Gondwana Research最新文献

{"title":"Sr–Nd–Hf isotope evidence from Paleoproterozoic mafic–ultramafic intrusions, Pechenga belt, Russia: Implications for recycled oceanic crust in mantle plume","authors":"Sakine Moradi ,&nbsp;Lie-Meng Chen ,&nbsp;Qiao Su ,&nbsp;Valery F. Smol’kin ,&nbsp;Song-Yue Yu ,&nbsp;Amjad Hussain","doi":"10.1016/j.gr.2025.07.019","DOIUrl":"10.1016/j.gr.2025.07.019","url":null,"abstract":"<div><div>The mafic–ultramafic rocks in the Pechenga belt offer new insights into intraplate magmatic processes associated with mantle plumes within the Fennoscandian Shield. This study presents new major- and trace element data, along with Sr–Nd–Hf isotope compositions for wehrlite, clinopyroxenite, and gabbro rocks from the 1980 Ma ore–bearing Western and Southeastern Pilgujarvi intrusions. These data are used to constrain the nature of the mantle source and tectonic setting of these intrusions. All rocks show enrichment in LREEs, slight enrichment to depletion in Nb and Zr, weak to strongly positive Ti anomalies, and depletion in LILEs (e.g., Ba and Sr). The E–MORB–like wehrlites have positive initial ε_Nd (+0.7 to +2.3) and ε_Hf (+2.4 to +5.5) values in both intrusions and show low ⁸⁷Sr/⁸⁶Sr_(i) ratios (0.70163–0.70353) in the Western intrusion but slightly elevated ones (0.70240–0.70719) in the Southeastern intrusion. The Western clinopyroxenites have positive initial values of ε_Nd (+0.6 to +1.2) and ε_Hf (+1.6 to +3.1) with low ⁸⁷Sr/⁸⁶Sr_(i) ratios (0.70061–0.70256). The OIB–like gabbros in both intrusions are marked by slightly negative to positive initial values of ε_Nd (−0.2 to +2) and ε_Hf (−0.76 to +8.7), with low ⁸⁷Sr/⁸⁶Sr_(i) ratios (0.70109–0.70386). Trace elements ratios (e.g., La/Yb and Dy/Yb) and isotopic compositions indicate that all rocks were formed by partial melting of a garnet–bearing asthenospheric mantle source. This source was previously metasomatized by young altered oceanic crust and subducted components (i.e., fluids and melts), leading to HIMU–like signatures. The contribution of recycled oceanic crust resulted in a hybrid mantle source, dominated by pyroxenite/eclogite rather than peridotite. The parental magma of these rocks underwent variable degrees of closed–system crystallization, and minimal wall–rock contamination (∼1–5 %) during ascent. We infer that both Western and Southeastern Pilgujarvi intrusions were genetically related to an asthenosphere–derived mantle plume during an intra–extensional regime. This model is consistent with geological, geochemical, and isotopic evidence from other Paleoproterozoic mafic–ultramafic rocks across the eastern Fennoscandian Shield.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 312-330"},"PeriodicalIF":7.2,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144886735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Model-based estimation of microplastic stock in China’s reservoirs: A continental assessment","authors":"Yu Chen ,&nbsp;Yuchuan Meng ,&nbsp;Guodong Liu ,&nbsp;Xiaohua Huang ,&nbsp;Ke Chen ,&nbsp;Yichen Liu ,&nbsp;Shijing Wan","doi":"10.1016/j.gr.2025.07.017","DOIUrl":"10.1016/j.gr.2025.07.017","url":null,"abstract":"<div><div>Reservoirs act as important vectors for land-to-ocean plastic transport and long-term sinks for plastics, where the accumulation of microplastics poses potential risks to the freshwater ecosystems. Despite increasing public concern about microplastic pollution in reservoirs, it remains challenging to conduct large-scale assessments of microplastic stocks in reservoirs required for developing effective mitigation, due to the large amount of labor needed in the microplastic sampling and analysis and the data incomparability among the existing microplastic data. To address this gap, here we introduce a modeling approach based on geographically distributed plastic waste in the reservoir-specific watershed and reservoir characteristics to estimate the microplastic stock in freshwater reservoirs. Microplastic data in global reservoirs were first collected and screened based on their reliability scores, followed by realigning the abundance to the full microplastic continuum (1–5000 μm). Combined with reservoir