Search

Plate subduction links the Earth’s surface and interior and may change the redox state of the Earth’s mantle. Mantle wedges above subduction zones have high oxygen fugacity compared with other mantle reservoirs, but the cause is debated. Here we analyze high-pressure metamorphic rocks derived from ferromanganese pelagic sediments in the Qilian subduction complex, northwest (NW) China. We show that progressive metamorphism is a process of reducing reactions, in which Mn4+ is reduced to Mn2+. On the global scale, such reactions would release significant amounts of oxygen (~1.27 × 1012 g year−1), estimated from the global flux of MnO in sediments passing into subduction zones. This budget is sufficient to raise the oxygen fugacity of the mantle wedge, hence arc magmas, to a higher level than other mantle reservoirs. In contrast, ferric iron (Fe3+) enters hematite, aegirine, and garnet, without valence change and plays little role in the oxidation of the mantle wedge. Fe3+ remains stable to depths of >100 km but will transfer to the deeper mantle along with the subducting slab. The manganese reduction process provides a new explanation for high oxygen fugacity in the mantle wedge.

Quantifying the rhythms and rates of magmatic-hydrothermal systems is critical for a better understanding of their controls on ore formation and the dynamics of magmatic reservoirs that feed them. We reconstructed the evolution of ore-forming fluids using hydrothermal quartz from the 17.4 Ma Zhibula skarn, Tibet. Ion probe analysis reveals sharp and dramatic changes in quartz δ18O values between 5‰ and −9.3‰, with fluid δ18O values varying between 2.8‰ and −18.2‰, which are best explained by transient meteoric water incursion into a hydrothermal system dominated by magmatic fluids. Two pulses of magmatic fluids and a meteoric water incursion event are inferred, which operated at the millennium scale (760−1510 yr) as constrained by the aluminum diffusion chronometer. Our results indicate that magmatic reservoirs are likely water unsaturated for most of their lifetime (>105−106 yr), with transient and episodic fluid exsolutions (~103 yr) being driven by magma replenishment or crystallization-induced water saturation. With focused and efficient metal deposition, multiple pulses of metalliferous fluids favor the formation of giant deposits with high grade. Meteoric water δ18O values (−25.4 ± 2.3‰) derived from Zhibula quartz further suggest a paleo-elevation of 5.9 ± 0.3 km; this transient early Miocene surface uplift plausibly was due to break-off of the oceanic slab attached to the Indian Plate. Our research highlights that ubiquitous hydrothermal quartz in orogenic belts can probe the dynamics of magmatic-hydrothermal systems and also quantify paleo-elevations, which has significant tectonic implications.

The Arabia-Eurasia collision, which started during Late Eocene (~35 Ma) or afterward across the Bitlis-Zagros suture, resulted in the formation of the Turkish – Iranian Plateau. Even though the average elevation throughout the plateau is around 2 km, the lithospheric structures between East Anatolian and the Iranian parts may be different. For instance, seismological studies suggest that East Anatolia is underlain by anomalously low-speed anomalies/hot asthenosphere whereas the Iranian part is associated with a rather thick (>200 km in some places) and strong lithosphere. Therefore, the area may be regarded as two distinct regions, namely, the East Anatolian Plateau and the Iranian Plateau. The growth of the plateau is mostly attributed to slab break-off combined with crustal shortening. Other processes often associated with the collision are lithospheric delamination and tectonic escape of microplates. These hypotheses suggested for the growth of the plateau are yet to fully explain the dualistic nature of the lithosphere in a region where elevations are roughly similar. In this work, by using 2D numerical experiments we aim to investigate the physical, geometric, and rheological parameters affecting the deformation of the plate during pre-, syn-, and post-collision. Our preliminary model results show an extension (up to ~70 km) on the terrane that is dragged behind the subducting plate, while the overriding plate undergoes shortening during the collision. The collision results in ~100 km of underthrusting in 50 Myrs which is in the range for the measured amounts of underthrusting across the plateau. We aim to expand the study by creating comparative model sets (i.e., models representing East Anatolia vs. models representing Iran) with a parameterization of varying lithospheric structures (e.g., different crust and mantle thicknesses), and strength profiles, which will help us to understand the kinematics and dynamics of such orogenic growth.

The development of trench-arc-backarc (TABA) systems is uniquely associated with modern-style plate tectonics on Earth. The Qilian orogenic belt in NW China records the evolution history of the Proto-Tethys Ocean at the transition time from the Proterozoic to Phanerozoic. This paper presents systematic studies of petrography, U-Pb chronology and geochemistry on various rocks from a MOR-type ophiolite belt, active continental margin and back-arc basin in the Qilian orogenic belt to address the development of a modern-style TABA system. Arc magmas include felsic intrusions with ages of 530–477 Ma and felsic-mafic arc volcanic rocks with ages of 506–439 Ma, showing distinctive features of typical magmatic rocks formed at an Andean-type continental margin. The back-arc basin is recorded by a 490–448 Ma SSZ-type ophiolite with boninite, and Silurian turbidite flysch formation. We establish a three-stage tectonic history from the initiation of subduction to the formation of a mature Japan-Sea-type back-arc basin at the active continental margin in the Early Paleozoic era. (1) Northward subduction of Proto-Tethys Ocean initiated and the Andean-type continental arc developed at ~530–500 Ma with continual crustal thickening; (2) a tectonic transition occurred from an Andean-type active continental margin to a West Pacific-type active continental margin at ~500–490 Ma with rapid thinning of crust to ~35 km, and (3) mature ocean basins and back-arc-basin (BAB) ophiolites were formed in the back-arc extensional environment at ~ 490–450 Ma.

