT) ophiolites formed above a west-dipping subduction zone in the Panthalassa Ocean. • The SMT ophiolites were obducted onto Yukon Tanana Terrane (YTT) during the Permian Klondike Orogeny; YTT was the lower plate • The SMT ophiolites were generated west of YTT in the Panthalassa Ocean, not in the Slide Mountain Ocean. • Subduction stepped-back into the Angayucham Ocean after obduction, leading to extension and exhumation in YTT. • Parts of the Australia-Pacific plate boundary zone are a modern analogue fort the Klondike tectonic events. [ABSTRACT FROM AUTHOR]

The Cantabrian orocline is a major orocline that bends the Variscan belt of Western Europe. Despite a wealth of studies, its timing and relationship with the late-Variscan folding stages in the Iberian Massif are still debated. This study provides an integrated structural analysis of the Variscan fold generations and associated W-Sn bearing vein systems within the southern Central Iberian Zone (Regoufe, Portugal), giving insight into their kinematic relationship with oroclinal buckling. Two superimposed fold generations with mutually parallel, steep to vertical fold axes have been identified. Isoclinal F 1 folds with E-W striking axial planes formed during coaxial shortening and are spatially localised. F 3 folds with NW-SE axial planes are associated with late-Variscan transpressional deformation and constrain the structural outline of the major folds. Temporal and kinematic considerations indicate that vertical-axis, asymmetric F 3 folding corresponds with the expected deformation style within the southern limb of the Cantabrian orocline. The Regoufe area is characterised by two types of W-Sn vein-type mineralisation. Granite-hosted hydrothermal quartz veins show a concentric distribution and are associated with the stress regime during granite emplacement. The vein system within the metasedimentary host rock, however, is emplaced along a regional, subhorizontal cross-fold joint system. This cross-fold joint system developed orthogonal to the subvertical F 3 fold axes, and is interpreted to be coeval with oroclinal buckling. These results impact the understanding of (i) the relative significance and geometry of the main deformation stages in the Iberian massif, reconciling the timing and kinematics of F 3 regional folding with oroclinal buckling, and (ii) the kinematic relationship between late- to postorogenic deformation and W-Sn vein-type mineralisation. [ABSTRACT FROM AUTHOR]

Investigation of large scale suture zones in old continental interiors offers insights into the evolution of continents. The Dharwar Craton (DC) and the Southern Granulite Terrain(SGT) of the Indian shield represent large segments of Precambrian middle to lower crust and preserve a geological record spanning from Mesoarchean to Cambrian. This study illuminates the deep structure of the Palghat-Cauvery Shear Zone System (PCSS) and the Palghat-Cauvery Suture Zone (PCSZ) that comprise crustal-scale structures related to multiple episodes of orogeny, crust formation and reworking. We utilize here 3202 high quality P-receiver functions computed using new data from a 23 station seismic network operated by us. Results show a thick (>38 km) mafic (Poisson's ratio >0.25) crust beneath the SGT. The change in crustal thickness is gradual, with a shallower Moho towards the south of PCSZ. We found little evidence for drastic changes in crustal thickness across prominent shear zones like the PCSZ and Moyar-Bhavani. Few seismic stations located along these boundaries have shown evidence for dipping reflectors around 8–20 km depth, with strikes matching well with the trends of surface geological sutures. We opine that these suture zones do not show indications of a terrane boundary. However, a drastic change in the crustal thickness is observed around the prograde metamorphic transition zone or broadly, the “Fermor line”, which separates rocks of Chanockitic (Orthopyroxene bearing granitoid) and non-Charnockitic (Orthopyroxene-free granitoid) mineral assemblage, further north beneath the DC. We suggest that thicknening of crust north of Moyar-Attur Shear Zone (MASZ) and around Fermor line is related to subduction processes operative during the Precambrian. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is located in the eastern part of the Tethys-Himalayan megatectonic domain and consists of a series of microplates that successively accreted to the southern edge of the Eurasian Continent. These microplates have undergone complex evolutionary processes during rifting, drift and collision. The gravity and magnetic anomalies show that the anomaly characteristics on the Tibetan Plateau is significantly different in the north-south direction, from the Qaidam Microplate to the Lhasa Microplate. In this paper, we apply an improved Logistic Filter method, combined with the upward continuation of gravity anomalies, to identify multi-scale tectonic boundaries in the Tibetan Plateau region. The results show that the edge detection results correspond well in space with fracture zones and suture/ophiolite zones. Also, there are clear discontinuities along both sides of the middle and western sections of the Bangong-Nujiang Suture Zone and the eastern section of the Jinshajiang-Ailaoshan Suture Zone. We refined the boundaries of five microplates, including the South and North Qiangtang and the South, Central and North Lhasa, in the southern Tibetan Plateau. Then, we analyzed the evolutionary processes of these microplates and the transformation of the types to which the microplates belonged during different historical periods by combining relevant evidences from other geological records and plate reconstruction. These microplates are strongly related to the evolutionary history of the Tethys Ocean. The closure of the Neo-Tethys Ocean triggered a large-scale orogeny between the Indo-Asian continents, and these microplates were eventually accreted in the orogenic belt. We analyze the formation patterns and boundary types of microplates in the evolutionary process and then divide into three stages, i.e., rifting-derived, accretion-derived, and subduction-derived stages. The transformation patterns of microplate types at different stages provide a new perspective for the study of the evolution of mega-orogenic belts. • Tectonic interpretation and microplate division of the Tibetan Plateau with gravity and magnetic data. • Multi-scale edge detection at different depths on the Tibetan Plateau by the improved Logistic Filter method. • A transformation pattern of microplate types during the evolution of Qiangtang and Lhasa microplates. [ABSTRACT FROM AUTHOR]

