Marine Geology最新文献

{"title":"Mid to late Holocene Indian monsoon variability, aridification and civilization changes in the Deccan Plateau, India","authors":"Tyson Sebastian ,&nbsp;Sunil Vadakkepuliyambatta ,&nbsp;B.V. Lakshmi ,&nbsp;B. Mohammed Shafeeq ,&nbsp;P. John Kurian","doi":"10.1016/j.margeo.2024.107412","DOIUrl":"10.1016/j.margeo.2024.107412","url":null,"abstract":"<div><div>Climate change has been a key driver throughout human history and has frequently been associated with the rise and fall of civilizations. Holocene settlement changes or population displacements were almost always preceded by changes in climate. A high-resolution sedimentary record from the western Bay of Bengal offers insights to centennial-scale mid- to late-Holocene Indian summer monsoon (ISM) variability and its role in the decline of chalcolithic human settlements on India's Deccan Plateau. Increased erosion in the Indian peninsula during the mid- to late-Holocene, due to aridification and agricultural expansion, is evidenced by higher sedimentation, more magnetic mineral content, coarser magnetic grain size, and increased sand content. The results from mineral magnetic and textural analyses reveal centennial-scale abrupt weak ISM during the Bond events in the core monsoon zone of India. The Deccan Chalcolithic civilizations flourished between ∼4.0–3.0 ka BP owing to the favorable climatic conditions, but most of the settlements were deserted after ∼3.0 ka BP. We argue that the abrupt weakening of ISM during Bond event 2 (∼3.1–2.8 ka BP) caused this collapse of Deccan Chalcolithic. The results from this study together with the published records of number of settlements and summed radiocarbon dates suggest a climate-culture link in the Deccan Plateau. The weak ISM periods in this study are coherent with the records of total solar irradiance and the percentage of hematite-stained grains from the North Atlantic and suggest solar control on these abrupt climatic events.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107412"},"PeriodicalIF":2.6,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442097","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":"Geomorphic processes within the La Gomera-Tenerife Channel (Canary Islands): Decoding the interaction of bottom currents with seabed topography","authors":"E. Martorelli ,&nbsp;F. Falcini ,&nbsp;G. La Forgia ,&nbsp;A. Bosman ,&nbsp;M. Cuffaro ,&nbsp;L. Petracchini","doi":"10.1016/j.margeo.2024.107406","DOIUrl":"10.1016/j.margeo.2024.107406","url":null,"abstract":"<div><div>The La Gomera-Tenerife Channel is a narrow passage between La Gomera and Tenerife Islands, i.e., two volcanic edifices of the Canary Archipelago (Atlantic Ocean). A geophysical study was conducted to identify the main geomorphic processes affecting the seabed and their interplay. In particular, submetric resolution bathymetric and side scan sonar backscatter data were collected in the southern sector of the Channel, down to 1200 m water depth. Their integrated analysis revealed a complex seabed morphology and a variety of morpho-sedimentary features, resulting from three main geomorphic processes: submarine volcanic activity, mass wasting (e.g., turbidity currents, small landslides and exotic blocks emplaced by a massive landslide event), and bottom currents activity. Bottom currents strongly reshaped the seabed into bedforms, confined drifts, and moats. Although the flanks of volcanic islands are typically dominated by mass wasting and volcanic features, our results indicate that bottom current activity can be predominant in confined settings and around topographic features due to modification of flow patterns and enhancement of current flows.</div><div>This study is the first to document volcanic, mass wasting and bottom current features within the La Gomera-Tenerife Channel. Furthermore, it provides insights on: i) morpho-sedimentary reconstructions of narrow passages between volcanic islands; ii) interplay among different geomorphic processes; iii) oceanographic reconstructions. The variety of geomorphic processes shaping the La Gomera-Tenerife Channel makes this area significant for high-resolution studies. Moreover, it provides new insights on poorly known processes, such as: the interaction of bottom currents with complex topography and bottom current morpho-dynamic in curved moats.