capacity and watershed plastic waste data, the microplastic stocks in reservoirs formed the dataset for model development, which was partitioned into the calibration (<em>n</em> = 42) and validation (<em>n</em> = 49) sets. The model achieves a goodness-of-fit of 0.79 for the calibration set and 0.833 for the validation set, to predict the microplastic number stock. Regarding the microplastic mass stock, the goodness-of-fit is 0.76 and 0.826 for the calibration and validation sets, respectively. We subsequently apply this model to estimate microplastic stocks in China’s reservoirs. We estimate that ∼ 10 (range: 2.5–24.7) thousand metric tons of microplastics are present in the reservoir surface waters in China, with large-scale reservoirs accounting for the majority of microplastic stock. The applicability of our approaches goes beyond the context of reservoirs in China, potentially enhancing the understanding of the plastic pollution state in global reservoirs.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 210-219"},"PeriodicalIF":7.2,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Core-refracted shear-wave anisotropy beneath the Korean Peninsula: insights into its tectonic evolution","authors":"Samuel Celis,&nbsp;Tae-Kyung Hong,&nbsp;Junhyung Lee,&nbsp;Seongjun Park,&nbsp;Yanbing Liu,&nbsp;Byeongwoo Kim,&nbsp;Jeongin Lee,&nbsp;Dong Geon Kim","doi":"10.1016/j.gr.2025.07.018","DOIUrl":"10.1016/j.gr.2025.07.018","url":null,"abstract":"<div><div>The tectonic history of the Korean Peninsula is marked by the Permo-Triassic collision between the North and South China blocks and the subsequently openings of the Yellow and East Seas during the Late Oligocene and Miocene. Despite well-constrained timing, the mechanisms behind these major tectonic episodes remain the subject of ongoing scientific debate. We studied seismic anisotropy from core-refracted shear-wave splitting to place constraints on lithospheric-scale and upper mantle structures and dynamics and provide insights into the tectonic evolution of the Korean Peninsula. We implemented the eigenvalue-based method to measure the splitting parameters and used the transverse energy minimization and cross-correlation techniques to validate our results. We found delay times ∼ 1.5 s which is consistent with anisotropy residing in the asthenospheric and/or lithospheric mantle. Our results strongly suggest that the anisotropy signature of past tectonic events have been preserved and that the upper asthenosphere and lithosphere have undergone coherent deformation. Based on our model, we interpret that the Hongseong-Imjingang belt is part of the collision boundary, since we observed a lateral variation of the splitting parameters coinciding with it. We suggest two possible scenarios for the continuation of the collision suture beyond this belt: (1) one offshore with the boundary coinciding with the West Marginal Fault Zone, and (2) another one onshore along the southern limit of the Gyeonggi massif. Our observations support a fan-shaped opening mechanism for the East Sea and an eastward post-collisional extension for the Yellow Sea. Lastly, the measured splitting parameters beneath the western Gyeonggi and Yeongnam Precambrian massifs appear to be in good agreement with a possible fossil anisotropy.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 220-239"},"PeriodicalIF":7.2,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linkage of paleolake to climate change during the Early Permian Artinskian warming","authors":"Anbin Wu ,&nbsp;Jian Cao ,&nbsp;Jingkun Zhang ,&nbsp;Wenxuan Hu ,&nbsp;Yuce Wang ,&nbsp;Chenjia Zhang ,&nbsp;Yong Tang","doi":"10.1016/j.gr.2025.07.005","DOIUrl":"10.1016/j.gr.2025.07.005","url":null,"abstract":"<div><div>The linkage of paleolake to past climate change is an important but under-recognized problem of broad geological interest. Here we present a pilot study on the Early Permian Artinskian warming (<em>ca</em>. 