The structural framework of the Alto Pajeú Terrane, Borborema Province (NE Brazil) records a complex tectonic evolution related to the Neoproterozoic amalgamation of Western Gondwana. Combined, multiscale geophysical and litho-structural datasets for the Central Borborema Province constrain the regional crustal architecture. Magnetic and radiometric lineaments mostly follow N E -SW and E-W trends that correlate to strike-slip shear zones and associated subvertical mylonitic foliations. Regional, outcrop-scale and microstructural kinematic indicators consistently assign sinistral and dextral motion sense for N E -SW and E-W shear zones, respectively. Four sectors with contrasting litho-geophysical and structural patterns are juxtaposed across major shear zones: the Alto Pajeú, Alto Moxotó and Piancó-Alto Brígida terranes, plus a small portion of the Northern Borborema Province. Expressive magnetic lineaments highlight the boundary between the Alto Pajeú and Alto Moxotó terranes, represented by a pair of sinistral strike-slip shear zones. At outcrop scale, relic thrust surfaces (top-to-NW vergence) with associated flat-lying foliation and down-dip mineral stretching lineations affecting Tonian orthogneisses and metapelites disclose a contractional episode of uncertain age. Transposition of the shallowly-dipping foliation in highly sheared domains imply it is older than the shear-related deformation. The shear zone system and associated structures record the transpressional regime that characterizes the late stages of the Brasiliano/Pan-African Orogeny in the region (ca. 575–565 Ma). Microstructures of a mylonitic orthogneiss from the Juru-Belém shear zone reveal greenschist to amphibolite facies deformational conditions, with increasing importance of subgrain rotation mechanisms at higher strain rates and/or temperature. Microstructural similarities between this rock and tectonites along the southern Patos lineament suggest that bordering and internal regions of the Alto Pajeú terrane were subject to similar thermodynamic conditions during the late Brasiliano transpression. • Central Borborema Province displays polyphase Neoproterozoic evolution. • Integrated geophysical-structural data reveal complex orogenic framework. • Transpressional deformation is a regional feature of Brasiliano orogeny. [ABSTRACT FROM AUTHOR]

Because of its economic importance for hydrocarbon development, the tectonostratigraphic development of the Triassic–Middle Jurassic succession across the Barents Sea shelf (BSS) has been of particular interest. Much of this succession was deposited across Timanian (late Neoproterozoic–early Cambrian) to Caledonian (at least Devonian)-age structural elements that were later reactivated by far-field responses to periods of Uralian–Pai–Khoi–Novaya Zemlya and North Atlantic tectonism. The timing and nature of these far-field responses are analyzed in this study by applying the backstripping method for analysis of tectonic mechanisms and structural responses, based on stratigraphic thicknesses across multiple south-central BSS structural elements. Based on ten tectonic subsidence curves from these structural elements generated by backstripping calculations, it is suggested that structural reactivation occurred at various times during latest Permian to Middle Jurassic time. The many tectonic mechanisms interpreted in several BSS backstripping curves suggest that the mechanisms were not homogeneous and that the stress regimes under which these structures reactivated were diverse. The backstripping analysis also shows that among the majority of structural elements analyzed, subsidence predominated across the southern BSS during Early–Middle Triassic time, followed largely by uplift in Late Triassic time, and subsequently, by subsidence in Jurassic time. Tectonostratigraphic interpretations extracted from the backstripping curves suggest that regional structural reactivation generated by Novaya Zemlya compressional tectonism was significant during at least Late Triassic–Early Jurassic time. • The backstripping method highlights the nature and timing of tectonic mechanisms. • Far-field structural responses are tied to compressional and extensional tectonics. • Non-uniform far-field responses in space and time reflect BSS basement complexity. [ABSTRACT FROM AUTHOR]

