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Throughout northeast China, eastern and southern Mongolia, and eastern Russia there is widespread Mesozoic intracontinental magmatism. Extensive studies on the Chinese magmatic rocks have suggested lithospheric mantle removal was a driver of the magmatism. The timing, distribution and potential diachroneity of such lithospheric mantle removal remains poorly constrained. Here, we examine successions of Mesozoic lavas and shallow intrusive volcanic plugs from the Gobi Altai in southern Mongolia that appear to be unrelated to regional, relatively small-scale deformation; at the time of magmatism, the area was ~ 200 km from any active margin, or, after its Late Jurassic-Early Cretaceous closure, from the suture of the Mongol-Okhotsk Ocean. 40Ar/39Ar radiometric age data place magmatic events in the Gobi Altai between ~ 220 to 99.2 Ma. This succession overlaps Chinese successions and therefore provides an opportunity to constrain whether Mesozoic lithosphere removal may provide an explanation for the magmatism here too, and if so, when. We show that Triassic to Lower Cretaceous lavas in the Gobi Altai (from Dulaan Bogd, Noyon Uul, Bulgantiin Uul, Jaran Bogd and Tsagaan Tsav) are all light rare-earth element (LREE) and large-ion lithophile element (LILE)-enriched, with negative Nb and Ta anomalies ( Nb La and Ta La ≤ 1). Geochemical data suggest that these lavas formed by low degrees of partial melting of a metasomatised lithospheric mantle that may have been modified by melts derived from recycled rutile-bearing eclogite. A gradual reduction in the involvement of garnet in the source of these lavas points towards a shallowing of the depth of melting after ~ 125 Ma. By contrast, geochemical and isotope data from the youngest magmatic rocks in the area — 107-99 Ma old volcanic plugs from Tsost Magmatic Field — have OIB-like trace element patterns and are interpreted to have formed by low degrees of partial melting of a garnet-bearing lherzolite mantle source. These rocks did not undergo significant crustal contamination, and were derived from asthenospheric mantle. The evidence of a gradual shallowing of melting in the Gobi lava provinces, culminating in an asthenospheric source signature in the youngest magmatic rocks is similar to examples from neighboring China, emphasising the wide-scale effect of a regional Mesozoic magmatic event during similar time periods. We suggest that Mongolia underwent lithospheric thinning/delamination during the Mesozoic (between ~ 125 and ~ 107 Ma) with patchy areas thinning sufficiently to enable the generation of relatively small-scale asthenospheric-derived magmatism to predominate in the late Cretaceous.

My thesis aims to resolve two main outstanding problems that occur when trying to numerically simulate the 3D complexity of lithosphere subduction evolution through geological time: high computational cost and the efficient constructing of complicated 3D initial conditions mimicking a subduction setting in the geological past or at the present-day. The issue of high computational cost is mostly due to the required use of nonlinear rheologies which are needed to realistically include temperature-, pressure- and stress dependent material properties of rock deformation. The resulting nonlinear Stokes equations require an iterative solving strategy, which can require a lot of iterations with the simple to implement Picard iteration. The Picard iteration is robust, but slow to converge. The convergence rate can be greatly improved by using a Newton iteration, which may fail to converge if the iteration solution far from the real solution, but will converge very fast when it is near the real solution. We discovered that the linear system produced by the Newton iteration may in some cases not be solvable. We provide a general remedy for this issue by forcing the system to be solvable at a minimum amount of convergence loss. We also show that this solution works well for large 3D tectonic settings. The issue concerns setting up initial conditions for the geometric complexity of realistic 3D subduction settings involving creating 3D fields of initial temperature and of materials (e.g. crust, mantle, tectonic plates, faults and weakness zones, 3D slab geometry). An initial condition may concern the earliest stage of a subduction or other geodynamic system as well as an advanced stage, depending on our knowledge of the tectonic evolution. In this thesis, I developed a generic way for setting up initial numerical models leading to a stand-alone code library called the Geodynamic World Builder (GWB), which implements this. We show that the code library is already successfully coupled to three different geodynamic codes. The new generic approach together with the code library renders relatively easy initial-model construction as well as modification of initial settings. In addition, it creates a platform to make initial setups reproducible for use in different geodynamic codes. In the last main chapter, I use these new developments to investigate a complicated and realistic 3D subduction evolution that resembles the eastern Caribbean subduction setting since 10 Ma. The GWB allowed for flexible construction of the initial settings of tectonic plates, weakness zones, and 3D slab geometry at 10 Ma, while the Newton solver allowed for obtaining modelling results relatively fast. The modelling results show that slab dragging, i.e. lateral transport of the slab through the mantle by the trench-parallel motion of the North American plate, has a strong effect on the slab geometry and the slab stress field. Slab stress is displayed with the direction of maximum shear stress in the slab, which may align with potential fault slip directions of earthquakes. This shows that when slab dragging occurs major stress orientations are generally not trench-perpendicular, as is usually perceived for slab stress.