290 Ma) during the Late Paleozoic Ice Age (LPIA), using comprehensive records of organic-rich fine-grained rocks in a large paleo-lake system in the mid-latitudes of Northern Pangea, i.e., the Early Permian Lucaogou Formation in the paleo-Junggar lake, one of the largest known Phanerozoic lakes. Results show that the elevated continental chemical weathering (evidenced by elevated CIA [chemical index of alteration] values) and negative carbon isotopic excursions (CIEs) in the Lucaogou Formation reveal that climate warming occurred during the Artinskian warming event. Paleoenvironmental parameters associated with<!--> <!-->climate warming such as Cu/Ti and Sr/Ba ratios and P and total organic carbon (TOC) contents exhibit synchronous changes, indicating that climate warming during the Artinskian intensified the hydrological cycle, causing an increase in riverine nutrient input and an enhancement of aquatic primary productivity. Coupled with stable salinity stratification in the lake, these processes facilitated the enrichment of organic carbon (TOC ∼5.0 %). Further evidence from the ¹³C-enriched (δ¹³C = 3.2–12.3 ‰; average = 6.1 ‰) signals in authigenic dolomites reveal that intense microbial methane cycling occurred in the lake. Moreover, the co-variation of unusually high sediment mercury concentrations with CIEs, high CIA values and TOC contents indicates that volcanism was likely the key initial factor driving climate warming and the hydrological cycle, as well as promoting the burial of organic carbon and methane release in lakes. It is estimated that ∼290 Gt of organic carbon was extracted and sequestered in the paleo-Junggar lake from the atmosphere–ocean system during ∼3 Ma. The organic carbon burial rate is estimated at ∼1 × 10¹¹ gC/yr, accounting for approximately 0.1–0.2 % of the global organic carbon burial rates over the same period, and generated ∼540 Gt of methane during the Artinskian warming. Our new insights highlight the importance of terrestrial carbon cycling during the critical geological transition intervals. The carbon sequestration in these lakes could have had a global effect, with negative feedbacks in the exogenous carbon cycle, whereas the emissions of methane contributed to global warming as a carbon source.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 125-138"},"PeriodicalIF":7.2,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144830542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tectonic and paleogeographic evolution during closure of the Paleo-Asian Ocean and their effects on biosphere","authors":"Yongfei Ma ,&nbsp;Yongjiang Liu ,&nbsp;A.Y. Peskov ,&nbsp;M.V. Arkhipov ,&nbsp;Li Zhang ,&nbsp;Sihua Yuan ,&nbsp;Qingbin Guan ,&nbsp;Boran Liu ,&nbsp;Hongru Wang ,&nbsp;Xiaoyan Liu","doi":"10.1016/j.gr.2025.07.014","DOIUrl":"10.1016/j.gr.2025.07.014","url":null,"abstract":"<div><div>The tectono-paleogeographic processes that operated during the closing of the Paleo-Asian Ocean had a significant influence on the biosphere but poorly understood.The Zhesi Formation, which formed during the middle Permian, consists of marine facies strata, whereas the Linxi Formation, which accumulated in the late Permian, comprises terrestrial facies sediments, indicating a coeval marine-to-terrestrial transition. The biosphere evolution was strongly affected by this tectonics process. During the middle Permian, the movement of the Xilinhot Block from the southern Paleo-Tethys Ocean to the northern Paleo-Asian Ocean broke up the magmatic arcs that existed in the region between the two systems. This enabled the flow of a warm current from the Paleo-Tethys Ocean into the Paleo-Asian Ocean, causing an increase in the sea water temperature and the extinction of cold-water-acclimatized brachiopod fauna at middle Permian. During the late Permian, the amalgamation of the Central Asian Orogenic Belt and North China Craton led to the mixing of the Angara and Cathaysia realms, which previously isolated by Paleo-Asian Ocean to the north and south, respectively. Successfully mixing of the two species motivated by tectonic processes of i) The continuously southward accretion of the Central Asian Orogenic Belt during Paleozoic has significantly extended the habitat of the Angara flora from a high-latitude cold region to a mid-latitude warm region; ii) the northward movement of the North China Craton from tropics and subtropics regions near equator to a mid-latitude warm region has adapted the Cathaysia flora to gradually colder conditions; These two tectonic processes together forced originally distinct temperature acclimatized species evolved convergently through time. Finally, the amalgamation of the Central Asian Orogenic Belt and North China Craton was following a “soft collision” model that did not produce large mountains and Palaeogeographic barriers, which enabled the mixing of the Angara and Cathaysia floras.