Marine Geology最新文献

{"title":"Quaternary floodings in the Zanzibar Channel (NW Indian Ocean, Tanzania) – Identifying palaeoceanographic patterns and palaeoenvironment using a multiproxy study","authors":"","doi":"10.1016/j.margeo.2024.107366","DOIUrl":"10.1016/j.margeo.2024.107366","url":null,"abstract":"<div><p>Multiproxy palaeoenvironmental analyses represent a promising tool for complex reconstructions of continent-sea or air-sea interactions in shallow marine environments. This is in particular illustrated by the case of strong climatic variations in the late Pleistocene to mid-Holocene. A unique combination of geochemical proxies (¹⁴³Nd/¹⁴⁴Nd, ⁸⁷Sr/⁸⁶Sr, δ¹⁸O and δ¹³C isotope analyses, <em>n</em>-alkane analysis and biomarker study) together with micropalaeontological data (foraminifera, calcareous nannoplankton and diatoms) allowed to precisely characterise two marine floodings (mid-Holocene and late Pleistocene) in the Zanzibar Channel (NW Indian Ocean, Tanzania). The climate of the late Pleistocene interval was arid compared to the Holocene. The fully oligotrophic environment characteristic of the late Pleistocene flooding (∼115–130 ka) was episodically interrupted by intervals of intense rainfall with episodes of increased nutrient input during the mid-Holocene (∼5–10 ka). The dominance of seaweed meadows in the Holocene and late Pleistocene contrasts with the modern environment dominated by seagrass ecosystems. Relatively non-radiogenic ε_Nd signatures in the Zanzibar Channel during the Holocene and late Pleistocene indicate a strong influence of riverine input draining the Precambrian basement on the African mainland. The main inflow of seawater was from the south, consistent with the flow direction of the East African Coastal Current and the directions of the March to October monsoon winds. A promising tool for future applications as indicators of seagrass/seaweed meadow type ecosystems may be the presence of specific diatom taxa.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084067","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":"Defining an exposure index along the Schleswig-Holstein Baltic Sea coast","authors":"","doi":"10.1016/j.margeo.2024.107382","DOIUrl":"10.1016/j.margeo.2024.107382","url":null,"abstract":"<div><p>A wind exposure index (EI), which indicates the main physical driver of a coastal system, was developed along the Schleswig-Holstein Baltic Sea (SH) coast – Germany, to demonstrate the highly dynamic coastal stretches (i.e., potential erosion hotspots). The approach used three steps to define more accurate EIs. Initially, a representative wind year (RWY), which has similar physical characteristics as in the long-term data, was defined by analysing measured wind data from 2000 to 2019 at four stations distributed in the entire area of interest. The RWY was identified by a statistical comparison of wind speeds in 5 classes and 36 directional sectors between summer to summer yearly wind and the overall data. The selected RWY spanned from 01.09.2016 to 31.08.2017 and showed a reasonable agreement with the overall data (<em>Skill</em> = 0.77 and <em>rmsd</em> = 0.56 m/s). Next, high spatiotemporal nearshore hydrodynamics over the RWY were predicted using a model nesting approach of two domains in Delft3D. The predicted nearshore hydrodynamics indicated fair agreements with the measured data (<em>R</em>^<em>2</em>: 0.87–0.90 for water levels and 0.75–0.86 for wave heights). Finally, the predicted water level and wave height time series in the nearshore area (∼ 5 m MSL depth) were used for the analysis of the EI adopting a 2-step procedure capturing short- and long-term correlations as well as seasonal long-range dependencies of the time series. This approach allows to model the clustering behaviour of extreme values of both parameters and provides reasonable EIs along the SH coast. The exposed areas display high EIs (e.g., 1 at the east of Fehmarn), while sheltered areas and bays have low values (e.g., 0 at Eckernförde Bay). The higher the EI the stronger the coastal dynamics and thus strong erosion can be expected. Interestingly, the EI varies considerably even along the exposed coastal stretches with long fetches, which indicates the sensitivity of the EI to the local morphology, which determines the nearshore hydrodynamics. Therefore, a definition of the EI based on nearshore hydrodynamics provides an accurate index of local physical drivers of a coastal system. The developed approach can be adopted to any coast, and provides useful information on the potential erosion areas for the coastal managers.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141992580","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":"Shelf-break glaciation and an extensive ice shelf beyond northwest Greenland at the Last Glacial Maximum","authors":"","doi":"10.1016/j.margeo.2024.107375","DOIUrl":"10.1016/j.margeo.2024.107375","url":null,"abstract":"<div><p>The analysis of seafloor glacial landforms can provide important constraints on the past behaviour of ice sheets, including their extent at the Last Glacial Maximum and the controls on their subsequent retreat. The continental shelf and slope offshore of northwest Greenland have been sparsely surveyed, however, limiting our understanding of ice sheet extent and dynamics in this sector during the pre-satellite era. Here we use newly acquired high-resolution geophysical data to map and interpret the distribution of glacial landforms across the hitherto unexplored banks of northern Melville Bay and the adjacent slope and deep-sea basin. In contrast to previous conceptual models, our seafloor observations suggest that shelf-break glaciation was attained along the entire northwest Greenland margin at the Last Glacial Maximum, including beyond the shallow banks. The landforms that we map on the continental slope provide strong support for the existence of an ice shelf spanning northern Baffin Bay. Sub-ice shelf keel scours in water depths of down to 1220 m reveal that this ice shelf was at least 1100 m thick at its grounding zone. The orientation of sub-ice shelf landforms suggests that the ice shelf was fed mainly by the supply of ice to northern Baffin Bay from the Lancaster Sound Ice Stream of the Canadian Arctic Archipelago. The Baffin Bay ice shelf buttressed several large ice streams of the Greenland, Innuitian and Laurentide ice sheets at the Last Glacial Maximum, and its break-up may have contributed to instigating the deglacial retreat of these ice streams from the shelf edge.