GPS satellite observations indicate that in the tectonically complex eastern Mediterranean and east African regions microplates rotate counterclockwise with respect to the neighboring African plate. Using 3D numerical models, Glerum relates these observations of crustal deformation to the dynamics of the lithosphere and the underlying mantle that may cause this deformation. Glerum first describes her additions to the ASPECT software necessary for numerically modeling the upper mantle and lithosphere dynamics of convergent and divergent plate boundaries. These additions include the tracking of multiple materials with different physical properties and nonlinear viscous as well as viscoplastic rheologies. The implementations of complex, multi-material rheologies are verified with well-known 2D benchmarks and multi-material viscoplasticity is applied in 3D time-dependent thermomechanical models of oceanic subduction. Subsequently, Glerum uses ASPECT to investigate the sensitivity of horizontal surface motions to individual geodynamic processes in the eastern Mediterranean. Identification of all mantle drivers that should participate in modeling attempts to explain observations of crustal flow is essential to fully exploit the information contained by surface motions about their driving processes. Glerum therefore employs 3D data-driven instantaneous dynamics models of compressible flow including a complete set of possible mantle drivers of surface deformation. The reference instantaneous flow model results indicate that mantle processes can explain a large part of the crustal motion of the Aegean-Anatolian microplate. Subsequent systematic perturbations of model properties with respect to this reference model help estimate the individual contributions of tectonic plate motions, slab pull and trench suction, and density-induced mantle flow interacting with the slab and overlying plates while moderated by the mantle’s bulk viscosity. In order of regional importance, the predicted crustal flow of the Aegean-Anatolian region is most sensitive to slab pull, followed by slab-mantle interaction and basal drag, mantle rheology, and the absolute plate motion reference frame. Lastly, Glerum demonstrates a possible mechanism for the counterclockwise rotation of the Victoria microplate in the East African Rift System, which is in striking contrast to the clockwise motion of the surrounding plates. 3D models of the divergent system show that Victoria’s rotation can be caused by the drag of the African and Somalian plates along the strong edges of the microplate, while the rift segments along inherited lithospheric weaknesses facilitate Victoria’s rotation. The amount of rotation is therefore primarily controlled by the distribution of preexisting stronger regions and the weaker Precambrian mobile belts that surround Victoria. The induced counterclockwise rotation of the microplate leads to a clockwise shift of the local extension direction from E-W to more WNW-ESE along the overlapping rift branches. Comparison of the resulting predicted stress field and tectonic regimes to observations helps to elucidate the interpretation of local stress and strain indicators and to reconcile different opening models used to interpret the East African Rift System.

Compared to continental lithosphere, oceanic lithosphere has a limited lifespan at the Earth’s surface. As a result of its continuous subduction and formation at mid-ocean ridges, modern oceanic crust is almost nowhere older than ~200 Ma. This implies that the lithosphere that was underlying ancestral oceans, such as the Panthalassa Ocean surrounding Pangea during its culmination in late Paleozoic – early Mesozoic times, has (almost) all been lost to subduction. As a result, deep-time plate tectonic reconstructions rely primarily on geological, paleontological and paleomagnetic data from the continents. Such reconstructions portray the distribution of plates that host continents through geological time, but generally lack (or include only conceptual) plate motions and -geometry in the oceanic domains. In this thesis, approaches are developed and data is collected that improve deep-time global plate kinematic reconstructions of the Panthalassa Ocean through quantitative restoration of lost oceanic plates. First, all available data from oceanic lithosphere of the present-day descendant of the Panthalassa, the Pacific Ocean, that did not (yet) subduct is used. The oldest part of the Pacific Plate, which originated in Jurassic time, contains magnetic lineations in three orientations that constrain relative plate motions of three conceptual plates conjugate to the Pacific (Izanagi in the northeast, Farallon in the northeast and Phoenix in the south) back to ~190 Ma. In chapter 1, the plate tectonic configuration that led to the birth of the Pacific Plate is reconstructed. Second, the location and tectonic nature of the boundaries of the Panthalassa Ocean through time are defined, which relies on reconstruction of Pangea’s (and post-Pangea’s) external trenches relative to the surrounding continents, and involves the restoration of complex crustal deformation at subduction plate boundary zones. In chapters 2-5 regional reconstructions are presented of the Pacific margin of Mexico and Caribbean region. The third step involves the use of data from fully subducted lithosphere. This includes paleomagnetic and stratigraphic data from ‘Ocean Plate Stratigraphy’ materials that were scraped off during subduction and are now exposed in the circum-Panthalassa accretionary complexes. Furthermore, seismic tomographic images reveal the locations of subducted material in the mantle that are correlated to reconstructed intra-oceanic or continental margin subduction zones, thereby constraining the position of these subduction zones relative to the mantle. Chapters 6 and 7 present reconstructed Permian-Cretaceous plate motions of the Farallon, Izanagi and Phoenix plates based on paleomagnetic data from OPS remnants exposed in the accretionary prisms of Mexico, Costa Rica, Japan and New Zealand, as well as of an intra-oceanic subduction zone of which the remnant arc is exposed in Japan.

The Gobi Altai region of southern Mongolia has been in the Eurasian plate interior since the mid-Mesozoic, yet has experienced episodic phases of deformation since that time. In this paper, we document field evidence to characterize and date the intra-plate tectonic history of the Gobi Altai region from the Triassic to the present. To this end, we provide detailed mapping of the structure and stratigraphy of the eastern flanks of Mt. Ih Bogd that contains the widest variety of rock-time units in the area. We carry out geochronological analysis of basaltic lavas and basement granite in the area. We demonstrate that a crystalline basement with a 502 ± 8 Ma granitoid (U/Pb) underwent two phases of basin formation in the Mesozoic, which we date with new 40Ar/39Ar lava ages of 218.5 ± 1.5, 123.2 ± 0.7 and 124.8 ± 1.2 Ma, respectively. Both phases are linked to deposition of fluvio-lacustrine sediments and trap-like basaltic volcanics, with cumulative thicknesses of 1000–1500 m. Both basins were likely north-facing half-grabens that developed under ∼N–S extension, but were subsequently overthrusted by Paleozoic and older crystalline basement during a less well constrained, but likely mid-Cretaceous phase of N–S shortening and basin inversion. Our results are consistent with recent seismic imaging of rift basins ∼100 km to the NE of the study area where a similar history was reconstructed. The multiple phases of intra-plate deformation appear to have parallel structural trends, most likely due to reactivated Paleozoic basement structures created during the original terrane amalgamation of the Central Asian Orogenic Belt continental crust. This strong basement heterogeneity may predispose it to reactivation, and make it sensitive to changes in the overall stress field of the Eurasian plate driven by forces at its margins and base. Detailed study of Mongolia's multi-stage tectonic history may thus provide a key proxy for the long-term dynamics of the Eurasian plate. In addition, the repeated reactivation of the Gobi Altai region during the last 200 My supports the contention that non-cratonized continental interior regions composed of Phanerozoic terrane collages are particularly susceptible to fault reactivation, much more than older cratonized continental crust.