Processes related to the subduction of the South China Block beneath the North China Block and collision of the two blocks along the Qingling–Dabie–Sulu Orogenic Belt have been well studied. Different tectonic models have been proposed based on time constraints of metamorphism and magmatism and the uplift and exhumation of the HP–UHP metamorphic belt. However, propagation of the foreland thrust belt during the collision along the eastern North China Block has not been well documented, leading to a weak understanding of the collision process. The Liaodong Peninsula, 200–300 km northeast of the Sulu Orogenic Belt, is an essential area for the study of the foreland thrust belt. The rocks of the peninsula record at least three deformation events during the Mesozoic: D 1 NW–SE folds and thrust faults that were strongly overprinted by D 2 NE–SW thrusts and folds and D 3 large-scale regional extensional structures. According to detailed geological investigation and tectonic stress reconstruction using striations and dolomite twins, seven imbricate fold–thrust units in the Pulandian, Guiyunhua and Qingchengzi areas of Liaodong Peninsula were defined as representing the D 1 deformation. Together with thrust units in the southernmost part of Liaodong Peninsula and on the northern Jiaodong Peninsula, a top-to-the-NE propagated fold–thrust belt is proposed for the eastern North China Block. U Pb ages of zircons from three post-tectonic dyke samples in the Qingchengzi area, combined with previous geochronological results, constrain the D 1 deformation at 249–224 Ma. We suggest that the collision of the South China and North China blocks along the Sulu Orogenic Belt and the subduction of the South China Block beneath the North China Block resulted in NE–SW compression, formation of a detachment fault in the deep crust, and propagation of a fold–thrust belt toward the NE in the upper plate along the eastern margin of the North China Block. [Display omitted] • Middle-Late Triassic fold-thrust belts with top-to-the-NW kinematics were distinguished in Liaodong Peninsula. • New and previous age results constrain the fold-thrust deformation at 249–224 Ma. • The collision between the NCB and SCB is proposed to result in the propagation of foreland thrust belt in northeast China. [ABSTRACT FROM AUTHOR]

The Lhasa terrane of the southern Tibetan Plateau participated in a Mesozoic Andean-type orogeny caused by the northward subduction of the Neo-Tethyan oceanic lithosphere. However, metamorphic rocks, which can unravel details of the geodynamic evolution, are rare and only exposed in the south-eastern part of the Lhasa terrane. Therefore, we conducted a detailed petrological, geochemical and U–Pb zircon geochronological study of the late Cretaceous metamorphic rocks and associated gabbros from the Nyemo inlier of the southern Lhasa terrane. The Nyemo metamorphic rocks including gneisses, schists, marbles and calc-silicate rocks, experienced peak amphibolite-facies contact metamorphism under P–T conditions of 3.5–4.0 kbar and 642–657 °C with a very high geothermal gradient of 45–50 °C/km, revealing a distinct deflection from the steady-state geotherm during low-pressure metamorphism. Inherited magmatic zircon cores from the metamorphic rocks yielded protolith ages of 197–194 Ma, while overgrowth zircon rims yielded metamorphic ages of ca. 86 Ma. Whole-rock chemistry and zircon Hf isotopes suggest that the protoliths of the gneisses and schists are andesites and tuffs of the early Jurassic Sangri Group, which were derived from a depleted mantle source of a continental arc affinity. The coeval intimately-associated gabbro (ca. 86 Ma) crystallized under P–T conditions of 3.5–5.3 kbar and 914–970 °C, supplying the heat flux high enough to cause the contact metamorphism of the Sangri Group rock types. We propose that the intrusion of the gabbro and a simultaneous pressure increase of up to 4.0 kbar, which is related to crustal thickening due to crustal overthrusting and the intrusion of mafic material, resulted in the late Cretaceous metamorphism of the early Jurassic Sangri Group during an Andean-type orogeny. Furthermore the Nyemo metamorphic rocks, which have previously been considered to represent slivers of the Precambrian metamorphic basement of the Lhasa terrane, are late Cretaceous metamorphic supracrustal rocks. [ABSTRACT FROM AUTHOR]

Across the entire mantle we interpret 94 positive seismic wave-speed anomalies as subducted lithosphere and associate these slabs with their geological record. We document this as the Atlas of the Underworld , also accessible online at www.atlas-of-the-underworld.org , a compilation comprising subduction systems active in the past ~ 300 Myr. Deeper slabs are correlated to older geological records, assuming no relative horizontal motions between adjacent slabs following break-off, using knowledge of global plate circuits, but without assuming a mantle reference frame. The longest actively subducting slabs identified reach the depth of ~ 2500 km and some slabs have impinged on Large Low Shear Velocity Provinces in the deepest mantle. Anomously fast sinking of some slabs occurs in regions affected by long-term plume rising. We conclude that slab remnants eventually sink from the upper mantle to the core-mantle boundary. The range in subduction-age versus – depth in the lower mantle is largely inherited from the upper mantle history of subduction. We find a significant depth variation in average sinking speed of slabs. At the top of the lower mantle average slab sinking speeds are between 10 and 40 mm/yr, followed by a deceleration to 10–15 mm/yr down to depths around 1600–1700 km. In this interval, in situ time-stationary sinking rates suggest deceleration from 20 to 30 mm/yr to 4–8 mm/yr, increasing to 12–15 mm/yr below 2000 km. This corroborates the existence of a slab deceleration zone but we do not observe long-term (> 60 My) slab stagnation, excluding long-term stagnation due to compositional effects. Conversion of slab sinking profiles to viscosity profiles shows the general trend that mantle viscosity increases in the slab deceleration zone below which viscosity slowly decreases in the deep mantle. This is at variance with most published viscosity profiles that are derived from different observations, but agrees qualitatively with recent viscosity profiles suggested from material experiments. [ABSTRACT FROM AUTHOR]

