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The onset of the big mantle wedge (BMW) structure beneath the North China Craton remains debated. Research on the genesis of Late Mesozoic granites associated with gold deposits in the Jiaodong Peninsula above the BMW could provide fresh insights into this question. The monzogranite from the Zhaoxian-Shaling gold district was intruded during 154–148 Ma. This I-type granite has high-K calc-alkaline and metaluminous characteristics. The monzogranite formed at medium temperatures (718–770 °C) and was generated in a thickened lower crust at depths within the stability field of garnet. The monzogranite's high zircon Ce4+/Ce3+ and EuN/EuN* values and low FeOT/MgO ratios, suggest that it formed in a high oxygen environment. Its variable εHf(t) values with TDM2 of 1.93–2.87 Ga imply that it originated from the melting of ancient crust basement, with contributions from mantle-derived materials. The granite's enrichment in LREEs and LILEs, and depletion in HREEs and HFSEs, along with its trace element tectonic discrimination diagrams and medium Sr/Y, indicate an adakite affinity in an active continental margin setting. The transition from S-type granites to I-type granites and finally to A-type granites observed in the eastern part of North China Craton suggests a shift in the tectonic environment from compression to extension. This change is also reflected in the transition from flat subduction to steep subduction. Therefore, the monzogranite was formed in a tectonic transition setting triggered by a change in the subduction angle of the Paleo-Pacific Ocean slab during the Late Jurassic. This event may have marked the initiation of the BMW above the North China Craton. [ABSTRACT FROM AUTHOR]

The Antigonish sub-basin lies within the late Paleozoic Maritimes Basin of Atlantic Canada. Late Devonian to early Carboniferous basin development resulted in a basin-and-range topography, within which the clastic Horton Group was deposited in grabens and half-grabens. The overlying Viséan Windsor Group contains substantial evaporite units; later basin development was accompanied by expulsion of these evaporites. In the Antigonish sub-basin, a significant stratigraphic omission surface initially described as a thrust was subsequently reinterpreted as the extensional Ainslie Detachment. This surface can be examined in drill-core, where the halite-bearing interval is reduced to 3.8 m of halite-cemented breccia of sedimentary rock fragments. The halite cement is sub-horizontally foliated and lineated. At Lakevale, an outcrop section of the Windsor Group is reduced in thickness to tens of metres. Above a basal limestone unit containing pseudomorphs of gypsum, most of the Windsor Group is represented by sedimentary-clast breccias that resemble those seen in core, but with the halite removed by solution in the near-surface environment. The stratigraphic record within the sub-basin implies that expulsion of lower Windsor salt was initially toward the edges of the basin where rising diapirs blocked the deposition of middle Windsor group, but in the basin centre a second salt unit was deposited. Subsequently, during contractional inversion of basin-bounding faults, the middle Windsor salt was expelled into diapirs near the centre of the basin. The Ainslie Detachment is reinterpreted as a primary salt weld: a boundary between units formerly above and below expelled lower Windsor evaporites. The resulting stratigraphic omissions and structures match those seen above expelled evaporite layers on continental margins. [ABSTRACT FROM AUTHOR]

Finite-element paleogeologic restoration of southwestern North America at 60 Ma shows the western edge of Cretaceous granodiorite plutons, formed as a continuous magmatic arc above the Franciscan subduction zone, to be offset ~400 km in southern California, USA. This offset is successfully restored by reversing sinistral slip along a proposed Nacimiento-Caborca-Durango-Zacatecas (NCDZ) fault trace active approximately from 75 Ma to 60 Ma. The Franciscan trench west of the finite-element model can be restored by extending the NCDZ fault northward through coastal Franciscan terrane, where it formed a trench-trench-fault triple junction. As the trench-trench-fault triple junction migrated southeastward along the continental margin, a new forearc margin was exposed sequentially from NW to SE, beneath which the Pelona-Orocopia-Rand Schist was underplated. NCDZ fault displacement occurred concurrently with Laramide flat-slab subduction and intersection of the continental margin with an aseismic oceanic ridge. The trench-trench-fault triple junction would have tracked the intersection point of the NE-SW ridge with the NW-SE continental margin. Tests of this model (following palinspastic restoration) include: (1) The oldest ages of Pelona-Orocopia-Rand Schist should young NW-SE, (2) the initiation of forearc deep-marine sedimentation directly on Mesozoic magmatic-arc basement of Salinia should young NW-SE, (3) the detrital-zircon age spectra and other provenance indicators should correlate with potential source areas, (4) the metamorphic and plutonic belts of the batholithic belt should realign, (5) the Great Valley forearc belts should realign, and (6) the Franciscan belts should realign. Finite-element modeling provides rigorous constraints on paleogeologic and paleogeographic reconstructions and suggests additional avenues of investigation. [ABSTRACT FROM AUTHOR]

The Lomagundi-Jatuli Event (LJE) is a significant positive δ13Ccarb anomaly in Paleoproterozoic carbonates globally. In the northeast São Francisco Craton (SFC), this event is documented in phosphorous (P)-rich marbles, along with subordinate graphite schists and iron formations, located in the Tanque Novo-Ipirá Complex (TNIC), Jacurici Valley (JV) and Rio Salitre Complex (RSC). Although the TNIC, JV, and RSC share comparable geological, geochronological, and mineralization characteristics, their connection and phosphogenic ties to the LJE are still uncertain. By combining new and reviewed C and O isotopes, cerium (Ce) anomalies relative to an array of rare earth elements, and yttrium (REY), we aim to constrain the paleoenvironmental conditions governing the phosphogenesis in the northeast SFC and its cause-and-effect relationship with the LJE. The Ce anomalies between 0.12 and 0.67 reveal a connection between the TNIC, JV, and RSC marbles and an oxic-suboxic shallow ocean influenced by detritus inflow. The remaining dataset links the carbonate protoliths to a continental margin of a paleocean and continental rift. Additionally, The positive δ13C excursions in the marbles, ranging from 5. 38 to 9.69‰, in conjunction with available geochronological data, indicate a maximum deposition age within 2.20 and 2.02 Ga. Our results indicate that the carbonate protoliths in the TNIC, JV, and RSC were deposited in similar paleoenvironmental conditions during the Paleoproterozoic. During this time, factors such as elevated oxygen levels, oceanic primary paleoproductivity, and organic matter burial played a crucial role in determining P supply, precipitation, and accumulation. These factors ultimately led to the positive δ13C excursions observed in the SFC, which are consistent with marine carbonates found around the world towards the end of the LJE. [ABSTRACT FROM AUTHOR]

Magmatism at continental margins is of great significance in understanding the continental rifting. We present a twodimensional P-wave velocity model derived from an ocean bottom seismometer experiment, conducted across the middle northern continental margin of the South China Sea (SCS). The detailed velocity structures reveal significant heterogeneities extending from the continental shelf to the continent-ocean transition zone. The crust exhibits its greatest thickness below the continental shelf, measuring ~23 km and gradually thins to ~13 km at the distal margin. Furthermore, a narrow and distinct continent-ocean transition with only 40-km width is revealed. We also observe a high-velocity layer within the transition zone, reaching thickness of up to 4 km, characterized by P-wave velocities ranging from 7.0 km/s to 7.6 km/s in the lower crust. Based on the syn-rift melt generation using decompression melting model, we ascertain that syn-rift magmatism cannot fully account for the observed thick high-velocity layer. By integrating findings from previous geophysical and geochemical studies presenting extensive volcanic edifice on the seafloor at the northern margin, as well as ocean-island-basalt-type magmatic samples in the SCS area, we propose that post-rifting magmatism associated with the Hainan Plume may have influenced the formation of the high-velocity lower crust within the transition zone and the northern margin of the SCS can thus be recognized as magma-poor type margin. [ABSTRACT FROM AUTHOR]

The geologic evolution of the Gondwanide orogen recorded during the late Palaeozoic along the Panthalassan border of Gondwana is related to an active continental margin, though it is still debatable whether it was built by collision or accretion. To disentangle its orogenic processes and provide constraints on the orogen type, we characterize the physicochemical conditions of metamorphism and associated deformation of the Mina Gonzalito Metamorphic Complex from northern Patagonia (41°28'30" S-65°40'30" W). New field mapping and comprehensive petrochronologic analysis constrain the evolution of a thick-skinned fold and thrust belt in a retroarc setting, which is spatially and temporally related to the geometry and kinematics of the right-lateral reverse El Jagüelito ductile shear zone. Metamorphic evolution resulted in a clockwise P‐T‐t-D path reflecting three stages of continuously changing P-T conditions under high-pressure (8.0–9.9 kbar) amphibolite facies (540–680°C) during a single-phase progressive ductile deformation event. Monazite ages ranging from 303 ± 5 to 252 ± 6 Ma account for the single-phase regional tectono-metamorphic event spanning ~ 50 My. Our results, integrated with regional data, led to interpreting the late Palaeozoic Gondwanide orogen developed along the Panthalassan margin of Gondwana as accretionary in advancing-mode. [ABSTRACT FROM AUTHOR]

Stratonikeia, a city in the interior of the Caria region, is located at the settlement of Eskihisar within the borders of Yatağan District in Muğla Province. The ancient city's foundation dates back to 5000 BC, making it one of the oldest settlements in southwest Türkiye. It is strategically located between the Inner Aegean and Eastern Mediterranean regions. Due to its location, the city has been important throughout its history. The Greek type of theater, which is the main topic of this paper, is one of the most remarkable structures known to date from the Hellenistic period and is made of marble blocks. Macroscopic investigations reveal that the marble blocks of the theater are pure white, medium-to-fine crystalline, and their dimensions range from 165 χ 45 χ 40 to 210 χ 50 χ 90 cm. In addition to their whiteness, the most characteristic feature of these marble blocks is that they are almost entirely pure (they do not contain opaque or accessory minerals or colored veins). Microscopically, the white marble blocks have heteroblastic polygonal (less heteroblastic mosaic) textures and chiefly consist of calcite minerals (negligible amounts of dolomite, quartz, muscovite, and opaque minerals). These results are supported by X-ray powder diffraction and confocal Raman spectrometer studies. Field observations, mineropetrographic data, and geochemical data suggest that the theater marble may have been obtained from ancient marble quarries around Eskihisar. Based on the results of optically stimulated luminescence (OSL), it can be suggested that the construction of the theater building began around the 2nd century BC and lasted until the 1st century AD. After that, it was strengthened in the 3rd--4th century and later repurposed as an open-air church, with additional reinforcement in the 5th--6th century. The OSL ages calculated from the experimental results match the known archaeological record of the theater's construction. [ABSTRACT FROM AUTHOR]

