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Paleomagnetic data constrain paleogeographic motion of rocks relative to the Earth's spin axis, which is a sum of plate motion relative to the mantle and true polar wander. Discerning between these effects is challenging for studies aiming to reconstruct paleo-plate motions from deformed orogenic terranes. Here, we study the paleolatitudinal drift history of the Lhasa terrane of southern Tibet that migrated from the northern Gondwana to the southern Eurasian margin between late Triassic and early Cretaceous time. Previous work identified a 180 Ma near-equatorial Lhasa latitude and assumed near-constant paleolatitudinal drift. Large-scale true polar wander at this time, however, which has been argued for in previous work, requires highly variable Lhasa plate motion rates relative to Gondwana. Here, we test whether the alternative interpretation of constant plate motion rates provides a better prediction of paleomagnetic data. To this end, we present a new paleomagnetic pole from ∼155 Ma volcanics (here dated by U/Pb zircon) of the Lhasa terrane. Our pole comprises site mean directions from 46 lavas, passes a fold test, and is supported by an extensive rock magnetic and microscopic analysis that reveals no evidence of remagnetization. Our results give an average direction of D±ΔDx=337.1°±2.6°, I±ΔIx=−13.8°±4.9°, and a corresponding paleopole position at λp=45.3°N, φp=295.3°E with K=69.8 and A95=2.5°, predicting a similar near-equatorial, paleolatitude as at 180 Ma. This paleolatitudinal standstill is consistent with predicted paleolatitudes from global APWPs that account for Jurassic TPW and assume a constant Lhasa-Gondwana (India) oceanic spreading rate of ∼8 cm/a during the 215-130 Ma opening of the Neotethys and closure of the Mesotethys oceans. Contemporaneous arc magmatism on the Lhasa terrane was previously interpreted to indicate that the Lhasa terrane was located above a subduction zone during its northward journey to Tibet: our results show that if our reconstruction is accurate, then trench migration rates also must have been ∼8 cm/a. Our results are consistent with the range of rates of global long-lived trench migration that have been reconstructed in other studies, but they are much higher than measured in most modern systems. Our results more completely document the Lhasa terrane's separation from Gondwana and provide a straightforward methodology of using paleomagnetic data to test plate kinematic scenarios, overcoming the problem of the unknown effect of true polar wander on paleomagnetic data from deformed terranes.

The high-pressure metamorphic Nevado-Filábride Complex (NFC) in the Betics mountain range of southeastern Spain exhibits continental and ocean-derived tectonic units, which are key for understanding the geodynamic evolution of the Western Mediterranean. We address the current debate in the definition of tectonic units, the emplacement of (ultra)mafic rocks, and the timing of burial metamorphism by conducting a structural study combined with single grain fusion 40Ar/39Ar dating of white micas in structurally critical outcrops of the eastern Sierra de Los Filábres. One older 40Ar/39Ar age population (38–27 Ma) is found at distance from the main shear zones in the relics of an early foliation, while a younger 40Ar/39Ar population (22–12 Ma) is dominant in the vicinity of these shear zones, where the early foliation is obliterated. Both age groups are interpreted as the record of deformation or fluid-induced recrystallization during distinct fabric-forming events, while alternative scenarios are discussed. A key observation is the presence of an ophiolitic mélange, which—together with new and published geochronological data—allows for a new tectonic hypothesis. This considers Paleogene subduction beneath a Jurassic oceanic lithosphere, followed by the continued subduction of NFC and overlying ophiolites below the Alpujárride Complex. Exhumation during westward slab roll-back led to the formation of an extensional detachment system that obliquely cut nappe contacts. Although the timing constraints for high pressure-low temperature (HP-LT) metamorphism in the NFC remain inconclusive, the new tectonic hypothesis provides a solution that can account for both Paleogene and Miocene ages of HP-LT metamorphism.

We present a model for the lattice vibrational density of states of MgTiO3 (geikielite) and FeTiO3 (ilmenite) that predicts thermodynamic properties, in agreement with observational data. The model is based on Kieffer’s method combined with spectroscopic data. For both substances experimental data sets are influenced by non-stoichiometry. For geikielite that affects the volume, whereas for ilmenite volume and bulk modulus are affected. We show that Kieffer’s method enables predicting bulk moduli in pressure–temperature space. We demonstrate that intrinsic anharmonicity or electronic effects significantly affect the heat capacity of ilmenite, whereas that is not the case for geikielite. We use Kieffer’s method to derive multiple-Einstein models, from which we demonstrate that thermodynamic properties are insignificantly influenced by dispersion in Grüneisen, mode-q and anharmonicity parameters for both substances. We show that our results enable predicting thermodynamic properties and shear modulus of the solid solution formed from geikielite and ilmenite. Geikielite and ilmenite are added to our thermodynamic database for the system MgO–SiO2–FeO, to enable modeling phase stability and physical properties of titanium-rich reservoirs in the Earth’s Moon.

To determine a paleopole, the paleomagnetic community commonly applies a loosely defined set of quantitative data filters that were established for studies of geomagnetic field behavior. These filters require costly and time-consuming sampling procedures, but whether they improve the precision and influence the position of paleopoles has not yet been systematically analyzed. In this study, we performed a series of experiments on four datasets which consist of 73–125 lava sites with 6–7 samples per lava. The datasets are from different regions and ages, and are large enough to represent paleosecular variation, yet include demonstrably unreliable paleomagnetic directions. We show that the systematic application of data filters based on within-site scatter (a maximum angular deviation filter on individual directions, a k-cutoff, a minimum number of samples per site, and eliminating the farthest outliers per site) cannot identify unreliable directions. We find instead that excluding unreliable directions relies on the subjective interpretation of the expert, highlighting the importance of making all data available following the FAIR principles. In addition, data filters that decrease the number of sites even have an adverse effect; they decrease the precision of the paleopole. Between-site scatter often outweighs within-site scatter, and when collecting paleomagnetic poles, the extra efforts put into collecting multiple samples per site are more effectively spent on collecting more single-sample sites.

Knowledge of the thermal history of the Linzizong Group (69–47 Ma) within the Gangdese arc is critical for interpreting the geologic evolution and isotope-based paleoaltimetric results of the southern Lhasa terrane of the Tibetan Plateau. Here, we combine results from geochronologic and thermochronologic studies of this group (divided into Dianzhong, Nianbo, and Pana formations upsection) and the structurally overlying Qianggeren granite (∼52 Ma) in the Linzhou basin. Whole rock 40Ar/39Ar ages of volcanic rocks from the stratigraphically lower Dianzhong and Nianbo formations are ∼10 Myr younger than their corresponding zircon U-Pb ages, suggesting a thermal disturbance of the argon system. Zircon (U-Th)/He ages (ZHe, 63 dates) range from 54 to 24 Ma, and apatite (U-Th-Sm)/He ages (AHe, 43 dates) range from 27 to 4 Ma. Inverse modeling of the thermochronologic data from the Qianggeren granite indicates rapid cooling between 42 and 26 Ma, possibly induced by movement of the Gulu-Hamu thrust. Positive correlations between ZHe ages and effective uranium and other geologic observations provide evidence that the Dianzhong and Nianbo formations were heated 300 °C at 54–50 Ma, and that the entire Linzizong Group was variably heated to 130–170 °C at 42–27 Ma. These findings, together with published geochronologic and thermochronologic data, suggest that abundant 50–45 Ma zircon fission track and ZHe ages from the Gangdese arc likely reflect conductive cooling of the Gangdese arc after a ∼52 Ma magmatic flare-up episode rather than rapid regional exhumation. Areas far from Cenozoic faults and deeply incised river valleys in southern Tibet have experienced only ∼3 km of exhumation since 45 Ma, consistent with the establishment of a low-relief, plateau-like physiography by Eocene time. The (hydro)thermal events are also manifested by widespread calcite recrystallization and δ18O and Δ47 alteration in most carbonates from the Linzizong Group, which must be taken into account in past and future carbonate-based paleoaltimetric studies.

