Marine Geology最新文献

{"title":"Seafloor morphology and recent dynamics in the Scoglio d'Affrica (Northern Tyrrhenian Sea)","authors":"Anna Saroni ,&nbsp;Federica Maurantonio ,&nbsp;Daniele Casalbore ,&nbsp;Francesco L. Chiocci ,&nbsp;Ettore Cimenti ,&nbsp;Massimo Coltorti ,&nbsp;Maurizio Demarte ,&nbsp;Martina Pierdomenico ,&nbsp;Daniele Spatola ,&nbsp;Roberta Ivaldi","doi":"10.1016/j.margeo.2025.107518","DOIUrl":"10.1016/j.margeo.2025.107518","url":null,"abstract":"<div><div>From 2017 to 2023, the offshore area nearby the Scoglio d'Affrica islet, located in the Northern Tyrrhenian Sea, has been surveyed and monitored after a violent fluid emission from a shallow-water mud volcano that caused an outburst rising 10 m above the sea surface. This transient phenomenon occurred very localized and short-lived. Assessing the complexity of this kind of event requires an integrated monitoring system, which allows us to characterize the seafloor morphology and recent dynamics through high resolution swath bathymetry and direct visual seafloor observation. These data allow also the identification of new features produced by recent seafloor dynamics and fluid seepage related to mud volcanism, obtaining insights on the temporal and spatial evolution of the seafloor morphology related to cold seeps in the area. In particular, the mud volcano responsible for the 2017 gas outburst is made up of two shallow water mounds characterized by different seafloor evolutionary records, including sediment consolidation, fracturing and variation in morphology and height, likely related to inflation/deflation processes as well as to the sediment reworking by wave action.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"484 ","pages":"Article 107518"},"PeriodicalIF":2.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620377","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":"Discoveries on coastal retrogressive breach failures inspired by failure of an underwater fixed platform","authors":"Xiamei Man ,&nbsp;William R. Dally ,&nbsp;David P. Callaghan ,&nbsp;Peter Nielsen","doi":"10.1016/j.margeo.2025.107530","DOIUrl":"10.1016/j.margeo.2025.107530","url":null,"abstract":"<div><div>Retrogressive breach failures (RBF) are submarine landslides that result in a nearly vertical sand wall above and below the water surface. Previous studies suggest a four-phase mechanism of RBFs, including triggering, propagation, termination, and recovery phases. There have been both laboratory and field studies on the later three phases, while the triggering mechanism of RBFs remain unknown given the event occurrence is unpredictable both spatially and temporally.</div><div>Amity Point on North Stradbroke Island, 37 km Northeast from Brisbane, Australia is a valuable coastal flow slide study site with frequent occurrence of approximately every two weeks (<span><span>Beinssen et al., 2014</span></span>) of them at a fixed location. Aiming at revealing the triggering mechanism of flow slides, an eight-meter-tall underwater tripod was manufactured and anchored on the seabed. The tripod location was designed to be fixed at a point with minimum bathymetry change during flow slide events referring to existing studies (<span><span>Beinssen et al., 2014</span></span>) with between 1.5 m and 2 m deep helical anchors. The tripod collapsed overnight by the undermining of two of the three helical anchors, including the 2 m deep anchor, by a significant underwater flow slide while there was minimal flow slide evidence on the beach.</div><div>The short lifespan of the tripod presents the complexity of RBFs (especially underwater) and the limitations of existing research. Underwater RBF events that do not propagate to the shore (or slightly erode the shore) occur more frequently than previous research reported (<span><span>Beinssen et al., 2014</span></span>). While it does not propagate to the shore, the event still erodes a significant amount of sand underwater. It indicates the triggering occurs at 10 m underwater or even deeper.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"484 ","pages":"Article 107530"},"PeriodicalIF":2.6,"publicationDate":"2025-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143592045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The tsunami history and prehistory of Nuʻu Refuge, Maui, Hawaiʻi","authors":"Scott Fisher ,&nbsp;James Goff ,&nbsp;Andrew B. Cundy ,&nbsp;David Sear","doi":"10.1016/j.margeo.2025.107522","DOIUrl":"10.1016/j.margeo.2025.107522","url":null,"abstract":"<div><div>In the 21st century tsunamis have claimed the lives of at least 253,000 people globally, making them one of the deadliest natural disasters. In Hawai'i, destructive events occur, on average, every 11 years. This study takes a multi-proxy approach to understand the magnitude and frequency of tsunamis at the Nuʻu Refuge, Kaupō, Maui, Hawai'i. Research there revealed sedimentary evidence of four tsunami or storm events dating from as early as 1837 CE from both local and distant sources. Sedimentary evidence from the wetlands indicates a depositional environment dominated by tsunami inundation coupled with increasing isolation from the sea. Understanding (a) the source, magnitude and frequency of tsunami events and (b) ongoing geomorphological change provides a foundation for developing mitigation strategies to reduce the destructive potential of future tsunamis.