The continuation of the Caledonides into the Barents Sea has long been a subject of discussion, and two major orientations of the Caledonian deformation fronts have been suggested: NNW-SSE striking and NE-SW striking. A regional NW-SE oriented ocean bottom seismic profile across the western Barents Sea was acquired in 2014. In this paper we map the crust and upper mantle structure along this profile in order to discriminate between different interpretations of Caledonian structural trends and orientation of rift basins in the western Barents Sea. Modeling of P-wave travel times has been done using a ray-tracing method, and combined with gravity modeling. The results show high P-wave velocities (4 km/s) close to the seafloor, as well as localized sub-horizontal high velocity zones (6.0 km/s and 6.9 km/s) at shallow depths which are interpreted as magmatic sills. Refractions from the top of the crystalline basement together with reflections from the Moho give basement velocities from 6.0 km/s at the top to 6.7 km/s at the base of the crust. P-wave travel time modeling of the OBS profile indicate an eastwards increase in velocities from 6.4 km/s to 6.7 km/s at the base of the crystalline crust, and the western part of the profile is characterized by a higher seismic reflectivity than the eastern part. This change in seismic character is consistent with observations from vintage reflection seismic data and is interpreted as a Caledonian suture extending through the Barents Sea, separating Barentsia and Baltica. Local deepening of Moho (from 27 km to 33 km depth) creates “root structures” that can be linked to the Caledonian compressional deformation or a suture zone imprinted in the lower crust. Our model supports a separate NE-SW Caledonian trend extending into the central Barents Sea, branching off from the northerly trending Svalbard Caledonides, implying the existence of Barentsia as an independent microcontinent between Laurentia and Baltica. [ABSTRACT FROM AUTHOR]

The structure and geodynamics of the southern margin of the Bay of Biscay have been investigated from a set of 11 multichannel seismic reflection profiles, recorded also at wide angle offsets in an onshore-offshore network of 24 OBS/OBH and 46 land sites. This contribution focuses on the analysis of the wide-angle reflection/refraction data along representative profiles. The results document strong lateral variations of the crustal structure along the margin and provide an extensive test of the crustal models previously proposed for the northern part of the Iberian Peninsula. Offshore, the crust has a typical continental structure in the eastern tip of the bay, which disappears smoothly towards the NW to reach crustal thickness close to 10 km at the edge of the studied area (~ 45°N, 6°W). The analysis of the velocity-depth profiles, altogether with additional information provided by the multichannel seismic data and magnetic surveys, led to the conclusion that the crust in this part of the bay should be interpreted as transitional from continental to oceanic. Typical oceanic crust has not been imaged in the investigated area. Onshore, the new results are in good agreement with previous results and document the indentation of the Bay of Biscay crust into the Iberian crust, forcing its subduction to the North. The interpreted profiles show that the extent of the southward indentation is not uniform, with an Alpine root less developed in the central and western sector of the Basque-Cantabrian Basin. N-S to NE-SW transfer structures seem to control those variations in the indentation degree. [ABSTRACT FROM AUTHOR]

The crustal structure in Western Iberia, is the result of a complex geodynamic history. Most of the surface is covered by rocks dating to the Variscan orogeny, the coastal ranges dominated by Mesozoic structures and Mesocenozoic basins covering partially the mainland. In this study we present the results of a local earthquake tomographic study, performed to image in depth this complex crustal structure down to 24 km depth. The obtained tomograms present a good correlation with the surface geology, in general with higher Vp velocities in the north, and lower Vp velocities in the south. The heterogeneity observed on the surface geology of the Galicia-Tras-os-Montes Zone is well marked, being a relatively thin layer over the smoother structure of the Centro Iberia Zone CIZ. The CIZ crustal block confined between the Porto-Tomar-Ferreira do Alentejo and the Manteigas-Bragança faults having higher Vp values, enhancing the contrast to the Lusitanian Basin to the west. The Ossa-Morena Zone corresponds to the unit presenting the greater heterogeneity in both Vp and Vp/Vs models, showing also with a complex transition to the South Portuguese Zone and a relatively smooth transition to the Centro Iberian Zone. Unexpectedly, the South Portuguese Zone present an east-west velocity variation with no apparent correspondence with the surface geology. The transition to the coastal Mesocenozoic basins is clearly marked, the Lower Tagus Valley corresponding to a ~ 4 km thick low velocity region. The relocation inland recorded seismicity in the period 2000–2014 allows cleansing some of the alignments and establish their correlation with some of the active structures in Portugal. The model features and seismicity pattern reveal the strong role played by the Variscan heritage. [ABSTRACT FROM AUTHOR]

