Marine Geology最新文献

{"title":"Channel function shift around a recently-colonised estuarine mangrove shoal","authors":"Amin Rahdarian ,&nbsp;Karin R. Bryan ,&nbsp;Mick Van Der Wegen","doi":"10.1016/j.margeo.2024.107440","DOIUrl":"10.1016/j.margeo.2024.107440","url":null,"abstract":"<div><div>Large sediment loading to the coast can accelerate estuarine infilling, which promotes the establishment of salt marsh or mangroves. Bio-geomorphic feedback ensues where channels and shoals gradually evolve in tandem as the vegetation gains a foothold. The aim of this work is to explore the governing dynamics of a recently evolving estuarine, mangrove-covered channel-shoal system in Whitianga Estuary, Aotearoa New Zealand. Observations of water level, flow velocity, suspended sediment concentration (SSC) and bed sediment characteristics were used to infer flow asymmetry and sediment transport pathways around the shoal. Historical images were combined with the measurements to qualitatively link the observed, short-term processes to the influence of expanding vegetation on multi-decadal evolution. Comparisons of flow asymmetry in two contrasting drainage channels (in close proximity) on the shoal show that rapid colonisation by mangroves can quickly change the flow asymmetry from flood to ebb dominant. Mangroves opportunistically colonise the higher ground at the centre of the shoal. Meanwhile they become eco-engineers creating their own environment as evidenced by the abrupt change in the sediment textural environment, even outside the immediate area of new vegetation. Although many studies have focused on spatial flow patterns associated with mangrove vegetation, our observations show evidence of the speed at which colonisation fuels geomorphologic change.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"479 ","pages":"Article 107440"},"PeriodicalIF":2.6,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747096","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 eastward intrusion of the Lena River into the East Siberian Sea since the early Holocene","authors":"Kunshan Wang ,&nbsp;Xuefa Shi ,&nbsp;Zhengquan Yao ,&nbsp;Aleksandr A. Bosin ,&nbsp;Qiuling Li ,&nbsp;Shuqing Qiao ,&nbsp;Anatolii S. Astakhov ,&nbsp;Jiang Dong","doi":"10.1016/j.margeo.2024.107436","DOIUrl":"10.1016/j.margeo.2024.107436","url":null,"abstract":"<div><div>The sedimentary environments and material sources of the eastern and northeastern Lena Delta differ in coarse-grained components and garnet geochemistry, particularly in the Buor-Khaya Bay, where the material composition is primarily influenced by the Lena River, while the Yana Bay sediment is controlled by the Yana River. Analysis of detrital minerals in core LV83–32-3, located in northern Yana Bay, indicates dominant primarily fluvial input from the Yana River, with secondary contributions from the Lena River and minor inputs from coastal permafrost erosion since the early Holocene. During the sea-level rise period from 8.5 to 5 ka, four significant fluvial discharge events from the Yana River were identified, marked by high mica contents, associated with multiple climate warming events. From ∼5 to 1.6 ka, an increasing Lena River runoff transported coastal permafrost material via river flow or river ice, evident in a gradual rise in plagioclase content. After 1.6 ka, a sharp decrease in hypersthene and garnet contents suggests reduced Lena River discharge, coinciding with a similar decline in hypersthene content in the core of the East Siberian Sea since 1.8 ka. Two prominent Lena River fluvial events, dated to 7.1 and 3.7 ka, are identified by the event layers containing minerals typical of the Lena River, rich in hypersthene, garnet and zircon, along with substantial coarse-grained debris such as quartz, plagioclase, siderite and clayey tubes. These two events are also recorded in the East Siberian Sea. The 7.1 ka discharge event may coincide with the separation of the New Siberian Islands from the mainland, while the 3.7 ka event represents a widely distributed Lena River floodplain event.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"479 ","pages":"Article 107436"},"PeriodicalIF":2.6,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747097","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":"Reduced bottom water oxygenation in the northern Indian Ocean during the Last Glacial Maximum","authors":"Kumari Nisha ,&nbsp;Sushant Suresh Naik","doi":"10.1016/j.margeo.2024.107437","DOIUrl":"10.1016/j.margeo.2024.107437","url":null,"abstract":"<div><div>Reconstructing variations in the past bottom water oxygenation of the oceans is crucial for understanding the current global ocean deoxygenation and increased respired carbon storage. Changes in the deep water circulation have significantly influenced the oxygenation conditions of bottom water in the past. This study tracks the changes in bottom water oxygenation and carbonate dissolution in the northern Indian Ocean for the past 25 kyr BP using a multi-proxy record of surface porosity of epifaunal benthic foraminifera <em>Cibicidoides wuellerstorfi</em>, foraminiferal fragmentation percentage, CaCO₃ content, size index, and authigenic uranium concentration in sediments, from a gravity core SSD-044/GC-01 recovered from a water depth of 3160 m. Results suggest that during the Last Glacial Maximum (LGM) and the Heinrich Stadial 1 (HS1), low-O₂ and CO₂-rich deep water mass existed in the northern Indian Ocean, probably due to an increased proportion of southern sourced Antarctic Bottom Water (AABW) at the core location, which indicates increased respired carbon storage in the deep water of the northern Indian Ocean, suggesting it was part of a large carbon reservoir. At the onset of the Bølling-Allerød (at around ∼14.5 kyr BP), there was an incursion of O₂-rich and CO₂-poor NADW at the core site. Furthermore, a well‑oxygenated deep water mass prevailed in the northern Indian Ocean during the Holocene.