Marine Geology最新文献

{"title":"Seafloor topographic modulation of sediment dispersal and polymetallic nodule genesis in the western Clarion-Clipperton Zone (CCZ), Pacific Ocean","authors":"Zeren Zhang ,&nbsp;Zhenggang Li ,&nbsp;Hao Wang ,&nbsp;Xibin Han ,&nbsp;Yuwei Liu ,&nbsp;Xuan Zeng ,&nbsp;Yanhui Dong ,&nbsp;Zhimin Zhu ,&nbsp;Kehong Yang ,&nbsp;Jie Li ,&nbsp;Huaiming Li ,&nbsp;Xiaohu Li","doi":"10.1016/j.margeo.2026.107730","DOIUrl":"10.1016/j.margeo.2026.107730","url":null,"abstract":"<div><div>This study addresses unresolved scientific issues regarding the spatial distribution and genetic controls of polymetallic nodules in the western Clarion-Clipperton Zone (CCZ), focusing on the A-5 block within China Minmetals' contract area. By integrating multibeam bathymetry, optical imaging, and geological sampling data, we systematically elucidate the coupled relationships among seafloor topography, sedimentary dynamics, and nodule formation. Results show that nodules in the study area can be classified into three types: low-coverage high‑nickel (Cov &lt; 30%, Ni &gt; 1.1%), medium-coverage high‑nickel (Cov = 30–40%, Ni &gt; 1.1%), and high-coverage low-nickel (Cov = 40–60%, Ni = 0.5–0.9%). These correspond to three geomorphological units: basin (Zone I), platform (Zone II), and transitional zone (Zone III). Principal component analysis indicates that the spatial zonation of nodules is primarily controlled by a sedimentary dynamic framework shaped by the interaction between topography and bottom currents. Hydrodynamic intensity (PC1) drives sediment erosion–transport–redeposition cycles and the lateral transport of clay-sized particles from Zone II to Zone I. Sedimentation rate (PC2) modulates redox conditions, favoring hydrogenetic-mixed-type nodules in Zones I/II versus hydrogenetic-type nodules in Zone III. This local current-topography interaction generates substantial spatiotemporal heterogeneity in nodule formation across the CCZ, with a general tendency toward stronger hydrogenetic contributions in the west and enhanced diagenetic contributions in the east. Furthermore, the coupling of bottom currents and topography implies significant secondary transport of mining-plume sediments, leading to pronounced attenuation of plume deposit thickness in distal areas, thereby effectively reducing potential ecological risks associated with plume redeposition.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"494 ","pages":"Article 107730"},"PeriodicalIF":2.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sediment characteristics, distribution and pathways on a macro-tidal, energetic and sediment-limited embayed coast","authors":"Wassim Seksaf,&nbsp;Tim Scott,&nbsp;Gerd Masselink,&nbsp;Nieves García Valiente,&nbsp;Daniel Conley","doi":"10.1016/j.margeo.2026.107734","DOIUrl":"10.1016/j.margeo.2026.107734","url":null,"abstract":"<div><div>In addition to external hydrodynamic forcing, the behaviour of beach–dune systems is strongly controlled by nearshore sediment availability and coastal transport pathways. Here we integrate new sedimentological observations, shoreface geomorphological analysis, and regional hydrodynamic modelling to improve understanding of the distribution, characteristics, and connectivity of mobile sediments along a macro-tidal, high-energy, sediment-limited embayed coastline in Cornwall, United Kingdom. We first map the spatial extent of mobile sand bodies along a 45-km coastline and assess headland bypassing potential to define coastal embayments. Coast-wide sediment samples (<em>n</em> = 348), spanning dunes to the lower shoreface, were classified using K-means clustering of grain-size and mineralogical data to quantify spatial variability in sediment character, refine the identification of closed/constrained embayments, and evaluate existing regional sediment transport modelling. Eight closed coastal cells and four major sediment sinks, associated with large dune systems, were identified, together with a dominant southwest-to-northeast transport pathway. Sediment-starved regions exhibited the highest calcium carbonate contents (45–57%), consistent with long-term sediment supply limitations. These results demonstrate the value of spatially comprehensive sediment resource and geomorphological datasets for constraining sediment pathway modelling and provide a scientific basis for evaluating long-term coastal evolution.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"494 ","pages":"Article 107734"},"PeriodicalIF":2.