The dynamics of slab detachment and associated geological fingerprints have been inferred from various numerical and analog models. These invariably use a setup with slab-pull-driven convergence in which a slab detaches below a mantle-stationary trench after the arrest of plate convergence due to arrival of continental lithosphere. In contrast, geological reconstructions show that post-detachment plate convergence is common and that trenches and sutures are rarely mantle-stationary during detachment. Here, we identify the more realistic kinematic context of slab detachment using the example of the India-Asia convergent system. We first show that only the India and Himalayas slabs (from India's northern margin) and the Carlsberg slab (from the western margin) unequivocally detached from Indian lithosphere. Several other slabs below the Indian Ocean do not require a Neotethyan origin and may be of Mesotethys and Paleotethys origin. Additionally, the still-connected slabs are being dragged together with the Indian plate forward (Hindu Kush) or sideways (Burma, Chaman) through the mantle. We show that Indian slab detachment occurred at moving trenches during ongoing plate convergence, providing more realistic geodynamic conditions for use in future numerical and analog experiments. We identify that the actively detaching Hindu Kush slab is a type-example of this setting, whilst a 25–13 Ma phase of shallow detachment of the Himalayas slab, here reconstructed from plate kinematics and tomography, agrees well with independent, published geological estimates from the Himalayas orogen of slab detachment. The Sulaiman Ranges of Pakistan may hold the geological signatures of detachment of the laterally dragged Carlsberg slab.

Following hundreds of millions of years of subduction in all circum-Pacific margins, the Pacific Plate started to share a mid-ocean ridge connection with continental Antarctica during a Late Cretaceous south Pacific plate reorganization. This reorganization was associated with the cessation of subduction of the remnants of the Phoenix Plate along the Zealandia margin of East Gondwana, but estimates for the age of this cessation from global plate reconstructions (∼86 Ma) are significantly younger than those based on overriding plate geological records (105–100 Ma). To find where this discrepancy comes from, we first evaluate whether incorporating the latest available marine magnetic anomaly interpretations change the plate kinematic estimate for the end of convergence. We then identify ways to reconcile the outcome of the reconstruction with geological records of subduction along the Gondwana margin of New Zealand and New Caledonia. We focus on the plate kinematic evolution of the Phoenix Plate from 150 Ma onward, from its original spreading relative to the Pacific Plate, through its break-up during emplacement of the Ontong Java Nui Large Igneous Province into four plates (Manihiki, Hikurangi, Chasca, and Aluk), through to the end of their subduction below East Gondwana, to today. Our updated reconstruction is in line with previous compilations in demonstrating that as much as 800–1100 km of convergence occurred between the Pacific Plate and Zealandia after 100 Ma, which was accommodated until 90–85 Ma. Even more convergence occurred at the New Zealand sector owing to spreading of the Hikurangi Plate relative to the Pacific Plate at the Osbourn Trough, with the most recent age constraints suggesting that spreading may have continued until 79 Ma. The end of subduction below most of East Gondwana coincides with a change in relative plate motion between the Pacific Plate and East Gondwana from westerly to northerly, of which the cause remains unknown. In addition, the arrival of the Hikurangi Plateau in the subduction zone occurred independent from, and did not likely cause, the change in Pacific Plate motion. Finally, our plate reconstruction suggests that the previously identified geochemical change in the New Zealand arc around 105–100 Ma that was considered evidence of subduction cessation, may have been caused by Aluk-Hikurangi ridge subduction instead. The final stages of convergence before subduction cessation must have been accommodated by subduction without or with less accretion. This is common in oceanic subduction zones but makes dating the cessation of subduction from geological records alone challenging.

A hitherto unknown Neoproterozoic orogenic system, the Saharides, is described in North Africa. It formed during the 900–500-Ma interval. The Saharides involved large subduction accretion complexes occupying almost the entire Arabian Shield and much of Egypt and parts of the small Precambrian inliers in the Sahara including the Ahaggar mountains. These complexes consist of, at least by half, juvenile material forming some 5 million km(2) new continental crust. Contrary to conventional wisdom in the areas they occupy, evolution of the Saharides involved no continental collisions until the end of their development. They formed by subduction and strike-slip stacking of arc material mostly by precollisional coastwise transport of arc fragments rifted from the Congo/Tanzania cratonic nucleus in a manner very similar to the development of the Nipponides in east Asia, parts of the North American Cordillera and the Altaids. The Sahara appears to be underlain by a double orocline similar to the Hercynian double orocline in western Europe and northwestern Africa and not by an hypothetical “Saharan Metacraton.” The method we develop here may be useful to reconstruct the structure of some of the Precambrian orogenic belts before biostratigraphy became possible.

Global reorganizations of tectonic plates may be caused by a trigger such as a continental collision or a rising mantle plume. However, whether and how such a trigger propagates through a plate circuit remains unclear. Here we use a plate kinematic model to quantify relative motions between the African and Eurasian plates following a plume-induced plate motion change that triggered formation of a new subduction zone within the Neotethys Ocean at 105 Ma. We constrain the plate kinematic model by geomagnetic intensity variations recorded in Atlantic quiet zone crust that formed during the Cretaceous Normal Superchron (126–83 Ma), during which magnetic reversals were absent. We find that convergence rate changes between Africa and Eurasia are well explained by the initiation and arrest of the plume-induced subduction zone. Our plate kinematic model also reveals that the plate acceleration that followed upon subduction initiation changed the Africa–Eurasia convergence direction, which in turn was accommodated by subsequent subduction initiation about 85 Ma in the Alpine region that then triggered a cascade of regional tectonic events. This plate tectonic chain reaction illustrates how changes in plate motion, underpinned by mantle dynamics, may self-perpetuate through a plate circuit.

The India–Asia collision zone is the archetype to calibrate geological responses to continent–continent collision, but hosts a paradox: there is no orogen-wide geological record of oceanic subduction after initial collision around 60–55 Ma, yet thousands of kilometers of post-collisional subduction occurred before the arrival of unsubductable continental lithosphere that currently horizontally underlies Tibet. Kinematically restoring incipient horizontal underthrusting accurately predicts geologically estimated diachronous slab break-off, unlocking the Miocene of Himalaya–Tibet as a natural laboratory for unsubductable lithosphere convergence. Additionally, three endmember paleogeographic scenarios exist with different predictions for the nature of post-collisional subducted lithosphere but each is defended and challenged based on similar data types. This paper attempts at breaking through this impasse by identifying how the three paleogeographic scenarios each challenge paradigms in geodynamics, orogenesis, magmatism or paleogeographic reconstruction and identify opportunities for methodological advances in paleomagnetism, sediment provenance analysis, and seismology to conclusively constrain Greater Indian paleogeography.

Subduction zones are pivotal for the recycling of Earth’s outer layer into its interior. However, the conditions under which new subduction zones initiate are enigmatic. Here, we constructed a transdisciplinary database featuring detailed analysis of more than a dozen documented subduction zone initiation events from the last hundred million years. Our initial findings reveal that horizontally forced subduction zone initiation is dominant over the last 100 Ma, and that most initiation events are proximal to pre-existing subduction zones. The SZI Database is expandable to facilitate access to the most current understanding of subduction zone initiation as research progresses, providing a community platform that establishes a common language to sharpen discussion across the Earth Science community., Despite numerous advances in our understanding of subduction since the theory of plate tectonics was established, the mechanisms of subduction zone initiation remain highly controversial. Here, the authors present a transdisciplinary and expandable community database of subduction zone initiation events in the last 100 Ma, which establishes a clear direction for future research.