The Retortillo Syncline is part of a major late-Variscan structure that runs for > 120 km from Figueira de Castelo Rodrigo (Portugal) to Tamames (Spain), affecting Neoproterozoic and Lower Paleozoic metasediments in the Central Iberian Zone, and delineated by the Armorican Quartzite. This tectono-metamorphic study gives new insights on the Variscan evolution of this region, showing that it was affected at least by two contractional Variscan stages (C 1 and C 3 ) and by one extensional (E 1 ). The first contractional event (C 1 ), and perhaps an overriding thrust sheet (C 2 ), presently eroded, produced a low-grade Barrovian assemblage (M 1 ) and induced enough load to trigger the formation of high temperature–low pressure (HT-LP) thermal domes (M 2 ) that characterize the regional syn-orogenic extensional event (E 1 ). This allowed the appearance of typical minerals such as andalusite, biotite and/or cordierite. Later, during the C 3 stage, the HT-LP isograds were folded and sheared together with the metasediments and a new axial planar slaty cleavage developed surrounding the M 2 blasts. Finally a late- to post-kinematic thermal (M T ) event associated with the intrusion of a late-Variscan granodiorite led to the growth of new HT-LP minerals and rim overgrowths around previously formed porphyroblasts in a contact metamorphic aureole. The fabric-porphyroblast relations confirm that the Retortillo syncline forms part of a major C 3 fold. Interestingly, it is located at the hinge zone of and arcuate structure whose existence is currently under discussion, the Central Iberian Orocline. [ABSTRACT FROM AUTHOR]

To better constrain the structure of the Laurentian – Peri-Gondwana suture zone, maps and a 2-dimensional regional cross-section model constrained by seismic data and surface geology have been developed by forward and inverse modeling the aeromagnetic and gravity fields. The Central Piedmont Suture (CPS), the boundary between the Laurentian Inner Piedmont and the Peri-Gondwanan Carolina terrane is a low-angle thrust fault (~ 30°) ramping up from an Alleghanian mid-crustal detachment at depths of about 12 km. ADCOH and COCORP seismic data image anticlinal structures in the footwalls of the Hayesville thrust and the CPS, above the Alleghanian decollement. The footwall rocks have previously been interpreted as Paleozoic shelf strata on the basis of sub-horizontal seismic reflectors; however, the high densities required to fit the observed gravity anomaly suggest that the folded footwall reflectors may need to be reinterpreted as horse blocks or duplex structures of Grenvillian basement. The Appalachian paired gravity anomaly can be explained by an increase in crustal thickness and a decrease in upper crustal density moving northwestward from the Carolina Terrane toward the Appalachian core. A change in lower crustal density is not required, so that Grenville basement rocks may extend farther to the southeast than previously thought. The 5 to 10 km of Alleghanian uplift and exhumation predicted by P-T crystallization data compiled in this paper can be easily accommodated by thrusting on four major low-angle thrust systems: Great Smoky Mountain Thrust (GSMT), Hayesville, Brevard, and CPS. Unroofing of metamorphic core complexes by normal faulting may therefore not be required to explain the observed exhumation. Alleghanian collision along the southeastern Appalachian margin was predominately orthogonal to strike consistent with the previous reconstructions that call for the counter-clockwise rotation of Gondwanan West Africa, creating head-on collision in the southern Appalachians and at least 370 km of shortening. [ABSTRACT FROM AUTHOR]

Using the Khao Khwang fold–thrust belt in central Thailand as case study, we handled data from calcite twinning analysis in order to propose the quantification of the effective principal palaeostresses magnitudes since the onset of the early stages of the Indosinian orogeny. We also combined the differential stress estimates from mechanically-induced calcite twins with geochronological data in order to constrain the timing of the palaeoburial depth and subsequent uplift by folding within the Khao Khwang fold–thrust belt. The proposed mechanical scenario is based on the time-constrained kinematic sequence of fracturing, faulting, and folding in the strata of the carbonate formations of the Saraburi Group. Cross-checking the data on the palaeostress orientations, regimes, and differential stress magnitudes with rock mechanics analysis; we provided data on the principal stress magnitudes for each tectonic stage that developed during the Indosinian orogeny. Further, 40 Ar/ 39 Ar and U-Pb geochronological data allowed to place reliable constraints on the amount and rate of vertical uplift of the carbonate formations of the Saraburi Group. [ABSTRACT FROM AUTHOR]