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"483 ","pages":"Article 107522"},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drilling the New Jersey shallow shelf to evaluate Miocene continental margin sequences, sea level, and resources","authors":"K.G. Miller ,&nbsp;G.S. Mountain ,&nbsp;J.N. Proust ,&nbsp;A. Mukhatzhanov ,&nbsp;J.V. Browning ,&nbsp;W.J. Schmelz ,&nbsp;S.P. Hesselbo ,&nbsp;D.M. Hodgson ,&nbsp;M.E. Katz ,&nbsp;J. Lofi ,&nbsp;P.J. Sugarman ,&nbsp;D. Monteverde","doi":"10.1016/j.margeo.2025.107521","DOIUrl":"10.1016/j.margeo.2025.107521","url":null,"abstract":"<div><div>We review scientific ocean drilling of the New Jersey passive continental margin and the success of Integrated Ocean Drilling Program (IODP¹) Expedition 313 in addressing long-standing, fundamental issues of sequence stratigraphy, sea-level change, and resources. The New Jersey margin was targeted for study by several generations of ocean drilling because of its thick, prograding Oligocene to Quaternary sequences bounded by unconformities. Coring and logging on the onshore coastal plain (Ocean Drilling Program [ODP] Legs 150X<span><span>http://www-odp.tamu.edu/publications/citations/cite150X.html</span><svg><path></path></svg></span> and 174AX), outer continental shelf (Leg 174A), and continental slope and rise (Legs 95, 150, and 174A) provided a chronology of sea-level lowerings but did not sample facies needed to evaluate Miocene sea-level amplitudes. Expedition 313 used a Mission Specific Platform (L/B <em>Kayd</em>) to drill on the shallow continental shelf, recover critical Miocene facies, particularly on clinoform foresets, and capture the full amplitudes of relative sea-level changes. Expedition 313 overcame challenging borehole conditions and recovered a total of 1311 m of core at three sites (81 % recovery) that:<ul><li><span>(1)</span><span><div>correlated difficult-to-date nearshore-shelf facies to the time scale with resolution better than ±0.5 million years (Myr);</div></span></li><li><span>(2)</span><span><div>tested and confirmed that sequence boundaries are a primary cause of seismic reflections on siliciclastic shelves;</div></span></li><li><span>(3)</span><span><div>tested sequence stratigraphic models with core-log-seismic integration; and.</div></span></li><li><span>(4)</span><span><div>provided a record of paleodepth changes through time that constrained amplitudes of Miocene sea-level change, including the influence of mantle dynamic topography. The New Jersey relative sea-level estimates are similar to those obtained using stable isotopes and Mg/Ca paleothermometry, showing that GMGSL (“eustasy”) varied with 10–60 m scale amplitudes on the Myr scale.</div></span></li></ul></div><div>Drilling beneath the shallow continental shelf also identified groundwater sources, including seawater, deep-sourced brines, and meteoric fresh water, that represent potential resources for future generations. Studies of this margin have implications for future subsurface storage of supercritical CO₂ and geotechnical issues relating to the location of offshore wind infrastructure. Expedition 313 demonstrated the feasibility of continuously recovering and logging strata in shallow water, providing constraints on sea level, sequences, hydrogeology, and resources.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"484 ","pages":"Article 107521"},"PeriodicalIF":2.6,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decadal shifts and future projections of the Han River Delta coastline","authors":"Xiu Juan Liu ,&nbsp;Jie Ni Xü ,&nbsp;Albert J. Kettner ,&nbsp;Yang Wang ,&nbsp;Jia Ji Yi","doi":"10.1016/j.margeo.2025.107520","DOIUrl":"10.1016/j.margeo.2025.107520","url":null,"abstract":"<div><div>The Han River Delta, the sixth largest delta in China, has received decreasing amounts of fluvial sediments over the last decades. Here, we use satellite images for 1981–2020 and a conceptual geometric model to investigate recent and future evolution of the delta coastline. Satellite images were able to capture the transition from a more natural coastline with sandy beaches to an artificial structure since 2015. This transition has been accompanied by rapid seaward migration of a portion of the artificial coastline due to land reclamation. Furthermore, most of the coastline has remained stable (showing no significant advance or retreat), except for coastlines that are dominated by mangrove forest. The coastline has not always remained stable. Before the 1980s, the coastline was continuously advancing. Modeling results reveal that a significant reduction of fluvial sediment, mainly caused by