Several alternative gravity forward modelling methodologies and associated numerical codes with their own advantages and limitations are available for the Solid Earth community. With the upcoming state-of-the-art lithosphere density models and accurate global gravity field data sets it is vital to understand the opportunities and limitations of the various approaches. In this paper, we discuss the four widely used techniques: global spherical harmonics (GSH), tesseroid integration (TESS), triangle integration (TRI), and hexahedral integration (HEX). A constant density shell benchmark shows that all four codes can produce similar precise gravitational potential fields. Two additional shell tests were conducted with more complicated density structures: lateral varying density structures and a Moho density interface between crust and mantle. The differences between the four codes were all below 1.5 percent of the modeled gravity signal suitable for reproducing satellite-acquired gravity data. TESS and GSH produced the most similar potential fields (< 0.3 percent). To examine the usability of the forward modelling codes for realistic geological structures, we use the global lithosphere model WINTERC-G, that was constrained, among other data, by satellite gravity field data computed using a spectral forward modeling approach. This spectral code was benchmarked against the GSH and it was confirmed that both approaches produce similar gravity solution with negligible differences between them. In the comparison of the different WINTERC-G-based gravity solutions, again GSH and TESS performed best. Only short-wavelength noise is present between the spectral and tesseroid forward modelling approaches, likely related to the different way in which the spherical harmonic analysis of the varying boundaries of the mass layer is performed. The Spherical harmonic basis functions produces small differences compared to the tesseroid elements especially at sharp interfaces, which introduces mostly short-wavelength differences. Nevertheless, both approaches (GSH and TESS) result in accurate solutions of the potential field with reasonable computational resources. Differences below 0.5 percent are obtained, resulting in residuals of 0.076 mGal standard deviation at 250 km height. The biggest issue for TRI is the characteristic pattern in the residuals that is related to the grid layout. Increasing the resolution and filtering allows for the removal of most of this erroneous pattern, but at the expense of higher computational loads with respect to the other codes. The other spatial forward modelling scheme HEX has more difficulty in reproducing similar gravity field solutions compared to GSH and TESS. These particular approaches need to go to higher resolutions, resulting in enormous computation efforts. The hexahedron-based code performs less than optimal in the forward modelling of the gravity signature, especially of a lateral varying density interface. Care must be taken with any forward modelling software as the approximation of the geometry of the WINTERC-G model may deteriorate the gravity field solution.

This article is composed of three independent commentaries about the state of Integrated, Coordinated, Open, Networked (ICON) principles (Goldman et al., 2021, https://doi.org/10.1002/essoar.10508554.1) in the Geomagnetism, Paleomagnetism, and Electromagnetism (GPE) section and discussion on the opportunities and challenges of adopting them. Each commentary focuses on a different topic: Global collaboration, reproducibility, data sharing and infrastructure; Inclusive equitable, and accessible science: Involvement, challenges, and support of early career, BIPOC, women, LGBTQIA+, and/or disabled researchers; Community engagement, citizen science, education, and stakeholder involvement. Data sharing practices and open repository use still varies strongly between GPE communities. Some have a long tradition of data sharing; others are only starting it. Globally, GPE leadership is strongly dominated by white males and diversity may increase through the creation of Science Equality Commissions. Improved global stakeholder involvement can increase research impacts and help fight inequalities. In all investigated topics we see promising beginnings but also recognize obstacles that include a lack of funding, a lack of understanding of diversity, and prioritizing short-term gain over long-term benefit. Nonetheless, we are hopeful that our community will embrace ICON science.

Paleomagnetic poles used to compute apparent polar wander paths (APWPs) are strongly dispersed, which was recently shown to cause a large fraction (>50%) of these poles to be statistically distinct from the APWP to which they contributed, suggesting that current statistical approaches overestimate paleomagnetic resolution. Here, we analyze why coeval paleopoles are so dispersed, using the paleopoles behind the most recent global APWP and a compilation of paleomagnetic data obtained from

Geodynamic modelling provides a powerful tool to investigate processes in the Earth's crust, mantle, and core that are not directly observable. However, numerical models are inherently subject to the assumptions and simplifications on which they are based. In order to use and review numerical modelling studies appropriately, one needs to be aware of the limitations of geodynamic modelling as well as its advantages. Here, we present a comprehensive yet concise overview of the geodynamic modelling process applied to the solid Earth from the choice of governing equations to numerical methods, model setup, model interpretation, and the eventual communication of the model results. We highlight best practices and discuss their implementations including code verification, model validation, internal consistency checks, and software and data management. Thus, with this perspective, we encourage high-quality modelling studies, fair external interpretation, and sensible use of published work. We provide ample examples, from lithosphere and mantle dynamics specifically, and point out synergies with related fields such as seismology, tectonophysics, geology, mineral physics, planetary science, and geodesy. We clarify and consolidate terminology across geodynamics and numerical modelling to set a standard for clear communication of modelling studies. All in all, this paper presents the basics of geodynamic modelling for first-time and experienced modellers, collaborators, and reviewers from diverse backgrounds to (re)gain a solid understanding of geodynamic modelling as a whole.

Orogens that form at convergent plate boundaries typically consist of accreted rock units that form an incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed lithosphere of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the pre-orogenic paleogeographic distribution of oceans and continents, as well as bathymetric and topographic features that existed thereon such as igneous plateaus, seamounts, microcontinents, or magmatic arcs. Current classification schemes of orogens divide between settings associated with termination of subduction [continent-continent collision, continent-ocean collision (obduction)] and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications, particularly of collisional orogenesis, hinge on dynamic interpretations linking downgoing plate paleogeography to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave as accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or mélanges) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrust lower crustal and mantle lithospheric underpinnings. Upper plate deformation and paleogeography respond to the competition between absolute motions of the upper plate and the subducting slab. Our navigation approach through orogenic architecture aims to avoid a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate, to provide an independent basis for geodynamic analysis. From our analysis we identify ‘rules of orogenesis' that link the rules of rigid plate tectonics with the reality of plate deformation. We use these rules for a thought experiment, in which we predict orogenic architecture that will result from subducting the present-day Indian Ocean and colliding the Somali, Madagascar, and Indian margins using a published continental drift scenario for a future supercontinent as basis. We illustrate that our inferred rules (of thumb) generate orogenic architecture that is analogous to elements of modern orogens, unlocking the well-known modern geography as inspiration for developing testable hypotheses that aid interpreting paleogeography from orogens that formed since the birth of plate tectonics.

We provide new kinematic data from the Potwar Plateau (Pakistan) to evaluate the tectonic evolution of the region during the Neogene. The plateau is bound by two major strike-slip faults in the west and the east, accommodating its southwards translation. We have recognized two Neogene deformation phases in the plateau, based on paleostress inversion and Anisotropy of Magnetic Susceptibility (AMS) tensors. The first phase lasted until the early Pliocene and was characterized by vertical minor stress and N-S compression, implying thrust tectonics. The second deformation phase is characterized by a near-vertical intermediate principal stress and near-horizontal major and minor stresses, interpreted to be associated with strike-slip tectonics since the late Pliocene. K-int vectors from 21 sites are relatively compatible with the major principal stress orientations (sigma(1)) and indicate two distinct domains. This is possibly because K-min orientations are related to compaction, whereas K-int orientations were always parallel to tectonic shortening and hence compression direction during both strike-slip (post-late Pliocene) and thrusting (pre-late Pliocene) phases. These phases are characterized by swapping of (sigma(2)) and (sigma(3)) orientations while (sigma(1)) maintained its orientation. The most prominent change occurs at the western part of the Potwar Plateau, where major principal stress directions (sigma(1)) and K-int axes fan out south-westwards. The eastern domain is dominated by NE-SW trending folds and thrust faults, which are absent in the western domain. These structural features are interpreted to be the result of the distribution of deposits of the Neoproterozoic Salt Range Formation as a substratum below the Potwar Plateau. The Salt Range Formation is very thick and widespread in the west area and almost absent in the east. This factor led to unconstrained southwards gliding of the Potwar Plateau over the salt deposits in the west as opposed to frictional sliding and substantial internal deformation in the east.

We provide an independent test for the proposed pre-breakup fits between the South American and African continental margins based on new palaeomagnetic data. In the course of modelling the opening of the South Atlantic Ocean, several reconstructions have been proposed, which correspond to different estimates of the amount of pre-drift extension in the South American and African continental margins, and amounts of displacement along intracontinental accommodation zones. The Parana–Etendeka Large Igneous Province erupted during a brief time interval between ~ 136 and ~ 131 Ma, just prior to opening of the South Atlantic, and has magmatic products on both the African (Etendeka lavas) and South American (Parana lavas) plates. Here we provide new palaeomagnetic constraints on the Etendeka volcanic rocks. These yield a declination of D ± ∆ Dx = 314.4 ± 7.0° and inclination of I ± ∆ Ix = − 42.7 ± 8.3° (Plat = 47.5, PLon = 88.9, K = 26.1, A95 = 6.3, n = 21). When our results are combined with another recently published dataset, we obtain an Etendeka palaeopole at 49.1° S, 87.6° E (D ± ∆ Dx = 315.9 ± 3.8°, I ± ∆ Ix = − 43.9 ± 4.4°, K = 23.4, A95 = 3.5, n = 75). We compare three recent models for South Atlantic Ocean opening, discuss which of the models best fits the palaeomagnetic data, and present a revised reconstruction for West Gondwana during the Early Cretaceous.