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 167-191"},"PeriodicalIF":7.2,"publicationDate":"2025-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Refined U-Pb zircon age of the Kusandong Tuff: A key stratigraphic marker for Cretaceous arc magmatism in northeast Asia","authors":"Yong-Un Chae ,&nbsp;Keewook Yi ,&nbsp;Youn-Joong Jeong ,&nbsp;Sujin Ha ,&nbsp;Jong-Sun Kim ,&nbsp;Young Ji Joo ,&nbsp;Sandra L. Kamo ,&nbsp;Hyoun Soo Lim","doi":"10.1016/j.gr.2025.07.013","DOIUrl":"10.1016/j.gr.2025.07.013","url":null,"abstract":"<div><div>The Kusandong Tuff is a prominent stratigraphic unit within the Gyeongsang Basin, the largest Cretaceous sedimentary basin on the Korean Peninsula in East Asia. Extending approximately 200 km in a north–south direction, it serves as a key marker bed within the basin. Located in the upper part of the Hayang Group, the Kusandong Tuff records the onset of subduction-related arc magmatism that followed extension-related volcanism in the Gyeongsang Basin. Overlying the Hayang Group with Kusandong Tuff, the Yucheon Group in the eastern basin reflects the development of the Gyeongsang Arc System through subduction. The Kusandong Tuff thus represents an initial phase of subduction-related volcanism prior to Yucheon deposition. Despite its significance, establishing the precise eruption age of the tuff has been challenging, with previous zircon U-Pb dating studies reporting ages ranging from approximately 97 Ma to 103–104 Ma. These discrepancies have hindered consistent stratigraphic correlations and geological interpretations. In this study, we analyzed five samples from different outcrops using three zircon U-Pb dating methods to refine the eruption age. The results confirmed that the tuff erupted during the late Albian of the Early Cretaceous, approximately 103 Ma. These findings provide a refined temporal framework for understanding the tectonic evolution, stratigraphy, and volcanic activity of the Cretaceous in northeast Asia, and enhance the stratigraphic correlation within the Gyeongsang Basin.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 157-166"},"PeriodicalIF":7.2,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancing environmental quality and mitigating climate change: a renewable energy policy perspective based on evidence from most polluted European countries","authors":"Muhammad Sadiq ,&nbsp;Muhammad Atif Nawaz ,&nbsp;Fengsheng Chien ,&nbsp;Arshian Sharif ,&nbsp;Sobia Hanif","doi":"10.1016/j.gr.2025.07.007","DOIUrl":"10.1016/j.gr.2025.07.007","url":null,"abstract":"<div><div>With increased climate change issues, renewable energy has become important for ensuring environmental quality. Using fossil fuels or other pollutants in energy production adversely influences human life and threatens environmental well-being by reducing environmental quality. The present research highlights renewable energy policy and its ability to enhance environmental quality and mitigate climate change issues in the most polluted European countries. The study has adopted a secondary approach for quantitative research. Data has been collected from 2008 to 2022 and analysed using the method of moments quantile regression (MMQR). The model provides beneficial insights, showing non-linearity and asymmetries in the variables. The outcomes show that renewable energy has no significant effect on environmental quality and plays a substantial negative role in climate change mitigation. Moreover, environmental taxes and urbanization are found to play positive roles in climate change mitigation and environmental quality. The research has numerous theoretical and practical implications as it extends the growing body of literature regarding renewable energy policies, environmental quality, and the mitigation of climate change. Furthermore, the practical insights of the study provide beneficial guidelines for governments regarding improving environmental sustainability through renewable energy policies.