Marine Geology最新文献

{"title":"Discovery of the world's largest cliff-top boulder: Initial insights and numerical simulation of its transport on a 30–40 m high cliff on Tongatapu (Tonga)","authors":"Martin Köhler ,&nbsp;Annie Lau ,&nbsp;Koki Nakata ,&nbsp;Kazuhisa Goto ,&nbsp;James Goff ,&nbsp;Daniel Köhler ,&nbsp;Mafoa Penisoni","doi":"10.1016/j.margeo.2025.107567","DOIUrl":"10.1016/j.margeo.2025.107567","url":null,"abstract":"<div><div>This study provides the first scientific investigation of the <em>Maka Lahi</em> boulder, a large limestone cliff-top boulder, measuring 14 × 12 × 6.7 m and weighing approximately 1180 t, located 200 m inland at 39 m elevation on the southern coast of Tongatapu, Tonga. The boulder is one of the largest known wave-transported boulders worldwide. Fieldwork conducted in 2024 revealed its presence, geomorphic setting, and karstification features. Utilizing numerical modelling, we established that wave heights of approximately 50 m and periods of 90 s were required to transport the boulder from its cliff-edge origin, suggesting that its emplacement likely resulted from a landslide-triggered tsunami event. U/Th dating of flowstone on the surface is indicative of a minimum age of 6891 cal yr BP and contributes critical evidence of a significant early Holocene tsunami event in Tonga. Notably, this represents the earliest known Holocene tsunami in the Pacific, offering new insights into the long-term history of extreme wave events in the region. This research strengthens the understanding of megaclast transport mechanisms and their implications for coastal hazard assessments in tsunami-prone regions.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"487 ","pages":"Article 107567"},"PeriodicalIF":2.6,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143942626","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":"A coral microatoll record of sea-level rise, interseismic deformation, and El Niño in La Union, Philippines since 1906 CE","authors":"Gina M. Sarkawi ,&nbsp;Aron J. Meltzner ,&nbsp;Dongju Peng ,&nbsp;Joanne T.Y. Lim ,&nbsp;Xinnan Li ,&nbsp;Rohan Gautam ,&nbsp;Anandh Gopal ,&nbsp;Andrew Mitchell ,&nbsp;Loraine Faye Sarmiento ,&nbsp;Jennifer Weil-Accardo ,&nbsp;Kathrine V. Maxwell ,&nbsp;Junki Komori ,&nbsp;Noelynna T. Ramos","doi":"10.1016/j.margeo.2025.107565","DOIUrl":"10.1016/j.margeo.2025.107565","url":null,"abstract":"<div><div>Relative sea level (RSL) along western Luzon is influenced by climate change, tectonic deformation, and the El Niño–Southern Oscillation. Long, high-resolution records of past changes in sea level and land level are crucial to distinguish these contributions for forecasting future RSL or identifying tectonic hazards. Coral microatolls are invaluable proxies for reconstructing RSL, but their interpretation relies on understanding how short- and long-term changes are recorded in the coral skeleton. We analyzed growth bands from 1906 to 2018 CE of a <em>Porites</em> microatoll from Balaoan, La Union, Philippines, using X-rays of vertical cross sections. The microatoll's surface morphology, annual banding, and growth history reveal RSL rise during its lifetime punctuated by 17 diedowns. Coral diedowns generally coincide with low water near the site, often resulting from El Niño events. Excluding eroded sections, 10 of the 11 strongest El Niños since 1918 produced a diedown. Similarly, excluding a diedown caused by the coral tilting, 10 of the 12 preserved diedowns exceeding 3 mm in amplitude occurred during strong El Niños. Between 1948 and 2018 CE, RSL rose at 1.3 ± 1.8 mm/yr (2σ). Comparing sea-level rates from satellite altimetry and RSL from the coral, we estimate vertical land motion at −0.1 ± 12.1 mm/yr between 1995 and 2018 CE. The indicative meaning at Balaoan, defined as the relationship between local water levels and the highest level of growth of a coral microatoll before its most recent diedown, is estimated at 31.5 ± 10.0 cm (2σ) above lowest astronomical tide.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"486 ","pages":"Article 107565"},"PeriodicalIF":2.6,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927514","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 source - sink processes in a typical tidal inlet bay system under intense human activities, Dingzi Bay, China","authors":"Yang Wang ,&nbsp;Rijun Hu ,&nbsp;Xiaodong Zhang ,&nbsp;Jiandong Qiu ,&nbsp;Naishuang Bi ,&nbsp;Longhai Zhu ,&nbsp;Yongchen Xu ,&nbsp;Jingrui Li ,&nbsp;Zhaohan Yi","doi":"10.1016/j.margeo.2025.107564","DOIUrl":"10.1016/j.margeo.2025.107564","url":null,"abstract":"<div><div>Tidal inlet bays are regions of intense material and energy exchange between the land and the sea. In this study, based on surface sediment grain size, geochemistry, bathymetric topography, and 1354 satellite images from 1984 to 2022, we used numerical modeling, bathymetric comparison methods to examine the sediment transport, sediment