We applied a lattice vibrational technique, based on representing the vibrational density of states with multiple-Einstein frequencies, to determine consistency of data on thermophysical properties and phase diagrams in the system MgO–FeO–SiO 2 . We present analyses of these data in the temperature range between 0 and 2000 K and pressure range between 0 and 20 GPa. The result is a database containing phases relevant to the Earth upper mantle and transition zone. We show that consistency of different datasets associated with the dissociation of the ringwoodite form of Fe 2 SiO 4 depends on the crucible material that has been used to perform partitioning experiments between ringwoodite and ferropericlase, and that this results in different phase diagrams for FeSiO 3 and the post-spinel part of Mg 2 SiO 4 –Fe 2 SiO 4 . We show that the existence of a phase field coesite + ringwoodite in the phase diagram of FeSiO 3 is possible and that it might be used to fine-tune pressure scales. We demonstrate that the phase boundary between coesite and quartz is very sensitive to the low-temperature heat capacity of coesite and that heat capacity data of β-quartz are too large to be reconciled with the phase boundary between β-quartz and coesite. We compare our results with seismic data associated with the 410 km seismic discontinuity.

We document the geochemistry of calcite veins in the Late Cretaceous Tikihore Formation (Raukumara Peninsula, New Zealand) to characterize their fluid composition and source and to help establish the age of subduction initiation at the Hikurangi margin of the Australia-Pacific plate boundary. The calcite veins occur within normal faults offsetting turbidites that accumulated in a lower slope basin. Vein calcite trace metal content and rare earth element patterns are consistent with a seawater-derived brine composition. Oxygen isotope (δ18O) values range from −6.1 to +8.4‰ and are −0.2‰ VPDB on average; positive δ13C values of up to +28‰ VDPB reflect methanogenesis. Oxygen isotope temperature data indicate that calcite vein mineralization occurred at temperatures in the range of 29°C–48°C. This is markedly less than the maximum burial temperature experienced by the host rocks, which we estimate to be 104 ± 10°C at 30–27 Ma from the inverse modeling of apatite fission track data. The vein calcite has a 28.5 ± 4.9 Ma U-Pb age. From these data, we infer that the succession above Tikihore Formation was removed by slumping, thereby resulting in fluid overpressure in the reservoir, followed by hydraulic fracturing and the precipitation of the vein calcite. Ultimately, the data presented here from the Tikihore veins are consistent with subduction initiation at 30–27 Ma, based on the U-Pb age of the vein calcite and modeling of apatite fission track data for the host sandstone, corroborated by the 30–27 Ma timing of back thrusting on the Taranaki Fault and related foredeep development in eastern Taranaki Basin.

Eastern Mediterranean subduction accommodated Africa‐Eurasia convergence since Mesozoic time and produced multiple subducted slab fragments in the mantle below Anatolia. These included the north dipping Cyprus and ENE‐dipping Antalya slabs, which are currently separated by an upper mantle slab gap. Segmentation of these slabs, and associated mantle flow, may have contributed to 400 km of post to middle Eocene plate convergence was accommodated between the Taurides and its Beydağları platform foreland and instead must have been accommodated south of Beydağları. The associated southward plate boundary jump separated the Antalya slab from the African plate and the Cyprus slab. The isolated Antalya slab was left in an intraplate setting and is probably still attached to Beydağları today. We suggest the continental composition of the Antalya slab may have prevented its detachment. Finally, the gap between the Antalya and Cyprus slabs existed since at least Eocene time; their decoupling likely did not contribute to late Neogene Central Anatolian Plateau uplift., Key Points The Taurides fold‐thrust belt contains a minimum of 90.5‐km shortening that occurred in Eocence and Mio‐Pliocene phasesThe Antalya slab has been decoupled from the Cyprus slab and isolated in an upper plate position since Eocene timesThe Antalya slab consists mostly of continental lithosphere, which may have prevented it from sinking and detaching

International audience; Paleogeographic maps are essential tools for understanding Earth system dynamics. They provide boundary conditions for climate and geodynamic modelling, for analysing surface processes and biotic interactions. However, the temporal and spatial distribution of key features such as seaways and mountain belts that govern climate changes and biotic interchange differ between various paleogeographies that require regular updates with new data and models. We developed a reproducible and systematic approach to paleogeographic reconstruction and provide a set of worldwide Cenozoic paleogeographic maps at 60, 40 and 20 Ma. We followed a six-stage methodology that integrates an extensive review of geological data into a coherent plate tectonic model using the open source software GPlates. (1) We generated a global plate kinematic model, and reconstructed intensely-deformed plate boundaries using a review of structural, paleomagnetic and other geologic data in six key regions: the Andes, the North American Cordillera, the Scotia Arc, Africa, the Mediterranean region and the Tibetan-Himalayan collision zone. (2) We modified previously published paleobathymetry in several regions where continental and oceanic crust overlap due to differences in the plate models. (3) We then defined paleoshorelines using updated fossil and geologic databases to locate the terrestrial to marine transition. (4) We applied isostatic compensation in polar regions and global eustatic sea level adjustments. (5) Paleoelevations were estimated using a broad range of data including thermochronology and stable isotopes, combined with paleobotanical (mostly pollen and leaf physiognomy), structural and geomorphological data. We address ongoing controversies on the mechanisms and chronology of India-Asia collision by providing alternate reconstructions for each time slice. We finally discuss the implications of our reconstructions on the Cenozoic evolution of continental weatherability and review methodological limitations and potential improvements. Future addition of new data, tools and reconstructions can be accommodated through a dedicated interactive website tool (https://map.paleoenvironment.eu/) that enables users to interactively upload and download data and compare with other models, and generate their own plots. Our aim is to regularly update the models presented here with new data as they become available.

International audience; The eastern margin of the world's largest and highest orogenic plateau, the Tibetan Plateau, shows contrasted edges, with a steep topographic gradient along the Longmen Shan (LMS) north of the Xianshuihe strike-slip fault (XF), and gentler slopes across the Yalong margin to the south (Figure 1a). The driving mechanism(s) leading to such contrasts between margins are still poorly understood and have given rise to end-member models of plateau growth with different crustal structures: either a weak lower crust localizing crustal thickening ("channel flow model," e.g., Clark & Royden, 2000), or a more rigid crust, with thickening that includes the upper crust, in a brittle manner ("stepwise model," Tapponnier et al., 2001). Those two end-member models can be tested by investigating the role of thrusting mechanisms in SE Tibet. At present, upper crustal deformation of the LMS is dominated by reverse faulting with a small component of right-lateral motion, as shown by recent earthquake focal mechanisms such as that of the 2008 Mw7.9 Wenchuan earthquake (e.g., de Michele et al., 2010; Fielding et al., 2013). This event ruptured two subparallel reverse structures, the Guanxian and Beichuan thrusts (Figure 1b), with steep shallow ramps (up to 70°) which root between 15 and 25 km-depth on a sub-horizontal décollement zone (e.g.

Structural restoration is commonly used to assess the deformation of geological structures and to reconstruct past basin geometries. To replace geometric criteria, linear elastic behavior and frictionless fault contact assumptions used in existing restoration approaches, we study the possibility of using a creeping flow behavior in geomechanical restoration. Indeed, salt rock in particular has been shown to behave as a Stokes viscous fluid over geological time scales, and faults appear in rocks reaching a plastic limit inside a shear zone. We have therefore developed a new approach for restoration based on considering geologic materials as highly viscous quasi-static fluids. The Stokes equations are solved for the velocity inside a model at each time step using only the material properties of the objects inside the model, their geometry and the current state of boundary conditions. The restoration is then achieved by advecting the material in the opposite direction of the forward velocity. Several benchmarks are presented to validate the results of the simulation code used to test the approach. This method is applied on simple two-dimensional geological cross-sections in confined conditions and shows that reasonable restored geometries can be obtained.