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"479 ","pages":"Article 107437"},"PeriodicalIF":2.6,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719745","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 critical metals enrichment of ferromanganese precipitates from Jiawang Seamount (Hook Ridge) Antarctica: Geochemistry and isotope evidence","authors":"Hao Zhang ,&nbsp;Yingchun Cui ,&nbsp;Shi Zong ,&nbsp;Shaocong Chen ,&nbsp;Lijie Ma ,&nbsp;Weixuan Wang ,&nbsp;Xuejiao Wang ,&nbsp;Shenggui Li ,&nbsp;Chenguang Liu","doi":"10.1016/j.margeo.2024.107435","DOIUrl":"10.1016/j.margeo.2024.107435","url":null,"abstract":"<div><div>Marine ferromanganese precipitates are globally recognized as significant minerals resources within the world's oceans. Our study presents an analysis of isotopic geochemistry of ferromanganese precipitates from the Jiawang Seamount in Antarctica, comparing them with typical low-temperature hydrothermal ferromanganese precipitates found in oceanic settings. We discuss the genesis of ferromanganese precipitates and the characteristics of critical metals' enrichment. The chemical compositions imply that the ferromanganese precipitates from Jiawang Seamount are of hydrothermal origin. However, the enrichment characteristics of critical metals such as Co, Ni, Cu, Zn, Mo, Pb, REE, aside from Fe and Mn, are not conspicuous and possess relatively inferior potential compared with typical hydrothermal ferromanganese precipitates in the oceans. These critical metals originate from hydrothermal fluid, and their enrichment is positively correlated with the precipitation process of Mn oxides. The Sr isotope results reveal that the formation of ferromanganese precipitates underwent at least two distinct periods of hydrothermal activity, respectively at 9.5 Ma and 15–16 Ma. The chemical composition and Nd - Pb isotopic characteristics of ferromanganese precipitates suggest that the hydrothermal fluid composition is substantially similar during different periods. The formation of ferromanganese precipitates from Jiawang Seamount is closely related to regional hydrothermal activities that accompany basin development. Based on the Sr isotope estimation of hydrothermal activity, the Bransfield Strait basin is at least older than 16 Ma.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"479 ","pages":"Article 107435"},"PeriodicalIF":2.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719744","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 hydrothermal particles from the ridge axis to the sediment column along the Endeavour segment of the Juan de Fuca Ridge","authors":"Melissa Mills ,&nbsp;Jay T. Cullen ,&nbsp;Jody Spence ,&nbsp;Patrick A. Rafter ,&nbsp;Steve Mihaly ,&nbsp;Laurence A. Coogan","doi":"10.1016/j.margeo.2024.107432","DOIUrl":"10.1016/j.margeo.2024.107432","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Elemental fluxes associated with mid-ocean ridge hydrothermal systems are thought to be important in the ocean budgets of many elements but quantitative models of these fluxes, and how they vary in space and time due to different boundary conditions, are in their infancy. This is especially true for non-conservative elements that can be involved in multiple processes transforming them between the dissolved and particulate phases both in the water column and after sedimentation. To help develop a more robust database for parameterizing the processes operating, we undertook a coupled sediment trap and sediment core study of hydrothermal sediments on the west flank of the Endeavour segment of the Juan de Fuca Ridge. Sediment traps deployed in the Main Endeavour Field (MEF) and 3 and 9 km southwest of this field, along the mean flow direction of the hydrothermal plume, show that the rate of change of the concentration of sulfide-associated elements (Cu, Zn, Cd, Pb, Ag, As, Mo) in sediment settling from the plume differs between elements. We interpret this as indicating both different dissolution rates of phases containing these elements and different rates of scavenging of these elements from seawater. Scavenging is most readily tracked using elements for which the scavenged fraction is large relative to the hydrothermally derived fraction. For such elements, the relative efficiency of scavenging from seawater (REE &gt; Cr &gt; Ni &gt; V &gt; P &gt; U) matches that previously reported from the TAG system on the Mid-Atlantic ridge despite different vent fluid