Permian–Triassic eclogites exposed on the Tibetan Plateau have traditionally been attributed to Paleo-Tethys oceanic subduction. Here we report new data that indicate a continental-subduction origin of the Pianshishan eclogites along the Longmuco-Shuanghu Paleo-Tethys suture in northern Tibet. Phase equilibrium modeling and zircon U-Pb dating constrain eclogite-facies metamorphism of ∼2.1 GPa/530 °C to have occurred ca. 235 Ma. Xenocrysts of ca. 1850 Ma metamorphic zircons and crustal trace element signatures reveal a continental protolith for the Pianshishan eclogites, demonstrating deep subduction of continental passive margins during the early Late Triassic. The Qianmai eclogites along the Changning-Menglian suture in Southwest China have the same petrogenesis, indicating that these two coeval eclogites resulted from continental subduction that extended over 2500 km along the Paleo-Tethys suture. This collision not only marks the end of the Paleo-Tethys Wilson cycle but also could have formed a high-elevation range, comparable in length to the Himalaya, that amplified Tethyan megamonsoons during the Late Triassic Carnian Pluvial Episode. [ABSTRACT FROM AUTHOR]

Large-scale topography is usually associated with tectonic plate boundaries, but the Scandinavian mountains (Scandes) are located far from any active tectonic setting, and their origin is unknown. We demonstrate that the Precambrian lithospheric structure of Fennoscandia controlled both the Cenozoic ocean opening and mountain rise in the North Atlantic region. Our new seismic receiver function analysis reveals a block of thick continental crust formed by Proterozoic crustal stacking. We propose that this block created a wide continental shelf bounded by two transform fault systems during continental breakup. This geometry resulted in the formation of lithospheric steps at the continental margin on both sides of the stacked crustal structure, coinciding with the highest Southern and Northern Scandes. We propose that edge-driven convection at these steps caused the mountain rise. This study presents a general model for the formation of high elevation behind passive margins. [ABSTRACT FROM AUTHOR]

Rocks of the Lesser Himalayan Sequence are important from a global tectonic perspective as they represent a crucial evolutionary chronicle of the Indian continent from the Paleoproterozoic to the Cenozoic Himalayan orogeny. Eroded remnants of tectonically transported crystalline thrust sheets overlying the Lesser Himalayan metasedimentary zone along the Main Central thrust are represented by the Almora, Baijnath, Askot, and Chiplakot klippen belts in the Kumaun Himalaya, India. In this work, we present the deformation history, geochemistry, and U-Pb zircon-apatite geochronology of the Baijnath klippe rocks and its footwall. Our age and tectonic setting results for the klippe rocks help to illustrate the continental accretion processes that prevailed during Paleoproterozoic-Neoproterozoic time along the northern Indian cratonic margin. Granitoids within the Baijnath klippen yield crystallization ages varying from ca. 1870 Ma to ca. 1850 Ma, while the supracrustal sequence preserves a prominent age signature of ca. 1855 Ma. The metasediments of the Berinag Formation at the klippe footwall yield a detrital age of ca. 1810 Ma. Based on these results and the geochemistry, we infer that the Baijnath klippe rocks bear an affinity with the inner Lesser Himalayan Sequence, and the granitoid magmatism took place within a span of ~20 m.y. (1870-1850 Ma) in an arc setting linked to active subduction along the north Indian continental margin, possibly due to the formation of the Columbia supercontinent during the Paleoproterozoic. Textural and mineralogical data from the amphibolite-facies supracrustals of the Baijnath klippe suggest that the progressive metamorphism (M1) reached peak at ~580 °C and ~8.6 kbar followed by a decompression-dominated retrogression (M1R) down to ~450 °C and ~5.8 kbar, possibly through a clockwise pressure-temperature (P-T) trajectory that was overprinted by the Cenozoic reworking (M2 metamorphism?) and deformation (D2) related to the Himalayan orogeny. Texturally constrained apatite grains from M1 metamorphic domains preserve traces of a Neoproterozoic-age tectonothermal imprint that affected the Lesser Himalayan Sequence rocks, possibly during the assembly of the Gondwana supercontinent. [ABSTRACT FROM AUTHOR]

The 2.1-1.79 Ga Trans-Australian and Canadian Trans-Hudson orogens preserve a common record of Himalayan-scale orogenesis and voluminous Cordilleran-style magmatism behind which turbidite-dominated sedimentary sequences evolved in a backarc or retroarc foreland setting. Successive cycles of subduction retreat and advance drove the orogenic process, culminating in continentcontinent collision and closure of a shared and formerly contiguous ocean basin--the Paleoproterozoic Diamantina and Manikewan oceans. Cordilleran-style arc magmatism in proto-Australia commenced along the southern reaches of the Diamantina Ocean with emplacement of the 2005-1975 Ma Dalgaringa Batholith along the leading edge of the Pilbara Craton (Gascoyne Province) before both it and its host craton docked against the Yilgarn Craton, resulting in the Glenburgh Orogeny. After a brief episode of postkinematic granitic magmatism from 1965 Ma to 1945 Ma, tectonic activity switched to the opposing margin of the Diamantina Ocean in what is now northern Australia, where three more cycles of upper plate orogenesis and Cordilleran-style magmatism occurred from 1890 Ma to 1850 Ma, 1840 Ma to 1810 Ma, and 1810 Ma to 1760 Ma along a convergent continental margin extending from the Kimberley and Pine Creek regions southward through the Mount Isa domain into the eastern Gawler Craton. Batholiths developed along this margin include granites of both low- and high-Sr/Y composition, with the more adakitic varieties interpreted to have been intruded during periods of enhanced asthenospheric upwelling accompanying the opening of one or more slab windows following slab breakoff, tearing, and/or subduction of an actively spreading oceanic ridge. Terminal collision between the North and South Australian (Mawson) cratons at ca. 1790 Ma brought this succession of subduction-related events to a close, although neither this event nor the corresponding Trans-Hudson Orogen need equate to final assembly of the Nuna supercontinent. Instead, the 1870 Ma peak in global compilations of magmatic and detrital zircon ages may be interpreted more simply as the result of elevated tectonism and magmatism along a Paleoproterozoic Cordilleran-style continental plate margin that was transcontinental in scale and continued uninterrupted from proto-Australia into northern Canada and beyond. [ABSTRACT FROM AUTHOR]

The initial timing and history of subduction of the Paleo-Pacific Plate beneath Eurasia are controversial. The crustal thickness variations at a convergent margin typically reflect the convergent process between the two plates. This study used a recently proposed machine-learning model to estimate the crustal thickness variations along the northeast Asian continental margin during the Mesozoic. The northeast Asian continental margin, particularly the eastern North China Craton, had its thickest crust during the Early Triassic and underwent crustal thinning during the Middle-Late Triassic. The former reflects the subduction and collision between the South China Block and North China Craton, and the latter occurred in a post-orogenic extensional setting. From the Early to Middle Jurassic, sustained crustal thickening occurred along the northeast Asian continental margin, which coincided with initial subduction of the Paleo-Pacific Plate beneath Eurasia. From the Early to Late Cretaceous, the northeast Asian continental margin generally underwent crustal thinning, but crustal thickening events occurred at 130 Ma, 110 Ma, and 90 Ma, which is consistent with rollback of the subducted Paleo-Pacific Plate beneath Eurasia. The relationship between crustal thickness and mineralization suggests that thicker crust favored the formation of porphyry-type Cu-Mo deposits, whereas thinner crust in an extensional setting favored the formation of epithermal Au deposits related to magmatism. [ABSTRACT FROM AUTHOR]