Reactivation of inherited nappe contacts is a common process in orogenic areas affected by back-arc extension. The amount of back-arc extension is often variable along the orogenic strike, owing to the evolution of arcuated mountain chains during stages of rapid slab retreat. This evolution creates low rates of extension near rotation poles, where kinematics and interplay with the pre-existing orogenic structure are less understood. The amount of Miocene extension recorded by the Pannonian Basin of Central Europe decreases SE-wards along the inherited Cretaceous – Paleogene contact between the Dinarides and Carpathian Mountains. Our study combines kinematic data obtained from field and micro-structural observations assisted with fission track thermochronological analysis and U-Pb zircon dating to demonstrate a complex poly-phase evolution in the key area of the Jastrebac Mountains of Serbia. A first event of Late Cretaceous exhumation was followed by latest Cretaceous – Eocene thrusting and magmatism related to a continental collision that sutured the accretionary wedge containing contractional trench turbidites. The suture zone was subsequently reactivated and exhumed by a newly observed Miocene extensional detachment that lasted longer in the Jastrebac Mountains when compared with similar structures situated elsewhere in the same structural position. Such extensional zones situated near the pole of extensional-driven rotation favour late stage truncations and migration of extension in a hanging-wall direction, while directions of tectonic transport show significant differences in short distances across the strike of major structures. [ABSTRACT FROM AUTHOR]

The Tianshan mountains have complex and variable topography and documenting their growth is important for understanding both intracontinental mountain building and the evolution of the global climate. We investigate whether this topography is in equilibrium with crustal influx (thickening) and sediment outflux (denudation). Based on literature, we estimate that the eastern Tianshan has been subject to a total crustal shortening rate of ∼9.4 mm/a across the Kuitun–Kuche transect, implying ∼1.3 mm/a of crustal thickening and a total crustal influx of ∼9 × 107 m3/a. We measured in-situ cosmogenic 10Be concentrations in modern river sands of 34 catchments to constrain recent (0–6 ka) basin-averaged denudation rates within the range and on its two flanks. Denudation rates range from 0.020 ± 0.002 to 0.53 ± 0.07 mm/a, averaging 0.20 ± 0.04 and 0.11 ± 0.02 mm/a in the north and south, respectively; these rates correspond to respective total sediment outfluxes of (542 ± 69) × 104 and (164 ± 24) × 104 m3/a. To ensure that these values can be compared to Pleistocene tectonic rates, we reconstructed Pleistocene denudation rates in seven of the studied basins. For this, we determined inherited in-situ cosmogenic 10Be concentrations from 11 cosmogenic depth profiles of abandoned fluvial terraces deposited in the Tianshan piedmonts. These data indicate that denudation rates have been relatively steady since the Pleistocene and thus that recent and Pleistocene sediment fluxes can be compared. These results show that crustal thickening outpaced denudation and sediment outflux by a factor of ∼10. Therefore, the Tianshan topography is not in dynamic equilibrium and is growing, even if materials are being subducted into the mantle. Consequently, to sustain this disequilibrium, the range grew laterally. This lateral growth and the inheritance of structures and basins are likely responsible for the complex topography of the range. • The Tianshan mountains have complex and variable topography characterized by intermountain basins separated by individual ranges. • The eastern Tianshan underwent ∼9.4 mm/a and ∼1.3 mm/a of crustal shortening and thickening rates and a total crustal influx of ∼9 × 107 m3/a. • Denudation rates range from 0.020 ± 0.002 to 0.53 ± 0.07 mm/a, averaging 0.20 ± 0.04 and 0.11 ± 0.02 mm/a in the north and south, respectively • The total sediment outfluxes exported to the basin of (542 ± 69) × 104 and (164 ± 24) × 104 m3/a in the north and south, respectively. • Crustal thickening outpaced denudation and sediment outflux by a factor of ∼10, the topography is not in dynamic equilibrium and is growing laterally [ABSTRACT FROM AUTHOR]

Forming the northwestern branch of the Chinese Tian Shan, the Keguqin mountain located north of the Yili basin is characterized by Mesozoic relict landscapes and active faults, which recorded abundant information of long term tectono-geomorphologic evolution of the Tian Shan mountain range. However, the post-Jurassic deformation history of the Keguqin mountain is unclear. In this study, we applied apatite fission track, apatite (U Th)/He and geomorphologic analyses to reconstruct the landscape evolution of the Keguqin mountain and the northern Yili basin. Our results suggest that this region underwent three stages of accelerated cooling/exhumation in the Permian, Late Triassic-Jurassic and Cretaceous. The Permian cooling event likely reflects post magmatic cooling related to the Paleozoic orogeny of the Tian Shan. Late Triassic-Jurassic exhumation is possibly a far field response of the Qiangtang collision. The Cretaceous differential exhumation in the study area was controlled by activation of the Kashihe fault zone and secondary faults. As the Cretaceous cooling is widely observed in the vast Central Asia region, northern Tibet and Southern Pamir, and coeval with the Mongol-Okhotsk orogeny, Qiangtang collision and Karakorum collision. It is difficult to decipher the tectonic drive of the Cretaceous activation of the Kashihe fault zone. Relict landscapes in the Keguqin mountain were firstly established after the Paleozoic, slightly exhumed during the Cretaceous, and were uplifted and tilted by Late Cenozoic deformation. The latest uplift magnitude of the Keguqin mountain is estimated to be ∼250–500 m and ∼ 380–430 m of the hanging wall of the Kashihe fault zone and the Keguqin fault, respectively. • The Keguqin mountain has experienced three stages of cooling/exhumation in in the Permian, Late Triassic-Jurassic and Cretaceous. • The Late Triassic-Jurassic exhumation of the Keguqin mountain was probably far field reponse of the Qiangtang collision. • The Cretaceous differential exhumation represents the reactivations of the Kashihe fault zone. • The latest uplift magnitude is estimated to be ∼250–500 m and ∼ 380–430 m on the hanging wall of the Kashihe fault zone and the Keguqin fault, respectively, in the Keguqin mountain. [ABSTRACT FROM AUTHOR]