Subduction and closure of the Proto-Tethys and Palaeo-Tethys oceans were important events in the assembly of Eurasia, and created the Central China Orogenic Belt (CCOB). This paper presents a new tectonic model for the CCOB in which we propose that elongate Precambrian basement blocks within the CCOB were originally part of a single ribbon continent, here named K-Qubed after the Kunlun-Qaidam-Qilian-Qinling regions. K-Qubed separated from the South China Block in the Neoproterozoic. Dextral-oblique subduction of the Proto-Tethys Ocean took place southwards (present co-ordinates) under K-Qubed in latest Precambrian - Cambrian times (ca. 550–500 Ma). Subduction-accretion complexes were generated alongside the basement, while arc magmatism overprinted both basement and accretionary crust. Initial collision of the northern side of the ribbon continent and the North China and Tarim blocks occurred at ca. 500 Ma. High-pressure and ultrahigh-pressure metamorphism resulted by ca. 490 Ma, in the North Qilian, South Altun/North Qaidam and North Qinling regions. Collision triggered a flip in subduction polarity, and caused a subduction-accretion complex and magmatic arc to build out southwards from K-Qubed, as Palaeo-Tethys was consumed northwards in the Ordovician. Magmatic timings were similar between different tectonic units; twin peaks in magmatism at ca. 500–490 Ma and ca. 440–430 Ma occurred in several terranes. Oblique subduction caused strain partitioning, in turn causing slivering and across-strike repetition of basement and accretionary crust. Tectonic units in the Qilian Shan and Kunlun can be partly correlated with equivalents in the Qinling Orogen. We suggest a match between the North Qilian Orogenic Belt and the Erlangping Unit, between the Central Qilian Block and the North Qinling Belt, between the South Qilian Accretionary Belt and the Shangdan Suture Zone. Basement terranes of the Qaidam region and the East Kunlun Orogen have no obvious lateral equivalents in the Qinling, and are truncated at the eastern margins by the West Qinling Belt. There are similar ages for peak metamorphism at ca. 440–420 Ma in an eclogite belt in the North Qaidam Ultra High-pressure Metamorphic Belt (NQUB) and eclogite localities in the East Kunlun Orogen. We interpret this metamorphism to be result of slab break-off beneath the K-Qubed continent, with metamorphic rocks repeated across-strike by dextral shear. The component of Precambrian crust in the Kunlun diminishes westwards into the West Kunlun, where Early Palaeozoic accretion of crust was more continuous. A magmatic gap throughout the CCOB between ca. 370 and ca. 290 Ma was possibly related to extremely oblique and/or slow plate convergence, or represents a time through which subduction stopped. Renewed northwards subduction of the Palaeo-Tethyan Ocean took place under the south side of the Kunlun and Qinling in the Permian, completed by Triassic collisions of the Qiangtang and South China blocks with the southern side of the CCOB. This model for the CCOB is an alternative to collisional and accretionary end members for orogeny, whereby oblique subduction and collision of a ribbon continent produces interleaving of basement and more juvenile terranes. Closure of Proto-Tethys did not involve multiple, separate and synchronous subduction zones, or repetition of a subduction zone by oroclinal bending, as previously proposed.

Intra-oceanic arcs are one of the major building blocks of continents, and the rarely exposed calc-alkaline plutons in intra-oceanic arcs are a critical component of arc crust. These calc-alkaline plutons provide juvenile crustal materials to the continental crust, and thus their petrogenesis has important implications for the formation and evolution of continental crust. Here, we present the results of an integrated study, involving field investigation, petrology, geochronology and geochemistry, on calc-alkaline intermediate–felsic plutons and their mafic magmatic enclaves (MMEs) within a Proto-Tethyan intra-oceanic arc in the Lajishan terrane of the Qilian Orogen, northern Tibetan Plateau. These calc-alkaline intermediate–felsic plutons range from gabbroic diorites, through diorites, to granodiorites. In situ zircon U–Pb dating demonstrates that these plutons were emplaced in the Early Paleozoic (474–460 Ma), slightly older than previously identified 460–440 Ma intra-oceanic arc volcanics (boninites, ankaramites, high-Mg basaltic andesites, high-Al andesites, sanukites) in the Lajishan terrane. The geochemistry of these plutons indicates that they were differentiation products of subduction-metasomatized arc mantle-derived melts, and isotope modeling constrains that their mantle source was metasomatized by less than 10% addition of slab-derived fluids/melts. Their parental melts experienced polybaric medium- to high-pressure fractional crystallization to generate the compositional variation of these plutons. There are two types of MMEs according to their different geochemistry (high- and low-MgO MMEs) and both of them are early crystallized melts derived from the heterogeneous subduction-metasomatized arc mantle wedge, captured by evolving magmas. Alkaline high-MgO MMEs represent near-primitive alkaline melts derived from melting of pyroxenite with phlogopite-enriched veins in the heterogeneous arc mantle wedge, while low-MgO MMEs stand for relatively evolved calc-alkaline melts formed during differentiation of the melts parental to their host. The upper crustal construction of this Proto-Tethyan intra-oceanic arc was achieved through earlier emplacement of 474–460 Ma calc-alkaline plutons followed by slightly later eruption of arc volcanics at 460–440 Ma above these plutons. As approximated by the composition of these calc-alkaline plutons and arc volcanics, the upper crustal composition of this Proto-Tethyan intra-oceanic arc is still juvenile and primitive. This juvenile intra-oceanic crust was accreted to continental blocks through arc–continent collision at 440–420 Ma, in response to closure of the Proto-Tethys Ocean. The accreted intra-oceanic crust represents addition of juvenile crustal materials to existing continents and has remained primitive and intact, which could be balanced by other more evolved crustal components to form a mature bulk continental crust.

Mantle plumes are thought to play key roles in Earth's geodynamics, including mantle convection, continental formation, and plate tectonics. The connection between plume activity and continental dispersion, as exemplified by the breakup of Gondwana and the generation of the Neo-Tethys Ocean, is a key question for the geosciences. Here, we present detailed investigations for the picrite-basalt sequence in the Baoshan-Gongshan Block of the northern Sibumasu terrane, southwest China. Field relations and petrological and geochemical data reveal that these volcanic rocks are continental flood picrites and basalts, consistent with a mantle plume origin. The estimated mantle potential temperatures range from 1527 ± 86 °C to 1546 ± 98 °C, and melting depths vary from the spinel to garnet stability fields (1.1–5.3 GPa), similar to Cenozoic Hawaiian picrites. Zircon geochronological data show that the mantle plume activity started at ca. 335 Ma and lasted to 280 Ma; this range is earlier than the breakup of the Gondwana continent and opening of the Neo-Tethys Ocean (270–260 Ma). We conclude that the long-lived mantle plume impacted the continental lithosphere but it did not drive continental breakup and the opening of Neo-Tethys Ocean, which took place because of the subduction-induced stress generated by initial subduction of the Paleo-Tethys Ocean.