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107406"},"PeriodicalIF":2.6,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529853","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":"Discerning sediment provenance in the Outer Banks (USA) through detrital zircon geochronology","authors":"John W. Counts ,&nbsp;Jared T. Gooley ,&nbsp;Joshua H. Long ,&nbsp;William H. Craddock ,&nbsp;Paul O'Sullivan","doi":"10.1016/j.margeo.2024.107409","DOIUrl":"10.1016/j.margeo.2024.107409","url":null,"abstract":"<div><div>Detrital zircon data from modern barrier island and estuarine environments in the Outer Banks (Atlantic Coast, USA) were statistically compared to sands from nearby rivers to assist in determining source-to-sink pathways. Fluvial samples, collected from near the Fall Line contact between the Appalachian Orogen and sediments of the coastal plain, all have age unique distributions, making them ideal for tracing provenance. Three samples from the Atlantic foreshore showed high similarities to one another, as well as to three samples from the estuarine (back-barrier) Pamlico and Albemarle Sounds. Mixture modeling with multiple data reduction methods and three different statistical tests for similarity consistently indicated that the nearby Potomac River was the primary source for all Atlantic foreshore and estuarine zircons, followed by minor contributions from the James River in some models. The models indicate little or no sediment contribution from the Susquehanna, Roanoke, Tar, Neuse, Cape Fear, and Peedee Rivers. Both Atlantic foreshore and estuarine sands are therefore interpreted to have initially originated from Appalachian bedrock to the north of their present-day location, and subsequently to have been transported southward through the Chesapeake Bay watershed before deposition in Virginia and North Carolina. Prior to barrier island formation in the last several thousand years, differing geomorphology of the Chesapeake Bay facilitated southward movement of sediments from its constituent rivers via longshore drift, where they were deposited in coastal settings on the mainland. The modern barrier islands, formed during the most recent post-glacial transgression, may be reworked from these deposits, but may also include a contribution from sediments that were derived more recently from relict deposits on the shelf. Oceanographic and sedimentological evidence suggests that movement of sand-sized grains from southern rivers across the back-barrier sounds is unlikely. These findings can assist with coastal resilience planning and resource management in a region under severe threat from climate change and rising sea levels.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107409"},"PeriodicalIF":2.6,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423067","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":"Hawaiian legends of coastal devastation and paleotsunami reconstruction, Nu'u, Kaupō, Maui, Hawai'i","authors":"Scott Fisher ,&nbsp;James Goff ,&nbsp;Andrew Cundy ,&nbsp;David Sear ,&nbsp;James Terry ,&nbsp;Randall J. LeVeque ,&nbsp;Loyce M. Adams ,&nbsp;Diana Sahy","doi":"10.1016/j.margeo.2024.107408","DOIUrl":"10.1016/j.margeo.2024.107408","url":null,"abstract":"<div><div>In Hawaiʻi, tsunamis are often described in orally transmitted legends (<em>moʻolelo</em>). This study examines sedimentary evidence of a possible local submarine landslide-generated tsunami, described in a legend from the south east coast of Maui which originated between the 15th Century CE and the first arrival of Europeans in 1778 CE. Physical evidence for a tsunami, found at the Nu'u Refuge, Maui, is primarily comprised of an extensive coral clast deposit (found 8.5 m above msl and 251 m inland from the shoreline) together with waterworn cobbles which form fracture-embedded wedge clasts in a local basalt escarpment (at up to 8 m above msl). U/Th dating of the coral clasts gives a maximum tsunami deposit age of 1671 CE for the event that may have inspired the local <em>moʻolelo</em>. This depositional sequence is used to characterize the nature of the assumed tsunami in terms of inundation distance, maximum wave runup and minimum flow velocities. A numerical model developed using GeoClaw matches well with the physical evidence. The data and modeling presented here suggest that locally-generated tsunamis from submarine landslides warrant further research attention as sources of destructive high energy marine inundation events.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107408"},"PeriodicalIF":2.6,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423066","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":"Sedimentological evidence of Late Pleistocene Shorelines in Oman","authors":"V. Decker ,&nbsp;M. Falkenroth ,&nbsp;G. Hoffmann","doi":"10.1016/j.margeo.2024.107407","DOIUrl":"10.1016/j.margeo.2024.107407","url":null,"abstract":"<div><div>As the climate crisis intensifies, estimating sea-level rise will become increasingly relevant, in particular assessing changes in the relative sea level in different regions. One key to comprehending global sea-level changes is the study of past sea-level highstands. Many regional studies help refine the reconstruction of paleo sea levels globally. Thus far, the Middle East remains understudied.