provenance, and relative contributions in the Dingzi Bay area. It summarizes the source-sink patterns under intense human activities. Dingzi Bay is predominantly erosive, with differences in the erosion and deposition of tidal flats on both sides of the bay, characterized by erosion on the north tidal flat and deposition on the south tidal flat. The main sources of bay sediments are river sediment transport and erosion from the north coast. The south tidal flat inside the bay and the south beach outside the bay are the few sink areas in the bay. The sediment transport path in the study area is from river sediments transported into the bay, with some bay sediments being moved out of the bay with the ebb current. Eroded sediments from the north beach are transported along the coast to the bay mouth, and some sediments are moved into the bay with the flood current. Intense human activities in the river basin leading to a reduction in terrestrial sediment supply are the main cause of bay erosion, and the ebb current-dominated tidal current further exacerbates the erosion of the bay.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"486 ","pages":"Article 107564"},"PeriodicalIF":2.6,"publicationDate":"2025-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143869009","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":"The geomorphic evolution of the Tasmantid Seamount Chain","authors":"Alysha M. Johnson ,&nbsp;Mark E. Dickson ,&nbsp;Sarah Hamylton ,&nbsp;Colin D. Woodroffe","doi":"10.1016/j.margeo.2025.107560","DOIUrl":"10.1016/j.margeo.2025.107560","url":null,"abstract":"<div><div>Oceanic volcanoes develop distinct post-eruptive morphologies depending on the geomorphic conditions they experience. Submerged, truncated, flat-topped volcanoes, known as guyots, result from marine erosion and subsidence, whereas on reefs or carbonate-capped volcanoes, carbonate accretion veneers the summit. New and existing bathymetric data are utilised to identify different geomorphic forms of oceanic volcanoes in the Tasmantid Seamount Chain, a hotspot chain off the east coast of Australia, dated from ∼6 Ma in the south to &gt;50 Ma in the north. Profiles and slope calculations across long and short axes provide morphometric values on the basis of which four morphologic forms are identified: seamount, guyot, modern reef, and carbonate-capped guyot. Volcanoes which erupted on oceanic lithosphere are estimated to have subsided at an average rate of 46.5 mMyr⁻¹, faster than the subsidence rate of volcanoes that erupted on continental lithosphere (33.0 mMyr⁻¹). The guyots are estimated to have eroded at an average rate of 1.9 ± 0.5 kmMyr⁻¹. Substantial carbonate accretion has formed on the summits of eleven volcanoes, ranging in thickness from 1146 m in the north to 93 m in the south. The geomorphic evolution of the Tasmantid Seamount Chain, since the Oligocene, is synthesised into a conceptual model. This study finds that the post-eruptive morphology of each volcano in the chain is a product of the combined influence of the northward movement of the Australian Plate, erosion, subsidence, and carbonate accretion.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"486 ","pages":"Article 107560"},"PeriodicalIF":2.6,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143859018","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":"Suspended sediment pattern along the Mekong Delta's west coast induced by strong southwest monsoon activities and extreme events","authors":"Nguyen Nguyet-Minh ,&nbsp;Tu Duy Le ,&nbsp;Hiep Van Pham ,&nbsp;Hoang Thai Duong Vu ,&nbsp;Sylvain Ouillon ,&nbsp;Thanh Cong Nguyen","doi":"10.1016/j.margeo.2025.107563","DOIUrl":"10.1016/j.margeo.2025.107563","url":null,"abstract":"<div><div>Coastal suspended sediment dynamics and distributions are driven by complex forces and factors mainly related to wind-wave, currents and tide actions which resuspend unconsolidated sediment in the water-seabed layer and/or rework sediment in the seabed. Understanding the suspended sediment dynamics and their time- and space distribution are prominent issues for better understanding sediment transport processes, and morphological changes. Reliable estimated values of suspended sediment concentration (SSC) are key values for reliable modeling of coastal sediment transport. This study aims to investigate the spatial-temporal distribution of SSC along the west coast of the Vietnamese Mekong Delta forced by tides, currents and wind-wave factors which were generated during a strong activity of the southwest monsoon and extreme conditions caused by a tropical depression/storm circulation and thunderstorms. Our results showed that coastal currents and wind-wave actions mainly drove the SSC distributions. During the 12-day field survey, a high-turbidity front existed parallel and close to the coast at an average distance of 5 km where water depths range from 2 to 5 m. This front was likely related to the longshore drift current system which was partly captured by field survey data. The mean SSC value over an area of 400 km² was 80 mg/l, much larger than the values reported in numerical simulations or measurements elsewhere along the subaqueous Mekong Delta. This led to a requirement for reassessment and reanalysis of coastal sediment dynamics based on numerical models and this dataset will serve as an important benchmark for improving the performance of numerical models.