The great M ~ 8 1920 Haiyuan earthquake (HYEQ) was one of the largest and most deadly earthquakes in China in the last century, with ~ 234,000 deaths. The earthquake occurred within the Loess Plateau of northern China, where Quaternary loess deposits form a distinctive blanket across the landscape. Large regions of this loess cover experienced co-seismic landslides. Based on an analysis of the original disaster reports, field surveys, and satellite image interpretation, we have compiled the shaking effects of the earthquake, including the distribution of landslides, fatalities, and structural damage. Landslides triggered by the HYEQ (n > 7,000) are concentrated south of the Haiyuan fault, in a region that has both thick loess cover and long-term relief generated by the drainage network. This distribution is spatially separated from landslides triggered by other earthquakes. We find that in contrast to previous studies, the most important factor in the severe death toll of the HYEQ was the collapse of housing by ground shaking, including collapse of loess house-caves. Landslides were a secondary factor; although up to 32,000 deaths occurred in areas with intense landsliding. Based on the revised distribution pattern of landslides and damage (e.g., house collapses), we suggest that the isoseismal intensity IX line extends south of previous locations. We have also identified 126 dammed lakes created by co-seismic landslides, which form major modifications of this semi-arid landscape. The research methods in this paper, combining historical review, satellite image interpretation, and field validation of landslides, can be used as a reference for studies of other areas affected by historical earthquakes and co-seismic landslides, elsewhere in the Loess Plateau and beyond.

The relationships between large‐scale depositional processes and the stratigraphic record of alluvial systems, e.g. the origin and distribution of channel stacking patterns, changing architecture and correlation of strata, are still relatively poorly understood, in contrast to marine systems. We present a study of the Castillian Branch of the Permo‐Triassic Central Iberian Basin, north‐eastern Spain, using chemostratigraphy and a detailed sedimentological analysis to correlate the syn‐rift Triassic fluvial sandstones for ~80 km along the south‐eastern basin margin. This study investigates the effects of Middle Triassic (Ladinian) Tethyan marine transgression on fluvial facies and architecture. Chemostratigraphy identifies a major, single axially flowing fluvial system lasting from the Early to Middle Triassic (~10 Ma). The fluvial architecture comprises basal conglomerates, followed by amalgamated sandstones and topped by floodplain‐isolated single‐ or multi‐storey amalgamated sandstone complexes with a total thickness up to ~1 km. The Tethyan marine transgression advanced into the basin with a rate of 0.04‐0.02 m yr‐1, and is recorded by a transition from the fluvial succession to a series of maximum flooding surfaces characterised by marginal marine clastic sediments and sabkha evaporites. The continued, transgression led to widespread thick carbonate deposition infilling the basin and recording the final stage of syn‐rift to early‐post rift deposition. We identify the non‐marine to marine transition characterised by significant changes in the Buntsandstein succession with a transition from a predominantly tectonic‐ to a climatically‐driven fluvial system. The results have important implications for the temporal and spatial prediction of fluvial architecture and their transition during a marine transgression.

Middle-Late Jurassic high Sr/Y granitic intrusions are extensively exposed in the Liaodong Peninsula, in the eastern part of the North China Craton (NCC). However, the genesis of the high Sr/Y signature in these intrusions has not been studied in detail. In this study, we report results of zircon U-Pb dating, Hf isotopic analysis and zircon and whole-rock geochemical data for the Late Jurassic Zhoujiapuzi granite in the middle part of the Liaodong Peninsula. The Zhoujiapuzi granite is high-K (calc-alkaline) and peraluminous in nature, with high SiO2 (68.1–73.0 wt %) and Al2O3 (14.5–16.8 wt %), low in TFe2O3 (1.10–2.49 wt %) and MgO (0.10–0.44 wt %), and with high Sr/Y (19.9–102.0) and LaN/YbN (14.59–80.40). Morphological and chemical studies on zircon grains show that there are two stages of zircon growth, interpreted as magmatic evolution in two distinct stages. The early stage of zircons (ESZ) reflects a crystallization environment of low oxygen fugacity and high TZr-Ti (Ti-in-zircon thermometer values: 669–792 °C); the late stage of zircons (LSZ) formed with high oxygen fugacity and lower TZr-Ti (498–720 °C). LA-ICP-MS U-Pb zircon dating yielded the formation ages of the ESZ and LSZ of ~162 ± 1 Ma and ~158 ± 1 Ma, respectively, with similar εHf(t) values in the range of &minus26.3– −22.8. Interpretation of the elemental and isotopic data suggests that the Zhoujiapuzi granite was a I-type granite derived from partial melting of basement in the region: ~2.17 Ga Liaoji granites. The high Sr/Y signature is most likely inherited from these source rocks. Based on the geochemical features and regional geological data, we propose that the Liaodong Peninsula in the Late Jurassic was part of a mature continental arc, with extensive melting of thick crust above the Paleo-Pacific subduction zone.

During continental collision, considerable amounts of buoyant continental crust subduct to depth and subsequently exhume. Whether various exhumation paths contribute to contrasting styles of magmatism across modern collision zones is unclear. Here we present 2D thermomechanical models of continental collision combined with petrological databases to investigate the effect of the main contrasting buoyancy forces, in the form of continental crustal buoyancy versus oceanic slab age (i.e., its thickness). We specifically focus on the consequences for crustal exhumation mechanisms and magmatism. Results indicate that it is mainly crustal density that determines the degree of steepening of the subducting continent and separates the models' parameter space into two regimes. In the first regime, high buoyancy values (∆ρ > 500 kg/m3) steepen the slab most rapidly (to 45–58°), leading to opening of a gap in the subduction channel through which the subducted crust exhumes (“subduction channel crustal exhumation”). A shift to a second regime (“underplating”) occurs when the density contrast is reduced by 50 kg/m3. In this scenario, the slab steepens less (to 37–50°), forcing subducted crust to be placed below the overriding plate. Importantly, the magmatism changes in the two cases: Crustal exhumation through the subduction channel is mainly accompanied by a narrow band of mantle melts, while underplating leads to widespread melting of mixed sources. Finally, we suggest that the amount (or density) of subducted continental crust, and the resulting buoyancy forces, could contribute to contrasting collision styles and magmatism in the Alps and Himalayas/Tibet., Key Points We analyse buoyancy forces in 2D thermomechanical‐petrological models of continental collision and resulting postcollisional magmatismCrustal buoyancy controls whether subducting crust exhumes between plates with only mantle melts or underplates with mixed meltingTiming and distribution of crust and melting for two endmembers fits Alps and Himalaya/Tibet

The thermal and chemical state of the early Archaean deep mantle is poorly resolved due to the rare occurrences of early Archaean magnesium-rich volcanic rocks. In particular, it is not clear whether compositional heterogeneity existed in the early Archaean deep mantle and, if it did, how deep mantle heterogeneity formed. Here we present a geochronological and geochemical study on a Palaeoarchaean ultramafic–mafic suite (3.45-Gyr-old) with mantle plume signatures in Longwan, Eastern Hebei, the North China Craton. This suite consists of metamorphosed cumulates and basalts. The meta-basalts are iron rich and show the geochemical characteristics of present-day oceanic island basalt and unusually high mantle potential temperatures (1,675 °C), which suggests a deep mantle source enriched in iron and incompatible elements. The Longwan ultramafic–mafic suite is best interpreted as the remnants of a 3.45-Gyr-old enriched mantle plume. The first emergence of mantle-plume-related rocks on the Earth 3.5–3.45 billion years ago indicates that a global mantle plume event occurred with the onset of large-scale deep mantle convection in the Palaeoarchaean. Various deep mantle sources of these Palaeoarchaean mantle-plume-related rocks imply that significant compositional heterogeneity was present in the Palaeoarchaean deep mantle, most probably introduced by recycled crustal material. Deep mantle heterogeneity and large-scale deep mantle convection has been operating since the Palaeoarchaean, according to enriched plume signatures found in a 3.45-billion-year-old ultramafic–mafic suite from the North China Craton.