I present a new family of analytical flow solutions to the incompressible Stokes equation in a spherical shell. The velocity is tangential to both inner and outer boundaries, the viscosity is radial and of power-law type, and the solution has been designed so that the expressions for velocity, pressure, and body force are simple polynomials and therefore simple to implement in (geodynamics) codes. Various flow average values, e.g. the root mean square velocity, are analytically computed. This forms the basis for a numerical benchmark for convection codes and I have implemented it in two finite element codes ASPECT and ELEFANT. I report on error convergence rates for velocity and pressure.

The plate kinematic history of the South China Sea opening is key to reconstructing how the Mesozoic configuration of Panthalassa and Tethyan subduction systems evolved into today's complex Southeast Asian tectonic collage. The South China Sea is currently flanked by the Palawan Continental Terrane in the south and South China in the north and the two blocks have long been assumed to be conjugate margins. However, the paleogeographic history of the Palawan Continental Terrane remains an issue of uncertainty and controversy, especially regarding the questions of where and when it was separated from South China. Here we employ detrital zircon U–Pb geochronology and heavy mineral analysis on Cretaceous and Eocene strata from the northern South China Sea and Palawan to constrain the Late Mesozoic–Early Cenozoic provenance and paleogeographic evolution of the region testing possible connection between the Palawan Continental Terrane and the northern South China Sea margin. In addition to a revision of the regional stratigraphic framework using the youngest zircon U–Pb ages, these analyses show that while the Upper Cretaceous strata from the Palawan Continental Terrane are characterized by a dominance of zircon with crystallization ages clustering around the Cretaceous, the Eocene strata feature a large range of zircon ages and a new mineral group of rutile, anatase, and monazite. On the one hand, this change of sediment compositions seems to exclude the possibility of a latest Cretaceous drift of the Palawan Continental Terrane in response to the Proto-South China Sea opening as previously inferred. On the other hand, the zircon age signatures of the Cretaceous–Eocene strata from the Palawan Continental Terrane are largely comparable to those of contemporary samples from the northeastern South China Sea region, suggesting a possible conjugate relationship between the Palawan Continental Terrane and the eastern Pearl River Mouth Basin. Thus, the Palawan Continental Terrane is interpreted to have been attached to the South China margin from the Cretaceous until the Oligocene oceanization of the South China Sea. In our preferred paleogeographic scenario, the sediment provenance in the northeastern South China Sea region changed from dominantly nearby Cretaceous continental arcs of the South China margin to more distal southeastern South China in the Eocene.

Along-strike variations in orogenic development can be difficult to constrain. Resulting assumptions projecting similarity or variability along strike can lead to erroneous conclusions at the orogen scale. Young orogens provide opportunities to document limits of along-strike projection and test factors that may control lateral variability. Here we present new constraints on the history of uplift, exhumation and shortening in the Timor orogen from West Timor, Indonesia. Structural mapping documents a foreland thrust stack of Jurassic-Miocene Australian margin strata and a hinterland antiformal stack of Permo-Triassic Australian continental units duplexed below Banda Arc lithosphere. Biostratigraphy within the piggyback Central Basin reveals earliest deepwater synorogenic deposition at 5.57–5.53 Ma, uplift from lower to middle bathyal depths at 3.35–2.58 Ma, and uplift from middle to upper bathyal depths at 2.58–1.30 Ma. Hinterland Permo-Triassic strata yield apatite (U-Th)/He ages of 0.33–2.76 Ma, apatite fission track ages of 2.19–3.53 Ma and partially reset zircon (U-Th)/He ages. These thermochronology ages are youngest or most strongly reset in the center of the antiformal stack and yield modeled exhumation rates of 0.45–3.31 km/Myr. A balanced cross section reveals a minimum of 300 km of shortening including 210 km of Australian continental subduction below the Banda forearc. When compared to published results from Timor-Leste, these data show that the timing of initial collision, synorogenic basin uplift, and total shortening amount were broadly similar across the island. Therefore, despite along-strike changes in orogen morphology and significant small-scale spatial variability in deformation, first-order structural similarity dominates at large scales. We suggest that along-strike variations in orogen morphology are due to changes in the distribution of deformation within the orogen driven by differences in backstop strength, internal wedge strength and basal decollement friction as well as the presence of the wedge-top Central Basin in West Timor.