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical characteristics of seabed sediments from Molloy Basin (ODP Site 909, in the Fram Strait) and the Nansen Basin (Arctic Ocean)","authors":"Belinda Flem ,&nbsp;Jochen Knies ,&nbsp;Morten Smelror ,&nbsp;Christoph Vogt","doi":"10.1016/j.margeo.2026.107719","DOIUrl":"10.1016/j.margeo.2026.107719","url":null,"abstract":"<div><div>This study investigates the geochemical and mineralogical characteristics of Neogene deposits from the Fram Strait (ODP Site 909) and seabed sediments from the Nansen Basin to reconstruct sediment provenance and depositional conditions during the late Early Miocene (∼13–16 million years ago, Ma) and compare them with modern sedimentation patterns. Major and trace element concentrations, rare earth element (REE) distributions, and clay mineral assemblages reveal long-term sediment transport pathways from Eurasian continental margins, particularly the Laptev and Kara Seas. The Miocene sediments exhibit low Mn:Al ratios and depleted REE concentrations, indicating sub-oxic depositional conditions and limited bottom water ventilation. In contrast, modern Nansen Basin sediments show higher Mn and REE levels, reflecting more oxic environments and increased glacial and fluvial input. Mineralogical data suggest a persistent dominance of smectite and kaolinite, with variations linked to climatic and tectonic shifts. The REE patterns, including Eu and Ce anomalies, provide insights into redox conditions and sediment provenance. These findings contribute to understanding Arctic Ocean evolution, sediment dynamics, and the establishment of geochemical baselines critical for future seabed resource assessments and climate impact monitoring.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"494 ","pages":"Article 107719"},"PeriodicalIF":2.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Biogeochemical processes in Baltic Sea sediments as a recorder of environmental change over the Holocene","authors":"Lina Piso ,&nbsp;Ian P.G. Marshall ,&nbsp;Caroline P. Slomp ,&nbsp;Niels A.G.M. van Helmond","doi":"10.1016/j.margeo.2026.107718","DOIUrl":"10.1016/j.margeo.2026.107718","url":null,"abstract":"<div><div>The Baltic Sea has been subject to significant environmental change over the Holocene, driven by climatic variability, glacio-isostatic rebound and anthropogenic activities. During the Integrated Ocean Drilling Program (IODP) Expedition 347, “Baltic Sea Paleoenvironment”, unique, long sediment cores were retrieved, enabling the reconstruction of environmental conditions and the temporal evolution of key biogeochemical processes in the Baltic Sea over the Holocene. Here, we review major findings from geochemical and microbial analyses of well-dated sedimentary records from three of the IODP sites, combining literature data with newly generated phosphorus speciation data for one of the IODP sites (the Little Belt) and reanalysed metagenomic datasets. Sedimentary redox proxies (Mo, C_org/P_tot and Fe/Al) are used to illustrate that two past intervals of deoxygenation in the Holocene were particularly pronounced in the central part of the Baltic Sea. By combining our proxy records with recent water column data, we show that present-day anthropogenically-driven deoxygenation developed faster, covers a larger area and is more intense than in the past. Sedimentary records of the nutrient phosphorus point towards the widespread occurrence of vivianite, an authigenic iron(II) phosphate mineral, which can form diagenetically in and below the methanogenic brackish/marine sediments. While vivianite likely acted as a major phosphorus sink in the Baltic Sea in the past, this is no longer the case because of eutrophication. Methanogenesis is a key pathway of organic matter degradation in deep Baltic Sea sediments. While upward diffusing methane is oxidized with sulfate as an electron acceptor in near-surface sediments, oxidation of methane that diffuses downwards into freshwater sediments may be coupled to iron-oxide reduction. Metagenomic analyses reveal the adaptation of the sediment microbial community to present-day salinity and methane concentrations, illustrating the need to understand changes that occur long after deposition. Our findings underscore the dynamic interplay between climate, geology, and anthropogenic influence in shaping Baltic Sea biogeochemistry, offering a glimpse into how other coastal marine systems may respond to projected global change in the future.