Central Anatolia (Turkey) is a small and nascent example of a high orogenic plateau, providing a natural laboratory to study processes driving plateau rise. The 1-km-high plateau interior uplifted since c. 8–5 Ma, with a further phase of kilometre-scale uplift affecting the southern plateau margin since 0.45 Ma. Several causes of plateau rise have been proposed: peeling or dripping delamination of the lithospheric mantle; asthenospheric upwelling through slab gaps created by slab fragmentation or break-off, and; continental underthrusting and crustal shortening below the southern plateau margin. The Neogene history of the plateau has not been diagnostic of the causes of plateau rise. We thus evaluate proposed uplift causes in the context of the Anatolian orogenesis, which formed the plateau lithosphere during subduction since the Cretaceous. We combine this analysis with available constraints on uplift, and geophysical data that illuminate the modern mantle (and crustal) structure. Our analysis suggests that lithospheric dripping, which followed arc magmatism and shortening in the Kirsehir Block (eastern Central Anatolia), is the most likely cause of plateau interior uplift. Lithospheric dripping is, however, an unlikely sole driver of multi-phase uplift along the southern plateau margin. There, underthrusting of the African continental margin, recorded by c. 11–7 Ma thrusting on Cyprus, is a viable cause of uplift since 0.45 Ma, but cannot account for earlier uplift since c. 8–5 Ma. Instead, slab break-off below the southern plateau margin is likely in light of geophysical data. On the SW plateau margin, small-scale peeling delamination of the Central Taurides by the Antalya slab since early Miocene times accounts for >150 km slab retreat with no corresponding upper-plate deformation. A southwest-travelling wave of subsidence and uplift signalled this retreat and may have contributed to coeval oroclinal bending of the western Central Taurides and southeastward thrusting of the Lycian Nappes.

Plate reconstructions of the Panthalassa Ocean typically portray a simple system of diverging plates surrounded by active margins, yet geological and seismic tomographic records demonstrate that intra-oceanic subduction existed. Here, we reconstruct the plate tectonic evolution of the pre-Cretaceous intra-oceanic Oku-Niikappu island arc, remnants of which are exposed on Hokkaido, Japan. This arc formed at a Jurassic subduction zone separating two oceanic plates: the Izanagi Plate and the here proposed ‘Izanami’ Plate. The Oku-Niikappu arc was previously shown to have gone extinct in an intra-oceanic setting, was subsequently (hyper)extended, and overlain by Berriasian cherts. The extinct arc remained on the Panthalassa ocean floor for ∼45 Myr until its ∼100 Ma accretion to Hokkaido, revealing an original position far from the continental margin and likely above the previously identified Telkhinia slabs. We show that arc extinction coincided with a northwestern Panthalassa plate reorganization recorded by a ∼30° change in spreading direction, and that extinction and subsequent extension of the arc is straightforwardly explained by subduction of the Izanami-Pacific ridge followed by continued divergence between the Izanagi and Pacific plates. From our reconstruction, it follows that the outer zone of Japan, to which the accretionary complex in which the Oku-Niikappu Complex resides belongs, was separated from the inner zone by a back-arc basin during the Early to mid-Cretaceous. This study illustrates the value of accretionary orogens in the development of plate reconstructions of lost oceanic plates and ancient continental margins, particularly when combined with seismic tomographic and marine geophysical data sets., Tectonics, 40 (8)

International audience; Subduction polarity reversal during arc-continent collision has been proposed as a key mechanism to initiate new subduction zones. Despite often interpreted, well-exposed geological record that document the reversal is sparse. The ophiolitic lithounits of the Andaman and Nicobar Islands have been proposed to have formed during the initiation of a new subduction zone following the collision of the Woyla Arc of Sumatra with Sundaland (Eurasia). We here present new field, petrological and geochronological data to evaluate the timing of the initiation of Andaman subduction. We targeted the previously inferred but unstudied metamorphic sole of the Andaman ophiolites that witnessed juvenile subduction. Thermodynamic modeling reveals that the exposed amphibolites of the sole formed at around 0.9 GPa and 675°C. We dated two samples of the metamorphic sole using the Ar/Ar method on amphibole, giving cooling ages of 106.4 ± 2.1 and 105.3 ± 1.6 Ma. This is similar to published ages from plagioclase xenocrysts in recent Barren Island volcanics and in zircons from a gabbro sample from the Andaman ophiolite, which we interpret as the age of the original ophiolite formation. The Ar/Ar ages are considerably older than arc magmatic gabbros and plagiogranites of the overlying ophiolite previously dated at 99-93 Ma and thought to reflect the ophiolite age but recently reinterpreted as a volcanic arc built on the ophiolite. Combined with the ages of Woyla-Sundaland collision, we argue that subduction polarity reversal occurred in a transient period of perhaps some 10 Myr, similar to recent settings.

The Cap de Creus peninsula in NE Spain exposes Variscan amphibolite-facies rocks, transected by greenschist-facies mylonitic shear zones accommodating displacements of up to 1 km. One of these shear zones contains pseudotachylytes with 1–4 mm thick fault veins and cm-scale high-angle injection veins and breccias. The pseudotachylyte matrix encloses mm-to μm-scale wallrock fragments and consists of ultrafine biotite and feldspar, often with a microporphyritic structure suggesting crystallization from a melt. Recent dating of the host shear zone yielded a Jurassic (170-160 Ma) age. Here we present 40Ar/39Ar dating of the pseudotachylytes yielding Early Eocene ages between 52.76 ± 1.64 Ma and 44.55 ± 0.77 Ma, indicating Alpine brittle faulting at times that Jurassic low-angle ductile shears had been tilted to their present vertical position following Alpine thrusting in the Pyrenees. The kinematics of the pseudotachylytes suggest strike-slip reactivation along the host shear zone, consistent with plate-kinematic analyses indicating coeval Iberia - Europe motion dominated by strike-slip. The dimensions of the pseudotachylyte-bearing zone and estimated brittle displacements suggest a moment magnitude of ~4.7–4.9. The average thicknesses of the fault veins indicate deformation at ≥4 km depth, an energy density of ~9.106 J/m2 and a frictional resistance of ~23 MPa.

The mass-density distribution of the Earth drives mantle convection and plate tectonics but is poorly known. We aim to predict gravity fields as a constraint for geodynamical modelling. In order to compute synthetic Earth gravity one must define a spherical geometry filled with a density model. Density models for the whole mantle down to the CMB come from tomographic models which therefore require converting speed waves velocities to density using a scaling factor.We use a discretised integration method to compute globally gravity acceleration, gravity anomalies, potential and gradients, in the state of the art finite element code ASPECT.Three density models are tested separately: a density field obtained from SL2013 and S40RTS tomographic models for the deep mantle, and the density model CRUST1.0 for the thin upper lithosphere layer. We combine these 3 datasets into one to create a composite model which is compared to the global seismic model LLNL-G3D-JPS of Simmons et al. (2015). We test the sensitivity of gravity prediction on the use of various conversion scaling factors of shear wave velocity to density. We find that the scaling factor profile also has a major impact on gravity prediction.Finally, we present early results of the gravity field prediction for two local areas, the Indian-Tibet plate boundary and the Mediterranean Sea. Gravity predictions are compared to satellite gravity.

The Messinian Salinity Crisis (5.97–5.33 Ma) was caused by the closure of the Atlantic‐Mediterranean gateways that cut through the Gibraltar orogenic system. The geodynamic drivers underlying gateway closure and re‐opening are still debated. Here, we interrogate the gateway successions to find the imprints of surface deformation, infer the timing and nature of associated geodynamic drivers, and test such inferences against numerical simulations of slab dynamics. We find that since the latest Miocene, a tectonic framework was established in the gateway region dominated simultaneously by (a) relative plate convergence, (b) slab tearing under the eastern Betic Cordillera and (c) mantle resistance against north‐northeastward dragging of the Gibraltar slab by the African plate's absolute motion. We propose that mantle‐resisted slab dragging and slab tearing operated in concert closing the gateways that caused the Messinian Salinity Crisis, whereas sinking of heavy oceanic lithosphere located between buoyant continental plates re‐opened the Strait of Gibraltar at 5.33 Ma.