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 96-105"},"PeriodicalIF":7.2,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144779527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry and zircon U-Pb-Hf isotopic analysis of the Paleoproterozoic granitoids (ca. 1997–1967 Ma) in the northeastern Yeongnam Massif, central-eastern Korean Peninsula: Geological significance and metallogenic potential","authors":"Sung Won Kim ,&nbsp;Bo Young Lee ,&nbsp;Seung Hwan Lee ,&nbsp;Weon-Seo Kee ,&nbsp;Byung Choon Lee ,&nbsp;Haozheng Wang","doi":"10.1016/j.gr.2025.07.008","DOIUrl":"10.1016/j.gr.2025.07.008","url":null,"abstract":"<div><div>Paleoproterozoic granitoids of the Buncheon and Hongjesa suites, distributed in the central–eastern Korean Peninsula, were investigated to constrain their petrogenesis, tectonic setting, and metallogenic potential. The Buncheon granitoids exhibit porphyritic textures, whereas the Hongjesa granitoids are equigranular; both are composed mainly of alkali feldspar, plagioclase, microcline, quartz, biotite, and muscovite, with minor opaque minerals. Zircon U–Pb dating indicates that the Hongjesa granitoids crystallized earlier (ca. 1997–1971 Ma) than the Buncheon granitoids (ca. 1980–1967 Ma), implying temporally distinct magmatic pulses during the Early Orosirian. Whole-rock and zircon Lu–Hf isotopic compositions suggest derivation from reworked ancient continental crust within a subduction-related arc setting. These findings are consistent with previously documented Early Orosirian arc magmatism in the Korean Peninsula and coeval arc activity in the Japanese Islands, indicating that a magmatic arc belt developed across southeastern Northeast Asia during this period. Notably, the Orosirian arc magmatism in the southeastern part of the Korean Peninsula differs from the Orosirian orogeny-related magmatism in the eastern North China Craton suggesting that the southeastern part of the Korean Peninsula might be separated crustal units from the eastern North China Craton. While some samples exhibit elevated fluorine concentrations and moderate to strong magmatic differentiation, most granitoids display geochemical features characteristic of barren arc-related intrusions, suggesting limited metallogenic potential.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"149 ","pages":"Pages 141-157"},"PeriodicalIF":7.2,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145045734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global redox and bio-productivity changes during the oceanic anoxic event 2 (OAE2): Insights from combined U-C isotopes of the Trans-Saharan epicontinental Seaway","authors":"Usman Abubakar ,&nbsp;Simon V. Hohl ,&nbsp;Sebastian Viehmann ,&nbsp;Stefan Weyer ,&nbsp;Musa Bappah Usman ,&nbsp;Johanna Krayer ,&nbsp;Brahimsamba Bomou ,&nbsp;Thierry Adatte","doi":"10.1016/j.gr.2025.07.009","DOIUrl":"10.1016/j.gr.2025.07.009","url":null,"abstract":"<div><div>The Cenomanian-Turonian boundary marks a global ocean anoxic event (OAE2), leading to the widespread deposition of black-shales due to enhanced primary productivity and O2<!--> <!-->consumption. However, recent studies predict contradictory redox conditions from the open ocean to the epicontinental seas. This study combined existing C and U isotopic compositions of marine OAE2-bearing sediments to understand global redox-variations better and introduce the previously overlooked Trans-Saharan Epicontinental Seaway. We examined the first integrated geochemical dataset from the Ashaka section, Nigeria, including δ¹³C_org, δ²³⁸U, TOC, redox-sensitive and bio-essential trace metal concentrations in authigenic sediments. We propose the potential location of the OAE2 and reconstruct local variations in redox and bio-productivity in the Trans-Saharan Seaway. The chemo-stratigraphic onset of the OAE2 is marked by a globally occurring positive δ¹³C_org <!