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"494 ","pages":"Article 107718"},"PeriodicalIF":2.2,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146193061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sedimentation behavior of deep-sea mining plumes in a marine ionic environment: Insights from the west Philippine Basin","authors":"Ning Ma ,&nbsp;Xian Zhang ,&nbsp;Zhengqi Wu ,&nbsp;Xuguang Chen ,&nbsp;Xingzheng Gao ,&nbsp;Fengpeng Zhang","doi":"10.1016/j.margeo.2025.107703","DOIUrl":"10.1016/j.margeo.2025.107703","url":null,"abstract":"<div><div>Benthic plumes generated by deep-sea polymetallic nodule mining pose significant threats to the marine ecological environment and represent one of the primary challenges hindering the commercialization of deep-sea mining. This study investigates the sedimentation behavior of deep-sea sediment plumes in the West Philippine Basin to assess the potential environmental impacts of mining activities. The results reveal that the presence of marine inorganic salts markedly enhances the sedimentation efficiency of suspended sediment particles, and the settling rate in seawater was approximately two to three times higher than that in pure water, highlighting the strong promotion effect of inorganic ions—especially divalent cations such as Ca²⁺ and Mg²⁺—on particle aggregation and sedimentation efficiency. A characteristic thickness parameter introduced through numerical simulations quantitatively describes interparticle electrostatic interactions and provides a predictive tool for plume-settling behavior under different salinity and concentration conditions. By linking plume sedimentation kinetics with marine physicochemical processes, this study enhances understanding of how electrochemical properties of particles influence plume motion and dispersion in deep-sea environments.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107703"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145895937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of cobble extraction on two beaches in Northwestern Baja California","authors":"Amaia Ruiz de Alegría-Arzaburu ,&nbsp;Christian Zlolniski","doi":"10.1016/j.margeo.2026.107714","DOIUrl":"10.1016/j.margeo.2026.107714","url":null,"abstract":"<div><div>Cobble extraction is a widespread socio-economic activity along the Pacific coast of Baja California, Mexico, with potential long-term impacts on coastal stability. This study evaluates the morphological response of two beaches exposed to prolonged cobble removal in locations where cobble extraction provides employment for local low-income communities. Morphological changes were analyzed using long-term satellite-derived shoreline data complemented by recent topographic surveys. The two studied beaches were San Jacinto, where cobbles overlie a rocky platform, and La Chorera, a former composite cobble-sand beach transformed into a predominantly sandy system following sustained cobble extraction. Their morphological evolution was compared with a nearby natural sandy beach, San Ramón. Results reveal contrasting responses: San Jacinto experienced chronic shoreline recession of nearly 0.5 m per year, while La Chorera exhibited long-term shoreline stability (+0.2 m/year) but recent supratidal erosion and duneface retreat. In contrast, the sandy beach of San Ramón showed an accretionary trend (+1.1 m/year) and dune stability. Beach volume changes between 2023 and 2025 indicate the most severe erosion at La Chorera (50 m³/m), followed by San Jacinto (32 m³/m) and minimal change at San Ramón (4 m³/m). These findings reveal that morphological responses to sustained cobble extraction are influenced by sediment composition. In any case, cobble removal compromises beach stability, increasing susceptibility to high-energy storms and threatening coastal ecosystems. In regions where extraction supports livelihoods for local low-income communities, it underscores the need for sustainable and equitable management practices.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107714"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbonate platform evolution in response to the Mid - Pleistocene climate transition on the North-West Shelf of Australia: Insights from forward stratigraphic modelling","authors":"Carra Williams ,&nbsp;Jody M. Webster ,&nbsp;Tristan Salles ,&nbsp;Victorien Paumard ,&nbsp;Camille Grimaldi ,&nbsp;Mostfa Lejri","doi":"10.1016/j.margeo.2026.107716","DOIUrl":"10.1016/j.margeo.2026.107716","url":null,"abstract":"<div><div>This study presents the first forward stratigraphic model of Scott Reef - two isolated carbonate platforms on the Northwest Shelf (NWS) of Australia, spanning the Middle Pleistocene Transition (MPT; ca. 1.2–0.7 Ma). Scott Reef preserves a unique archive of reef growth sequences paced by millennial (10³-year) to orbital (10⁴–10⁵-year) scale sea-level variability under continuous high subsidence, providing valuable analogues for Quaternary reef dynamics and potential future reef responses to accelerated climatic change. We apply forward stratigraphic modelling (FSM) to reduce uncertainty in the existing chronostratigraphic models of Scott Reef, generate synthetic data to improve seismic interpretation, and to test how changing eustatic and environmental conditions during and after the MPT influenced carbonate production, facies distributions, and platform morphology. The model is calibrated using modern bathymetry, seismic sequence stratigraphy, sedimentary facies, coralgal assemblages, U/Th ages, and temporal changes in