</div><div>This paper presents evidence for Quaternary sea-level variations along the shores of the western Indian Ocean. Eight coastal outcrops along the northern and eastern coasts of Oman are presented in detail. The sedimentological evidence for sea-level highstands varies within the study area. However, in relation to recent sea-level conditions, all of these marine and beach deposits are now found well above the environments where such formations would typically form. Dating the timing of sea-level highstands remains a challenging task within the study area. In different studies, attempts to ¹⁴C date samples from that area were unsuccessful, as the time of sediment deposition lies beyond the dating limit of ¹⁴C, precluding a Holocene formation of these sediments. Thus, the sediments are regarded as deposits formed during Pleistocene sea-level highstands, presumably during MIS 5e. For some sections, optically stimulated luminescence dating could provide a solution, as igneous source rocks supply quartz and feldspar. This paper aims to localise eight sea-level related outcrops along the Omani coast and depict their potential for future work, which should include dating and elevation measurements. Through this, our work contributes to the ongoing effort to globally identify records of sea-level changes, as well as providing insights into the regional setting in Oman.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107407"},"PeriodicalIF":2.6,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423064","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":"Twenty years of MSPs: Technologies and Perspectives","authors":"David McInroy","doi":"10.1016/j.margeo.2024.107403","DOIUrl":"10.1016/j.margeo.2024.107403","url":null,"abstract":"<div><div>Mission-Specific Platforms (MSPs) have been important members of the scientific ocean drilling family for two decades, operating alongside their impressive siblings <em>JOIDES Resolution</em> and <em>D/V Chikyu</em>. Over this time, 10 MSP expeditions were implemented in 7 different oceans and seas. These MSPs capitalised on alternative platforms and methods, and enabled the scientific community to access new geographical areas and new geological targets that could not be drilled by the <em>JOIDES Resolution</em> or <em>Chikyu</em>. Offshore heave-compensated wireline coring, onshore-mining-style wireline coring, remote seafloor drilling and giant piston coring have all featured on MSP expeditions. Equally diverse were the environments in which these technologies were deployed, from the ice-covered Arctic Ocean to the tropical seas of the Great Barrier Reef, and from the shallow waters of the Yucatan shelf to the ultra-deep hadal depths of the Japan Trench. In this paper we reflect on the diverse technologies of MSPs, how they increased scientific ocean drilling capability in the Integrated Ocean Drilling Program (2003−2013) and International Ocean Discovery Program (2013–2024), and the scientific achievements that they enabled.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107403"},"PeriodicalIF":2.6,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423063","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":"Drowned barriers and valleys: A morphological archive of base level changes in the western South Atlantic","authors":"Antonio R. Ximenes Neto ,&nbsp;Valéria S. Quaresma ,&nbsp;Pedro S. Menandro ,&nbsp;Paulo H. Cetto ,&nbsp;Alex C. Bastos","doi":"10.1016/j.margeo.2024.107404","DOIUrl":"10.1016/j.margeo.2024.107404","url":null,"abstract":"<div><div>Drowned paleo-coastal and fluvial landforms preserved on continental shelves are important indicators of sea-level changes during the Quaternary. Morphological analyses of paleo-coastal and fluvial submerged features using multibeam bathymetry as basic datasets, were carried out on the Southeast Brazilian Shelf. The aim was to investigate the interaction between incised valleys and submerged barriers and their temporal relationship. Six partially infilled incised valleys with sinuous and meandering features, and up to ∼40 m of fluvial incision were observed, including several morphologies associated with meanders (e.g., point bars, neck, cut-bank). Paleo-coastal features, mainly related to barriers, were found at four depth ranges (DR) in a dip orientation: DR1 (&gt;60 m); DR2 (55 m–60 m); DR3 (50 m–55 m); DR4 (45 m–50 m). The geomorphic results show that valleys and coastal barriers coexisted and that lower and narrower barriers tend to occur near the shelf break. Preliminary geomorphic evolution between incised valleys and coastal barriers encompasses two possible origins: I) paleo-coastal features of DR 2–4 developed during the interstadial fluctuations of sea-level in MIS 3–5 and/or multiple genetic phases with different base level cycles. The valleys had two phases of incisions related to the base level drop below the shelf break: MIS 4 in the shallow incisions (terraces) and MIS 2 in the main incisions. Moreover, the development of DR 1 was related to the post-LGM base level rise; II) All submerged coastal (DR 1–4) and fluvial features developed during post-LGM base level rise (i.e., fluvial and coastal dynamics in the same cycle of base level change). The multiple phases of base-level changes inducing phases of valley incisions and barrier formation is more likely the be a better explanation. From this perspective, geochronological studies using sedimetary cores in the paleo-coastal and fluvial features are crucial to validate these scenarios, and thus contributing to fill knowledge gaps regarding morphosedimentary responses to base-level changes on the western Atlantic margin.