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River Project (2001–2010) and present new data which leads to a revised stratigraphical model for the Early Pleistocene development of this fluvial system. In previous work we confirmed the preservation of eleven buried Early Pleistocene fluvial terraces of the Gediz River (designated GT11, the oldest and highest, to GT1, the youngest and lowest) which lie beneath the basalt-covered plateaux of the Kula Volcanic Province. Deciphering the information locked in this fluvial archive requires the construction of a robust geochronology. Fortunately, the Gediz archive provides ample opportunity for age-constraint based upon age estimates derived from basaltic lava flows that repeatedly entered the palaeo-Gediz valley floors. In this paper we present, for the first time, our complete dataset of 40Ar/39Ar age estimates and associated palaeomagnetic measurements. These data, which can be directly related to the underlying fluvial deposits, provide age constraints critical to our understanding of this sequence. The new chronology establishes the onset of Quaternary volcanism at ∼1320ka (MIS42). This volcanism, which is associated with GT6, confirms a pre-MIS42 age for terraces GT11-GT7. Evidence from the colluvial sequences directly overlying these early terraces suggests that they formed in response to hydrological and sediment budget changes forced by climate-driven vegetation change. The cyclic formation of terraces and their timing suggests they represent the obliquity-driven climate changes of the Early Pleistocene. By way of contrast the GT5-GT1 terrace sequence, constrained by a lava flow with an age estimate of ∼1247ka, span the time-interval MIS42 – MIS38 and therefore do not match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruptions and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lava-dammed lake drainage. Establishing a firm stratigraphy and geochronology for the Early Pleistocene archive provides a secure framework for future exploitation of this part of the archive and sets the standard as we begin our work on the Middle-Late Pleistocene sequence. We believe this work forms a benchmark study for detailed Quaternary research in Turkey.

A conspicuous 60° bend of the Hawaiian-Emperor Chain in the north-western Pacific Ocean has variously been interpreted as the result of an abrupt Pacific plate motion change in the Eocene (∼47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of these two causes. Palaeomagnetic data from the Emperor Seamounts prove ambiguous for constraining the Hawaiian hotspot drift, but mantle flow modelling suggests that the hotspot drifted 4–9° south between 80 and 47 Ma. Here we demonstrate that southward hotspot drift cannot be a sole or dominant mechanism for formation of the Hawaiian-Emperor Bend (HEB). While southward hotspot drift has resulted in more northerly positions of the Emperor Seamounts as they are observed today, formation of the HEB cannot be explained without invoking a prominent change in the direction of Pacific plate motion around 47 Ma., The Hawaiian-Emperor Chain has a 60° bend that has been interpreted as the result of Pacific plate motion at 47 Ma or drift of the Hawaiian hotspot. Here, the authors show that hotspot drift cannot be the dominant mechanism for bend formation, but involves a change in the direction of Pacific plate motion at ∼47 Ma.

The eustatic sea-level curves published in the seventies and eighties have supported scientific advances in the Earth Sciences and the emergence of sequence-stratigraphy as an important hydrocarbon exploration tool. However, validity of reconstructions of eustatic sea level based on sequence stratigraphic correlations has remained controversial. Proposed sea level curves differ because of site-to-site changes in local tectonics, depositional rates, and long-wavelength dynamic topography resulting from mantle convection. In particular, the overall amplitude of global Phanerozoic long-term sea level is poorly constrained and has been estimated to vary between ~ 400 m above present-day sea level to ~ 50 m below present-day sea level. To improve estimates of past sea level, we explore an alternative methodology to estimate global sea level change. We utilise the Phanerozoic-Neoproterozoic 87Sr/86Sr record, which at first order represents the mix of inputs from continental weathering and from mantle input by volcanism. By compensating for weathering with estimates of runoff from a 3D climate model (GEOCLIMtec), a corrected 87Sr/86Sr record can be obtained that solely reflects the contribution of strontium from mantle sources. At first order, the flux of strontium from the mantle through time is due to increases and decreases in the production of oceanic crust through time. Therefore, the changing levels of mantle-derived strontium can be used as a proxy for the production of oceanic lithosphere. By applying linear oceanic plate age distributions, we compute sea level and continental flooded area curves. We find that our curves are generally within the range of previous curves built on classical approaches. A Phanerozoic first order cyclicity of ~ 250 Myr is observed that may extend into the Neoproterozoic. The low frequency (i.e., on the order of 10 to 100 My) sea level curve that we propose, while open for improvement, may be used as baseline for refined sequence-stratigraphic studies at a global and basin scale.

In a previous paper, we showed a technique that simplifies Kieffer’s lattice vibrational method by representing the vibrational density of states with multiple Einstein frequencies. Here, we show that this technique can be applied to construct a thermodynamic database that accurately represents thermodynamic properties and phase diagrams for substances in the system MgO–SiO2. We extended our technique to derive shear moduli of the relevant phases in this system in pressure–temperature space. For the construction of the database, we used recently measured calorimetric and volumetric data. We show that incorporating vibrational densities of states predicted from ab initio methods into our models enables discrimination between different experimental data sets for heat capacity. We show a general technique to optimize the number of Einstein frequencies in the VDoS, such that thermodynamic properties are affected insignificantly. This technique allows constructing clones of databases from which we demonstrate that the VDoS has a significant effect on heat capacity and entropy, and an insignificant effect on volume properties.

At two trench segments below the Andes, the Nazca Plate is subducting sub-horizontally over ∼200–300 km, thought to result from a combination of buoyant oceanic-plateau subduction and hydrodynamic mantle-wedge suction. Whether the actual conditions for both processes to work in concert existed is uncertain. Here we infer from a tectonic reconstruction of the Andes constructed in a mantle reference frame that the Nazca slab has retreated at ∼2 cm per year since ∼50 Ma. In the flat slab portions, no rollback has occurred since their formation at ∼12 Ma, generating ‘horse-shoe' slab geometries. We propose that, in concert with other drivers, an overpressured sub-slab mantle supporting the weight of the slab in an advancing upper plate-motion setting can locally impede rollback and maintain flat slabs until slab tearing releases the overpressure. Tear subduction re-establishes a continuous slab and allows the process to recur, providing a mechanism for the transient character of flat slabs., How flat slabs at subduction zones are created remains unclear. Here, the authors show that the Nazca slab has retreated at ∼2 cm per year since 50 Ma but no rollback has occurred in the last ∼12 Myr in the flat slab, implying that an overpressured sub-slab mantle can impede rollback and maintain a flat slab.