Field and laboratory studies including textural, petrological and geochronological analysis of migmatites of the Xolapa Complex affected by the same deformational event suggests that the deformation occurred during crystallization of neosome. The deformation represents sub-horizontal spreading of middle to lower crust according to structural data, and occurred during the Paleocene as inferred from U-Pb laser ablation dating of zircon. According to a compilation of stratigraphic, magmatic and deformational data reported in southern Mexico, the sub-horizontal spreading occurred after the culmination of the Upper Cretaceous Laramide orogeny. Compiled regional data indicate (a) coast-to-coast mass transfer in the upper crust from Zihuatanejo to Veracruz from the Cretaceous–Tertiary boundary until the mid-Eocene; (b) contemporaneous adakite-like magmatism; and (c) extension in the Mixteco and Oaxaca terranes of southern Mexico coeval to compression in the surrounding crust. Because all these observations are spatially associated to areas of the Mixteco and Oaxaca terranes, we propose that these areas experienced a post-orogenic gravitational collapse since the Cretaceous–Tertiary boundary until the mid-Eocene. This proposal implies that the gravitational collapse was recorded in the Xolapa Complex by migmatite formation in response to ascent of the brittle-ductile transition, decompression of the orogenic root, and/or shear-driven asthenospheric upwelling. Gravitational collapse deformation was accommodated by the subsequent flow of the migmatites towards the foreland, preceding the eastward escape of the Chortis Block. [ABSTRACT FROM AUTHOR]

Multi–method geo- and thermochronological data obtained for Palaeo- and Mesoproterozoic granitoids traversing the main structural architecture of the eastern Musgrave Province within South Australia reveal multiphase cooling histories. Apatite U-Pb dating on six samples yield consistent ages of ~ 1075–1025 Ma, suggesting a thermal reset coinciding with mantle-derived magmatism of the greater Warakurna Large Igneous Province (~ 1080–1040 Ma). Apatite fission track (AFT) analysis indicate that four discrete thermal events affected the study area, inducing cooling through the AFT partial annealing zone (~ 60–120 °C), supported by apatite and zircon (U-Th-Sm)/He data. Late Neoproterozoic cooling from deep crustal levels to temperatures < 200 °C was discerned, which is thought to be related to exhumation and denudation during the Petermann Orogeny. Subsequent cooling events at ~ 450–400 Ma (Silurian–Devonian) and ~ 310–290 Ma (Late Carboniferous) are interpreted to represent exhumation associated with the Alice Springs Orogeny. The latter event exhumed the sampled plutons to shallow crustal depths. An additional Triassic – early Jurassic thermal event, likely recording elevated geothermal gradients at that time, was observed throughout the study area, however, more data is needed to further support this interpretation. The high sample density across the structural architecture of the study area furthermore reveals patterns of fault reactivation and resulting differential exhumation, indicating shallower exhumation levels in the centre and deeper exhumation towards the margins of the sampled transect. The observed differential exhumation patterns match with existing seismic data and fit a model of an inverted graben system for the Phanerozoic evolution of the eastern Musgraves. The results highlight a complex Phanerozoic thermal history for the eastern Musgraves and help to elucidate the poorly appreciated tectonic evolution of inland Australia. This study further demonstrates how high-density sample transects across structural architecture can assess the relative crustal level and associated preservation of the thermal history record within fault-reactivated terranes. [ABSTRACT FROM AUTHOR]