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107404"},"PeriodicalIF":2.6,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327705","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":"Morphological evidence of an explosive eruption event in October 2023 at Sofu Seamount in the Izu-Bonin Arc","authors":"Hiroki Minami ,&nbsp;Kenichiro Tani","doi":"10.1016/j.margeo.2024.107405","DOIUrl":"10.1016/j.margeo.2024.107405","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Sofu Seamount is one of the poorly studied submarine edifices in the Izu-Bonin Arc. There is no known historical record of volcanic activity, thus its eruptive history and volcanic features are completely unknown. However, on October 9, 2023, at least 14 &lt;em&gt;T&lt;/em&gt;-phases originating near Sofu Seamount were observed. An 80 km-long raft of floating pumice was observed off Sofu Seamount on October 20. These spatially and temporally coherent observations indicate that an eruption occurred from a deep seafloor vent somewhere near Sofu Seamount. In order to investigate the origin of this submarine eruption, we collected new bathymetric data in 2024 and compared it with older bathymetric data collected in 2022, 2007 and 1987. The bathymetric comparison revealed evidence for explosive eruptions at Sofu Seamount between 2022 and 2024. During this time, a crater, 1.6 km wide and 400 m deep, was formed at the pre-existing central cone on the western part of Sofu Seamount, whose pre-eruption summit depth was 737 m. The maximum negative depth change was 451 m and a volume of 430 × 10&lt;sup&gt;6&lt;/sup&gt; m&lt;sup&gt;3&lt;/sup&gt; was removed due to the crater formation. A dome-like structure, 1 km wide and 100 m high was constructed northeast of the crater, part of which collapsed as a result of the crater formation. The volcanic products were transported over 6 km downslope and emplaced on the adjacent seafloor where positive depth changes up to 75 m were observed. Landslides also occurred around the crater. The largest slide on the northern flank formed a slide scar that is 3.8 km long and 1 km wide. Here, the maximum negative depth change was 148 m and 140 × 10&lt;sup&gt;6&lt;/sup&gt; m&lt;sup&gt;3&lt;/sup&gt; of material was removed. The slide materials were deposited downslope where positive depth changes up to 61 m were observed. Considering the occurrence of the earthquake swarm on October 2–8, 2023 and &lt;em&gt;T&lt;/em&gt;-phase swarm on October 9, the timing of the eruption can be constrained within October 2023.&lt;/div&gt;&lt;div&gt;An analysis of volcanic and tectonic morphology reveals a distinct tectonic influence on volcanism at Sofu Seamount. Sofu Seamount is located in a back-arc rift zone where the N–S trending Torishima and Sofu Rifts have formed. The new bathymetric data showed that the rifts have an asymmetric structure and can be divided into two segments, which are identified here as inner and outer rifts. The inner rifts are bounded by steeper fault scarps that have experienced more subsidence than the outer rifts. The western part of Sofu Seamount, where the eruption occurred, is located within the inner rifts, and is heavily dissected by rifting-related normal faults, while the eastern part is located outward of the inner rifts and is not dissected by faults. The October earthquake swarm was more concentrated in the area of the inner rifts and some large earthquakes showed normal fault focal mechanisms with a tension axis approximately in E–W direction. Our morphological observations comb","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107405"},"PeriodicalIF":2.6,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142423062","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":"Storm-Driven Tree Exposure and Geomorphic Change: Predicting the Distribution of Preserved Late Pleistocene Tree Stumps on the Outer Alabama Continental Shelf","authors":"Kelli L. Moran ,&nbsp;Kehui Xu ,&nbsp;Jeffrey Obelcz ,&nbsp;Kristine L. DeLong ,&nbsp;Kendall Fontenot ,&nbsp;Carl A. Reese ,&nbsp;Grant L. Harley ,&nbsp;Douglas Jones ,&nbsp;Alicia