upstream dam emplacement, had a key role in the shifting status of the delta coastline evolution. Additionally, model results suggest that if fluvial sediment supply had remained consistent with pre-dam levels, the more abundant fluvial sediment supply could counteract the effects of a maximum sea-level rise scenario for decades. However, a sustained decrease of the fluvial sediment supply, at rates similar to the less abundant sediment supply at present, is expected to dominate the evolution of the delta coastline under a conservative sea level rise scenario. In the case of a medium or maximum sea level rise scenario, the future evolution of the delta coastline will be dominated by the rate at which sea level rises, rather than a further decrease of riverine sediment. The large-scale land reclamation has a negligible impact on the advance or retreat rate of the delta coastline. These findings offer valuable insights for the management of delta coastlines.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"484 ","pages":"Article 107520"},"PeriodicalIF":2.6,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143550557","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":"Tracking diagenetic alteration of magnetic susceptibility in thrust ridge and slope basin sediments of the Cascadia margin (ODP Sites 1249 and 1252; IODP Site U1325)","authors":"Stephen C. Phillips ,&nbsp;Joel E. Johnson ,&nbsp;William C. Clyde ,&nbsp;Wei-Li Hong ,&nbsp;Jacob B. Setera ,&nbsp;Marta E. Torres","doi":"10.1016/j.margeo.2025.107519","DOIUrl":"10.1016/j.margeo.2025.107519","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We investigated sediment core records from the Cascadia Margin (Ocean Drilling Program Sites 1249 and 1252 at Hydrate Ridge; Integrated Ocean Drilling Program Site U1325 offshore Vancouver Island) using a Zr/Rb heavy mineral proxy from X-ray fluorescence (XRF) core scanning to identify intervals of primary detrital magnetic susceptibility (κ) and predict intervals where diagenesis caused magnetite dissolution by hydrogen sulfide. We also measured total sulfur (TS) content, grain size distributions, total organic carbon (TOC) content, and the magnetic mineral assemblage to further constrain the role of diagenesis on κ. Understanding how κ can be used to better characterize the varied effects of detrital and diagenetic signals in marine settings is important for understanding biogeochemical cycling and records of paleoenvironmental change. The upper 100 m of slope basin Site 1252 contains multiple intervals (&gt; 90 m total) of decreased κ correlated with elevated TS content, consistent with dissolution of magnetite and precipitation of pyrite, iron monosulfides, and/or elemental sulfur. Similarly at the other slope basin site, Site U1325, κ is lower and TS is elevated in the interval between 24 and 51 mbsf, due to sulfide formation. At both slope basin sites, these low κ intervals correspond with high TOC, suggesting the possibility that organoclastic sulfate reduction (OSR) is likely a major driver of diagenetic alteration of κ at these sites. High TS:TOC ratios at Site U1325 suggests anaerobic oxidation of methane (AOM) during sulfate-methane transition zone (SMTZ) migration may have contributed to alteration of κ. In contrast, within the upper 90 m of Site 1249, a methane seep site at the summit of Hydrate Ridge, κ is almost entirely altered by diagenetic processes, with much of the low κ explained by a high degree of iron sulfide formation, while some intervals are affected by precipitation of magnetic iron sulfides that maintain or even increase κ. The presence of abundant methane seepage and gas hydrate as well as chemosynthetic seafloor fauna at this site, suggests that sulfide is released to the water column and AOM, rather than OSR, drives diagenetic alteration of κ at this site. Overall, the slope basin sites show episodic variation of κ that is influenced by TOC content, likely driven by changes in marine primary productivity and sedimentation rate, while the seep site shows consistently altered κ with lower TS content and no correlation with TOC. Methane seep environments likely experience loss of hydrogen sulfide to the water column and oxidation of hydrogen sulfide by seafloor seep fauna, which limits the amount of solid phase sulfur (pyrite, iron monosulfides, elemental sulfur) that can be precipitated within the sediments. In contrast, the migration of a buried SMTZ at slope basin sites results in enhanced sulfur precipitation within the sediments. This integrated magnetic and geochemical approach reveals the diagenetic p","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"483 ","pages":"Article 107519"},"PeriodicalIF":2.6,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143512207","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":"Genesis and preservation of composite (Miocene to Holocene) gravel deposits on the accommodation-limited continental shelf of south-central Namibia","authors":"A.N. Green ,&nbsp;T. Heeralal ,&nbsp;J.A.G. Cooper ,&nbsp;H. Labuschagne ,&nbsp;L. Meltzer","doi":"10.1016/j.margeo.2025.107517","DOIUrl":"10.1016/j.margeo.2025.107517","url":null,"abstract":"<div><div>Gravel accumulations on the Namibian shelf off Hottentots Bay have developed during successive transgressions since the Late Oligocene. Using more than 12,000 line km of seismic data coupled with &gt;6000 boreholes, the palaeo-land surface (H1) on which the gravel deposits occur was mapped. This is a weathered bedrock surface overlain by saprolite or clay and mantled by Eocene-age sandstones. Despite high sediment input, the limited accommodation space on the uplifted shelf means that unconsolidated sediment has accumulated only in localized depressions and topographically sheltered zones on this palaeo-land surface. The overlying unconsolidated sediment consists of four seismic and lithostratigraphic units (C<img>F), including lowermost gravel Units C and D that were deposited in multiple phases from late Oligocene to late Pliocene/Pleistocene. These accumulated locally in relict fluvial valleys and in a bedrock-hosted embayment that provided preferential accommodation for multi-stacked gravel beaches. They formed initially as lowstand lags in small tidal channels and developed into thick embayed beaches through aggradation. By the Holocene, accommodation in the embayment was filled and excess material spilled into a palaeo-strait, forming linear gravel beaches and a gravel spit anchored by a landward bedrock high. These were preserved through overstepping during rapid sea level rise during MWP-1B.</div><div>The preservation of each package during multiple transgressions over 20 million years without major reworking during intervening occupations of sea level is ascribed to a combination of:<ul><li><span>(i)</span><span><div>inertia associated with voluminous gravel deposits;</div></span></li><li><span>(ii)</span><span><div>rapid burial by successive gravel shorelines;</div></span></li><li><span>(iii)</span><span><div>a consistently high sediment supply (both transgressive and alongshore); and</div></span></li><li><span>(iv)</span><span><div>preferential deposition in wave-sheltered settings.</div></span></li></ul></div><div>The multiple recurrence of gravel shorelines in the same locations reflects the persistence of depositional conditions in geologically constrained settings; elsewhere shoreline deposits did not survive transgression. The latest (Holocene) phase of deposition coincided with a sea-level slowstand during which a spit prograded alongshore. Subsequent rapid sea-level rise prevented its breakdown and/or rollover and left it stranded on the shelf as a discrete palaeo-shoreline feature. Any Pleistocene precursors were destroyed via wave ravinement during multiple sea-level cycles.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"483 ","pages":"Article 107517"},"PeriodicalIF":2.6,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143519108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Early diagenesis of coral rubble on the high-energy platform of Ximen Reef in the southern South China Sea","authors":"Shengnan Zhou ,&nbsp;Qi Shi ,&nbsp;Hongqiang Yang ,&nbsp;Shichen Tao ,&nbsp;Xiyang Zhang ,&nbsp;Hongqiang Yan ,&nbsp;Zhiwei Hou ,&nbsp;Ji Yang ,&nbsp;Wenlong Jing ,&nbsp;Pin Yan","doi":"10.1016/j.margeo.2025.107510","DOIUrl":"10.1016/j.margeo.2025.107510","url":null,"abstract":"<div><div>Coral rubble is extensively distributed across high-energy coral reef platforms in the southern South China Sea (SCS), with certain areas forming unvegetated shingle cays. The rubble has undergone significant early diagenesis during its formation and accumulation; however, the specific early diagenetic processes affecting the rubble remain underexplored. Ximen Reef, a representative high-energy reef platform in the southern SCS, is characterized by a broad reef flat and a fully exposed unvegetated shingle cay predominantly composed of coral rubble. Coral rubble samples collected from both the reef flat and the cay of Ximen Reef were analyzed for chronology, mineralogy, petrography, and geochemistry to elucidate their early diagenetic characteristics. The rubble consists mainly of unconsolidated contemporary coral skeletal fragments and has undergone carbonate cementation, a key process in early diagenesis. The cementation is primarily characterized by the precipitation of secondary acicular aragonite and micritic high-Mg calcite. Additionally, other diagenetic processes, including bioerosion, encrustation, and internal deposition, have also occurred in the rubble. Early diagenesis has induced notable geochemical alterations in the rubble, with high δ¹³C, δ¹⁸O and Mg/Ca ratios, as well as low Sr/Ca ratios, compared to living corals. Both mineralogically and geochemically, the rubble on the reef flat and cay reflects a typical marine-meteoric mixing diagenetic environment. The early diagenesis of the rubble at Ximen Reef is relatively weak and remains in its initial stages, primarily due to the inherent instability of the rubble, which is influenced by high-energy hydrodynamic conditions. This may adversely impact the consolidation and development of coral reefs and islands in the southern SCS.