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"485 ","pages":"Article 107563"},"PeriodicalIF":2.6,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143847326","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":"Comment on Investigating the origin and dynamics of Carolina Bays by Mark Lundine and Arthur Trembanis [Marine Geology 480 (2025)]","authors":"Michael Ernest Davias,&nbsp;Thomas H.S. Harris","doi":"10.1016/j.margeo.2025.107556","DOIUrl":"10.1016/j.margeo.2025.107556","url":null,"abstract":"<div><div>The paper entitled Investigating the origin and dynamics of Carolina Bays by Mark Lundine and Arthur Trembanis, published in Marine Geology 480 [(2025) 107449] addresses the geomorphology of a collection of closed ovoid basins located on the Atlantic Coastal Plain of the USA. While we respect the excellent quality of the effort by Lundine and Trembanis on this topic, we offer a comment on their review of the runnable mental model presented in Davias and Harris (2022), and the companion paper Harris (2022). While there are several aspects of their review that we accept as debatable, central tenets of our hypothesis were overlooked. Primarily, Lundine and Trembanis (2025) entirely misrepresents our proposal as one which utilizes a mechanism of excavation of these shallow basins by secondary impacts into preexisting unconsolidated sediment. As clearly noted in the title, abstract and text of Davias and Harris (2022) we relate an interdisciplinary hypothesis that the basins were created within that sedimentary deposit during the catastrophic deposition of that sediment and manifested as cavitation artifacts at the surface. Our paper suggests a straightforward task to falsify: constrain the deposition date, method and source of the expansive conformal blanket we describe. Rather than being “thin ephemeral landforms” these basins should be viewed as robust structures, expressing to the surface and visible in our repository of LiDAR imagery despite having entire cities built across them. The lack of a prominent impact crater within the Great Lakes region of the USA is also addressed briefly here, as Lundine and Trembanis (2025) raised an objection. Among our supporting argument for such an impact is data from suborbital modeling of the Australasian tektites, combined with a tool kit for public use in Harris (2022).</div><div>The extensive runnable mental model of Davias and Harris (2025) address many of the concerns raised in Lundine and Trembanis (2025). We make no attempt here to defend the full interdisciplinary hypothesis as presented in the 30 pages of Davias and Harris (2022).</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"485 ","pages":"Article 107556"},"PeriodicalIF":2.6,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143843370","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 dynamics on the Maldives carbonate platform in response to Quaternary monsoonal forcing and sea-level changes","authors":"Andreas Paul ,&nbsp;Gatsby-Emperatriz López-Otálvaro ,&nbsp;John J.G. Reijmer","doi":"10.1016/j.margeo.2025.107561","DOIUrl":"10.1016/j.margeo.2025.107561","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Based on the sedimentological, geochemical and mineralogical analysis of two piston cores recovered from the Maldives, an isolated carbonate platform situated in the northern Indian Ocean, this study aims at unravelling the complex Quaternary glacial-interglacial variability within peri-platform ooze deposited in the Inner Sea sedimentary basin, compare sedimentation dynamics between proximal and distal basin locations, and develop a conceptual model, which characterises the interplay between highstand shedding, early diagenesis, water circulation and oceanic current amplification in response to sea level changes and the monsoon.&lt;/div&gt;&lt;div&gt;The results of this study show that at the proximal location, a pattern of re-sedimentation occurred over the last 280 ky, marked by the development of hiatuses during MIS 7 and partially during MIS4–2. Distally, a continuous sedimentation record was present covering the full glacial – interglacial cyclicity, including sediment production and export, over the same time interval.