Petrological, geochronological, and geochemical data from the volcano-sedimentary sequences, granitoids, and ophiolite relics of central Inner Mongolia, China, were used to reconstruct the subduction and final closure of the Hegenshan Ocean. Geochronological dating and compilation reveal four phases (ca. 360-355 Ma, 348-320 Ma, 320-310 Ma, and 310-275 Ma) of magmatism in the Uliastai continental margin. The ca. 356 Ma I-type Halatumiao granodiorite and Amanwusu ophiolite relics are subduction-related, and the Halatumiao granodiorite provides solid evidence of the northward subduction of the Hegenshan Ocean beneath the Uliastai continental margin at ca. 360-355 Ma. The ca. 348-320 Ma and 320-310 Ma volcanic rocks and granitoids constitute two linear magmatic belts roughly parallel to the Erenhot-Hegenshan ophiolite belt, which record two phases of continental arc magmatism in the Uliastai continental margin. Overall, the ca. 360-310 Ma arc magmatism shows landward migration and then oceanward migration in the Uliastai continental margin, which indicates advancing subduction and subsequent slab steepening of the Hegenshan Ocean. By contrast, the ca. 310-275 Ma magmatic rocks are dominated by I- and A-type felsic volcanic rocks, granites, and dikes, which are post-accretionary, extension-related, and pervasive in the Uliastai continental margin and Erenhot-Hegenshan ophiolite belt. A provenance shift was identified between the Benbatu and Amushan formations of the Amanwusu area of the Erenhot-Hegenshan ophiolite belt. The early detritus was derived from the early Paleozoic rocks in the Sonid Zuoqi arc belt, whereas the late detritus originated from the Early Carboniferous ophiolite relics in the Erenhot-Hegenshan ophiolite belt. The provenance shift and emplacement of pervasive extension-related magmatic rocks imply a Late Carboniferous closure of the Hegenshan Ocean. The Late Carboniferous oceanic closure event in the north of the southeast Central Asian Orogenic Belt is also evidenced by the transition of Hf isotopic composition of zircons dated between ca. 360-310 Ma and 310-275 Ma. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Palaeocene–Eocene Tethys Himalayan foreland basin plays a crucial role in reshaping the collisional orogenic process of the Yarlung–Tsangpo oceanic basin. However, studies examining the sedimentary response during the tectonic evolution of the foreland basin are lacking. In this study, through a detailed field investigation and analysis of Palaeocene–Eocene strata in the Tingri area, we clarified the evolution of the Tethys Himalayan tectonic regions and its sedimentary response. Carbon and oxygen isotopes, geochemistry and detrital zircon U–Pb dating demonstrated that the lower Palaeocene Jidula Formation and upper Palaeocene–lower Eocene Zongpu Formation were deposited in a coastal–shallow marine environment, with the detritus sourced from the northern Indian passive margin. The upper Eocene Pengqu Formation was deposited in a deltaic environment, with its detritus sourced from the Gangdese arc and the Yarlung–Tsangpo suture zone at the active continental margin. Combined with the nearshore subaqueous fan branch channel of the Jidula Formation and the slump deformation of the Zongpu Formation, the Palaeocene–Early Eocene southern Tethys Himalaya in the Tingri area was located in the forebulge of the peripheral foreland basin. The marine–continental interactive delta of the Pengqu Formation and its provenance from the Gangdese magmatic arc indicate that the Tingri area was situated in the foredeep of the peripheral foreland basin during the Late Eocene. The study provides valuable insights into the collisional orogenic processes between the Indian and Eurasian plates. [ABSTRACT FROM AUTHOR]

The northern continental margin of the South China Sea (SCS) is an important component of deep‐water circulation, providing excellent conditions for studying bottom currents in a marginal sea. Seismic data were employed to discern the sedimentary patterns prevalent in the deep‐water continental slope sediments on the northern continental margin of the SCS, encompassing gravity flow, contourite and mixed depositional systems. The contourite depositional system includes various types of deposits (such as separated mounded drifts, patch or channel‐related drifts, deformed sheeted drifts, composite drifts, bottom current sediment waves, plastered contourite drifts) and various morphologic erosional features eroded by the bottom current (such as moats, non‐depositional surfaces, troughs and scarps). These contourite features are related to the continental slope's morphology and its sources. The Dongsha slope exhibits distinctive characteristics marked by intense bottom current erosion and deposition, featuring separated mounded drifts and deformed sheeted drifts along its lower slope. The lower slope of the Pearl River showcases a spectrum of bottom current‐induced features, including sediment wave fields, erosion fields and contourite drifts. The southern flank of the Shenhu slope is characterised by a bottom current erosion field, a non‐depositional surface, a sediment wave field and isolated mounded drifts. On the Yingqiong slope, the contourite drifts are limited to its southern flank where gravity flow action is absent, and the complex geomorphology interacts with the bottom current, forming a complex contourite depositional system. The results of this study serve as a foundational framework for further global research on bottom current circulation and hydrodynamics. [ABSTRACT FROM AUTHOR]

The Offshore Indus Basin is a passive continental margin and a frontier zone for hydrocarbon exploration based on structural and stratigraphic features observed on seismic data. In this study, the seismic and biostratigraphic framework is established using seismic data, geophysical well logs, along with biostratigraphic information to define the depositional sequences in the study region. A re-examination of the seismic data exhibits normal faults and a total of six seismic sequences ranging from Cretaceous to Quaternary. Nummulites atacicus, Nummulites globulus, Discocyclina sp., Miscellanea miscella, and Ranikothalia sp. are the major identified fauna in the Karachi South A1 well (2030-2724 m). The Miscellanea miscella, Ranikothalia, and Discocyclina sp. ages range from 55 to 56.5, 55-59, and 55-59 Ma respectively. Employing biostratigraphy, Ranikothalia/Miscellanea miscella/Discocyclina biozone (55-59 Ma), a single sequence, a third order cycle of deposition and transgressive and highstand system tracts have been recognized in the Karachi South A1 well. Linking biostratigraphic results to seismic stratigraphy indicates that the strata located in the range of 2030-2724 m is of the Ranikot (Paleocene) Formation and has been previously given Eocene age rather than the Paleocene using vintage seismic data. The environment of deposition of the Ranikot Formation in the Karachi South A1 well is the subtidal environment of the middle-shelf (30-45m depth) setting. [ABSTRACT FROM AUTHOR]

The continental margin is a major repository for organic carbon; however, anthropogenic alterations to global sediment and particulate terrestrial organic carbon (TerrOC) fluxes have reduced delivery by rivers and offshore burial in recent decades. Despite the absence of mainstem damming, land use change in the Ayeyarwady and Thanlwin River catchments in Myanmar has accelerated over the last 50 years. As a result, deforestation and landscape erosion have likely altered fluvial fluxes to the Northern Andaman Sea shelf; however, the magnitude and preservation of geochemical signals associated with development are unknown. Utilizing elemental and bulk stable and radioisotope analysis, this study investigates spatial and temporal trends in sediment sources and TerrOC concentrations to identify the potential impacts of recent (<100 years) offshore development. While our results demonstrate an along-shelf trend in provenance and TerrOC concentrations, temporal (downcore) trends are not observed. We attribute this observation to frequent, large-scale seabed resuspension and suggest that extensive mixing on the inner shelf creates a low-pass filter that effectively attenuates such signatures. This is in contrast to other large Asian deltas, where signals of human landscape disturbance are clearly preserved offshore. We predict that planned mainstem damming in Myanmar will result in larger alterations in sediment and TerrOC supply that may become apparent offshore in the near future. [ABSTRACT FROM AUTHOR]

This study offers new insights into the internal architecture of shallow marine carbonate sediments deposited in an epeiric sea formed on a broadly flooded passive margin continental shelf. The Ullayah Member of the Late Jurassic Hanifa Formation is exposed along the Tuwaiq Mountain Escarpment in Central Saudi Arabia and serves as an example. High‐resolution drone imagery over a 4 × 4 km2 wadi system, measured‐sections and thin‐section petrography are utilized to develop the three‐dimensional architecture of the lagoonal sediments deposited in an inner‐ramp setting. Parasequence sets have been mapped on the digital outcrop models that demonstrate a high degree of lateral and vertical thickness variability associated with stromatoporoid/coral buildups and inter‐buildup sediments. The stromatoporoid/coral buildups have been interpreted to be deposited during the late Transgressive Systems Tract and Highstand System Tract. The positive relief developed by the stromatoporoid/coral buildups resulted in hydrodynamic acceleration of currents in the inter‐buildup areas, which limited sediment deposition. The incomplete filling of the inter‐buildup areas led to an undulating topography, which significantly influenced depositional architecture in the next parasequence set. This theme of sediment filling, also referred to as compensational stacking, was repeated over the next two parasequence sets, with an overall decreasing accommodation towards the late highstand, eventually levelling the uneven topography at the top of the Ullayah Member. The study offers insights into the processes of sediment accumulation in an inner ramp lagoon and/or on a flat‐top shallow marine epeiric carbonate shelf. Although accumulation is cyclic, neither strict facies patterns nor uniform cycle thicknesses can be discerned on a kilometre scale. This insight potentially provides a reason for the frequently debated correlation of cycles and facies patterns in carbonate sequences in shallow epeiric seas. [ABSTRACT FROM AUTHOR]

Shale deposits from Belata Formation outcrops were examined geochemically and mineralogically to establish their paragenesis and, subsequently, to identify factors that govern their depositional environment. Fifty representative samples were examined through SEM/EDX, XRD and XRF. The findings show the mineralogical composition was abundant in quartz, with pyrite and calcite in trace amount. Zr–TiO2 bivariate diagram showed predominantly felsic and intermediate igneous rocks, suggesting that the shales may be coming from the hidden basement rocks of Peninsular Malaysia. The diagenetic controls on the geochemistry are suggested by the changes in compositional trends. The samples exhibit CIA values ranging from 62.2 to 80.2, and PIA values ranging from 65 to 100. According to the V/Ni, Ni/Co, and V/Cr ratios, these black shales were formed in a suboxic environment. Additionally, the high V/Ni ratios (1.47) point to a marine source for the organic content that gives the shales their dark color. The paleoclimate during deposition was interpreted to be semiarid to warm. The black shale samples are inferred to have originated from a passive margin tectonic setting that followed continental collision and rifting stages of the foreland basin development phase of Peninsular Malaysia based on geochemical proxies and associated diagrams. Highlights: A detailed mineralogical and geochemical composition study of the black shales reveal variations in the mineralogy and a common and local source rock (provenance). The source rock of the Belata black shales is inferred to be from igneous rocks with contribution from subordinate intermediate igneous rocks. Dimensionless parameters such as CIA, PIA and ICV calculations infers the black shales to be formed in a humid and warm environment. The tectonic settings of the Belata black shales are revealed to be of passive continental margin as compared to other shales in the Peninsular. Black shales are deposited in a suboxic to anoxic marine environment. [ABSTRACT FROM AUTHOR]

Numerous landslides are located on the passive margin of Norway. According to their number and length of their headwalls, the margin can be divided into three segments (from south to north): Scandinavian, Barents Sea, and Svalbard. The fourth segment (Arctic) is the transition zone located north of the Svalbard archipelago. In the Scandinavian segment, on the continental slope and deeper, about 40 large underwater landslide bodies have been identified. The Barents Sea is dominated by deep-sea fan deposits, which are associated with landslides. No large landslides were found in the Svalbard segment. An analysis of published and original geological and geophysical data indicates that the most likely formation of new landslides can occur in the Svalbard segment, as well as on the Vestnesa Ridge. [ABSTRACT FROM AUTHOR]