The construction of five crustal-scale profiles across the Western Alps and the Ivrea mantle wedge integrates up-to-date geological and geophysical information and reveals important along strike changes in the overall structure of the crust of the Western Alpine arc. Tectonic analysis of the profiles, together with a review of the existing literature allows for proposing the following multistage evolution of the arc of the Western Alps: (1) exhumation of the mantle beneath the Ivrea Zone to shallow crustal depths during Mesozoic is a prerequisite for the formation of a strong Ivrea mantle wedge whose strength exceeds that of surrounding mostly quartz-bearing units, and consequently allows for indentation of the Ivrea mantle wedge and eastward back-thrusting of the western Alps during Alpine orogeny. (2) A first early stage (pre-35 Ma) of the West-Alpine orogenic evolution is characterized by top-NNW thrusting in sinistral transpression causing at least some 260 km displacement of internal Western Alps and E-W-striking Alps farther east, together with the Adria micro-plate, towards N to NNW with respect to stable Europe. (3) The second stage (35–25 Ma), further accentuating the arc, is associated with top-WNW thrusting in the external zones of the central portion of the arc and is related to the lateral indentation of the Ivrea mantle slice towards WNW by some 100–150 km. (4) The final stage of arc formation (25–0 Ma) is associated with orogeny in the Apennines leading to oroclinal bending in the southernmost Western Alps in connection with the 50° counterclockwise rotation of the Corsica-Sardinia block and the Ligurian Alps. Analysis of existing literature data on the Alps–Apennines transition zone reveals that substantial parts of the Northern Apennines formerly suffered Alpine-type shortening associated with an E-dipping Alpine subduction zone and were backthrusted to the NE during Apenninic orogeny that commences in the Oligocene.

We investigate the influence of absolute plate motion on regional 3-D evolution of subduction using numerical thermomechanical modeling. Building on our previous work, we explore the potential impact of four different absolute plate motion frames on subduction evolution in the western Mediterranean region during the last 35 My. One frame is data-based and derived from the global moving hotspot reference frame (GMHRF) of Doubrovine et al. (2012) and three are invented frames: a motion frame in which the African plate motion is twice that in the GMHRF, and two frames in which either the African plate or the Iberian continent is assumed fixed to the mantle. The relative Africa-Iberia convergence is the same in all frames. All motion frames result in distinctly different 3-D subduction evolution showing a critical dependence of slab morphology evolution on absolute plate motion. We attribute this to slab dragging through the mantle forced by the absolute motion of the subducting plate, which causes additional viscous resistance affecting subduction evolution. We observed a strong correlation between increase in northward Africa motion and decrease in the speed of westward slab rollback along the African margin. We relate this to increased mantle resistance against slab dragging providing new insight into propagation and dynamics of subduction transform edge propagator (STEP) faults. Our results demonstrate a large sensitivity of 3-D slab evolution to the absolute motion of the subducting plate, which inversely suggests that detailed modeling of natural subduction may provide novel constraints on absolute plate motions.

Advances in global seismic tomography have increasingly motivated identification of subducted lithosphere in Earth's deep mantle, creating novel opportunities to link plate tectonics and mantle evolution. Chief among those is the quest for a robust subduction reference frame, wherein the mantle assemblage of subducted lithosphere is used to reconstruct past surface tectonics in an absolute framework anchored in the deep Earth. However, the associations heretofore drawn between lower mantle structure and past subduction have been qualitative and conflicting, so the very assumption of a correlation has yet to be quantitatively corroborated. Here we show that a significant, time‐depth progressive correlation can be drawn between reconstructed subduction zones of the last 130 Myr and positive S wave velocity anomalies at 600–2300 km depth, but that further correlation between greater times and depths is not presently demonstrable. This correlation suggests that lower mantle slab sinking rates average between 1.1 and 1.9 cm yr−1., Key Points Significant correlation between reconstructed subduction of the last 130 Myr and mantle structure at 600 to 2300 km depthFurther correlation (beyond 2300 km/130 Ma) not presently demonstrable due to uncertainties in tomographic and paleogeographic modelsSubducted slabs sink through the lower mantle, on average, at rates between 1.1 and 1.9 cm yr−1