&lt;/div&gt;&lt;div&gt;The processes that may be associated with the abovementioned sedimentary evidence include strong forcing of monsoonal oceanic currents on sediment production and export, commonly referred to as highstand shedding, and on sediment distribution pathways, during Quaternary glacial and interglacial periods. This sediment distribution process includes forcing by oceanic water masses through narrow inter-atoll channels, also bathing the reef bodies on Ari atoll, and the off-bank transport of shallow-water skeletal and non-skeletal material towards the Inner Sea during interglacial periods.&lt;/div&gt;&lt;div&gt;Contrastingly, during glacial intervals, the major atolls were exposed, and oceanic currents associated with the summer monsoon were forced solely through the inter-atoll channels. As the water masses associated with these currents moved through a channel they were amplified, which in turn increased their capacity for erosion and bedload/suspension transport. This led either to the formation of sedimentary gaps or sedimentary hiatuses, but also of sediment drift bodies that moved large sediment masses back and forth along the channel axis. It is likely that these drift bodies switched direction between the summer and winter monsoon season and/or between periods of stronger summer monsoon and stronger winter monsoon throughout the middle and upper Pleistocene and the Holocene, which lead to the observed variations in sedimentation dynamics between the proximal and distal site.&lt;/div&gt;&lt;div&gt;As part of the study, a custom Dynamic Time Warping (DTW) algorithm was developed. Application of this methodology to a reference core showed that it quickly established an age model for a particular core, picking up glacial-interglacial variability and maximum age ranges very well. However, the methodology falls short of completely deciphering the complex sedimentary records as the proximal core discussed here exhibits a sedimentary sequence whi","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"485 ","pages":"Article 107561"},"PeriodicalIF":2.6,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833597","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":"Hydrodynamic processes and extreme events recognized from the sedimentary records at ancient Port Shuomen in the Oujiang River mouth, Southeast China","authors":"Xin Wei ,&nbsp;Yanhua Liang ,&nbsp;Tuanhui Liu ,&nbsp;Zhihang Ma ,&nbsp;Xiaolin Ma ,&nbsp;Shiyu Ji ,&nbsp;Fangyou Lin ,&nbsp;Hao Xu ,&nbsp;Zhanghua Wang (王张华)","doi":"10.1016/j.margeo.2025.107562","DOIUrl":"10.1016/j.margeo.2025.107562","url":null,"abstract":"<div><div>Identifying extreme events from geological records is fundamental to Paleotempestology. Archaeological excavations at the ancient Port Shuomen on the Southeast Chinese coast have provided high-resolution stratigraphic data for recognizing deposits associated with extreme events. This study examined three profiles from the Port and surficial sediments from modern colluvial and estuarine environments in the lower Oujiang River basin. Analyses including chronology, sedimentology, alkaline earth metal geochemistry, and ancient environmental DNA (eDNA) were performed on the sedimentary records to identify hydrodynamic processes and extreme events during the Song Dynasty (960–1279 CE). Comparisons of alkaline earth metal compositions between the profiles and surficial sediments suggest a reduction in salinity at the Port Shuomen, driven by increased freshwater discharge during the mid- to late-Northern Song Dynasty. High eDNA concentrations and consistent frequency distributions of fragment lengths further suggest rapid channel siltation during a single typhoon season. Following this typhoon season, the Port evolved into tide-dominated regime and experienced five periods of flooding, three of which were characterized by intensified salinity intrusion as evidenced by elevated Sr content. In particular, a mud unit (U10) exhibits the highest Sr content and is interpreted as a depositional record of extreme typhoon events that occurred in the 1160s CE. Furthermore, this study demonstrates that in estuarine environments, the preservation of eDNA is more impacted by sedimentary processes than grain size.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"486 ","pages":"Article 107562"},"PeriodicalIF":2.6,"publicationDate":"2025-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851841","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":"Coastal hydrodynamics at the sub-Antarctic Possession Island (Crozet archipelago) inferred from bedform structures and sediment properties","authors":"Yann Lelièvre ,&nbsp;Guillaume Lawnizack ,&nbsp;Nadia K. Ayoub ,&nbsp;Francesco d'Ovidio ,&nbsp;Éric Armynot du Châtelet ,&nbsp;Mario Zampolli ,&nbsp;Georgios Haralabus ,&nbsp;Lucie Courcot ,&nbsp;Pierre-Yves Collin ,&nbsp;Thomas Saucède","doi":"10.1016/j.margeo.2025.107559","DOIUrl":"10.1016/j.margeo.2025.107559","url":null,"abstract":"<div><div>Within the Southern Ocean, sub-Antarctic regions are anticipated to face significant impacts related to climate change. The alteration of the circulation and