The intracratonic Rae cover sequence, deposited ca. 2.2–1.9 Ga, forms a useful marker for unravelling tectonic events that affected the Archean Rae Province at ca.2.0, 1.9 and 1.85 Ga. Polyphase deformation is recognized within the Rae cover rocks, including the 70 × 10 km Montresor belt, and attributed to distal effects of the ca. 1.85 Ga Trans-Hudson orogeny. In this contribution we explore the 3D geometry and structural history of the Montresor belt, previously considered to be a simple syncline lying unconformably on Archean basement. New geological, geophysical and geochronological results define a more complex history in which lower Montresor units were thrust-imbricated with basement gneisses and metamorphosed to the amphibolite facies. Mid-to upper greenschist facies upper Montresor units, exposed in an open synform, are superficially less deformed. However, using high-resolution aeromagnetic data and distinct magnetic marker units considered proxies for bedding, we constructed a set of forward models to explore the three-dimensional geometry of the belt. The re-analysis outlines a set of pre-synform structures defined by low-angle truncations of the magnetic markers. Geometric relationships indicate the presence of at least three faults at low angles to bedding, interpreted as D 1 piggy-back thrusts, and bracketed by available geochronology between 1.924 and 1.87 Ga. D 1 strain in the upper Montresor strata is significantly less intense than that further south in Rae cover rocks, consistent with a more distal foreland setting during the Trans-Hudson orogeny. The Montresor belt preserves a record of the Trans-Hudson tectonic style at relatively shallow crustal levels as a result of its foreland setting and structural history including a syn-orogenic extensional detachment event. [ABSTRACT FROM AUTHOR]

Geohistory of the Yunkai massif in South China Block is important in understanding the geodynamics for the build-up of this block during the Phanerozoic orogenies. To investigate this massif, we conduct EMP monazite and U-Pb zircon geochronological determinations on mineral inclusions and separate for seventeen samples in four groups, representing metamorphic rocks from core domain, the Gaozhou Complex (amphibolite facies, NE-striking) and the Yunkai Group (greenschist facies, NW-striking) of this massif and adjacent undeformed granites. Some EMP monazite ages are consistent with the NanoSIMS results. Monazite inclusions, mostly with long axis parallel to the cleavage of platy and elongated hosts, give distinguishable age results for NW- and NE-trending deformations at 244–236 Ma and 236–233 Ma, respectively. They also yield ages of 233–230 Ma for core domain gneissic granites and 232–229 Ma for undefomed granites. Combining U-Pb zircon ages of the same group, ~ 245 Ma and ~ 230 Ma are suggested to constrain the time of two phases of deformation. Aside from ubiquity of Triassic ages in studied rocks, ages of detrital monazite in the meta-sandstone match the major U-Pb zircon age clusters of the metamorphic rock that are largely concentrated at Neoproterozoic (1.0–0.9 Ga) and Early Paleozoic (444–431 Ma). Based on these geochronological data, Triassic is interpreted as representing the time for recrystallization of these host minerals on the Early Paleozoic protolith, and the also popular Neoproterozoic age is probably inherited. With this context, Yunkai massif is regarded as a strongly reactivated Triassic metamorphic terrain on an Early Paleozoic basement which had incorporated sediments with Neoproterozoic provenances. Triassic tectonic evolution of the Yunkai massif is suggested to have been controlled by converging geodynamics of the South China and Indochina Blocks as well as mafic magma emplacement related to the Emeishan large igneous province (E-LIP). [ABSTRACT FROM AUTHOR]

The Chencai terrane in the northeastern Cathaysia Block forms part of the northeast extension of the Paleozoic orogeny in South China. Recent field investigations have revealed the occurrence of high grade rocks in this terrane including granulite facies metapelites (khondalites) and orthopyroxene-bearing granulites. However, the thermal gradients and metamorphic history of this region have not been well constrained, thus impeding a better understanding of the geodynamic history of the Paleozoic orogeny in South China. Here we report results from a systematic study on the metamorphic PT conditions and geochronology of the orthopyroxene granulites and metasedimentary rocks (metapelites) from the Chencai area. The orthopyroxene granulites preserve granulite facies peak assemblage of Opx + Grt + Pl + Kfs + Qtz and a retrograde P-T trajectory. Peak PT conditions are 845–860 °C and 0.83–0.86 Gpa, corresponding to a thermal gradient of ~ 30 °C/km which is much hotter than the normal thermal gradient of continental crust. Mineral compositions of the metasedimentary rocks re-equilibrated during retrograde metamorphism so that the peak PT conditions recorded by these rocks are much lower than those obtained from the orthopyroxene granulite. Peak PT conditions are 710–720 °C, 0.57–0.58 Gpa for garnet-biotite gneiss and 760–780 °C, 0.60–0.62 Gpa for biotite garnetite. Zircon U-Pb dating shows that this episode of granulite facies metamorphism occurred at 430–450 Ma and the detrital population shows minor or no contribution from the basement rocks of the Cathaysia Block. The Neoproterozoic rocks occurring along the Jiangnan belt are considered to have provided the sedimentary source as indicated by the two main age peaks of 0.79 Ga and 0.83 Ga from the detrital zircon cores. Lu-Hf isotope data on the zircons indicates extensive alteration and little new zircon growth during the Paleozoic metamorphism. The ε Hf (t) values and model ages (T DM1 ) of zircons suggest that the source rocks involved juvenile crustal components with Hf model ages of 1.1–1.5 Ga. Sedimentation of such a continental shelf sequence as well as the high thermal gradient of ~ 30 °C/km confirm the previously proposed continental arc formation and maturation model in the Chencai region. [ABSTRACT FROM AUTHOR]