and seawater chemistries that are expected to lead to both differing roles of Fe-sulfide and Fe-oxyhydroxides and different Fe oxidation rates. In the sediment trap samples collected 9 km off-axis, but not in those collected 3 km off-axis, the Mn and Ti concentrations correlate strongly despite these samples having much higher Mn concentrations than background sediment. Since Ti is sourced almost entirely from background terrigenous material such a correlation was not expected. The most reasonable explanation for this is that aggregation of hydrothermally derived particles with terrigenous material settling through the water column controls removal of hydrothermally derived particles from the water column. Changes in sediment composition with depth in the off-axis sediment core, along with differences between the composition of material from the sediment core and the off-axis sediment traps, are interpreted as indicating large post-deposition changes in sediment composition. For example, much or all of the Mn, P, As and Mo carried to the sediments with hydrothermally derived particles is released back into the water column during diagenesis. In contrast, V and REE concentrations in the sediment core are higher than those in the off-axis sediment trap samples, which may be due to continued scavenging in a benthic boundary layer post-deposition. Overall these data are interpreted as indic","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"478 ","pages":"Article 107432"},"PeriodicalIF":2.6,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662819","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":"Spatial heterogeneity of sediments on a topographically diverse descending plate at convergent margins: An example from the outer slope of the Mariana Trench","authors":"Yuhao Chen,&nbsp;Xing Jian","doi":"10.1016/j.margeo.2024.107430","DOIUrl":"10.1016/j.margeo.2024.107430","url":null,"abstract":"<div><div>Unraveling deep ocean sediment composition and its controlling mechanisms is crucial to understanding the interplay between the Earth's surface and the deep Earth. Convergent margins are generally featured by various seafloor landforms, but how submarine topography affects sediment accumulation processes remains poorly understood. Here we focus on submarine surface sediments from the outer slope of the Mariana Trench (covering water depths of 1218–6310 m) and combine microscopic observation, clay mineralogy, and elemental geochemistry to characterize sediment composition and to reveal physical, chemical, and biological sedimentary processes at topographically diverse convergent margins. Smear slide observations indicate that foraminifera shells dominate in shallow areas, while pelagic clays and diatom oozes prevail in trench and slope areas. Clay minerals primarily consist of illite (26–98 %) with low crystallinity index values and diverse chemical index values, followed by chlorite (0–45 %) and kaolinite (0–29 %). Smectite (0–61 %, 46 of 70 samples have smectite contents &lt;5 %) of the samples from the outer slope area is low but appears dominant close to the trench. Bulk element compositions are mainly affected by the relative calcareous, siliceous, and lithogenous components that dissolved or accumulated inconsistently as submarine topographic feature changes. Our results imply that submarine topography and sediment provenance lead to significant heterogeneity of sediment composition at topographically diverse convergent margins. The submarine topographic relief, together with associated bathymetry and deep-sea circulation primarily controls carbonate deposition on the Caroline Plateau, and influences the sinking particles (including diatom shells and arc volcanic-sourced materials) accumulation in the trench basin. Continent-derived aeolian dust introduces illite-rich detritus, while localized volcanism potentially contributes to smectite-rich sediment in certain topographic provinces. We propose that the deep sea sedimentation processes in the Mariana convergent system are more diverse and complex than those at the margins with relatively plain topographic characteristics (e.g., the Japan Trench). The significant heterogeneity on descending plates along convergent margins may lead to various subduction behaviors. These findings contribute to a better understanding of deep ocean sediment source-to-sink systems and have implications for Earth's material cycle and multi-sphere interaction studies.