The results of mineralogical and geochemical studies of terrigenous rocks of the Early–Middle Permian Reshetnikovka Formation of southwestern Primorsky krai are considered. Based on the data obtained, conclusions were drawn about the geodynamic nature of the deposits and the main sources of detrital material were determined. It has been established that, in terms of their parameters, the sandstones of the formation correspond to arkoses and are rock-forming, the formation of which occurred due to erosion of geochemically mature, largely weathered parent rocks in provenance areas. Judging from the mineralogical and geochemical characteristics of sandy rocks, as well as the position of their composition points on discriminant diagrams, in the Early–Middle Permian, sedimentation occurred in basins associated with the passive continental margin. These basins were intra- and intercontinental rifts and aulacogens. Sedimentation was primarily influenced by continental provenance areas: cratons and uplifted basement blocks, which were basement highs within rift zones. Felsic igneous rocks were washed away with little involvement of ancient sedimentary formations. [ABSTRACT FROM AUTHOR]

The geologic framework of western Washington, USA, is the result of collisional tectonics, where oceanic plate materials were subducted beneath the continental margin. As part of this process, fragments of mantle peridotites were transported into the upper crust along deep faults. The hydration of these ultramafic materials produced bodies of serpentinite. Subsequent regional metamorphism caused metasomatism of the serpentinite to produce a variety of minerals, which include nephrite jade, grossular, chlorite, diopside, vesuvianite, and pumpellyite. Many of the nephrite-bearing rocks are located along the Darrington–Devils Mountain Fault Zone in Skagit and Snohomish Counties. Intense prospecting has led to the establishment of many mining claims, but recreational collecting remains a popular activity. [ABSTRACT FROM AUTHOR]

Active and passive continental margins exhibit significant differences in sediment transport. However, opportunities to quantify these specific sedimentary processes remain limited. The northeastern South China Sea hosts both active and passive continental margins, offering a distinct opportunity to compare the relative contributions from a large passive continental margin with those from a smaller but more dynamic active margin. We present detrital zircon U-Pb ages from marine sediments in the northeastern South China Sea to decipher their provenance and reveal the control of transport processes in the margins. Our results show varied provenance of sediments from the shelf to the trench. In the continental shelf, sediments were primarily derived from the Jiulong and Gaoping rivers, controlled by the topography and ocean currents in the passive margin. In contrast, the sediments in the submarine canyons predominantly originated from the Gaoping and Zhuoshui rivers in western Taiwan Island. Quantitative results indicate that the Gaoping submarine canyon provided approximately 86.2% of sediments to the Manila Trench by directly linking to the Gaoping River in the active margin. Based on the provenance results, we propose a distinct sedimentary process in the active and passive margins. In passive margins, sediments from drainage systems enter the shelf and are transported by ocean currents, but topographic highs often block these sediments, preventing them from reaching the deep sea. In contrast, active margins feature narrow shelves, which facilitate direct connections between submarine canyons and river mouths, allowing gravity flows to carry sediments directly to the trenches. Our study provides an understanding of the sediments transported from rivers to trenches in the northeastern South China Sea and highlights the controls (ocean currents, dramatic topography, and gravity flows) during the sediment transport in the continental margins. [ABSTRACT FROM AUTHOR]

Four primary estuarine/marine ecotopes recognized in the North Atlantic continental littoral and continental terrestrial margins give rise to the following ecotypes: wrack generalists (=beach-hoppers), psammophilic talitrids (=sandburrowing-hoppers), palustral talitrids (=salt marsh-hoppers), and xylophagous talitrids (=driftwood hoppers). On the European continent, there are freshwater riverine and lacustrine talitrids. In addition, there are a few terrestrial ecotypes in the Northeast Atlantic Islands: rainforest leaflitter talitrids and one troglobiont (=cave-hopper). Wrack generalist species are phenotypically plastic and can live in one or more secondary ecotopes. It is hypothesized herein that switching on/off appropriate genes by cellular mechanisms (epigenesis) occurs during the microevolution of Talitridae. The generalist/specialist continuum concept supports our understanding of both the ecology and microevolution of talitrids. Microevolutionary characteristics of wrack generalists are that they exhibit the most phenotypic variability and occurrences of epigenesis, have the most extensive zoogeographic range, and have the lowest speciation potential and endemism rate. Examples where epigenesis may be part of the microevolutionary process include low/high salinity and hypogean/epigean combined switches giving rise to sibling (sister) species pairs. Current views of the phylogeny of the Talitridae based on either morphological characters used in taxonomy or molecular genetic methods are still under development. Molecular genetic methods show promise of providing a scientifically reproducible phylogeny and temporal history of talitrids (macroevolution), but insufficient coverage of genera within talitrids and of related groups is available to do so yet. [ABSTRACT FROM AUTHOR]

According to the results of U–Pb dating of zircons from igneous rocks of Central Chukotka area (the left bank of the Amguema River), there are two granitoid batholiths (Telekai and Chanuan) and a series of smaller bodies formed during the period 143–127 Ma, far beyond the age of most granitoids of North Chukotka (109–100 Ma). Together with previously published data, these results indicate the existence of a subduction-related magmatic belt at the margin of the Chukotka continental block during, at least, the Late Jurassic and Neocomian time span. In addition, the newly obtained Early Jurassic U–Pb age of igneous rocks (~196 Ma) indicates a more protracted magmatic activity at the margin of the Chukotka microcontinent. The emplacement of Albian (106–100 Ma) granitoids of the observed area was controlled by another fault system and probably related to a separate magmatic event. [ABSTRACT FROM AUTHOR]

Few studies have systematically investigated the factors controlling organic matter enrichment in shales from the Qiongzhusi Formation, within and surrounding the Sichuan Basin, under different depositional environments. This has resulted in different academic understandings and limited clarity on the mechanisms of organic matter enrichment. On this premise, in this study, the basic geological characteristics and depositional paleoenvironments of shales along the passive continental margin, the western Hubei Trough, and the western Sichuan Trough were compared and analyzed using core, outcrop, and mineral testing. Furthermore, data from organic geochemical and elemental analyses were utilized to investigate the different enrichment mechanisms and formation modes of the organic matter in different periods. The results reveal that the organic matter enrichment in this region should be mainly influenced by the preservation conditions, paleo-productivity, and terrigenous input. However, there were clear differences in the main controlling factors in the different periods. In the Q1 phase, the region had a high sea level, had the strongest rifting, had the largest accommodation space, and exhibited characteristics of low terrestrial input and bottom water hypoxia. The changes in the paleo-productivity caused by upwelling currents were the main factors controlling the variations in the organic matter enrichment. In the Q2 phase, the weakened decreasing sea level co-occurred with a reduction in the accommodation space across the region. The organic matter enrichment was significantly controlled by the paleoproductivity, preservation conditions, and terrigenous inputs, and the organic matter enrichment conditions deteriorated from the passive continental margin to the western Hubei Trough and western Sichuan Trough. The total organic carbon (TOC) content of the shale decreased significantly. In the Q3 phase, the entire region entered an infilling stage, which was dominated by an oxygen-rich environment, and the preservation conditions were the decisive factor controlling the organic matter enrichment. The TOC content was low overall, and there were no evident differences across the different zones. [ABSTRACT FROM AUTHOR]

The Ediacaran Period, immediately following the Neoproterozoic Cryogenian glaciations, marked a crucial phase in the Earth's evolutionary history. The paleo‐oceanic environment helped shape the habitability, yet the links between oceanic redox state, hydrochemistry, biological activity, and elemental cycling during this time remain poorly understood. Here, we address this scientific issue based on high‐resolution geochemical data from black shale‐hosted, manganese (Mn)‐rich carbonates within the upper Ediacaran Doushantuo Formation, located on the northern margin of the Yangtze Block, South China. Multiple redox proxies indicate that while the open ocean may have been intermittently oxygenated during the late Ediacaran glaciation, the continental margin slope was characterized by redox stratified conditions with a fluctuating redox interface. These fluctuations were driven by climatic shifts. During the deposition of black shales, a relatively warm and humid climate caused a notable increase in freshwater runoff and glacial meltwater, raising water levels and lowering salinity. The influx of bioessential elements carried by terrestrial runoff promoted primary productivity. By contrast, the deposition of the Mn(II) carbonates occurred under colder, more arid conditions, with limited terrigenous nutrient input, leading to lower organic carbon production. This resulted in the deepening of the redox chemocline over the continental shelf, promoting Mn(II) oxidation and subsequent mineralization. Paleoclimate‐driven redox fluctuations were key in controlling elemental cycling during the late Ediacaran. This may offer insights into similar processes throughout Earth's history. Plain Language Summary: If the late Ediacaran ocean is oxygenated or reducing remains a topic of debate. Here we propose a stratified scenario with an intermittently fluctuating redox interface between O2‐bearing surface waters and O2‐depleted deep waters on the continental margin slope as represented by the Doushantuo Formation of South China. We further establish coupled links between the ancient oceanic redox state, paleoclimate, marine hydrochemistry, biological activity, and Mn‐cycle during this period based on multiple geochemical proxies. Warm and humid climate supplied nutrient elements that fueled high primary productivity, sustaining higher redox interface and widespread H2S‐bearing conditions conducive to black shale deposition. In contrast, a colder, more arid climate limited nutrient supply and productivity, leading to diminished organic carbon synthesis, descending redox interface, and contracted deep O2‐depleted zone, which favored Mn(II) carbonate formation. The fluctuating redox interface created optimal conditions for Mn(II) oxidation, Mn(IV) reduction, and Mn(II) carbonate mineralization during the transformative phase of oxygenation event in the late Ediacaran. This might be general throughout geological history. Key Points: The redox conditions along the continental marginal slope were stratified and fluctuating in the late Ediacaran oceanPaleoclimate variations influenced the basin's hydrochemistry and biological activity, driving shifts in the redox chemoclineThe shifts in the slope's redox chemocline regulated distinct oceanic manganese cycling and mineralization processes in South China [ABSTRACT FROM AUTHOR]