carbonate production and wave energy. The best fit simulations require increased carbonate production and wave energy after ca. 0.5 Ma, coupled with reduced carbonate production on the South Reef leeward margin. Model results indicate that the first high-amplitude lowstand of MIS 12 initiated prolonged subaerial exposure, karstification, and the development of a bucket-shaped platform morphology, coincident with increased monsoonal intensification after ca. 0.5 Ma. Subsequent reef expansion during the long-duration MIS 11 highstand produced an 80 m thick aggradational reef rim and is consistent with timings of reef growth elsewhere along the NWS, although there are differences to timing and style of reef response to the MPT globally. Synthetic stratigraphy indicates a transition from thin (10–30 m), low-relief progradational-aggradational sequences prior to 0.5 Ma, to thicker (20–50 m) aggradational sequences in the post-MPT 100-kyr world. Constant subsidence rates used in the model (0.29 mm/yr at South Scott Reef and 0.45 mm/yr at North Scott Reef) indicate that increasing sea-level amplitude and reduced periodicity associated with the MPT modulated sequence thickness, resulting in changes in platform morphology and facies patterns after ca. 0.5 Ma. Coupled with continuous high subsidence and increasing monsoonal intensity, these changes indicate that both environmental and eustatic processes were major controls on Scott Reef evolution. Our model has broader implications for understanding the MPT globally, including timing and stratigraphic expression of carbonate platform responses. Trial-and-error style FSM, when ground-truthed to multi-scale observational data, remains a powerful tool to test hypotheses about carbonate platform and coral reef response to rapid environmental changes.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107716"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146024222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extreme wave events inferred from large subaerial carbonate boulders on a rocky coast in Pasuquin, Ilocos Norte, Philippines","authors":"Edrian M. Tubalado ,&nbsp;Noelynna T. Ramos ,&nbsp;Lyndon P. Nawanao Jr. ,&nbsp;Ace Matthew F. Cantillep ,&nbsp;Alec Benjamin G. Ramirez ,&nbsp;Jelian S. Reyes ,&nbsp;Kathrine V. Maxwell ,&nbsp;Shou-Yeh Gong ,&nbsp;Tsai-Luen Yu ,&nbsp;Chuan-Chou Shen","doi":"10.1016/j.margeo.2026.107704","DOIUrl":"10.1016/j.margeo.2026.107704","url":null,"abstract":"<div><div>Coastal boulder deposits serve as sedimentary markers of extreme wave events (EWEs), with their morphological analysis offering valuable insights into the nature of these events. In the coastal regions of Pasuquin, Ilocos Norte, and other parts of northwest Luzon Island in the Philippines, extensive fields of large carbonate boulders are often found on Holocene emergent reefs. We studied 198 carbonate boulders at two boulder field sites in Pasuquin (Davila and Dilavo). The emergent fringing reef, at an elevation of between −0.21 below to 1.5 m above mean sea level across the platform (corrected from the Currimao tide station), is characterized by spur-and-groove morphology with solution pans/pools, and occasional fossil microatolls. Boulders had varying orientations and were mostly flat blocks in shape, with the largest measured boulder weighing up to 31.49 t. Based on their overall shape, composition, and observed tilting/overturning, these boulders are inferred to have been sourced from the underlying reef platform. Spatial statistics, bivariate statistics, and frequency distribution of carbonate boulders in Dilavo (south boulder field) show clustering with multimodal weight distribution and include more boulders weighing over 9 t compared to Davila (north boulder field). Framework corals comprising the boulders reveal ²³⁰Th ages between 1262.6 ± 4.8 and 2815.9 ± 6.7 YBP (relative to 1950 CE), which may indicate the timing of initial displacement and deposition due to an extreme overwash event. Meanwhile, fossil corals within the emergent reef have ages between 444.9 ± 1.8 and 677.9 ± 2.2 YBP, possibly indicating a younger uplift event after boulder displacement and subsequent emplacement. This new information on the spatial distribution and morphology of large carbonate boulders in northern Luzon provides additional insights into the characteristics of past EWEs and may be useful in understanding and preparing for future coastal hazards in the region.