properties of the water masses is expected to have widespread impacts on sub-Antarctic nearshore marine ecosystems. Satellite data provides valuable insights into the global ocean circulation but information on fine-scale, local coastal dynamics remain limited and imprecise for the isolated sub-Antarctic territories. The present study aims to infer coastal hydrodynamic processes from the analysis of bedforms using seafloor imagery and sediment samples at two sites located on the eastern coast of <em>Ile de la Possession</em> (Crozet archipelago), <em>Baie du Marin</em> and <em>Crique du Sphinx</em>. Sedimentological and mineralogical analyses conducted on samples have revealed a typical volcanic nature of sediments, with a high proportion of pyroxenes, olivines and large plagioclases. Sediments were characterized by low carbonate and nitrogen contents, suggesting that organic matter is either rapidly depleted by microbial degradation, consumed by benthic detritus feeders, or the lithogenic material transported away from the coastal production area by local currents. Sedimentary structures analyses suggested that ocean circulation at <em>Baie du Marin</em> and <em>Crique du Sphinx</em> is influenced by residual flows that are likely driven by wind and ocean circulation at regional scales and that may result as well from tidal rectification by topography between <em>Ile de la Possession</em> and <em>Ile de l'Est</em>. This study provides a first attempt to analyze local, fine-scale hydrodynamic processes occurring along the eastern coast of <em>Ile de la Possession</em> and link these field observations to large-scale, regional processes formerly studied in the region.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"485 ","pages":"Article 107559"},"PeriodicalIF":2.6,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143825440","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":"The morphology and geochemistry of authigenic pyrite formed under methane seepage: Insights from the Laptev Sea","authors":"Alexey Ruban ,&nbsp;Anastasia Nikolaeva ,&nbsp;Vera Abramova ,&nbsp;Alexander Ignatiev ,&nbsp;Oleg Dudarev ,&nbsp;Igor Semiletov ,&nbsp;Maxim Rudmin","doi":"10.1016/j.margeo.2025.107558","DOIUrl":"10.1016/j.margeo.2025.107558","url":null,"abstract":"<div><div>In cold seep environments, intense sulfate-driven anaerobic oxidation of methane (SD-AOM) generates significant amounts of hydrogen sulfide, facilitating pyrite precipitation in the sulfate-methane transition zone (SMTZ). To enhance the understanding of pyrite formation processes within the SMTZ, we analyzed the morphology, size distribution, trace element content, and sulfur isotopic composition of framboidal pyrite hosted in methane-derived authigenic carbonate crusts. These crusts were collected from two active cold seep sites in the Laptev Sea: the outer shelf and the continental slope. The main textural forms of authigenic pyrite were found to include spherical and polygonal framboids and their clusters, sunflowers, and rod-like aggregates. The diameter of most measured framboids does not exceed 20 μm, but some reach up to 74 μm. Despite the small size, their association with methane-derived authigenic carbonates indicates that SD-AOM plays a dominant role in pyrite precipitation. Specific pyrite textures, such as rod-like aggregates, and the large size of certain framboids further support that pyrite formation occurred within the SMTZ. Different textural relationships between pyrite aggregates and carbonate cement reflect both pre‑carbonate and post‑carbonate pyrite precipitation. Their coexistence within a single carbonate crust sample suggests multiple episodes of pyrite formation. The obtained δ³⁴S values for pyrite (ranging from −35.6 ‰ to −28.1 ‰ V-CDT) reveal a depletion of heavy sulfur isotopes at both sites, which is uncharacteristic of SD-AOM-associated pyrite. This phenomenon is likely attributed to the open-system conditions of pyrite formation, which result from the shallow SMTZ. The content of some trace elements in pyrite from the outer shelf is significantly lower than that in pyrite from the continental slope. This difference in trace element composition may reflect varying conditions under which pyrite precipitated, highlighting the influence of fluid migration regimes on mineral-forming processes. Lower Co/Ni ratios in pyrite from the continental slope indicate its formation under more sulfidic conditions. Our findings suggest that the depth of the SMTZ relative to the seawater-sediment interface is a critical factor controlling the morphological, isotopic, and trace element characteristics of pyrite, which should be taken into account when identifying paleo-seepage.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"485 ","pages":"Article 107558"},"PeriodicalIF":2.6,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820656","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}