The East Kunlun Orogen (EKO) is the NW part of the Central China Orogenic Belt, which records the evolutionary history of the Proto- and Palaeo-Tethys Oceans from the Cambrian to the Triassic. An Early Palaeozoic eclogite belt has been recognized in recent years, which extends discontinuously for ∼500 km as three eclogite-bearing terranes. In this study, we report an integrated study of zircon grains from mica-schists accompanying the eclogites, in terms of mineral inclusions, U–Pb age systematics andP–Tconditions. The presence of coesite is identified, as inclusions within the metamorphic domain of zircons, which provides unambiguous evidence for subducted terrigenous clastic rocks of the Proto-Tethys Ocean exhumed from coesite-forming depths. U–Pb dating of the metamorphic zircons yields a concordia age of 426.5 ± 0.88 Ma, which is likely to be the time of ultrahigh-pressure metamorphism in the Kehete terrane.P–Tcalculations suggest that metapelite may have experienced a clockwiseP–Tpath with peakP/Tconditions of 685 ± 41 °C and >28 kbar, and equilibrated at 482–566 °C and 5.6–8.9 kbar during subsequent exhumation. The high-pressure – ultrahigh-pressure (HP-UHP) metamorphic belt within the EKO may have formed by collision between the Qaidam Block and the South Kunlun Block, as a consequence of the closure of the Proto-Tethys Ocean.

Mantle-derived magmatism provides important insights for understanding the mechanism of lithospheric thinning. Here we report the results of an integrated geochronological and geochemical study of Late Triassic mafic dykes in Eastern Hebei, northern North China Craton. In situ zircon U-Pb dating shows that the dykes were emplaced between 238 and 223 Ma; the coeval Gaojiadian and Mataizi dykes intruded Precambrian basement at 238–234 Ma and the Saheqiao dyke was emplaced into Neoarchean supracrustal rocks later at 223 ± 4 Ma (2s). Bulk-rock geochemistry indicates that the Late Triassic dykes in Eastern Hebei were produced by melting of ancient lithospheric mantle within the garnet-spinel transition zone (~70–80 km), heated by upwelling asthenosphere. This ancient lithospheric mantle had been metasomatized during previous subduction events. The Gaojiadian and Mataizi dykes resulted from higher degrees of partial melting at slightly lower pressures than the Saheqiao dyke. The melting depth of Late Triassic dykes in Eastern Hebei indicates that the intact ancient lithospheric mantle had been at least locally modified/thinned to ~70–80 km by the Late Triassic. The intrusion of these Late Triassic dykes took place at the onset of the lithospheric thinning of the North China Craton, caused by post-collisional extension after subduction and collision of neighboring blocks with the North China Craton.

East Asia experienced compressional deformation in the early Mesozoic, across the South China Block, North China Craton (NCC) and the part of the Central Asian Orogenic Belt to the north of the NCC. Deformation and magmatism resulted from Triassic collisions that accreted the continental blocks, and also Izanagi (Paleo-Pacific) Plate subduction from the east. We suggest that there was a single East Asian orogenic plateau by the Middle Jurassic, from NE Russia to SW China, with a length of ~4000 km. The causes and timings of the destruction of this plateau are unclear, especially loss of the lower lithosphere of the NCC. Here, we synthesize evidence for late Mesozoic and early Cenozoic crustal thinning via extension and denudation, to quantify the previous crustal thickness. We find that there was a ~50 km thick crust by the Middle Jurassic across much of the area between NE Asia and SW China, which has since undergone ~30% thinning. A force balance indicates that the buoyancy force produced by the gravitational potential energy of this thick crust drove extension from the latest Jurassic - Early Cretaceous (~145 Ma), when a rapid switch from orthogonal to oblique subduction at the Asia-Izanagi plate margin reduced the compressive boundary force by ~30%. Mantle lithosphere thinning of the NCC exceeds crustal thinning by a factor of ~2; extensional collapse cannot be the only cause of cratonic destruction, but played a major role, and potentially triggered mantle instability. Early Cretaceous extension was accompanied by a flare-up in volcanism along East Asia, which we speculate contributed to the Cretaceous hothouse climate.

Detecting and measuring transient episodes of crustal deformation is important for a wide range of solid earth and natural hazard applications, e.g. for improving understanding of seismic and volcanological hazards and for monitoring anthropogenic deformation. InSAR is one of the most suitable techniques for this purpose, due to the frequent, regular and global coverage of current-generation satellite missions. However, both the size of the global InSAR dataset, and the large magnitude of atmospheric and other nuisance signals relative to deformation signals of interest, makes this task difficult and precludes systematic manual analysis.In order to address this issue, here we have developed a new, state-of-the-art deep-learning based approach for the automatic identification of transient deformation events in noisy time-series of unwrapped InSAR images, without requiring supervision or labelling of known example events. To achieve this, we have adopted an anomaly detection framework where anomalies correspond to any transient phenomena that deviates from the ‘normal’ spatio-temporal pattern of phase-change (predominantly due to changes in atmospheric conditions). Our novel workflow learns such patterns in the InSAR dataset, leveraging the unique three-dimensional structure of the interferogram stack and its relationship to the unknown 2D fields of nuisance non-tectonic signals that correspond to individual SAR acquisition dates (epochs). This approach offers major benefits over previously published work using machine-learning to detect signals in InSAR data; those attempts have either largely focused on learning spatial or temporal patterns alone and/or have required an extensive ‘labelled’ dataset of known signals of interest, precluding detection of any signals with different or unexpected spatio-temporal characteristics.In detail, our framework includes fully convolutional autoencoders that embed and share the feature encodings of a sequence of interferograms, and then decode them to an estimation of their corresponding epochs. The autoencoders consist of convolutional LSTM (Long Short-Term Memory) cells that are trained on an InSAR dataset of a fixed size. First, in order to learn the general spatio-temporal structure of the dataset, a prior model is trained independently on overlapping sequences of 26 interferograms only (each made up of 9 epochs, covering 14 km by 12 km area on ground). We then successfully learn the temporal dependency when the weights of this model are used to initialize the succeeding model, which is trained iteratively by also considering features predicted in previous sequences. During testing, normal atmospheric signals are accurately reconstructed, while anomalies result in large residuals. The residuals are then passed to a detection algorithm that flags and estimates anomalous deformation.To initially train and test our method, we use InSAR data from several Sentinel-1 tracks in Turkey, obtained from COMET’s LiCSAR processing system. Here we present our initial results, showing that our unsupervised and event-agnostic pipeline accurately detects both real and synthesized anomalous signals and recovers both the spatio-temporal structure of flagged deformation events and the time-series of non-deformation ‘nuisance’ signals. This new approach presents great promise for future automated analysis of large, global InSAR datasets, and for automated and robust separation of deformation from nuisance signals in InSAR data.