Scientific communities are placing an increasing emphasis on the implementation of data management protocols concerning data archiving and distribution. For instance, every proposal submitted to the European Horizon 2020 program, as well as to the National Science Foundation in the USA, requires a dedicated section that outlines project data management and accessibility. The widely adopted FAIR data guidelines identify core principles concerning modern data management conventions. The wide variety of data formats, the low data volume, and the general lack of a culture of data sharing makes that the paleomagnetic community rarely follows any of the FAIR principles. Most institutions define their own data formats and use in‐house software to analyze their demagnetization data, which are critical to Paleomagnetic research. Efforts to overcome these problems exist in the form of the MagIC database for data archiving, and the online paleomagnetic data analysis and interpretation platform Paleomagnetism.org. In this contribution, we describe the second iteration of Paleomagnetism.org: an online multiplatform open‐source environment for paleomagnetic data analysis. This update comprises a full overhaul of the application to satisfy the increasingly demanding data management requirements. The application now facilitates a workflow that aligns with FAIR guidelines by documenting data provenance. All data analyzed through the application are easily submitted to a public data library that distributes data and results through an HTTPS web service that lives up to modern data management standards.

We present a map that correlates tectonic units between Alps and western Turkey accompanied by a text providing access to literature data, explaining the concepts used for defining the mapped tectonic units, and first-order paleogeographic inferences. Along-strike similarities and differences of the Alpine-Eastern Mediterranean orogenic system are discussed. The map allows (1) for superimposing additional information, such as e.g., post-tectonic sedimentary basins, manifestations of magmatic activity, onto a coherent tectonic framework and (2) for outlining the major features of the Alpine-Eastern Mediterranean orogen. Dinarides-Hellenides, Anatolides and Taurides are orogens of opposite subduction polarity and direction of major transport with respect to Alps and Carpathians, and polarity switches across the Mid-Hungarian fault zone. The Dinarides-Hellenides-Taurides (and Apennines) consist of nappes detached from the Greater Adriatic continental margin during Cretaceous and Cenozoic orogeny. Internal units form composite nappes that passively carry ophiolites obducted in the latest Jurassic–earliest Cretaceous or during the Late Cretaceous on top of the Greater Adriatic margin successions. The ophiolites on top of composite nappes do not represent oceanic sutures zones, but root in the suture zones of Neotethys that formed after obduction. Suturing between Greater Adria and the northern and eastern Neotethys margin occupied by the Tisza and Dacia mega-units and the Pontides occurred in the latest Cretaceous along the Sava-Izmir-Ankara-Erzincan suture zones. The Rhodopian orogen is interpreted as a deep-crustal nappe stack formed in tandem with the Carpatho-Balkanides fold-thrust belt, now exposed in a giant core complex exhumed in late Eocene to Miocene times from below the Carpatho-Balkan orogen and the Circum-Rhodope unit. Its tectonic position is similar to that of the Sakarya unit of the Pontides. We infer that the Rhodope nappe stack formed due to north-directed thrusting. Both Rhodopes and Pontides are suspected to preserve the westernmost relics of the suture zone of Paleotethys.

International audience; As subduction zones and their related processes are often studied in 2D, or cylindrical 3D sections, the dynamic effects of trench curvature and its evolution through time remain under-explored. Whereas temporal variations in trench trend may be estimated through restoring upper plate deformation, we investigate the forearc deformation history of the strongly curved northern Lesser Antilles trench, connecting the near-orthogonal Lesser Antilles subduction zone with the Motagua-Cayman transform plate boundary. Our new paleomagnetic dataset consists of 310 cores from Eo-Oligocene magmatic rocks and limestones from St. Barthélemy Island. The limestones yielded a post-folding magnetization containing a similar magnetic direction to those stored in magmatic rocks that intrude the folded carbonates, both indicating a post-Oligocene ~15°, and perhaps up to 25° counterclockwise rotation of the island. Our results highlight that the present-day trench curvature formed progressively during the Cenozoic, allowing us to discuss different tectonic scenarios explaining NE Caribbean plate deformation, and to identify key targets for future research on tectonic architecture and the potential present-day activity of intra-plate deformation that may pose seismic hazards.

Established theories ascribe much of the observed long‐term Cenozoic climate cooling to atmospheric carbon consumption by erosion and weathering of tectonically uplifted terrains, but climatic effects due to changes in magmatism and carbon degassing are also involved. At timescales comparable to those of Milankovitch cycles, late Cenozoic building/melting of continental ice sheets, erosion, and sea level changes can affect magmatism, which provides an opportunity to explore possible feedbacks between climate and volcanic changes. Existing data show that extinction of Neo‐Tethyan volcanic arcs is largely synchronous with phases of atmospheric carbon reduction, suggesting waning degassing as a possible contribution to climate cooling throughout the early to middle Cenozoic. In addition, the increase in atmospheric CO2 concentrations during the last deglaciation may be ascribed to enhanced volcanism and carbon emissions due to unloading of active magmatic provinces on continents. The deglacial rise in atmospheric CO2 points to a mutual feedback between climate and volcanism mediated by the redistribution of surface masses and carbon emissions. This may explain the progression to higher amplitude and increasingly asymmetric cycles of late Cenozoic climate oscillations. Unifying theories relating tectonic, erosional, climatic, and magmatic changes across timescales via the carbon cycle offer an opportunity for future research into the coupling between surface and deep Earth processes.

SE Asia comprises a heterogeneous assemblage of fragments derived from Cathaysia (Eurasia) in the north and Gondwana in the south, separated by suture zones representing closed former ocean basins. The western part of the region comprises Sundaland, which was formed by Late Permian‐Triassic amalgamation of continental and arc fragments now found in Indochina, the Thai Penisula, Peninsular Malaysia, and Sumatra. On Borneo, the Kuching Zone formed the eastern margin of Sundaland since the Triassic. To the SE of the Kuching Zone, the Gondwana‐derived continental fragments of SW Borneo and East Kalimantan accreted in the Cretaceous. South China‐derived fragments accreted to north of the Kuching Zone in the Miocene. Deciphering this complex geodynamic history of SE Asia requires restoration of its deformation history, but quantitative constraints are often sparse. Paleomagnetism may provide such constraints. Previous paleomagnetic studies demonstrated that Sundaland and fragments in Borneo underwent vertical axis rotations since the Cretaceous. We provide new paleomagnetic data from Eocene‐Miocene sedimentary rocks in the Kutai Basin, east Borneo, and critically reevaluate the published database, omitting sites that do not pass widely used, up‐to‐date reliability criteria. We use the resulting database to develop an updated kinematic restoration. We test the regional or local nature of paleomagnetic rotations against fits between the restored orientation of the Sunda Trench and seismic tomography images of the associated slabs. Paleomagnetic data and mantle tomography of the Sunda slab indicate that Sundaland did not experience significant vertical axis rotations since the Late Jurassic. Paleomagnetic data show that Borneo underwent a ~35° counterclockwise rotation constrained to the Late Eocene and an additional ~10° counterclockwise rotation since the Early Miocene. How this rotation was accommodated relative to Sundaland is enigmatic but likely involved distributed extension in the West Java Sea between Borneo and Sumatra. This Late Eocene‐Early Oligocene rotation is contemporaneous with and may have been driven by a marked change in motion of Australia relative to Eurasia, from eastward to northward, which also has led to the initiation of subduction along the eastern Sunda trench and the proto‐South China Sea to the south and north of Borneo, respectively., Key Points We present new paleomagnetic data from Eocene‐Miocene sedimentary rocks in Kutai Basin, Borneo, and compile all available paleomagnetic data from Mesozoic and Cenozoic rocks in Sundaland and BorneoWe compare reconstructed trenches with seismic tomography to evaluate the regional or local nature of paleomagnetic resultsWe provide a kinematic restoration of Borneo and Sundaland since the Eocene that is consistent with paleomagnetism and tomography

The modern physiography of central Turkey is dominated by the 1-km-high Central Anatolian Plateau and the Central Tauride mountains that form the southern plateau margin. These correspond to a Cretaceous–Eocene backarc extensional province and forearc fold-thrust belt, respectively. The extent to which the morphology of the Miocene plateau was inherited from the physiography of the Cretaceous–Eocene subduction zone that assembled the Anatolian crust has not been tested but is important if we are to isolate the signal of Miocene and younger subduction dynamics in the formation of the modern plateau margin. There is no known stratigraphic record of the post-Eocene pre-Miocene evolution of the Taurides. We therefore collected rock samples across the Taurides and used zircon (U-Th)/He (ZHe), apatite (U-Th)/He (AHe), and apatite fission-track (AFT) low-temperature thermochronometers to constrain cooling; we interpret these thermochronometers to signal erosional exhumation. We use inverse thermal modeling to aid interpretation of our results and find that: (1) thermochronometers across the Taurides were reset as a result of heating by the emplacement of the Antalya and Bozkır nappes; (2) AFT and ZHe Eocene cooling ages are related to structurally driven uplift and erosional exhumation on major thrust culminations; (3) dispersed AHe ages record low rates of Oligocene–early Miocene cooling and hence low rates of erosional exhumation; and (4) fast rates of cooling were determined for samples along the margin of the Köprüçay Basin. We interpret that early Miocene cooling is a signal of active erosion of the western Central Taurides at a time of marine sedimentation in the Mut Basin on the southern Central Taurides, and these differing histories may reflect evolution above the Antalya and Cyprus slabs. Our thermochronological data, the enigmatic development of the Antalya Basin, and thrusting within the basin may be explained as the surface expression of stepwise delamination of the Antalya slab from the Tauride hinterland to its current position below the Gulf of Antalya since early Miocene time over a distance of ∼150 km.