River‐dominated marginal seas play a crucial role in the global carbon cycle. However, the centennial burial record of organic carbon (OC) remains unclear. In this study, we conducted a comprehensive analysis of bulk OC, its isotopic composition (δ13C and Δ14C), biomarkers (lignin and n‐alkanes), and sedimentological evolution based on sediment core from the Yellow River‐dominated Bohai Sea (BS). We also compiled several published OC burial records from other river‐dominated coastal margins. Our findings indicated that since the 1950s, the accumulation of terrestrial OC in central BS has shown a concurrent decline, as evidenced by a ∼50% decrease in terrigenous/aquatic ratio of n‐alkanes (TAR), which accompanied by a significant reduction in sediment load due to the watershed human activities. More intense erosion and resuspension due to stronger hydrodynamic condition under the increasing frequency of winter storms could account for the observed sediment coarsening and concomitant increase of the degraded lignin and old‐OC since the 1980s, suggesting that delta erosion‐induced sediment redistribution could influence the selective transport and accumulation of the more woody allochthonous OC components. The temporal profiles of lignin records indicated a spatial heterogeneity of recent terrestrial OC burial among the large river‐dominated coastal margins under the enhanced global delta erosion. Compared to the fluvial input‐dominated OC burial in the Yangtze River, Pearl River and Mississippi River delta margins, a more hydrodynamic forcing impact on the terrestrial OC burial was discerned in the BS due to the coupled effect of recent climate change and substantial decline in sediment load. Plain Language Summary: Marginal seas play a crucial role in the global carbon cycle, especially under the influence of recent climate change and human activities. In this study, we use multiple indicators to elucidate the terrestrial organic carbon (OC) burial in the river‐dominated coastal margins. Our results suggest that human activities have caused a continuous decrease in terrigenous OC inputs in the Yellow River‐dominated Bohai Sea (BS) over the past decades. However, an enhanced sediment coarsening coupled with a marked increase in terrestrial OC signals, has been observed since the 1980s, reflecting a stronger hydrodynamic forced coastal erosion and the subsequent transport of more woody debris‐related terrigenous OC under the increased winter storms. In addition, under the enhanced global delta erosion, the spatial heterogeneity of lignin records indicates that the terrestrial OC burial in the offshore margins of the Yangtze River, Pearl River, and Mississippi River is primarily influenced by fluvial input, which is contrary to the hydrodynamic impacted OC burial observed in the BS. Our study provides a new insight into the burial patterns and fate of the terrestrial OC in these river‐dominated continental margins. Key Points: Changes in the terrestrial organic carbon (OC) accumulation was assessed in the Yellow River‐dominated coastal margin for the past decadesSediment coarsening and changed terrestrial OC burial could be ascribed to the hydrodynamic forcing under increased winter stormsOC accumulation in the river‐dominated coastal margins constrained by coupled impacts of climate change and anthropogenic activity [ABSTRACT FROM AUTHOR]

The tectonic of the Middle and Late Ordovician in the western margin of the north China Platform is complex, and the accumulation models of organic matter of the Wulalike Formation formed during this period are still unclear. Total organic carbon (TOC) content, mineral composition, organic carbon isotope composition, as well as the major and trace elements in the shale samples were all measured in this study. The Wulalike Formation was formed during a tectonic transition from a passive continental margin to an active continental margin. Hydrocarbon-forming organisms are mainly algae. Primary productivity, terrigenous input, and sedimentation rates influence input, dilution, and degradation of organic matter. The degree of degradation, redox, and basin restriction control the preservation of organic matter. The TOC of the Wulalike Formation is determined by the input and preservation degree of organic matter at different sedimentary periods. The organic matter accumulation model in the Wulalike Formation is controlled by regional structures, dominated by sedimentation rate and preservation conditions. [ABSTRACT FROM AUTHOR]

Core LC42, retrieved from the Central Basin of the northwestern Ross Sea, contains three distinct sediment facies (IRD (ice-rafted debris)-poor bioturbated sandy mud, IRD-rich massive sandy mud, and laminated mud) that are interleaved with each other and deposited over the last 1 Ma. The biogenic components (biogenic opal, total organic carbon, and total nitrogen) of the laminated mud layers are consistently higher than the other two facies throughout the core. Based on the depositional succession of sediment facies and IRD-related depositional processes in the Antarctic continental margin, the laminated mud layers without IRD have been deposited during the glacial periods, but the enhanced paleoproductivity in terms of biogenic components during the mud deposition is unexpected. Backscattered electron imagery substantiates distinctly different componentry of the alternating light and dark laminae in the laminated mud. In particular, the light laminae contain scattered diatom fragments and eroded sand-sized lumps of fossil-bearing mud, whereas the dark laminae are clayey and diatomaceous. Both laminae thus are characterized by the high biogenic components, but they are interpreted to have been principally recycled from older deposits because diatom fragments are mostly reworked and old and their archives are poorly preserved. During the glacial periods, these laminated muds were deposited downward by milky plumes of meltwater discharged underneath the advancing glaciers that scoured the earlier-deposited and semi-consolidated diatom-rich sediments. Our study thus highlights that the recycling of biogenic particles should be precautious to avoid the fallacy of paleoclimatic interpretation in formulating climate-productivity models in the Antarctic continental margin. [ABSTRACT FROM AUTHOR]

The initial disintegration of Gondwana during the Paleozoic laid the foundation for the formation of the Tibetan Plateau in the Cenozoic. Determining the relative positions of the microterranes in Gondwana during the Paleozoic not only informs the subsequent drift and accretion processes of these microterranes but is also crucial to the paleogeographic reconstruction of Gondwana. However, the lack of paleomagnetic constraints on the Devonian paleogeography of the microterranes in the northern part of Gondwana makes this effort challenging. Here, we report paleomagnetic results for the first time from the Early-Middle Devonian sediments of the Zhongba microterrane. The site-mean direction is declination (Ds) = 310.7°, inclination (Is) = -67.2°, ks = 31.2, a95 = 8.3°, and n = 11, in stratigraphic coordinates. Positive fold and reversal tests, together with rock magnetism results and microscopic observations, strongly suggest that the remanence carriers are of depositional origin. The paleomagnetic results meet the paleomagnetic reliability criteria and therefore can be used for tectonic reconstructions. Our results constrain the paleolatitude of the Zhongba microterrane to be 50.0°S ± 11.7°S in the Early-Middle Devonian. Combined with published detrital zircon ages as well as paleomagnetic results and geological data, our data indicate that the Zhongba microterrane, which had no tectonic affinity with the Lhasa terrane, was part of the northern margin of Greater India during 408-388 Ma and coupled with the South Qiangtang terrane, Tethyan Himalayas, and other terranes to form the continuous northern continental margin of East Gondwana. [ABSTRACT FROM AUTHOR]

The provenance history of the Pearl River Mouth Basin is of great significance for understanding how the South China margin evolved from a Mesozoic Andean-type subduction margin into the present-day rifted passive margin. However, the long-term provenance history of continental margin basins in the northern South China Sea is poorly understood. Newly identified Mesozoic-Cenozoic successions from the Lufeng Sag in the eastern Pearl River Mouth Basin provide valuable records of the provenance history and related evolution of the South China margin. Here, we trace the provenance of the eastern Pearl River Mouth Basin using U-Pb ages of zircon and ZTR values (proportions of zircon, tourmaline, and rutile in all transparent heavy minerals) of heavy minerals, and determine the tectonic setting and crustal thickness using trace element ratios and Eu anomalies in zircon. The results show that from the middle Eocene strata--which have a U-Pb age spectrum similar to strata of the Upper Cretaceous--to the Miocene strata, the proportion of Mesozoic age populations gradually increases, while the proportion of Paleozoic age populations decreases. In addition, following the middle Eocene high values, the ZTR values decreased during the late Eocene and then increased during the early Oligocene. Based on the variations in zircon age populations and ZTR values, the middle Eocene sediment is interpreted to have been recycled from Upper Cretaceous to middle Eocene successions, followed by an early Oligocene provenance change from intrabasinal to extrabasinal sources. Moreover, the zircon trace element ratios and Eu anomalies indicate that a widespread Mesozoic continental magmatic arc formed before ca. 90 Ma along the South China margin, and the crust simultaneously thickened during this time. In accordance with the provenance history, the evolution of the South China margin is divided into three tectonic phases: the Paleo-Pacific, Proto-South China Sea, and South China Sea. During the transition from the Paleo-Pacific to the Proto-South China Sea tectonic phase, sediment was recycled from Upper Cretaceous to middle Eocene successions in the eastern Pearl River Mouth Basin. During the transition from the Proto-South China Sea to the South China Sea tectonic phases, the provenance changed from intrabasinal to extrabasinal sources. [ABSTRACT FROM AUTHOR]