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"479 ","pages":"Article 107430"},"PeriodicalIF":2.6,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719743","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":"Exploring subaqueous bedforms and its relation to hydrodynamics in the Rio Grande Rise, Southwestern Atlantic","authors":"Giovanna Orletti Del Rey ,&nbsp;Pedro Walfir Souza-Neto ,&nbsp;Lucieth Cruz Vieira ,&nbsp;Antônio Cosme Del Rey ,&nbsp;Arthur Ayres Neto ,&nbsp;Maria Aline Lisniowski ,&nbsp;Roberto Ventura Santos","doi":"10.1016/j.margeo.2024.107434","DOIUrl":"10.1016/j.margeo.2024.107434","url":null,"abstract":"<div><div>This study investigates the interplay between hydrodynamics, sediment dynamics, and topography in the Rio Grande Rise (RGR) area. It addresses bedforms found in five different regions, attributing their formation to the interaction between unconsolidated carbonatic substrate and bottom currents, particularly the M2 tidal flow, the primary lunar semidiurnal constituent. The bedforms are shaped by the interplay of the M2 tidal current and local topography, with the bottom mean flow also contributing to specific areas. Generally, bedforms are classified as subaqueous dunes/tidal banks. The environmental sectorization within the RGR, driven by variations in bottom velocities related to flow-topography interaction, delineates deposition and non-deposition areas. Bathymetric data reveal that bedforms are present in shallower, lower-flow energy zones, whereas Fe<img>Mn crusts are located in more profound, higher-flow energy areas. They indicate that carbonate sediments are either being transported away from the crust regions or remobilized, leading to accumulation in the areas with bedforms. The flow velocity in Fe<img>Mn crust areas is able to cause sediment bypassing, resulting in areas where deposition does not occur. Furthermore, these velocities exceed the optimal flow conditions for Fe<img>Mn crust precipitation and could be eroding the previously formed Fe<img>Mn crusts. These findings imply that Fe<img>Mn crusts lie beneath the subaqueous dunes to some extent. This study highlights the complexity of the interaction of oceanic flow with the RGR substrate and its morphology, emphasizing the importance of local hydrodynamics and topography when analyzing these features.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"478 ","pages":"Article 107434"},"PeriodicalIF":2.6,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662830","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":"Provenance and sediment dispersal in Pearl River Estuary, southern China unraveled by magnetic properties","authors":"Mingkun Li ,&nbsp;Yongying Zeng ,&nbsp;Shanshan Liu ,&nbsp;Meng Tang ,&nbsp;Liang Chen ,&nbsp;Jiyu Chen ,&nbsp;Alessandro Amorosi ,&nbsp;Tingping Ouyang","doi":"10.1016/j.margeo.2024.107431","DOIUrl":"10.1016/j.margeo.2024.107431","url":null,"abstract":"<div><div>The Pearl River Estuary (PRE), with eight outlets supplied by multiple tributaries, is an excellent study area for reconstructing sediment provenance and transport pathways of a multi-sourced sediment-routing system. However, the sediment source to sink dispersal model is less well-known. This study aimed to estimate the PRE sediment budget by comparing the magnetic characteristics of estuarine surface sediments with those of all potential sources. In the bottom sediments of PRE and adjacent region, magnetic minerals, mainly magnetite and hematite, have a characteristic terrigenous signature. Source and sink comparison for magnetic parameters shows that the possible input of southwestern Taiwan rivers can be excluded, whereas the possibility of sediment contribution from nearby rivers, including Han, Rong, and Jiulong rivers, to the estuary could not be ruled out. Quantitative provenance analysis indicates that West River-sourced sediment dominates the western side of the estuary, the East River-sourced sediment is most important in the eastern side of the estuary, whereas sediment supplied by the North River is high only close to the outlets. A mixed-sediment contribution to the estuary is suggested, with a fluvial-dominated sediment input around the west river outlets and a tide-dominated sediment dispersal in the eastern side of the estuary. Overall, our study demonstrates the importance of fingerprinting changes in sediment supply using sediment magnetic properties and provides new insights into the PRE sediment-routing system.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"478 ","pages":"Article 107431"},"PeriodicalIF":2.6,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662827","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":"Bedform development in confined and unconfined settings of the Carchuna Canyon (Alboran Sea, western Mediterranean Sea): An example of cyclic steps in shelf-incised canyons","authors":"J. Cerrillo-Escoriza ,&nbsp;A. Micallef ,&nbsp;F.J. Lobo ,&nbsp;Á. Puga-Bernabéu ,&nbsp;P. Bárcenas ,&nbsp;I. Schulten ,&nbsp;R. Durán ,&nbsp;Á. Carrión-Torrente ,&nbsp;A. López-Quirós ,&nbsp;M. Luján ,&nbsp;O. Sánchez-Guillamón ,&nbsp;M.J. Sánchez","doi":"10.1016/j.margeo.2024.107429","DOIUrl":"10.1016/j.margeo.2024.107429","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Newly acquired high-resolution multibeam bathymetry in combination with sub-bottom acoustic profiles, surficial sediment samples, and three-dimensional flow simulations made possible the characterization of bedforms along the axial channel and depositional lobe of the shelf-incised Carchuna Canyon (Alboran Sea, western Mediterranean Sea). This study aims to describe the erosional and depositional bedforms in confined and unconfined settings of the Carchuna Canyon in order to determine the genetic constraints on sedimentary processes leading to bedform development along the canyon in recent times.