International audience; Abstract. The geotherm in subduction zones is thought to vary as a function of the subduction rate and the age of the subducting lithosphere. Along a single subduction zone the rate of subduction may strongly vary due to changes in the angle between the trench and the plate convergence vector, i.e., the subduction obliquity, due to trench curvature. We currently observe such curvature in, e.g., the Marianas, Chile and Aleutian trenches. Recently, strong along-strike variations in subduction obliquity were proposed to have caused a major temperature contrast between Cretaceous geological records of western and central Turkey. We test here whether first-order temperature variation in a subduction zone may be caused by variation in the trench geometry using simple thermo-kinematic finite-element 3-D numerical models. We prescribe the trench geometry by means of a simple mathematical function and compute the mantle flow in the mantle wedge by solving the equation of mass and momentum conservation. We then solve the energy conservation equation until steady state is reached. We analyze the results (i) in terms of mantle wedge flow with emphasis on the trench-parallel component and (ii) in terms of temperature along the plate interface by means of maps and the depth–temperature path at the interface. In our experiments, the effect of the trench curvature on the geotherm is substantial. A small obliquity yields a small but not negligible trench-parallel mantle flow, leading to differences of 30 °C along-strike of the model. Advected heat causes such temperature variations (linked to the magnitude of the trench-parallel component of velocity). With increasing obliquity, the trench-parallel component of the velocity consequently increases and the temperature variation reaches 200 °C along-strike. Finally, we discuss the implication of our simulations for the ubiquitous oblique systems that are observed on Earth and the limitations of our modeling approach. Lateral variations in plate sinking rate associated with curvature will further enhance this temperature contrast. We conclude that the synchronous metamorphic temperature contrast between central and western Turkey may well have resulted from reconstructed major variations in subduction obliquity.

The Panthalassa Ocean, which surrounded the late Paleozoic-early Mesozoic Pangea supercontinent, was underlain by multiple tectonic plates that have since been lost to subduction. In this study, we develop an approach to reconstruct plate motions of this subducted lithosphere utilizing paleomagnetic data from accreted Ocean Plate Stratigraphy (OPS). We first establish the boundaries of the Panthalassa domain by using available Indo-Atlantic plate reconstructions and restorations of complex plate boundary deformation at circum-Panthalassa trenches. We reconstruct the Pacific Plate and its conjugates, the Farallon, Phoenix, and Izanagi plates, back to 190 Ma using marine magnetic anomaly records of the modern Pacific. Then, we present new and review published paleomagnetic data from OPS exposed in the accretionary complexes of Cedros Island (Mexico), the Santa Elena Peninsula (Costa Rica), the North Island of New Zealand, and Japan. These data provide paleolatitudinal plate motion components of the Farallon, Phoenix and Izanagi plates, and constrain the trajectories of these plates from their spreading ridges towards the trenches in which they subducted. For 83 to 150 Ma, we use two independent mantle frames to connect the Panthalassa plate system to the Indo-Atlantic plate system and test the feasibility of this approach with the paleomagnetic data. For times prior to 150 Ma, and as far back as Permian time, we reconstruct relative and absolute Panthalassa plate motions such that divergence is maintained between the Izanagi, Farallon and Phoenix plates, convergence is maintained with Pangean continental margins in Japan, Mexico and New Zealand, and paleomagnetic constraints are met. The reconstruction approach developed here enables data-based reconstruction of oceanic plates and plate boundaries in the absence of marine magnetic anomaly data or mantle reference frames, using Ocean Plate Stratigraphy, paleo-magnetism, and constraints on the nature of circum-oceanic plate boundaries. Such an approach is a crucial next step towards quantitative reconstruction of the currently largely unknown tectonic evolution of the Earth9s oceanic domains in deep geological time.

Palaeomagnetic poles form the building blocks of apparent polar wander paths and are used as primary input for quantitative palaeogeographic reconstructions. The calculation of such poles requires that the short-term, palaeosecular variation (PSV) of the geomagnetic field is adequately sampled and averaged by a palaeomagnetic dataset. Assessing to what extent PSV is recorded is relatively straightforward for rocks that are known to provide spot readings of the geomagnetic field, such as lavas. But it is unknown whether and when palaeomagnetic directions derived from sedimentary rocks represent spot readings of the geomagnetic field and sediments are moreover suffering from inclination shallowing, making it challenging to assess the reliability of poles derived from these rocks. Here, we explore whether a widely used technique to correct for inclination shallowing, known as the elongation-inclination method (E/I), allows us to formulate a set of quality criteria for (inclination shallowing-corrected) palaeomagnetic poles from sedimentary rocks. The E/I method explicitly assumes that a sediment-derived dataset provides, besides flattening, an accurate representation of PSV. We evaluate the effect of perceived pitfalls for this assumption using a recently published dataset of 1275 individual palaeomagnetic directions of a >3 km-thick succession of ~69-41.5 Ma red beds from the Gonjo Basin (eastern Tibet), as well as synthetic data generated with the TK03.GAD field model. The inclinations derived from the uncorrected dataset are significantly lower than previous estimates for the basin, obtained using coeval lavas, by correcting inclination shallowing using anisotropy-based techniques, and by predictions from tectonic reconstructions. We find that the E/I correction successfully restores the inclination to values predicted by these independent datasets if the following conditions are met: the number of directions N is at least 100, the A95 cone of confidence falls within a previously defined A95min-max reliability envelope, no negative reversal test is obtained and vertical-axis rotation differences within the dataset do not exceed 15°. We propose a classification of three levels (A, B, and C) that should be applied after commonly applied quality criteria for paleomagnetic poles are met. For poles with classification ‘A’, we find no reasons to assume insufficient quality for tectonic interpretation. Poles with classification ‘B’ could be useful, but have to be carefully assessed, and poles with classification ‘C’ provide unreliable paleolatitudes. We show that application of these criteria for datasets of other sedimentary rock types classifies datasets whose reliability is independently confirmed as ‘A’ or ‘B’, and that demonstrably unreliable datasets are classified as ‘C’, confirming that our criteria are useful, and conservative. The implication of our analysis is that sediment-based datasets of quality ‘A’ may be considered statistically equivalent to datasets of site-mean directions from rapidly cooled igneous rocks like lavas and provide high-quality palaeomagnetic poles.