The Fossil Bluff Group of eastern Alexander Island records the exceptional preservation of more than 8 km of Mesozoic sedimentary rocks deposited into an accretionary forearc basin that developed unconformably above a late Paleozoic accretionary complex, and in proximity to a continental margin arc during a prolonged phase of enhanced magmatism. Through the Mesozoic, the Fossil Bluff Group evolved from a trench-slope environment to a forearc basin sourced from the continental margin arc. During this period, the Antarctic Peninsula's convergent margin was characterized by episodes of magmatic flare-ups that developed during tectonic compression, crustal thickening, extension, and uplift. U-Pb and Lu-Hf detrital zircon data are used to determine the provenance of the forearc succession and as a monitor of arc magmatic tempos during the late Mesozoic. The magmatic record in the adjacent arc is poorly preserved or partially absent, but the sedimentary record of the forearc basin preserves a largely uninterrupted record of arc magmatism that can be studied with detrital zircon geochronology and geochemistry. The basal succession of the Fossil Bluff Group is sourced from the adjacent accretionary complex, but thereafter it is strongly controlled by the proximal arc in western Palmer Land and is characterized by a mixed arc/recycled signature during episodes of renewed sedimentation. However, the main phases of deposition during the Early Jurassic (ca. 180 Ma), Early Cretaceous (141-131 Ma), and mid-Cretaceous (125-102 Ma) are dominated by arc-only sources. The Lu-Hf isotopic record supports a transition from convergence to extension and a return to convergence during the Mesozoic, which is consistent with accretionary orogens from elsewhere along the West Gondwanan margin. The provenance record during the depositional history of the basin points overwhelmingly to an autochthonous origin; as such, models for parts of the western province of the Antarctic Peninsula being allochthonous are unsupported. [ABSTRACT FROM AUTHOR]

Alkaline basalts produced in continental arcs should contain information different from the arc tholeiite-calc-alkaline-series magmas, and their origin could provide unique constraints on deep mantle composition and material cycling. However, due to their sparse occurrence, alkaline basalts in continental arcs have not been studied thoroughly, which hinders our understanding of the mantle diversity and subduction dynamics under continental arcs. In this study, we present new 40Ar/39Ar ages, major and trace elements, and Sr-Nd-Hf isotopic data for the International Ocean Discovery Program Site U1504 alkaline basalts in the continental arc developed on the South China Block (SCB). These alkaline basalts were generated at ca. 121 Ma and display typical oceanic-island basalt geochemical characteristics. Their relatively high eNd(t) (3.5-3.7) and low (87Sr/86Sr)i (0.7034-0.7040) and La/Nb (0.5-1.0) values suggest that they were mainly derived from an asthenosphere mantle source. Compared to alkaline basalts in the SCB inland, U1504 alkaline basalts exhibit lower K2O/Na2O, Zr/Sm, Zr/Y, eNd(t), and eHf(t) values, indicating the addition of minor sub-continental lithospheric mantle. The enrichment of Nb, Ta, light rare earth elements, and slight depletion of Zr, Hf, and Ti, as well as elevated Fe/Mn and Sm/Yb and low CaO, indicate that their mantle lithology was mainly garnet pyroxenite. Based upon these findings and previous studies, the garnet pyroxenite was probably formed by the interaction of upwelling asthenosphere with slab edges in the scenario of break-off of the Paleo-Pacific Plate, and such interaction diversified the mantle chemistry beneath continental arcs. In conjunction with other reported alkaline basalt data, it is proposed that the enriched asthenosphere mantle beneath the SCB had formed sequentially from inland to coastal since the late Mesozoic, and this may be related to lateral and vertical flow in the deep asthenosphere controlled by the break-off of subducted plates. [ABSTRACT FROM AUTHOR]

The Mesozoic and Cenozoic tectonic evolutionary history of the East Asian continental margin has been the focus of many researchers because of the overprinting of multiple tectonic domains. Previous studies have suggested that the westward subduction of the Paleo-Pacific Plate and the Pacific Plate resulted in the deconstruction of the North China Craton and controlled the formation of the related basins on the continental margin of East Asia. However, controversy remains regarding the tectonic transition processes and mechanisms that occurred from the Mesozoic to the Cenozoic. Since the Mesozoic, the Bohai Bay Basin on the eastern margin of the North China Craton of East China has been influenced by multiple tectonic domains of the Paleo-Tethys, Paleo-Pacific, and Pacific oceans, and there are complete records of these tectonic transition processes. The Bozhong Depression is a subbasin in the Bohai Bay Basin, which is a crucial area for researching the tectonic evolution of the Bohai Bay Basin throughout the Mesozoic-Cenozoic and the regional tectonic evolution of the eastern continental margin of China. Based on 3-D seismic data, logging core data, and a balanced cross section in the Bozhong area, combined with data from the apatite fission-track inversion model, we reconstructed the tectonic evolutionary history of central Bohai Bay Basin and established a three-cycle and eight-stage tectonic model of the central Bohai Bay Basin during the Mesozoic-Cenozoic. The three cycles are the Indosinian, the Yanshinian, and the Himalayan. (1) The Indosinian was marked by two stages. During the early Indosinian, NW-trending thrust faults were formed due to the collision and northward subduction of the South China Block underneath the North China Block. In the late Indosinian, the tectonic stress in the central Bohai Bay Basin shifted from compression to extension. Consequently, the thrust faults reversed, leading to the deposition of Early-Middle Jurassic strata. (2) The Yanshanian cycle comprises three main phases. Early Yanshanian transpressional shearing led to the formation of a NE/NNE-trending, left-lateral strike-slip fault due to NWW-directed subduction of the Paleo-Pacific Plate. Middle Yanshanian transtensional shearing was driven by Paleo-Pacific Plate rollback and resulted in regional extension and the negative inversion of previous compressive faults. Late Yanshanian compression gave rise to the basin reversion, which resulted from an increased subduction speed of the Paleo-Pacific Plate and a transition from a high angle to a low angle. (3) The Himalayan cycle was marked by three phases. During the early Paleogene, the region was characterized mainly by extension, and NEtrending, right-lateral strike-slip normal faults began to form. This coincided with a decrease in the Pacific Plate's subduction speed. In the late Paleogene, the subduction rate of the Pacific Plate increased, resulting in the change of the central Bohai Bay Basin from an extensional environment to one marked by regional differential compression. In the Neogene, regional thermal subsidence and depression sedimentation occurred, which were probably induced by the increasing subduction speed and rollback of the Pacific Plate. The Bozhong Depression has experienced multiple stages of tectonic evolution, which indicates the concurrent and superimposed effects and transition of multiple tectonic domains. [ABSTRACT FROM AUTHOR]

Although abundant Neoproterozoic igneous rocks exposed along the periphery of the Yangtze Block of the South China Craton record the tectonic processes of the assembly and breakup of the Rodinia supercontinent, the mechanism that induced the rifting of the South China Craton from Rodinia and reconstruction of the paleogeographic position of the South China Craton in Rodinia remain controversial. We document two episodes of bimodal intrusions with emplacement ages of ca. 785 Ma and ca. 750 Ma in the Diancangshan Massif that provide critical constraints on the rifting processes and mechanisms. The rock association and the elemental and Hf-O isotopic signatures of these two episodes of bimodal intrusions illustrate that they are an important component of the Panxi-Hannan magmatic arc in the western Yangtze Block. The spatial pattern of Neoproterozoic sedimentary rocks to the west of the Panxi-Hannan arc and their provenance indicate that intra- arc rifting promoted the separation of microplates such as the Xuelongshan and Diancangshan massifs and even the Yidun Block from the western Yangtze Block and the mechanism induced synchronous deposits in these regions. [ABSTRACT FROM AUTHOR]

Submarine landslides exhibiting extreme geometrical and run-out characteristics have been identified and mapped along most continental margins; raising concerns about potential risks to populations should similar events occur. Hazards associated with such events have frequently been assessed using approximations, resulting in data unsuitable for mitigation strategies. Three approximations appear consequential: (i) addressing the problem in two dimensions, thereby neglecting the effect of complex morphology; (ii) employing a deterministic approach that disregards uncertainty related to the heterogeneity of sediment properties; and (iii) treating the sediment as a perfectly elastic–plastic material, simplifying the mechanical behaviour and overlooking the degradation of sediment mechanical properties (strain softening) during different phases of slope movement. Here, we introduced the strain-softening behaviour into a 3D slope stability model. Identification of the critical failure surface was conducted in terms of the probability of failure, considering the influence of sediment parameter variability and uncertainty on the likelihood of failure. The developed model was then used to assess the slope stability of a well-studied example from the literature, the Nice slope (SE France). Our findings indicate that neglecting lateral morphological changes leads to an overestimation of the probability of failure. Additionally, we demonstrated that strain-softening behaviour could significantly affect the factor of safety and the probability of failure for the studied slopes. We argue that a risk assessment and definition of a mitigation strategy require well-advanced characterisation of the mechanical behaviour of sedimentary layers and an analysis incorporating the complex morphology of submarine slopes. [ABSTRACT FROM AUTHOR]

The structure, composition, and evolution of oceanic plateaus are poorly understood and strongly debated. Here, we compared the magmatic history and crustal structure of Afar with the Greenland–Iceland–Faroe Ridge and other oceanic plateaus. Key similarities indicate that Central Afar represents the early stage of development of a specific type of oceanic plateau: a rifted oceanic magmatic plateau (ROMP). These features begin their formation before continental rifting and develop into wide magmatic rift systems capable of isolating slivers of continental crust within the new igneous crust. Importantly, the anomalous magmatism continues through breakup and for several tens of millions of years afterward. The recognition of Central Afar as a precursor of this type of oceanic plateau allows us to better understand their formation. Increased melt production causes early and voluminous magmatism, ultrathick igneous crust, and repeated reorganization of the extension locus during rift/ridge jumps, which delay the onset of oceanization and Penrose-style crustal production. These factors differentiate ROMPs from many magma-rich rifted continental margins and from other types of oceanic plateaus, highlighting that Central Afar and other ROMPs should neither be considered as conventional magma-rich margins nor be considered as normal oceanic crust. [ABSTRACT FROM AUTHOR]