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"483 ","pages":"Article 107510"},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143528634","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":"Changes in sediment regimes and mass accumulation rates in Eeyou Istchee eelgrass habitat, James Bay, Canada","authors":"Madelyn A. Stocking ,&nbsp;Sophia C. Johannessen ,&nbsp;Zou Zou A. Kuzyk","doi":"10.1016/j.margeo.2025.107514","DOIUrl":"10.1016/j.margeo.2025.107514","url":null,"abstract":"<div><div>Fourteen sediment cores collected from shallow subtidal waters in 2017–2021 in northeastern James Bay, Canada (known as Eeyou Istchee) were analyzed for excess ²¹⁰Pb (²¹⁰Pb_ex), ¹³⁷Cs and fine particle content (% &lt;63 μm) to characterize sediment deposition within an eelgrass (<em>Zostera marina)</em> ecosystem recovering from a massive decline in the 1990s. A strong signature of surface soil input from nearby La Grande Rivière watershed is evident from high ¹³⁷Cs inventories and low ²¹⁰Pb_ex/¹³⁷Cs ratios. Mass accumulation rates (MARs) were established in five cores using a ²¹⁰Pb_ex model that accounts for bio-mixing and subsequently validated by ¹³⁷Cs. MARs are higher in this area (0.14–0.48 g cm⁻² yr⁻¹) than in nearby offshore Hudson Bay. Low inventories of ²¹⁰Pb_ex and ¹³⁷Cs and disturbances in particle size distribution (coarsening upwards) in the remaining cores indicate non-steady-state behaviour, most likely surficial erosion. Using well-preserved ¹³⁷Cs peaks and other core-specific methods, pre-disturbance MARs were estimated at between &lt;0.05 and 0.39 g cm⁻² yr⁻¹, indicating an environmental transition from net accumulation to erosion. Recent deposition of sediment is largely controlled by sediment focusing, resulting in high variability of inventories and MARs at small spatial scales. The loss of eelgrass has likely increased sediment resuspension and redistribution to deeper areas, contributing to decreased light availability for subtidal eelgrass and increased export of material to greater James Bay. The findings of this study show the foundational importance of small-scale assessment of MARs in river-dominated eelgrass ecosystems like those in Eeyou Istchee.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"483 ","pages":"Article 107514"},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143510400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Submarine canyon sediment transport and accumulation during sea level highstand: Interactive seasonal regimes in the head of Astoria Canyon, WA","authors":"E.J. Lahr ,&nbsp;A.S. Ogston ,&nbsp;J.C. Hill ,&nbsp;H.E. Glover ,&nbsp;K.J. Rosenberger","doi":"10.1016/j.margeo.2025.107516","DOIUrl":"10.1016/j.margeo.2025.107516","url":null,"abstract":"<div><div>The majority of submarine canyons on Earth today do not directly intersect littoral or fluvial sediment sources, yet these systems are rarely studied. The shelf-incised head of Astoria Canyon receives sediment from the nearby Columbia River and is subject to energetic forcing from shelf and slope processes, making it an ideal site to evaluate the modern activity of canyons in high-stand sea level conditions. This study uses in-situ data from Astoria Canyon to identify the active sediment transport processes and patterns of accumulation in temperate canyon systems that are decoupled from their sediment sources during sea level highstand. Hydrodynamic data from a benthic tripod deployment in the head of Astoria Canyon shows that sediment resuspension and transport during summer is driven by internal tides and plume-associated nonlinear internal waves. Observations of shoreward-directed currents and low shear stresses (&lt;0.14 Pa) along with sediment trap data suggest that seasonal loading of the canyon head occurs during summer. Nearby long-term wave data show that winter storm significant wave height often exceeds 10 m, driving shear stress capable of resuspending all grain sizes present within the canyon head. Swell events are generally concurrent with downwelling flows, providing a mechanism for episodic downcanyon sediment flux. Century-scale accumulation rates evaluated from sediment cores show slow accumulation in the upper canyon head, but rates progressively increase with depth to at least 300 m. The depositional environment in Astoria Canyon continues to respond to fluvial and oceanic forcing over an annual cycle. This study indicates that canyon heads can continue to function as sites of sediment winnowing and bottom boundary layer export even with a detached, shelf-depth canyon head.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"484 ","pages":"Article 107516"},"PeriodicalIF":2.6,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714734","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}