Most ophiolites have geochemical signatures that indicate formation by suprasubduction seafloor spreading above newly initiated subduction zones, and hence they record fore-arc processes operating following subduction initiation. They are frequently underlain by a metamorphic sole formed at the top of the downgoing plate and accreted below the overlying suprasubduction zone lithosphere immediately following ophiolite formation. Paleomagnetic analyses of ophiolites can provide important insights into the enigmatic geodynamic processes operating in this setting via identification of tectonic rotations related to upper plate extension. Here we present net tectonic rotation results from the Late Cretaceous Mersin ophiolite of southern Turkey that document rapid and progressive rotation of ophiolitic rocks and their associated metamorphic sole. Specifically, we demonstrate that lower crustal cumulate rocks and early dykes intruded into the underlying mantle section have undergone extreme rotation around ridge-parallel, shallowly-plunging axes, consistent with oceanic detachment faulting during spreading. Importantly, later dykes cutting the metamorphic sole experienced rotation around the same axis but with a lower magnitude. We show that these rotations occurred via a common mechanism in a pre-obduction, fore-arc setting, and are best explained by combining (hyper)extension resulting from detachment-mode, amagmatic suprasubduction zone spreading in a fore-arc environment with a recently proposed mechanism for exhumation of metamorphic soles driven by upper plate extension. Available age constraints demonstrate that extreme rotation of these units was accommodated rapidly by these processes over a time period of

We integrate structural, geophysical, and geodetic studies showing that the Dinarides-Hellenides orogen along the Adria-Europe plate boundary in the Western Balkan peninsula has experienced clockwise oroclinal bending since Eocene-Oligocene time. Rotation of the Hellenic segment of this orogen has accelerated since the middle Miocene and is associated with a north-to-south increase in shortening along the orogenic front. Within the Paleogene nappe pile, bending was accommodated by orogen-parallel extension, clockwise block rotation, and thrusting in the hanging wall of the Skhoder-Peja Normal Fault (SPNF). The SPNF and related faults cut the older Skhoder-Peja Transfer Zone with its pre-Neogene dextral offset of the West Vardar ophiolite nappe. Rotation of the SPNF hanging wall involved Miocene-to-recent, out-of-sequence thrusting that was transferred to the Hellenic orogenic front via lateral ramps on dextral transfer zones. Along strike of the Dinarides-Hellenides and coincident with the southward increase in Neogene shortening, the depth of the Adriatic slab increases from ~160 km north of the SPNF to ~200 km just to the south thereof, to several hundreds of kilometers to the south of the Kefalonia Transfer Zone. The geodynamic driver of tectonics since the early Miocene has been enhanced rollback of the Hellenic segment of the Adriatic slab in the aftermath of Eocene-Oligocene slab tearing and breakoff beneath the Dinarides, which focused slab pull in the south. The SW-retreating Hellenic slab segment induced clockwise bending of the southern Dinarides and northern Hellenides, including their Adriatic foreland, about a rotation pole in the vicinity of the Mid-Adriatic Ridge.

Plate kinematic reconstructions play an essential role in our understanding of global geodynamics, but become increasingly difficult to constrain back in geological time due to the subduction of oceanic lithosphere. Here, we attempt to kinematically reconstruct the Cretaceous and older plate tectonic history of the Caribbean Plate within the Mesozoic Panthalassa (paleo-Pacific) Ocean. To this end, we present new paleomagnetic data from Jurassic and Cretaceous oceanic sedimentary and volcanic Large Igneous Province-related rocks of the Nicoya Peninsula and Murciélago Islands of northwestern Costa Rica. We use these data, in combination with constraints from marine magnetic anomalies to infer the age of the lithospheric basement, seismic tomography to locate deep-mantle plume generation zones, and general kinematic feasibility, to test different reconstruction scenarios connecting the Caribbean Plate to the Farallon Plate as restored from Pacific spreading records. Our resulting reconstruction implies that the western Caribbean subduction zone initiated around 100 Ma, in an intraoceanic setting, breaking up oceanic lithosphere of at least 70 Myr old.

The Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

Intriguing latest Eocene land-faunal dispersals between South America and the Greater Antilles (northern Caribbean) has inspired the hypothesis of the GAARlandia (Greater Antilles Aves Ridge) land bridge. This landbridge, however, should have crossed the Caribbean oceanic plate, and the geological evolution of its rise and demise, or its geodynamic forcing, remain unknown. Here we present the results of a land-sea survey from the northeast Caribbean plate, combined with chronostratigraphic data, revealing a regional episode of mid to late Eocene, trench-normal, E-W shortening and crustal thickening by~25%. This shortening led to a regional late Eocene-early Oligocene hiatus in the sedimentary record revealing the location of an emerged land (the Greater Antilles-Northern Lesser Antilles, or GrANoLA, landmass), consistent with the GAARlandia hypothesis. Subsequent submergence is explained by combined trench-parallel extension and thermal relaxation following a shift of arc magmatism, expressed by a regional early Miocene transgression. We tentatively link the NE Caribbean intra-plate shortening to a well-known absolute and relative North American and Caribbean plate motion change, which may provide focus for the search of the remaining connection between 'GrANoLA' land and South America, through the Aves Ridge or Lesser Antilles island arc. Our study highlights the how regional geodynamic evolution may have driven paleogeographic change that is still reflected in current biology.

Seismic tomography reveals a wide variety of slab deformation in the mantle transition zone and shallow lower mantle. Numerical modeling of subduction has identified several factors that control slab deformation, among them the properties of the mechanical decoupling between subducting and overriding plates was shown to have a major influence on slab velocity, rollback and deformation in the transition zone. Models with weak crust generally yield fast rollback and slab stagnation while stronger crust results in slab penetration into the lower mantle. Here we perform a detailed analysis of the effects of this weak crustal layer. First, in models with constant crustal viscosity, we quantify combined effects of crustal viscosity and thickness. Further we apply nonlinear crustal rheology that combines dislocation creep and pseudoplastic deformation. We test the effects of varying parameterisations of the nonlinear rheological mechanisms and evaluate their effects on slab deformation. We conclude that the variations of subducting slab velocity (controlled by the buoyancy effects of the major phase transitions) induce strong time variations of the crustal viscosity that in turn enforce further acceleration or deceleration of the slab. This feedback between slab velocity and crustal viscosity strenghtens transient behavior of the subducting slabs and enforces slab penetration after a transient period of stagnation.

During evolution of the South Sandwich subduction zone, which has consumed South American plate oceanic lithosphere, somehow continental crust of both the South American and Antarctic plates have become incorporated into its upper plate. Continental fragments of both plates are currently separated by small oceanic basins in the upper plate above the South Sandwich subduction zone, in the Scotia Sea region, but how fragments of both continents became incorporated in the same upper plate remains enigmatic. Here we present an updated kinematic reconstruction of the Scotia Sea region using the latest published marine magnetic anomaly constraints, and place this in a South America-Africa-Antarctica plate circuit in which we take intracontinental deformation into account. We show that a change in fracture zone orientation in the Weddell Sea requires that previously inferred initiation of subduction of South American oceanic crust of the northern Weddell below the eastern margin of South Orkney Islands continental crust, then still attached to the Antarctic Peninsula, already occurred around 80 Ma. We propose that subsequently, between ~71-50 Ma, the trench propagated northwards into South America by delamination of South American lithosphere: this resulted in the transfer of delaminated South American continental crust to the overriding plate of the South Sandwich subduction zone. We show continental delamination may have been facilitated by absolute southward motion of South America that was resisted by South Sandwich slab dragging. Pre-drift extension preceding the oceanic Scotia Sea basins led around 50 Ma to opening of the Drake Passage, preconditioning the southern ocean for the Antarctic Circumpolar Current. This 50 Ma extension was concurrent with a strong change in absolute plate motion of the South American Plate that changed from S to WNW, leading to upper plate retreat relative to the more or less mantle stationary South Sandwich Trench that did not partake in the absolute plate motion change. While subduction continued, this mantle-stationary trench setting lasted until ~30 Ma, after which rollback started to contribute to back-arc extension. We find that roll-back and upper plate retreat have contributed more or less equally to the total amount of ~2000 km of extension accommodated in the Scotia Sea basins. We highlight that viewing tectonic motions in a context of absolute plate motion is key for identifying slab motion (e.g. rollback, trench-parallel slab dragging) and consequently mantle-forcing of geological processes.

We present heat transport characteristics for mantle convection in large terrestrial exoplanets ( M ⩽ 8 M ⊕ ) . Our thermal convection model is based on a truncated anelastic liquid approximation (TALA) for compressible fluids and takes into account a selfconsistent thermodynamic description of material properties derived from mineral physics based on a multi-Einstein vibrational approach. We compare heat transport characteristics in compressible models with those obtained with incompressible models based on the classical- and extended Boussinesq approximation (BA and EBA respectively). Our scaling analysis shows that heat flux scales with effective dissipation number as Nu ∼ Di eff - 0.71 and with Rayleigh number as Nu ∼ Ra eff 0.27 . The surface heat flux of the BA models strongly overestimates the values from the corresponding compressible models, whereas the EBA models systematically underestimate the heat flux by ∼10%–15% with respect to a corresponding compressible case. Compressible models are also systematically warmer than the EBA models. Compressibility effects are therefore important for mantle dynamic processes, especially for large rocky exoplanets and consequently also for formation of planetary atmospheres, through outgassing, and the existence of a magnetic field, through thermal coupling of mantle and core dynamic systems.