Ergunahe Formation is an important component of the metamorphic crystalline basement of Erguna Block, recording the Precambrian tectonic evolution history; however, it has small distribution area, poor natural outcrops, and relatively little research. Therefore, the systematic field geological survey of Ergunahe Formation in Enhehada area of Erguna Block combined with LA-ICP-MS zircon U-Pb dating, the characteristics of major and trace elements were analyzed; the formation age, protolith types, material source and sedimentary environments of Ergunahe Formation were explored. The results show that Ergunahe Formation is mainly a set of parametamorphic rocks, the sericite phyllite and chlorite schistose mylonite have similar overall petrogeochemical characteristics, showing rich Si (SiO2 content is 63.45%-79.01%), Κ (Κ2Ο content is 2. 22%-3.33%) and Al (Al2O3content is 9.76%17.10%); the zircon U-Pb weighted average age is (583.0±1.7) Ma, formed in Neoproterozoic Sinian. The chondrite normalized REE pattern shows a right-leaning pattern with enrichment of LREE and depletion of HREE, and a insignificant negative Eu anomaly. Trace elements are depleted in high field strength elements Nb, Ti, P, and large ion lithophile elements Ba, Sr, and enriched in high field strength elements Zr, Th. U. Hf, and large ion lithophile element Rb. The material source is dominated by felsic sandstone, with the protolith being sandy mudstone and intermediate-acidic volcanic rocks, indicating low maturity, proximal deposition, and a sedimentary environment of an active continental margin, and the presence of passive continental margin materials. [ABSTRACT FROM AUTHOR]

In this study, we reveal the deformational structure of the crust of the northern part of the Ryukyu Arc and Okinawa Trough using ambient noise tomography. Compared with southern Ryukyu, the northern segment exhibits a wide and shallow basin, a crust without localized thinning, slow extension rates, and highly arc‐oblique, right‐lateral retreat of the Ryukyu Arc. We present both isotropic and azimuthally anisotropic shear‐wave velocity models using data recorded by an ocean‐bottom seismometer array and nearby island stations. The isotropic model demonstrates a monotonic decrease in velocity from the backarc to the forearc, in accord with the accretionary‐prism origin of the latter. The resolved azimuthal anisotropy exhibits arc‐parallel and arc‐perpendicular fast shear‐wave polarization directions in the upper to mid‐crust and the lower crust to uppermost mantle in much of the arc and backarc, respectively. We interpret the arc‐parallel anisotropy as resulting from the anisotropic fabrics aligned by the vertical shearing imposed by the right‐lateral motion of the Ryukyu Arc. The underlying arc‐perpendicular anisotropy may be attributed to horizontal shearing driven by corner flow in the mantle wedge. We found arc‐perpendicular anisotropy in the forearc upper crust, which may reflect crack alignment caused by the collision of the Amami Plateau. The oblique arc retreat and the resolved deformation fabrics in the arc and backarc together attest to the shear‐dominant, transtensional nature of the northern Ryukyu continental rift system. Some of the features in northern Ryukyu may be better explained from the perspective of transtensional rifting. Plain Language Summary: The northeastern margin of the Eurasian Plate is currently separating from the continent, creating the non‐volcanic Ryukyu Arc and the Okinawa Trough backarc basin. Two‐dimensional cross‐arc seismic imaging has revealed significant variations in the seafloor morphology and crustal structure along the arc; however, some of the rifting characteristics are difficult to reconcile when they coexist in the same segment. Meanwhile, GPS (Global Positioning System) velocities measured along the arc indicate highly oblique arc retreat in the north and nearly orthogonal retreat in the south. The consequences of oblique rifting in northern Ryukyu remain poorly understood. To address these questions, three‐dimensional imaging of the crust is crucial. In this study, we construct an ambient noise‐based three‐dimensional tomographic model in the northern segment of this continental margin rift system constrained by ocean‐bottom seismometer and land station data. The anisotropic part of the model reveals the deformation structures of the backarc, arc, and part of the forearc, providing insights into the nature of the transtensional rifting and resolving apparent contradictions in coexisting features. Key Points: The upper–mid and lower crust of the northern Ryukyu arc–backarc exhibit arc‐parallel and arc‐normal anisotropy, respectivelyThe arc‐parallel anisotropy is driven by Ryukyu Arc retreat, and the arc‐normal anisotropy is driven by corner flow in the mantle wedgeSeveral crustal features in northern Ryukyu can be explained and reconciled given a shear‐dominant, transtensional rifting environment [ABSTRACT FROM AUTHOR]

A striking feature of Oxygen Deficient Zones (ODZs) on the eastern boundary of the Pacific Ocean are large subsurface plumes of iodide. Throughout the oceans, iodate is the predominant and thermodynamically favored species of dissolved iodine, but iodate is depleted within these plumes. The origin of iodide plumes and mechanism of reduction of iodate to iodide remains unclear but is thought to arise from a combination of in situ reduction and inputs from reducing shelf sediments. To distinguish between these sources, we investigated iodine redox speciation along the Oregon continental shelf. This upwelling system resembles ODZs but exhibits episodic hypoxia, rather than a persistently denitrifying water column. We observed elevated iodide in the benthic boundary layer overlying shelf sediments, but to a much smaller extent than within ODZs. There was no evidence of offshore plumes of iodide or increases in total dissolved iodine. Results suggest that an anaerobic water column dominated by denitrification, such as in ODZs, is required for iodate reduction. However, re‐analysis of iodine redox data from previous ODZ work suggests that most iodate reduction occurs in sediments, not the water column, and is also decoupled from denitrification. The underlying differences between these regimes have yet to be resolved, but could indicate a role for reduced sulfur in iodate reduction if the sulfate reduction zone is closer to the sediment‐water interface in ODZ shelf sediments than in Oregon sediments. Iodate reduction is not a simple function of oxygen depletion, which has important implications for its application as a paleoredox tracer. Plain Language Summary: Inorganic iodine has two stable forms in the ocean, iodate and iodide. In most of the subsurface ocean, iodate is the predominant compound, except in regions of the ocean without oxygen, where iodate is depleted and iodide accumulates. The causes of iodate to iodide conversion remains unclear, but it is often linked to denitrification since both iodate and nitrate can be used by anaerobic bacteria in respiration. We compared iodine behavior in the coastal margins of Oregon and Mexico's Pacific Coast. The former has no denitrification in the water column, whilst the latter has a vast subsurface zone where denitrification occurs. We sampled the low but nonzero oxygenated waters on the Oregon continental shelf. We did not observe iodide accumulation or iodate depletion, in contrast to the Mexican study area. Surprisingly, further analysis revealed that the difference is not about water column denitrification at all, but arises because processes in the shelf sediments are very different in the two regions. We now think that sulfide accumulation near the sediment water interface in Mexico but not Oregon contributes to this difference. Thus, linkage between sulfur and iodine geochemistry may determine the underlying differences between these two regimes. Key Points: Despite hypoxia and high Fe(II), iodide accumulation was not observed on the Oregon shelfRe‐analysis of Oxygen Deficient Zone data reveals that most iodate depletion is not linked to oxic or nitrogenous metabolismsWe propose iodate depletion occurs due to interaction between iodate and sulfide in sediments [ABSTRACT FROM AUTHOR]

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The recent discovery of large oil and gas fields in the deep-water of the Senegal Basin has drawn global attention. Despite this, several exploration wells in this area fail, which can be primarily contributed to a lack of understanding of the basin's structures and hydrocarbon accumulation conditions. This study examines these characteristics utilizing gravity, seismic and drilling data, and finally makes a comparison with the Cote d'Ivoire Basin, a typical transform margin basin in the South Atlantic. The results suggest that the Senegal Basin, influenced by multiple transform faults and a weak Paleozoic basement, experienced three evolutionary stages: rifting, transitional, and drifting. Each stage contributed to the development of distinct depositional sequences - syn-rift sequences, sag sequences, and continental margin sequences, respectively. The Triassic - Early Jurassic rifting stage predominantly formed continental deposits, like fluvial, lacustrine, and deltaic deposits, in the syn-rift sequences. The Middle-Late Jurassic transitional stage, influenced by transform faults, witnessed the formation of marginal ridges or submarine uplift zones. These zones, in conjunction with landward high terrains, formed a restricted environment promoting the development of source rocks in the sag sequences. During the drifting stage, three types of reservoirs, namely platform carbonate rocks, deltas, and slope-floor fans were formed. Notably, large-scale hydrocarbon reservoirs have been found in the deltas and the slope-floor fans both in the Senegal Basin and the Cote d'Ivoire Basin. The Upper Jurassic - Aptian platforms exhibit thick carbonate rocks and organic reefs on their edges, suggesting substantial potential for hydrocarbon exploration in the Senegal Basin. [ABSTRACT FROM AUTHOR]

We present significant findings of the Kausani Granite Gneiss within the Inner Lesser Himalayan Sedimentary Zone (iLHSZ) just north of the North Almora Thrust (NAT). The Kausani Granite Gneiss body lies within the quartzite of the Someshwar Formation and has a tectonized contact and a discordant relationship on the north side. Detailed seismic profiling across the body also confirms a similar result. Cathodoluminescence images of zircon from the Kausani body show no inheritance of older cores. The U–Pb ages from the zircon populations separated from the Kausani body give a crystallization age of 1866 ± 3 Ma. Along with the Upalda granite gneiss and Toneta granite gneiss near the Alakhnanda Thrust in the Garhwal Himalaya and the Dungeshwari granite gneiss near the Dailekh Thrust in Nepal, the Kausani Granite Gneiss north of NAT Kumaun Himalaya forms a major terrain boundary. These gneissic bodies mark the southernmost extent of felsic magmatism at NAT, rather than the Main Central Thrust. An about 1.8 billion years‐old magmatic event in the LHSZ suggests that it is a currently active continental margin inside the 'Greater India' region, now situated in the Himalayan domain. However, the Pb‐loss modelling of the U–Pb zircon data reveals thermal events during the Himalayan Orogeny (~45 Ma). [ABSTRACT FROM AUTHOR]