The timings of the onset of oceanic spreading, subduction and collision are crucial in plate tectonic reconstructions, but not always straightforward to resolve. The evolution of the Paleo-Tethys Ocean dominated the Paleozoic-Early Mesozoic tectonics of West Asia, but the timeline of events is still poorly-constrained. In this study we present detrital zircon ages from NE Iran, in order to determine the timing of tectonic events in the region, and the wider implications for regional tectonics, paleogeography and climate change. Paleozoic clastic rocks record two major age peaks at ~800 Ma and ~600 Ma. The consistency in age patterns shows a dominant provenance from the Neoproterozoic basement of northern Gondwana. We interpret deposition on a long-lasting passive continental margin after the initial spreading of the Paleo-Tethys Ocean. Initial collision between the South Turan (Eurasia) and Central Iran (Gondwana) blocks caused coarse clastic deposition, the protolith of the Mashhad Phyllite, in a peripheral foreland basin on the Paleozoic passive margin. The Mashhad Phyllite yields major zircon age clusters at 450-250 Ma and 1900-1800 Ma, with a clear provenance from the active, Eurasian, margin. The Paleozoic ages reveal a long-lived subduction zone under the South Turan Block began in the latest Ordovician. Analysis of the age spectra allows us to constrain the timing of initial collision as no later than 228 Ma, which is also a constraint on the maximum depositional age of the Mashhad Phyllite. Based on our new results and previous data, we discuss the interaction between the Rheic and Paleo-Tethys oceans, and explain how a new subduction zone may have initiated after continental collision. The timing of collision is similar to the Carnian Pluvial Event (CPE). Paleo-Tethys collision has previously been suggested as the trigger for this climatic change, and our study provides timing evidence that reinforces Paleo-Tethys closure as a causal mechanism for the CPE.

The formation and uplift history of the Tibetan Plateau, driven by the India-Eurasia collision, is the subject of intense research. We analyse the link between climate and tectonics in the central and eastern Tibetan Plateau using geomorphic indices of surface roughness (SR) hypsometric integral (HI) and elevation-relief ratio (ZR) and mean annual precipitation, thermochronology and erosion rate data. Geomorphic indices capture the landscape response to competition between climate and tectonics and reflect the spatial distribution of erosion. This is a region where competing tectonic models suggest either early Cenozoic plateau growth, or a late phase of crustal thickening, surface uplift and plateau growth driven by lower crustal flow (“channel flow”). Swath profiles of rainfall, elevation and the geomorphic indices were constructed, orthogonal to the internal drainage boundary. Each profile was analysed to find the location of maximum change in trend. We identify a broad ˜WSW-ENE trending transition in the landscape where changes in landscape and precipitation are grouped and in alignment. It represents, from east to west, a sharp decline in precipitation (interpreted as the western extent of the East Asian monsoon), a change to a low relief landscape at 4500-5000 m elevation, an increase in ZR and a transition to low HI and SR. This zone cuts across structural boundaries and is not a drainage divide: the main rivers have their headwaters further West, in the interior of the plateau. We argue that this geomorphic-climatic transition zone represents a change from incised to non-incised landscapes, the location of which is controlled by the western extent of the monsoon. Modern erosion rates are lower in the non-incised region, west of the monsoon extent (mean 0.02 mm/yr), than the incised region (mean 0.26 mm/yr). Compiled thermochronology data shows an increase in exhumation from ˜25 Ma in the incised area but no evidence of this increased exhumation in the non-incised area. This pattern supports a model of early Cenozoic growth of the eastern Tibetan Plateau, superimposed by incision driven by Miocene monsoon intensification. Our results do not support the channel flow model, which would predict an eastwards wave of surface uplift and therefore erosion and exhumation during the Miocene, which are not present in the data.

The tectonic evolution of the Proto- and Paleo-Tethys oceans had a significant influence on ocean-continent distributions in East Asia in the Phanerozoic, and major implications for continental growth in the region. However, it remains ambiguous when and how the Proto-Tethys Ocean transformed into the Paleo-Tethys Ocean. Here we present petrologic, mineralogical, chronological and geochemical data for Early Devonian mafic igneous rocks, located in the East Kunlun Orogen. The mafic igneous rocks include basaltic lavas and diabase dykes, and are tholeiitic in composition. Geochemical and Sr–Nd isotopic data indicate that the basaltic lavas were derived from melting of a spinel-bearing asthenospheric mantle (E-MORB) at normal mantle potential temperatures (1384–1400 °C) with negligible (1–4%) crustal contamination. The diabase dykes probably originated from melting of a spinel-bearing lithospheric mantle metasomatized by subduction-related fluids, with 5–20% crustal contamination, and crystallized at 1100–1135 °C. Both basaltic lavas and diabase dykes have the geochemical characteristics of within-plate basalts. Magmatic zircons from the mafic rocks yield Early Devonian ages (407–403 Ma), postdating the East Kunlun ultrahigh-pressure metamorphism by 19–25 Myr. Comparing our results with the location and timing of the high- and ultrahigh-pressure metamorphic belt, we conclude that the mafic igneous rocks formed in a post-collisional extensional setting. Their generation was associated with both the terminal stages of the Proto-Tethys orogenic belt, (with orogenic collapse promoted by repeated and localized delamination of lithospheric mantle), and early continental rifting related to the evolution of the Paleo-Tethys Ocean to the south. The period of ~426–390 Ma is important for the transition from Proto- to Paleo-Tethys oceans in the East Kunlun Orogen.