Paleogeographic reconstructions place the Chortis block adjacent to southern Mexico in the Late Cretaceous and earlier time, forming the tectonically disturbed southwestern tip of the North American plate. This study assesses the relative motion between Chortis and North America during the Laramide orogeny, later development of the North America-Caribbean plate boundaries. We carried out paleomagnetic analysis of rotations and latitudinal displacement using a total of 90 sites from the Atima Limestone and the Valle de Angeles Formation redbeds sampled at seven localities in Honduras. Two secondary but ancient magnetizations post-date Late Cretaceous folding at most localities. The oldest magnetization is a ChRM of high laboratory unblocking temperature in the redbeds (> 650 °C), and a moderate temperature in the limestones (500–600 °C). This component is WNW directed at five localities, varying somewhat in declination, having a consistent moderate positive inclination (mean I = 39.7°; α95 = 6.8°, n = 53 sites). The age of the ChRM is bracketed between 85 and 63 Ma, based on youngest zircon age and the age of a cross-cutting dike. An intermediate unblocking temperature component present in both units (Dec = 146.2°, Inc = − 28.5°; k = 13.1, α95 = 6.8°, n = 37 sites), is interpreted as an overprint. The ChRM indicates an average counterclockwise rotation of 55.4 ± 5.7°, with respect to the expected direction. The younger overprint was acquired between ~ 50 and 15 Ma; its mean is also discordant with the expected North America direction, implying some Neogene rotation of Chortis. Abundant late Albian-Turonian zircons in Valle de Angeles redbeds explicitly require extending the Laramide arc along western Mexico into Chortis. A reconstruction of Chortis south of Mexico that takes into account 55 degrees of rotation shows a gap between both continental blocks at about 70 Ma. We propose a model where this gap formed by back-arc extension creating the Late Cretaceous Chontal basin at the southern termination of the Laramide flat-slab.

The extended northern continental margin of Africa is currently colliding with and under-thrusting northward below Cyprus. The age of onset of this collision is poorly constrained, but is critical if we are to quantify continental subduction and evaluate its role during spectacular recent uplift of southern Turkey from ~7 Ma to the present. Here, we reevaluate the evolution of northern Cyprus and document the modern structure of the Kyrenia fold-thrust belt in a balanced cross section for the first time, to determine the timing and amount of shortening. The belt deformed an Upper Cretaceous to Miocene stratigraphy, which was deposited onto a metamorphic basement. The fold-thrust belt was previously proposed to have formed during two stages: in Eocene and late Miocene time, based on stratigraphic and limited structural evidence. We revaluate evidence for an Eocene phase of thrusting in Kyrenia and find that 1) repetitions of Eocene and older rocks are explained by Miocene thrusting, and newly documented olistoliths were misinterpreted as pre-Miocene thrust slices 2) uplift in Eocene time was not isolated to Kyrenia but also affected northern Arabia and results from regional dynamic topography or forebulge formation. Based on kinematic constraints from a plate reconstruction, we interpret that metamorphic rocks in Kyrenia were metamorphosed by Cretaceous burial below the Troodos ophiolite and were subsequently exhumed by upper plate extension during latest Cretaceous obduction onto the African margin. The latest Cretaceous-Miocene plate boundary between Africa and the Taurides was located to the north of Kyrenia. The Kyrenia fold-thrust belt accommodated a minimum of 17.5 km of shortening as a result of ~9–6 Ma thrusting as a result of initial Africa-Taurides collision. The northern edge of African continental crust arrived below the Taurides, where it has been seismologically imaged, in late Pleistocene time and may have caused or contributed to recently recognised major Tauride uplift since ~0.5 Ma.

The Payún Matrú Volcanic Field (Pleistocene-Holocene) is located in the Andean back-arc of the Southern Volcanic Zone, western Argentina, and is contemporaneous with the Andean volcanic arc at the same latitude. It includes two polygenetic, mostly trachytic volcanoes: Payún Matrú (with a summit caldera 8 km wide) and Payún Liso (a smaller stratovolcano). The volcanic field includes about 200 scoria cones and alkali basaltic and trachybasaltic lava flows, forming two basaltic fields around Payún Matrú. New 40Ar¯39Ar ages extend the activity of Payún Matrú up to 700 ka. The major and trace element and Sr-Nd isotopic compositions of the basaltic lavas and Payún Matrú rocks indicate that the trachytes of Payún Matrú are the result of fractional crystallization of basaltic parent magmas without significant upper crustal contamination, and that the basalts have a geochemical similarity to ocean island basalt (La/Nb=0·8-1·5, La/Ba =0·05-0·08). The Sr-Nd isotopic compositions of the basaltic to trachytic rocks range between 0·703813 and 0·703841 (87Sr/86Sr) and 0·512743 and 0·512834 (143Nd/144Nd). Mass-balance and Rayleigh fractionation models support the proposed origin of the trachytes, and an assimilation-fractional crystallization model indicates a low degree of upper crustal contamination in the youngest trachytes. Magnesium numbers (45-55) and contents of Ni(, Facultad de Ciencias Naturales y Museo, Centro de Investigaciones Geológicas

International audience; The Andaman Ophiolite remained little explored for long but recent studies yielded important first-order findings that hold promise for further research. Here we summarise these first-order constraints on the structure, geochemistry, and evolution of the Andaman Ophiolite and identify key frontiers for future research. The uniqueness of Andaman Ophiolite is their petrological and geochemical diversity in a 1 2 D. B a n d y o p a d h y a y e t a l. close spatial association. Among many unresolved issues the age, stratigraphic coherence , and emplacement mechanisms of Andaman Ophiolite remain enigmatic. In particular , although many of the elements of the typical ophiolitic pseudostratigraphy are present, they are not found in structural coherence, and available geochronological constraints suggest a much longer than normal time window for the amalgamation of the ophiolite's crust. We raise questions on the plate tectonic setting and evolution of the ophiolite, suggesting that a multi-phase history of magmatism and ophio-lite evolution is one of the key questions that deserves international geoscientific attention.