We investigate, using observations from seismic reflection data, the lateral variability in breakup extrusive magmatic addition along the strike of the Pelotas segment of the austral South Atlantic rifted margin and its control on post-rift accommodation space and sediment deposition. Our analysis of regional seismic reflection profiles shows that magmatic addition on the Pelotas margin varies substantially along strike from extremely magma-rich to magma-normal within a distance of ∼300 km. Using 2D flexural back-stripping, we determine the post-rift accommodation space above top volcanics. In the north, where volcanic seaward-dipping reflectors (SDRs) are thickest, the Torres High shows SDRs up to ∼20 km thick, and post-breakup water-loaded accommodation space is much less than in the south, where magmatic addition is normal and SDRs are thinner. We show that post-breakup accommodation space correlates inversely with SDR thickness, being less for magma-rich margins and more for magma-normal/intermediate margins. The Rio Grande Cone, with large sediment thickness, is underlain by small SDR thicknesses allowing large post-breakup accommodation space. A relationship is observed between the amount of volcanic material and the two-way travel time (TWTT) of first volcanics: first volcanics are observed between 1.2 and 2.2 s TWTT for the highly magmatic Torres High profile, while, in contrast, for the normally magmatic profiles in the south, first volcanics are observed between 4.2 and 6.5 s TWTT. The observed inverse relationship between post-breakup accommodation space and SDR thickness is consistent with predictions by a simple isostatic model of continental lithosphere thinning and magmatic addition melting during breakup. The methodology that we use in this paper provides a new approach for investigating the complex magmatic and sedimentary evolution of rifted continental margins. [ABSTRACT FROM AUTHOR]

This study focuses on the post-Miocene neotectonic evolution of the slope-perched sedimentary basins around the Eastern Korean Continental Margin and which category these basins could be classified into. The Hupo Basin, the largest neotectonic sedimentary basin on the Eastern Korean Continental Margin, comprises three key geological components: 1) Neotectonic Sequence, which has divergently filled the Hupo Basin since the Early Pliocene, 2) Hupo Fault, a N-S striking, high-angle thrust (or reverse) fault that bounds the Hupo Basin to the east, and 3) Hupo Bank, a N-S elongated submarine wave-cut platform that sits on top of the uplifted eastern Hupo Fault block. On the basis of stratigraphic and structural restoration, we conclude that the Hupo Basin was formed by the compressional uplift of the Hupo Bank during the incipient subduction of the Ulleung Basin crust after the Miocene. Given the morphostructural features of the Hupo Basin and its host incipient subduction system, we categorize it as a sort of piggyback basins. The basin-forming process shown in this study is commonly found in numerical models that simulate modern cases of subduction initiation around the world. [ABSTRACT FROM AUTHOR]

The subduction and rollback of the paleo-Pacific plate during Mesozoic time was the key engine for the evolution of the continental margin in eastern China. It led to lateral accretion of continental crust in Northeast China, lithospheric destruction beneath the North China Craton, and the generation of huge volumes of felsic magmatic rocks in South China. This had a profound influence on deep material cycles and the evolution of epigenetic environmental systems along the continental margin of East Asia. To fully understand the transformation of the dynamic mechanism during the subduction and rollback of the paleo-Pacific plate, we have attempted to trace the remnants and fragments of the subducted paleo-Pacific plate at great depths. Such remnants in both temporal and spatial dimensions can be tracked by using geochemical and geophysical approaches. Studies of the trace elements, Mg-Zn isotopes and Os-Nd-Hf-Pb-O isotopes in continental basalts from eastern China reveal a significant number of the remnants of subduction of the paleo-Pacific plate, and the initial subduction can be traced back to the Early Jurassic. Large-scale geophysical imaging unveils a multitude of high-velocity anomalies in the lower mantle of East Asia. Notably, many high-velocity bodies, aptly referred to as "slab graveyards", are nestled at the base of the lower mantle. Numerous isolated high-velocity anomalies are also present in the upper part of the lower mantle, creating conduits for the descent of the subducted slabs into the lower mantle. However, a resolution of the remnants for the subducted slabs within the lower mantle are quite low. Consequently, their impact on the lower mantle's dynamics is yet to be thoroughly investigated. Finally, the presently observed big mantle wedge (BMW) in East Asia has developed through subduction of the Pacific plate in the Cenozoic. However, following the rollback of the paleo-Pacific plate (began at ∼145 Ma), a Cretaceous BMW system would also form above the mantle transition zone in East Asia. There are significant differences in tectonic-magmatic processes and basin-forming and hydrocarbon-accumulation processes among different regions along the East Asian continental margin. Such differences may be controlled by variations in the speed and angle of rollback of the paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

The current study reports the occurrence of a deformed Paleoproterozoic K-rich metasedimentary rock unit at the eastern margin of Bastar Craton, India. Geochemical studies of the metasedimentary rocks suggest the presence of an active continental margin at the eastern part of the Bastar Craton. Detailed petrological and mineralogical studies suggest that K-feldspar, quartz, chlorite, muscovite, kaolinite, and ± biotite represent the primary mineral assemblage in the rock unit. Combined mineral thermobarometric and P–T pseudosection estimate the peak metamorphic condition (i.e. M3 metamorphic) at T ~ 550 °C, P ~ 0.5 GPa. Furthermore, monazite grains (about 20–60 μm in diameter) were dated using the in-situ U–Th–Pbtotal dating method under EPMA. Based on composition and texture, monazite spot ages can be categorized into four groups: Group I, Group II, Group III, and Group IV. The mean age of the oldest monazite population (Group I) at ~ 2100 Ma suggests vertical sagging of the sedimentary basin and the associated M1 metamorphism. The M2 metamorphic event is represented by the Group II monazite population's mean age of ~ 1629 Ma. Rhyolite magmatism in the eastern margin of the Bastar Craton may be connected to this specific event. The Group III monazite mean age of ~ 1533 Ma represents the M3 metamorphic event (peak metamorphic condition). This event could be linked to the accretionary growth at the Bastar Craton's eastern boundary during the assembly of the Columbia supercontinent. Furthermore, the M2 and M3 events may correlate with orogenic events recorded in the Central Indian Tectonic Zone at ca 1.62 and 1.5 Ga, respectively. Finally, the mean age of ~ 528 Ma for the Group IV monazite population represents Pan-African orogenic activity along the eastern margin of the Bastar Craton. [ABSTRACT FROM AUTHOR]

Submarine canyons, prominent features on continental margins, hold significant scientific and engineering implications. Despite extensive research on various types of submarine canyons, current understanding of those canyons developed on the upper continental slope, recognized as the most common type globally, remains limited. The Shenhu Canyons on the upper continental slope of the northern South China Sea, comprising over 19 subparallel features persistently developed from the Late Miocene to Quaternary, offer an excellent opportunity for in‐depth study. Previous assumptions suggested a unidirectional eastward migration of these canyons parallel to the host margin, primarily based on observations from two‐dimensional transverse seismic profiles. However, this study's analysis using three‐dimensional seismic data mapping reveals that not all canyons have migrated eastward; 28% display an opposite or a zigzag patterned migration, challenging previous assumptions. The eastward migration of the Shenhu Canyons on the eastern slope of the palaeo‐Pearl River shelf‐edge delta can be linked to the south‐east–southward progradation of the host margin and the palaeo‐shelf‐edge delta. However, the overall eastward migration pattern is complicated by submarine landslides and turbidity current processes. Landslides can influence the direction and magnitude of canyon migration through four mechanisms: turbidity current diversion; retrogressive development of canyon‐wall landslides; retrogressive landslides on surrounding open slopes; and emplacement of landslides in canyon thalwegs. These mechanisms may result in widening, bifurcation, confluence or obstruction of canyons, contributing to canyon migration. Erosion by turbidity currents can trigger canyon‐wall failures, which in turn promote the lateral migration of the canyons. If overspilled turbidity currents lead to the growth of levées in the lower reaches, canyon confinement increases, suppressing lateral migration. The inherited high‐gradient Palaeogene syn‐rift tectonic slope, combined with the depositional delta‐front slope of the palaeo‐shelf‐edge delta, creates favourable conditions for the initiation and persistent development of the straight Shenhu Canyons. This comprehensive analysis provides valuable insights into the complex dynamics and factors influencing the migration of upper continental slope submarine canyons. [ABSTRACT FROM AUTHOR]

The amalgamation and breakup of the West Gondwana shaped the South American platform. The dynamics during the processes can be reflected by crust anisotropy of the platform, but there are no specialized crustal anisotropic measurements yet. Splitting analysis of Moho-converted shear waves in P -wave receiver functions (Pms) can reveal crustal-scale anisotropy, which is important for understanding the dynamic evolution of the crust and for the interpretation of mantle anisotropy from splitting analysis of core–mantle refracted shear waves (XKS phases). This study measured crustal anisotropy for the old and stable South American platform by Pms splitting analysis. The splitting times vary mainly in the range of 0–0.5 s, with a regional mean of 0.2 s, slightly lower than that observed in tectonically active regions. The detected crustal anisotropy shows distinct characteristics and spatial zoning, providing insights into tectonic processes. (1) Fast polarization directions at stations close to the Transbrasiliano Lineament (TBL) are oriented NNE–SSW, generally consistent with the strike of the TBL but inconsistent with the maximum horizontal compressive stress, implying that they might be formed by dynamic metamorphism during the formation of the TBL. (2) Crustal anisotropy along the passive continental margin in the east and northeast is weak. Still, the fast polarization directions tend to be oriented along the margin, implying the existence of fossil extensional crustal fabrics formed during the continental rifting of West Gondwana. (3) The Paraná Basin, one of the world's largest Large Igneous Provinces (LIP) covered by continental flood basalts, shows distinctively strong anisotropy, with fast polarization directions highly aligned with mantle anisotropy, implying that synchronous crust–mantle deformation occurred in these regions as a result of magmatism during the breakup of West Gondwana. [ABSTRACT FROM AUTHOR]