Research into Arabia-Eurasia collision zone magmatism in Kerman Province, SE Iran, has largely focused on Late Cenozoic adakitic stocks or domes, with debate around lower crustal or subducted slab origins. Contemporary hawaiite-trachyandesite lava flows have been overlooked. New analyses for domes and lavas from near Dehaj show major and trace element distributions relating to two distinct compositional series. One contains medium-K domes with SiO2 > 60 wt.%, high Sr/Y and La/Yb and generally low MgO, Ni and Cr, showing high-silica adakite affinity. The other series has high-K affinity and includes both lavas and dome samples. The two suites partially mixed in the shallow crust, confirmed by fieldwork and petrography. Isotopically the two suites are indistinguishable, implying a geologically ‘young’ age for the source of the adakites. Given its geochemical signatures and non-relationship with the largely mafic, mantle-derived high-K series, we consider the adakite series to be derived from melting of eclogitized mafic lower crust. The high-K series relates to dehydration melting of mantle peridotite deeper within the ∼220 km thick lithosphere. We also explore adakitic magmas across Iran and their relationship to porphyry copper deposits. At Dehaj and several other Iranian centres, adakites are chemically controlled by garnet as a source or fractionating phase, and are barren, whereas the presence of amphibole as a key phase seems to correlate with Cu mineralisation. This study also shows the need for evidence from multiple datasets to constrain adakite genesis and warns of avoiding sampling bias towards felsic lithologies.

Landslides play an important role in landscape evolution of the Loess Plateau, northern China, but they have not been systematically analysed across the region. The contribution to regional rates of erosion and sediment budgets is poorly known as a consequence. Co-seismic landslides are a significant natural hazard, and exacerbate the threat posed by active faults in the region, but this aspect of the landslides is also poorly quantified. This paper presents inventories for ~80,000 landslides in the Loess Plateau, and analyses the distributions and extents. Four study areas focus on the epicentres of major (M > 7) historical earthquakes, from 1303 CE (Hongdong), 1556 (Huaxian), 1718 (Tongwei) and 1920 (Haiyuan), which are likely to have been major triggers for landslides in these regions. A fifth study area focuses on landslides in the aftermath of localised storms in 2010 in the Tianshui region, to allow comparison of landslides clearly triggered by rainfall with landslides in the regional inventories. Landslides predominantly resulted from failure of the regional loess blanket that gives the region its name, or the soil profile developed above it. Rainfall-generated landslides are dominantly surficial soil landslides. Landslides preserved in the four epicentral areas are larger and deeper, and resemble global bedrock landslides in the dimensions. Total volume of landslide in each of the four epicentral areas are on the order of 3–7 km3; these volumes are likely to be the cumulative totals of repeated earthquakes in the same regions, with each event reactivating landslide scarps on hillsides. Comparison of landslide distributions and modern settlement patterns suggests that future M > 7 earthquakes striking the Loess Plateau may trigger landslides that could directly hit 30–50% of the communities.

Jumps in the location of back-arc spreading centres are a common feature of back-arc basins, but the controlling factors are not understood. In several narrow subduction zones with a long subduction history, such as the Scotia arc or Tyrhennian Sea, several spreading centres have been active in the course of history with regular, quasi-instantaneous jumps towards the retreating trench. A prominent feature of these regions are large bounding transform (‘STEP’) faults. However, whether STEP faults influence the (unknown) dynamics spreading centre jumps remains to be explored. We therefore run 3D-models to simulate a long narrow subducting slab, bound by continents, which retreats and creates necessary STEP-faults self-consistently. The results offer a new mechanism for back-arc spreading jumps: After the creation of a back-arc spreading centre in the retreating subduction system, transform faults between trench and back-arc basin form. Spreading jumps are thus a consequence of the fact that these constantly elongating transform faults, which decouple the overriding plate from neighbouring plates, fail to remain active once a threshold length (~1.3x plate width) is reached. Subsequently, the back-arc basin and neighbouring plates are strongly coupled, and ongoing trench retreat localizes stresses and rapidly ruptures the overriding plate closer to the trench while the old spreading centre is abandoned. In a parameter study, the results further explain why the narrowest subduction zones, such as the Calabrian Arc, experience more frequent and closer spreading jumps than the long-period jumps of a wider subduction zone such as the Scotia Arc. The widest subduction zones should not undergo any back-arc spreading jumps with this mechanism, consistent with other natural examples.

The Andes Mountains are formed at a destructive plate margin, where dense oceanic crust descends beneath relatively buoyant continental crust. There are regions of the Andes where the range is narrow, but there is also the high plateau of the Central Andes. The reasons for this variation in structure of the overriding plate are not clear. Previous numerical modelling shows that slabs typically roll back, so that continents are stretched, causing tension and potentially back-arc extension. This model does not fit the Andes. Instead, the formation of a thick crust and sustained elevation of the Andes has been hypothesized to be due to a range of different processes, including anchoring of the slab in the lower mantle, subduction of buoyant features in the Nazca plate, or compression driven by large-scale convection cells underneath South America. The enigmatic formation of the Andes is the central theme of this thesis. Previous research suggests a clear correlation between slab age and overriding plate crustal thickness, globally, but in particular for South America. In this project, we hypothesize that this age variation plays a significant role in the formation of the Andes. As subducting slabs descend into the mantle, their properties differ in conjunction with their age affecting their buoyancy and strength, thereby generating different dynamics, surface tectonics, and slab morphologies. Using numerical modelling code ASPECT, we examined the role of slab properties and related dynamics on the state of stress in the overriding plate. We quantify how much compression occurs in the overriding plate, and use this as a proxy for topographic growth. Typically, older slabs cause more rollback and therefore extension. The models in this study however, predict that the stronger pull force from older slabs causes more vigorous subduction, in which mantle convection contributes to corner flow in the mantle wedge, thereby increasing compression. An increase in overriding plate thickness from 50 to 100km increases its overall density and therefore the amount of compression in the overriding plate by 10 MPa, while an increase in slab age from 40 to 80 Myr generates a similar increase in compression. Finally, slab morphology affects the geometry and vigour of convection cells beneath the overriding plate, which, in turn, affects the compressional state of the plate. This is affected by variation of parameters such as mantle viscosity and changes to frictional coupling, which is in qualitative agreement with previous work.