&lt;/div&gt;&lt;div&gt;The straight Carchuna Canyon, deeply incised in the shelf up to 200 m off the coastline, hosts: (1) crescentic-shaped bedforms (CSBs) that exhibit distinctive crest concavities, asymmetries, and lengths along the axial channel; (2) continuous lateral levees and; (3) a channel bend with three depressed stretches of the levee crest that are less than 20 m high. A set of concentric sediment waves and two scour trails were identified proximal to the channel bend over an overbank deposit east of the Carchuna Canyon. Four acoustic units with distinct acoustic facies were defined along the sediment wave field. The sediment transport simulation shows the highest flow velocities along the Carchuna Canyon thalweg, while over the overbank deposit the highest velocity values occur along the top of the bedform crests, with the higher Froude values being found over bedform lee sides.&lt;/div&gt;&lt;div&gt;The occurrence of CSBs along the canyon axial channel suggests the imprint of confined sediment-laden gravity flows descending from the canyon head and exhibiting a flow variability along the canyon induced by local variations of slope gradient and/or sediment concentration. A spatial relationship is identified between the development of sediment waves over the overbank deposit and lowered levee crest heights at the channel bend. In contrast, more energetic downstream turbiditic flows exceed the levee crest at the channel bend, focusing the overflow and promoting erosion of the overbank deposit, thereby generating the scour trains. Based on the recent history of overbank deposition, two alternating scenarios of flow behavior can be interpreted. In a high-density turbidity current setting, erosion would prevail along the axial channel. Widespread spillover flows of coarse-grained sediments would occur in both levees, forming heterogeneous sedimentary patterns that change downslope within the depositional lobe due to lesser turbulence of spillover turbidity currents and gentler slope gradients. In contrast, in a low-density turbidity current setting, turbidity currents flowing along the Carchuna Canyon would form depositional bedforms in the axial channel, while spillover processes would be localized at the channel bend, forming either depositional or erosional bedforms over the depositional lobe according to the frequency, magnitude and focusing of turbiditic ","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"478 ","pages":"Article 107429"},"PeriodicalIF":2.6,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662821","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":"A Northgrippian sedimentary magnetic enhancement along the western margin of India","authors":"Firoz Badesab ,&nbsp;R.P. Deepak ,&nbsp;Nitin Kadam ,&nbsp;Virsen Gaikwad ,&nbsp;Thejasino Suokhrie ,&nbsp;Mamilla Venkateshwarlu ,&nbsp;Rajeev Saraswat","doi":"10.1016/j.margeo.2024.107427","DOIUrl":"10.1016/j.margeo.2024.107427","url":null,"abstract":"<div><div>Sedimentary magnetic records of shelf region contains complex environmental evolution information, necessitating records from various global regions to accurately interpret its significance. A sediment core (SSD-39/GC-01) retrieved from the eastern Arabian Sea was analyzed to elucidate the geologic and climatic controls on the sediment rock magnetic and grain size properties. We report the first record of high energy sediment deposits linked with intense monsoon phases, sea level variations, and extreme natural events during the Northgrippian period (8.27 ka to 4.20 ka). The compilation of magnetic susceptibility profiles of six sediment cores from the western margin of India revealed the presence of multiple sedimentary intervals of enhanced magnetic susceptibility and most likely reflect periods of high sedimentation events controlled by the regional geologic and climatic processes. We identified two anomalous sedimentary magnetic zones (<em>Z</em>-II, Z-IV) marked by an elevated magnetite content and sediment grain size, which reflect the periods of high-sedimentation events on the shelf off Goa. A shift in the magnetic mineral composition, clastic grain size, calcium carbonate, and organic carbon content at ∼1.8 ka (<em>Z</em>-I) indicate a abrupt change in monsoon intensity. The elevated organic carbon content within Z-I indicates efficient preservation of labile organic matter which survived oxidation due to rapid sediment deposition. End-member modeling of rock magnetic and grain size properties enabled us to discriminate and quantify the contributions of terrigenous fluxes and post-depositional mineral phases to the bulk magnetic mineral assemblage. We demonstrate that rapid scanning of magnetic susceptibility of sediment cores has the potential to precisely detect the periods of increased continental (magnetic flux) inputs into the marine shelf system. The proposed magnetic mineralogical approach has wider scope to constrain the understanding of how shelf sedimentation responded to past geological and climatic conditions globally.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"478 ","pages":"Article 107427"},"PeriodicalIF":2.6,"publicationDate":"2024-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662820","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}