Caporaso","doi":"10.1016/j.margeo.2024.107402","DOIUrl":"10.1016/j.margeo.2024.107402","url":null,"abstract":"<div><div>The Alabama Underwater or Drowned Forest is a well-preserved Late Pleistocene (dated to 72–56 ± 8 ka, 2σ) terrestrial landform on the northern Gulf of Mexico continental shelf that provides geomorphic and ecosystem information rarely preserved during the glacial intervals. Stumps of bald cypress (<em>Taxodium distichum</em> (L.) Rich.) trees were exposed in ∼18 m of water following Hurricane Ivan in 2004. This research investigates geomorphic changes to the Mississippi-Alabama-Florida (MAFLA) sand sheet, which presents as shore-oblique Holocene sand ridges, and the exposure and burial of tree stumps following the passage of Hurricane Sally in 2020 using repeat sidescan and bathymetric surveys (2015–2016 and 2021). Using two newly identified tree exposure areas and their geological properties, this research also hypothesized a new location where tree stumps may be outcropping. The bathymetry indicates regions with up to ∼1 m of erosion and deposition over the five years between the two surveys. Similarly, the sidescan sonar indicates changes in the location and numbers of exposed tree stumps as well as between 47,000 and 62,500 tons of sediment erosion within the study area following Hurricane Sally. The 2015 and 2016 data found 25 tree contacts whereas the 2021 survey found 76 tree contacts and only 5 of them occurred in both surveys suggesting the tree exposures are dynamic and presumably changing with the passing of large tropical cyclones. Additionally, the hypothesized exposure location had 26 newly identified tree stump contacts within a mixed texture unit along the sand-mud boundary, confirming our understanding of the geomorphic characteristics leading to the exposure of the buried forest. This research will expand the potential areas for investigations into Late Pleistocene ecosystems and landforms and their associated climatic and ecologic conditions in the Gulf of Mexico as well as in other passive continental margins.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107402"},"PeriodicalIF":2.6,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142357014","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":"Formation and preservation mechanisms of magnetofossils in the surface sediments of muddy areas in the ye llow and Bohai Seas, China","authors":"XingZe Zhang ,&nbsp;YongHong Wang","doi":"10.1016/j.margeo.2024.107401","DOIUrl":"10.1016/j.margeo.2024.107401","url":null,"abstract":"<div><p>Magnetofossils in the continental shelf sediments of the Yellow and Bohai Seas have long been overlooked. Based on the magnetic results of 88 surface sediments (0–10 cm depth), first-order reversal curve (FORC) diagrams, isothermal remanent magnetization (IRM) acquisition curves from 6 representative samples, and transmission electron microscopy (TEM) observations of 2 samples, the formation and preservation mechanisms of magnetofossils in this region are elucidated. The FORC diagrams consistently show a clear central ridge feature, which indicates the presence of intact magnetofossils in all representative samples. The morphologies observed by TEM are primarily equant and elongated, with minimal or no bullet-shaped (magnetite) magnetofossils. Analysis further reveals a widespread distribution of magnetofossils in the mud areas of the Bohai Sea, North Yellow Sea, and South Yellow Sea, with proportions (contribution to SIRM; SIRM is defined as the remanent magnetization that remains constant as the external magnetic field increases) of &lt;32.5 %, 40.9 % ∼ 44.6 %, and 59.9 % ∼ 66.5 %, respectively. Despite the presence of non-biogenic single domain magnetite, the proportion of magnetofossils can be estimated by the χ_ARM/SIRM value, as they are positively correlated. The surface sedimentary environment of these mud areas is primarily suboxic and characterized by abundant dissolved iron, which facilitate the formation of magnetofossils by magnetotactic bacteria (MTB). It is unlikely that the surface sedimentary environment becomes sulphidic, thereby enabling the preservation of magnetofossils after their formation. The redox state of the study area, crucial for magnetofossil formation, is mainly controlled by the total organic carbon (TOC) content. From north to south, the higher proportion of magnetofossils is coupled with higher TOC content, possibly due to the intensified reducing degree of the suboxic environment, promoting MTB proliferation and thus forming more magnetofossils. The mechanisms governing the formation and preservation of magnetofossils proposed in this study may also be applicable to geological records.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"477 ","pages":"Article 107401"},"PeriodicalIF":2.6,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142271103","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}