The formation and uplift history of the Tibetan Plateau, driven by the India-Eurasia collision, is the subject of intense research. Geomorphic indices capture the landscape response to competition between climate and tectonics and reflect the spatial distribution of erosion. We analyse the link between climate and tectonics in the eastern part of the Tibetan Plateau using the mean annual precipitation, digital elevation data, and by calculating the geomorphic indices hypsometric integral (HI), surface roughness (SR) and elevation relief ratio (ZR). This is a region where competing tectonic models suggest either early Cenozoic plateau growth, or a late phase of crustal thickening, surface uplift and plateau growth driven by lower crustal flow (“channel flow”).Swath profiles of rainfall, elevation and the geomorphic indices were constructed, orthogonal to the internal drainage boundary. Each profile was analysed to find the location of maximum change in trend. A broad transition zone is present in the landscape, where changes in landscape and precipitation are grouped and in alignment. The zone cuts across structural boundaries. It represents, from East to West, a sharp decline in precipitation below ~650 mm/yr (interpreted as the western extent of the East Asian monsoon), a change from a high relief landscape to smoother elevations at 4500-5000 m, a transition to low HI (< 0.05), a decrease in SR and an increase in ZR. This zone is not a drainage divide: the main rivers have their headwaters further West, in the interior of the plateau.We argue that this geomorphic-climatic transition zone represents a change from incised to non-incised landscapes, the location of which is controlled by the western extent of the monsoon. Published low temperature thermochronology data suggest the plateau had reached its modern extent at the Eocene, but has been exhumed since ~15 Ma to the East of the transition zone, at least along major drainage networks. We therefore also suggest that the transition zone is the current position of a long-term wave of incision that has migrated from East to West, driven by late Cenozoic intensification of the monsoon climate. This work supports a model of early Cenozoic growth of the eastern Tibetan Plateau, superimposed by incision driven by climate change; it does not support the channel flow model.

Evolution of the Tibetan Plateau is important for understanding continental tectonics because of the plateau’s exceptional elevation (∼5 km above sea level) and crustal thickness (∼70 km). Patterns of long-term landscape evolution can constrain tectonic processes, but have been hard to quantify, in contrast to established data sets for strain, exhumation, and paleo-elevation. This study analyzes the relief of the bases and tops of 17 Cenozoic lava fields on the central and northern Tibetan Plateau. Analyzed fields have typical lateral dimensions of tens of kilometers, and so have an appropriate scale for interpreting tectonic geomorphology. Fourteen of the fields have not been deformed since eruption. One field is cut by normal faults; two others are gently folded, with limb dips 3 km) exhumation and plateau landscape development. This diachronous process took place between ∼32.5°N and ∼36.5°N and between ca. 40 Ma and ca. 10 Ma, advancing northwards at a long-term rate of ∼15 km/m.y. Results are consistent with incremental northward growth of the plateau, rather than a stepwise evolution or synchronous uplift.

Primitive arc magmas in oceanic island arcs are probes of sub-arc magmatic processes and are crucial for understanding oceanic subduction. We report data for an Early Paleozoic oceanic arc volcanic complex in the Lajishan-Yongjing terrane, South Qilian Accretionary Belt (SQAB), Qilian Orogen, including zircon U-Pb dating and Hf-O isotopes, mineral and whole-rock geochemistry, and Sr-Nd isotope compositions. New zircon ages of ∼455-440 Ma constrain the timing of arc volcanism and the subduction of the Qilian Ocean. Based on petrography and bulk-rock composition, five lithological types have been identified, including: (1) ankaramite; (2) high-Mg basaltic andesite; (3) high-Al andesite; (4) boninite; (5) sanukite. The volcanic sequence thus is one of the few island arcs where three types of near-primitive arc rocks including boninite, ankaramite and sanukite have been simultaneously produced. All these rocks have variably enriched Sr-Nd isotopic compositions, positive to slight negative zircon εHf(t) values and elevated zircon δ18O values. Boninites, ankaramites and sanukites are interpreted as contemporary, near-primitive, melts generated from different sources and conditions within an island arc setting. Boninites are characterized by low Ti, REE concentrations and high Cr# chrome spinel, and are interpreted as melts of refractory, Cpx-poor, spinel lherzolite or harzburgite at > 25% partial melting. Anomalous zircon δ18O values of 6.57‰-7.61‰ and Sr-Nd mixing calculations suggest less than 2% incorporation of subducted oceanic sediments into the mantle source of the magmas. The ankaramites are characterized by low SiO2, high MgO (Mg#), Cr, Ni and La/Yb ratios, and have similar isotopic ratios to tectonically adjacent OIB lavas. The ankaramite lavas are likely to have derived from mantle sources similar to those of OIB, i.e., pyroxenite-bearing garnet peridotite enriched in incompatible elements. High-Mg basaltic andesites and high-Al andesites may be derived from parental ankaramite magmas. Sr-Nd-Hf isotopic mixing modeling constrain the amount of silicic melt to ∼1-4% for ankaramite magma. Sanukites are of andesitic-dacitic composition with high Mg#, Cr and Ni, and enriched LILE and high La/Yb ratios. They are interpreted as having been generated by reaction of mantle peridotite with a silicic melt, itself derived from subducted sediments. Enriched Sr-Nd-Hf isotopic compositions constrain the amount of silicic melt to ∼10-15% for sanukite. Large compositional variations among the volcanic rocks from the same arc reflect heterogeneous mantle sources and variable degrees of mantle metasomatism by sediment-derived hydrous fluids or silicic melts, accompanied by secondary AFC processes during magma ascent to the surface.

We present an integrated study of ophiolite complexes and island arc rocks from the Tianshui-Wushan Accretionary Belt, West Qinling Orogen. The West Qinling Orogen is important because it links the Qinling orogen to the east and the Qilian and Kunlun orogens to the west. The link between these orogens is commonly assumed, but has little study in detail. Zircon U-Pb analyses from ophiolitic rocks indicate the oceanic lithosphere formed in the Cambrian (530–500 Ma). Pillow lavas in the ophiolite complex show geochemical signatures of enriched MORB, suggesting they represent remnants of an oceanic plateau or seamounts. The island arc rocks include a volcanic complex with basalt-andesite and boninite of Late Ordovician age (460–440 Ma), and a serpentinized peridotite massif. The serpentinized peridotite most likely represent a highly refractory mantle residue with subsequent melt-rock interaction at ~450 Ma, suggesting that it formed in a forearc setting. The co-occurrence of ophiolite complexes and island arc rocks indicates that Tianshui-Wushan Accretionary Belt is an oceanic suture zone caused by oceanic subduction in the Early Paleozoic. The island arc rocks most likely represent the early product of an Izu-Bonin-Mariana (IBM)-type intra-oceanic arc, developed in response to a collision between an oceanic plateau and a continental margin. Our study permits a tectonic correlation between the Tianshui-Wushan Accretionary Belt in the West Qinling Orogen and the South Qilian Accretionary Belt in the Qilian Orogen, thereby establishing the continuity between the Early Paleozoic orogenic belts along the southern margin of the North China Craton.