In many fold‐thrust belts, cross section–derived shortening estimates are significantly lower than predicted based on plate convergence. This has led to controversial hypotheses that shortening may be largely underestimated due to wholesale underthrusting (convergence without shortening) below far‐traveled continent or ocean‐derived nappes. The Late Cretaceous‐Eocene Taurides fold‐thrust belt (southern Turkey) may contain a highly incomplete shortening record of convergence likely caused by wholesale underthrusting. To estimate this underthrusting, we calculate convergence across the belt using a map‐view palinspastic reconstruction that takes into account major rotations of tectonic units during their accretion. We use paleomagnetic and fault kinematic analysis, timing of accretion, and Africa‐Eurasia convergence to constrain our reconstruction. Our paleomagnetic results confirm an ~40° clockwise vertical axis rotation of the Geyikdagi nappe that forms the core of the belt, which we interpret is accommodated by a lateral gradient in underthrusting on faults structurally above and below the Geyikdagi nappe. We reconstruct ~400–450 km of convergence across the Taurides during their accretion. We compare this predicted convergence to shortening calculated from balanced cross sections, in which we reconstruct a minimum of 154‐km shortening: 57 km within far‐traveled nappes, 70‐km thrusting of far‐traveled nappes over the Geyikdagi nappe, and 27‐km shortening within the Geyikdagi nappe. Shortening in the Taurides created a significant nappe stack, but the majority of convergence was accommodated by wholesale underthrusting with barely a trace at the surface, including ~160 km of convergence by rotation of the belt, and 90–130 km related to missing Africa‐Eurasia convergence.

Turkey contains a high, flat region known as the Central Anatolian Plateau, which formed in multiple phases over the past 8 million years. This high plateau formed in the upper plate of a subduction zone, above the subducting African plate. There has been great scientific interest in kilometre-scale rise of this plateau as an ideal place to study the interplay between subduction dynamics and surface uplift. The precise cause of uplift however, is hotly debated, and forms part of a wider debate in earth sciences: what drives the formation of high topography? The southern mountainous margin of the Central Anatolian Plateau is known as the Tauride Mountains. This mountain belt may contain a long-term geological record of subduction below Central Anatolia. In this thesis, I aim to use this record to establish the initial geodynamic conditions of plateau rise. To do this, I reconstruct the kinematic evolution of the Taurides fold-thrust belt and surrounding regions using balanced cross sections, fault kinematic observations, paleomagnetic data, and plate reconstructions. In addition, I use low-temperature thermochronology to constrain the surface evolution that followed the formation of the Taurides. I constrain the orogenic and topographic evolution of the plateau crust for the past ~100 million years, and define the subduction configuration at the onset of plateau rise. Previous models that aimed to explain plateau rise lacked these constraints, and therefore assumed initial geodynamic conditions that were inconsistent with the modern architecture and long-term evolution of Turkey. I conclude that the rise of the Central Anatolian Plateau occurred as a result of the interplay of four processes, on different temporal and spatial scales: 1) Local, slow crustal delamination in the western Central Taurides; 2) Previously proposed ‘drip-delamination’ in Central Anatolia; 3) Break-off of the African slab below southern Turkey; 4) Collision of the African continental margin in the southern Taurides and Cyprus.

Global tectonic reconstructions of pre‐Cenozoic plate motions rely primarily on paleomagnetic and geological data from the continents, and uncertainties increase significantly with deepening geological time. In attempting to improve such deep‐time plate kinematic reconstructions, restoring lost oceanic plates through the use of geological and seismic tomographical evidence for past subduction is key. The North American Cordillera holds a record of subduction of oceanic plates that composed the northeastern Panthalassa Ocean, the large oceanic realm surrounding Pangea in Mesozoic times. Here we present new paleomagnetic data from subduction‐related rock assemblages of the Vizcaíno Peninsula of Baja California, Mexico, which yield a paleolatitudinal plate motion history equal to that of the North American continent since Late Triassic time. This indicates that the basement rocks of the Vizcaíno Peninsula formed in the forearc of the North American Plate, adjacent to long‐lived eastward dipping subduction at the southern part of the western North American continental margin. Tomographic images confirm long‐lived, uninterrupted eastward subduction. We correlate episodes of overriding plate shortening and extension to flat and steep segments of the imaged slab. By integrating paleomagnetic, geological, and tomographic evidence, we provide a first‐order model that reconciles absolute North American plate motion and the deformation history of Mexico since Late Triassic time with modern slab structure.

In their recent paper, Barnett-Moore et al. (2016) reflect on current models of Iberian plate motion in the Jurassic and Cretaceous as well as ongoing debates on the reliability of the various types of kinematic data that form independent constraints on Iberia's motion relative to Eurasia. They question the validity of various marine geophysical, seismic, tomographic, geological, and paleomagnetic data sets from the Bay of Biscay, Central Atlantic Ocean, and Iberia for kinematic reconstruction of Iberia and conclude that neither models invoking Aptian-Albian transtension, nor compression, are consistent with currently available data. An important element in their analysis is that they discard the large paleomagnetic data set from the Jurassic and Cretaceous from Iberia based on perceived limitations of that data set. In addition, they argue that seismic tomographic images exclude a scenario of subduction in the Aptian-Albian in the Pyrenees, and based on this "question the validity of current plate reconstructions, their constraints, and geodynamic scenarios, which are in support of this scenario [e.g., Vissers et al., 2016]." We welcome the discussion raised by Barnett-Moore et al. (2016) on the reliability and usefulness of paleomagnetic data as independent constraint for Iberia's plate motion in the Mesozoic. Taking these paleomagnetic data at face value, Vissers et al. (2016) recently showed that these are consistent with an ~40° counterclockwise rotation of Iberia in the Aptian, requiring up to 500 km of Aptian convergence across the Pyrenees, that is, through subduction. In this comment, we aim to critically assess whether and how the concerns on the quality of paleomagnetic data raised by Barnett-Moore et al. (2016) may allow for an alternative explanation, particularly one with a Mesozoic rotation of Iberia that is small enough so as to not requiring subduction. We also reassess whether seismic tomographic images indeed refute subduction scenarios, using 8 S wave and P wave tomographic models including those used in Barnett-Moore et al. (2016).