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107704"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and evolution of giant comet marks along the North Atlantic Deep-Water flow on the Demerara plateau","authors":"Paul Blin ,&nbsp;Lies Loncke ,&nbsp;Xavier Durrieu De Madron ,&nbsp;Sébastien Zaragosi ,&nbsp;Kelly Fauquembergue ,&nbsp;Swanne Gontharet ,&nbsp;Ivane Pairaud ,&nbsp;Pauline Dupont ,&nbsp;Sandrine Caquineau ,&nbsp;Bruno Charriere ,&nbsp;Raphael Lagarde ,&nbsp;Christophe Basile ,&nbsp;Scientific Team DIADEM","doi":"10.1016/j.margeo.2026.107717","DOIUrl":"10.1016/j.margeo.2026.107717","url":null,"abstract":"<div><div>The Demerara Plateau, located in the equatorial Atlantic, is particularly well-suited for recording the activity of the Deep Western Boundary Current (DWBC), which transports North Atlantic Deep Water (NADW) southward into the Atlantic basin. This current, active between 1500 and 3500 m depth, constitutes the deep part of the global thermohaline circulation and plays a crucial role in climate regulation. The Demerara Plateau is remarkable for the abundance and wide distribution of comet mark-type sedimentary structures, which can reach several kilometres in length. These hydrodynamic bedforms, interpreted as erosional features associated with strong bottom currents, are currently used as proxies for deep currents velocities, with minimum formation thresholds estimated between 0.60 and 0.75 m/s according to the literature (<span><span>Rebesco et al., 2014</span></span>; <span><span>Werner et al., 1980</span></span>). The DIADEM (Dive At DEMerara) oceanographic cruise (<span><span>Basile and Loncke, 2023</span></span>) enabled detailed investigation of one such structure using a combination of complementary tools with the aim of better understanding their functioning and evolution with in-situ observation, physical records, and sampling. Those new data were also combined with formerly acquired high-resolution seismic data, allowing a new vision of these bedforms their formation, and their evolution over time.</div><div>The main findings are the following: (1) comet-marks localize on carbonate mass transported blocs outcropping on the seafloor; (2) Clearly show a polyphase evolution of the bedforms of comet mark presenting alternations of erosion and sedimentation phases. The bedforms therefore record long-term variations in bottom current activity with an alternation of intense hydrodynamic events (erosion) and quieter hydrodynamic periods (deposition) through time, reflecting a complex hydrodynamic history; (3) At present, comet-marks recorded a significant decrease in current velocity within the erosional zones located inside the comet tails associated with fined-grained sediments infill in this area, highlighting the need for cautious interpretation of such features as direct indicators of present-day current intensity; (4) Finally, a result that was not necessarily anticipated but documented by exploring those bedforms with the Nautile submersible, comet-marks host quite important benthic and epibenthic biodiversity with a wide variety of associated species.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107717"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variations in thermocline depth and their response to the East Asian Monsoon in the Northern South China Sea during the Early-Middle Miocene: Evidence from planktonic foraminifera","authors":"Yamin Lu ,&nbsp;Baoqi Huang ,&nbsp;Fang Chen","doi":"10.1016/j.margeo.2026.107721","DOIUrl":"10.1016/j.margeo.2026.107721","url":null,"abstract":"<div><div>This study reconstructs thermocline depth variations and their response to the East Asian Monsoon (EAM) in the northern South China Sea (SCS) during the early-middle Miocene (18–12 Ma) based on planktonic foraminifera analyses from IODP Hole U1505C. Stable oxygen isotope analyses were conducted on all planktonic foraminiferal species from four key time slices (11.99 Ma, 13.01 Ma, 14.87 Ma, and 17.35 Ma). By integrating cluster analysis results, the vertical distribution of planktonic foraminifera in the water column was reconstructed. Variations in thermocline depth were then inferred from the relative abundance ratio of shallow-dwelling to deep-dwelling species. When combined with other marine and terrestrial proxies, the upper water column evolution in the northern SCS primarily reflects EAM dynamics, showing consistency with multi-proxy records: (1) 18.0–17.2 Ma: weakening of the East Asian summer monsoon (EASM) with slight East Asian winter monsoon (EAWM) intensification; (2) 17.2–14.7 Ma: EASM peak intensity with stable EAWM conditions; (3) 14.7–13.8 Ma: EASM decline accompanied by EAWM intensification; and (4) 13.8–12.0 Ma: concurrent weakening of both EAWM and EASM. Furthermore, our synthesis suggests that the dominant forcing mechanism of the monsoon system shifted from regional tectonic control during the warm MCO to global climatic forcing during the MMCT, underscoring the differential sensitivity of the EAM to varying drivers across major climate thresholds.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"493 ","pages":"Article 107721"},"PeriodicalIF":2.2,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}