The CE 1303 Hongdong earthquake, with ~270,000 deaths, has been suggested as the first magnitude 8 earthquake recorded in North China. We use 31 AMS‐14C ages to date earthquakes recorded in the Huoshan Piedmont Fault, which is interpreted to be the causative fault for the event. We interpret fault traces and map the Hongdong earthquake surface rupture in detail. Four events are identified with timings constrained at 1,060–590 year BP (corresponding to the Common Era 1303 event), 3,310–3,210 year BP, 5,460–5,380 year BP, and 26,380 year BP, respectively. The later three events have a recurrence interval of ~2,000–3,000 years. We find that the Hongdong earthquake had a rupture length of ~98 km, a maximum throw of 5.0 m and a best estimate for magnitude in the range Mw 7.2–7.6. We suggest that previous magnitude estimates are overestimates. Normal fault earthquakes have smaller upper limits to their magnitudes than thrusts, because their relatively steep dips produce intersections at the base of the seismogenic layer at smaller downdip widths than gently dipping thrust faults. The Hongdong event was not an exception to this pattern. The historic released seismic moment may be closer to the accumulated moment than previously calculated.

Accommodation of plate convergence during the Arabia-Eurasia collision is expressed in the exhumation record of the broad collision zone. In order to better constrain the spatial and temporal patterns of exhumation, this paper presents new geochronology (zircon U-Pb) and thermochronology (zircon and apatite (U-Th)/He, and apatite fission track) data for 18 samples from the Talesh Mountains of northwest Iran. The Talesh and the adjacent Alborz Mountains form the northern side of the Iranian Plateau, itself a first order feature of the collision zone. Zircon U-Pb ages in the Talesh record late Neoproterozoic intrusion and metamorphism (~570 Ma), and a series of Jurassic, Cretaceous, and Oligocene intrusive events. Zircon U-Th/He ages are predominantly Mesozoic (150–90 Ma), whereas apatite (U-Th)/He ages are

Post-collisional magmatism contains important clues for understanding processes of orogenic belts, potentially including unrooting and collapse. Here we report new geochronological and geochemical data for a suite of post-collisional mafic dykes in the North Qaidam ultrahigh-pressure metamorphic (UHPM) belt. Two groups of magmatic rocks can be distinguished: (1) Middle Devonian (392–375 Ma) basic-intermediate dykes; (2) Upper Devonian (~360 Ma) ultrabasic dykes. Whole-rock geochemistry and zircon Hf isotopes reveal that the intermediate-basic dykes are derived from a lithospheric mantle source, whereas the ultrabasic dykes are melting of asthenosphere mantle. We suggest that such mantle-derived mafic magmatism is the critical indicator for the start of post-collisional magmatism and orogen unrooting and collapse. We propose a geodynamic model explaining the activities of the lithospheric and asthenospheric mantle during the post-collisional stage, which reveals a ~ 35 million year unrooting process, from slow lithospheric mantle erosion between ~395–375 Ma, to final collapse by lithosphere delamination and asthenosphere upwelling at ~360 Ma. Addition of juvenile mantle materials to the crust by the post-collisional mafic magmatism suggests that the post-collisional stage is an important period for continental growth in Earth's history.

Magmatism in eastern China in response to paleo-Pacific plate subduction during the Mesozoic was complex, and it is unclear how and when exactly the magmas formed via thinning and partial destruction of the continental lithosphere. To better understand this magmatism, we report the results of a geochronological and geochemical study of Early Cretaceous adakitic rhyolite (erupted at 125.4 ± 2.2 Ma) in the Xintaimen area within the eastern North China Craton (NCC). In situ zircon U-Pb dating shows that this adakitic rhyolite records a long (~ 70 Myrs) and complicated period of magmatism with concordant 206 Pb/ 238 U ages from 193 Ma to 117 Ma. The enriched bulk rock Sr-Nd isotopic compositions of the Xintaimen adakitic rhyolite, as well as the enriched zircon Hf and O isotopic compositions, indicate that the magmas parental to the adakitic rhyolite were derived from partial melting of the Paleoproterozoic mafic lower crust, heated by mafic melts derived from the mantle during the paleo-Pacific plate subduction. A minor older basement component is indicated by the presence of captured Neoarchean to Early Paleoproterozoic zircons. The Mesozoic zircons have restricted Hf and O isotopic compositions irrespective of their ages, suggesting that they formed from similar sources at similar melting conditions. The Xintaimen adakitic rhyolite offers an independent line of evidence that the ancient lower crust of eastern China underwent a long period (~ 70 Myrs) of destruction, melting or remelting, from ~ 193 to ~ 120 Ma, related to the subduction of the paleo-Pacific plate beneath eastern China.

The Kirkuk Embayment is located in the southwest of the Zagros fold-and-thrust belt of Iraq. Like fold-and-thrust belts worldwide, the Zagros is conventionally understood to have grown sequentially towards the foreland. Here we use landscape maturity analysis to understand anticline growth in the embayment. Digital Elevation Model (DEM)-based geomorphic indices Hypsometric Integral (HI), Surface Roughness (SR) and their combination Surface Index (SI) have been applied to quantify landscape maturity. The results inform new ideas for the sequence of anticline growth. Maturity indices are highest for the QaraChauq Anticline in the center of the Embayment, then Makhool/Himreen to the south and lastly, the Kirkuk Anticline to the north. The pattern suggests the growth sequence is not classical ‘piggy back’ thrusting. This result fits the exhumation record, which is loosely constrained by the stratigraphic exposure level. Favored hypotheses for fold growth order are either i) the folds have grown at different times and out of sequence (QaraChauq first, then Makhool/Himreen, and Kirkuk last), or, ii) the growth occurred with different rates of exhumation but at broadly the same time. There are few constraints from available data on syn-tectonic sedimentation patterns. Fold growth across much of the Embayment might have begun within a limited timeframe in the late Miocene–Pliocene, during the deposition of the Mukdadiyah Formation. Another hypothesis is that folds grew in sequence towards the foreland with different rates of exhumation, but we consider this less likely. We also construct a new cross-section for the Embayment, which indicates limited Cenozoic strain: ~ 5% shortening. Analysis of topography and drainage patterns shows two previously-undescribed anticlines with hydrocarbon trap potential, between the Makhool and QaraChauq anticlines.