Seismic travel-time tomography of the mantle under SE Asia reveals patterns of subduction-related seismic P-wave velocity anomalies that are of great value in helping to understand the region's tectonic development. We discuss tomography and tectonic interpretations of an area centred on Indonesia and including Malaysia, parts of the Philippines, New Guinea and northern Australia. We begin with an explanation of seismic tomography and causes of velocity anomalies in the mantle, and discuss assessment of model quality for tomographic models created from P-wave travel times. We then introduce the global P-wave velocity anomaly model UU-P07 and the tectonic model used in this paper and give an overview of previous interpretations of mantle structure. The slab-related velocity anomalies we identify in the upper and lower mantle based on the UU-P07 model are interpreted in terms of the tectonic model and illustrated with figures and movies. Finally, we discuss where tomographic and tectonic models for SE Asia converge or diverge, and identify the most important conclusions concerning the history of the region. The tomographic images of the mantle record subduction beneath the SE Asian region to depths of approximately 1600 km. In the upper mantle anomalies mainly record subduction during the last 10 to 25 Ma, depending on the region considered. We interpret a vertical slab tear crossing the entire upper mantle north of west Sumatra where there is a strong lateral kink in slab morphology, slab holes between c.200–400 km below East Java and Sumbawa, and offer a new three-slab explanation for subduction in the North Sulawesi region. There is a different structure in the lower mantle compared to the upper mantle and the deep structure changes from west to east. What was imaged in earlier models as a broad and deep anomaly below SE Asia has a clear internal structure and we argue that many features can be identified as older subduction zones. We identify remnants of slabs that detached in the Early Miocene such as the Sula slab, now found in the lower mantle north of Lombok, and the Proto-South China Sea slab now at depths below 700 km curving from northern Borneo to the Philippines. Based on our tectonic model we interpret virtually all features seen in upper mantle and lower mantle to depths of at least 1200 km to be the result of Cenozoic subduction.

The Central Anatolian Crystalline Complex (CACC) is a large continental domain exposed in central Turkey that was affected by high temperature metamorphism during the Late Cretaceous. As a result of this event, Paleozoic sediments became metamorphosed, initially under Barrovian conditions, then overprinted locally by high temperature–low pressure metamorphism, and intruded by widespread batholiths. In this study we focus on the crystalline Hirkadag Massif located in the central part of the CACC, where we applied an integrated approach involving metamorphic, structural and geochronological analysis in order to elucidate its tectonic history from burial to exhumation. Our metamorphic study reveals that conditions of metamorphism reached ~ 7–8 kbar/700 °C and were relatively homogeneous at the scale of the Hirkadag Massif. Coeval with the regional metamorphism, the rocks were intensely deformed as reflected by isoclinal folding, the development of a pervasive foliation and top-to-the-SE shearing. This was followed by decompression to pressures of ~ 3–4 kbar at 800 °C, which may be linked to the emplacement of local granodioritic intrusions at ~ 77 Ma. Subsequent cooling of the Hirkadag high-grade metamorphic and intrusive rocks is indicated by 40Ar/39Ar cooling ages of 68.8 ± 0.9 Ma (biotite) and 67.0 ± 1.2 Ma (potassium feldspar). Evidence for tectonic exhumation has been identified within the marbles at the NE margin of the Hirkadag Massif, in the form of discrete protomylonitic and mylonitic shear bands showing a consistent N40–60 top-to-NE sense of shear. Further east, the contact between brecciated mylonitic marbles and non-metamorphic conglomerates preserves the typical structural features of an upper-crustal detachment fault. Restoration of the Hirkadag Massif and the CACC to their late Cretaceous configuration suggests that the LP–HT metamorphism, magmatism and extensional structures evolved as a result of the development and exhumation of a ~ N–S trending magmatic arc experiencing regional E–W extension above an active subduction zone.

Kinematic reconstruction of modern ocean basins shows that since Pangea breakup a vast area in the Neotethyan realm was lost to subduction. Here we develop a first-order methodology to reconstruct the kinematic history of the lost plates of the Neotethys, using records of subducted plates accreted to (former) overriding plates, combined with the kinematic analysis of overriding plate extension and shortening. In Cretaceous-Paleogene times, most of Anatolia formed a separate tectonic plate—here termed “Anadolu Plate”—that floored part of the Neotethyan oceanic realm, separated from Eurasia and Africa by subduction zones. We study the sedimentary and structural history of the Ulukisla basin (Turkey); overlying relics of this plate to reconstruct the tectonic history of the oceanic plate and its surrounding trenches, relative to Africa and Eurasia. Our results show that Upper Cretaceous-Oligocene sediments were deposited on the newly dated suprasubduction zone ophiolites (~92 Ma), which are underlain by melanges, metamorphosed and nonmetamorphosed oceanic and continental rocks derived from the African Plate. The Ulukisla basin underwent latest Cretaceous-Paleocene N-S and E-W extension until ~56 Ma. Following a short period of tectonic quiescence, Eo-Oligocene N-S contraction formed the folded structure of the Bolkar Mountains, as well as subordinate contractional structures within the basin. We conceptually explain the transition from extension, to quiescence, to shortening as slowdown of the Anadolu Plate relative to the northward advancing Africa-Anadolu trench resulting from collision of continental rocks accreted to Anadolu with Eurasia, until the gradual demise of the Anadolu-Eurasia subduction zone.