-->excursion (−25.5 to –23.5‰). However, unlike many OAE2 sections (e.g., Tarfaya Basin and Demerara Rise in the N.-Atlantic), exhibiting high TOC, the Trans-Saharan Seaway records low TOC, comparable to the Western Interior Seaway and the Paleo-Pacific Ocean. These differences indicate poor regional preservation, contrasting with organic-rich, marine-dominated preservation in the deeper Tarfaya Basin and N. Atlantic. Micro-to-macronutrient ratios<!--> <!-->in the Trans-Saharan Seaway were low during the OAE2, suggesting suppressed productivity akin to the Western Interior Seaway and differing from the high-productivity regimes in the Tarfaya Basin and Tethys Sea. Furthermore, redox conditions highlight regional contrasts: predominantly oxic-suboxic conditions in the Trans-Saharan and Western Interior Seaway and Paleo-Pacific Ocean vs. anoxic in the Gubbio section and Demerara Rise. Despite partially oxygenated conditions, a negative δ²³⁸U_sw shift in the Trans-Saharan Seaway (−1.6‰) mirrors the Demerara Rise, Eastbourne, Western Interior Seaway, and Morelos Formation. However, the magnitude varies globally, with epicontinental seaways recording the largest shifts. These inconsistencies suggest that the extent of ocean anoxia undulates across basins calling for a cautious interpretation of U isotopes as a global redox proxy.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 192-209"},"PeriodicalIF":7.2,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144842951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Edge-attentive graph convolutional network and positive-unlabeled framework for landslide susceptibility mapping","authors":"Ruilong Wei ,&nbsp;Yamei Li ,&nbsp;Yao Li ,&nbsp;Zili Wang ,&nbsp;Chunhao Wu ,&nbsp;Jiao Wang ,&nbsp;Bo Zhang ,&nbsp;Chengming Ye","doi":"10.1016/j.gr.2025.07.010","DOIUrl":"10.1016/j.gr.2025.07.010","url":null,"abstract":"<div><div>Stable landslide susceptibility mapping (LSM) is crucial for disaster prevention and mitigation efforts. The exploration of factor interactions and the reliability of non-landslide sampling pose challenges for deep learning-based LSM. This study developed an edge-attentive graph convolutional network (EAGCN) and built a non-landslide sample optimization framework. Our methods consist of three steps. First, graph convolution constructs a graph structure for factors, calculating edges to extract their interaction features. Second, the attention mechanism weights the coupling features by incorporating factor feature distances to optimize neighborhood feature aggregation. Third, positive-unlabeled (PU) learning scores a large number of unlabeled samples through iterative sampling and classifier learning to select reliable non-landslide samples. Our designed module can extract and utilize coupling, and factor features of arbitrary dimensions and can be embedded into any neural network layer. In southeastern Tibetan Plateau (TP), data from 798 landslides and 9 conditioning factors were prepared for usability validation and regional LSM. The evaluation results indicated that the proposed EAGCN achieved the highest the Area Under the Receiver Operating Characteristic Curve (AUC) of 98.2%, demonstrating an improvement of 3.2% to 6.4% compared with traditional machine learning (ML) methods and 2.2% compared with deep learning (DL) method. The PU non-landslide optimization sampling framework enhanced the AUC of traditional ML methods by 2.4% to 8.9% and the AUC of DL method by 4.8%. Furthermore, hyperparameter analysis of the graph structure showed that using excessively high dimensions for coupling and factor features increases model complexity, leading to decreased accuracy. Additionally, visualized feature maps demonstrated that the proposed method effectively differentiates factor feature distances and attention weights to distinguish between landslide and non-landslide samples. Finally, comparative experiments confirmed the superiority of the proposed methods in LSM.</div></div>","PeriodicalId":12761,"journal":{"name":"Gondwana Research","volume":"148 ","pages":"Pages 240-254"},"PeriodicalIF":7.2,"publicationDate":"2025-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}