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001592/pdfft?md5=5652b294e01e2c01ee17c02305bb391e&pid=1-s2.0-S0025322724001592-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141998575","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":"Storm surge in Spain: Factors and effects on the coast","authors":"","doi":"10.1016/j.margeo.2024.107373","DOIUrl":"10.1016/j.margeo.2024.107373","url":null,"abstract":"<div><p>Storm surge is a fundamental process to understanding the behaviour of sea level. This variable, which depends on atmospheric pressure and wind action, has been widely documented. However, few studies quantify these relationships for various geographic areas. This study analyses the most influential factors in the variation of storm surges at several points on the Spanish coast. The results show that the event duration and the regional geographic factor are very relevant in the correlation of storm surge with pressure drop, so assigning a single value as has been commonly done, typically 1 cm/hPa, is an error. The Mediterranean Sea experiences a greater sensitivity to the atmospheric pressure drop than the Atlantic Ocean, with sea level rise of up to 2 or 3 cm/hPa for a storm surge event below 40 h, compared to those of 1.5 cm/hPa for the Atlantic Ocean. Additionally, higher wind speeds intensify storm surge, whether it results in positive or negative superelevation. However, the storm surge does not always increase when the wind blows towards the coast but also depends on the location of the water masses and the continent. Finally, there is no perception of a growing trend of storm surges in the context of climate change in a general way. A precise knowledge of these elements will help all those agents involved in coastal protection to define more accurate alert levels, enhancing safety along the waterfront.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001579/pdfft?md5=4ce8ab654f2cfc660a9dc72fa1703d3b&pid=1-s2.0-S0025322724001579-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978647","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":"Characterizing the sediment dynamics through in-situ measurements in the abyssal Manila Trench, northeast South China Sea","authors":"","doi":"10.1016/j.margeo.2024.107372","DOIUrl":"10.1016/j.margeo.2024.107372","url":null,"abstract":"<div><p>Abyssal sedimentary dynamic processes are crucial to be understanding the transport and distribution of material (sediment, carbon, plastics, etc.) and the formation of deep-sea bedforms. Accurately characterizing such complicated processes requires a multi-faceted approaches (e.g. numercial models, physical experiments, field observation), among which in-situ field data gathering has been the most challenging. In this study, we collected data from four bottom moorings deployed along the Manila Trench in the northeast South China Sea to investigate the sediment transport processes at the trench bottom. The events with high turbidity, including strong and fast gravity flow and weaker turbidity currents with speed similar to tidal currents, transport sediment down-trench. Sediment particles in the northern part of the trench were generally found to move northward (i.e. up the trench) with seasonal variations primarily influenced by the asymmetrical subtidal currents. During the intensification of northbound subtidal current, the benthic nepheloid layers in Gaoping Canyon, which feeds into the trench, might be transported to the north of trench. Furthermore, a weaker turbidity oscillation at S2 tidal frequencies was observed before turbidity current occurred, increasing sediment transport to the deep. It was hypothesized that multiple small turbidity currents may have been triggered by an earthquake, despite not reaching the mooring S2, with the fine sediment being transported downstream by abyssal tidal currents.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141963963","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":"Holocene palaeoenvironmental development of Prokljan Lake (Krka River, Croatia): Evolution from a calcareous tufa barrier system to a karst estuary","authors":"","doi":"10.1016/j.margeo.2024.107370","DOIUrl":"10.1016/j.margeo.2024.107370","url":null,"abstract":"<div><p>The upstream part of the karst estuary of the Krka River (Prokljan Lake) on the Eastern Adriatic Coast was studied by combining high-resolution seismic data, analyses on sediment cores, and radiocarbon dating to reconstruct the late Quaternary stratigraphy of the estuary. The sedimentary infill consists of up to 20 m of freshwater and estuarine deposits divided into four seismostratigraphic units corresponding to several stages of development since the last glacial period. The lowstand stage is assumed to correspond to fluvial incision and sediment bypass associated with glacial periods. The postglacial transgressive stage is marked by the growth of calcareous tufa barriers and fluvio-lacustrine deposition. The onset of marine influence in the estuary (Prokljan Lake) was recorded at the beginning of the Holocene (&gt;10,500 cal y BP) with the deposition of brackish sediments with a strong freshwater influence. Calcareous tufa barriers prevented direct rapid flooding of Prokljan Lake in the period from &gt;10,500 cal y to ∼7200 cal y BP. Finally, the transgressive brackish deposition changed to estuarine/marine highstand deposition in a salt-wedge estuary during the late Holocene (∼4000–3000 cal y BP). The late Quaternary deposition in this unique karst setting showed dramatic changes. It was primarily influenced by rapid sea-level rise, climate changes, estuarine geomorphology and relatively low sediment supply.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141944201","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":"Nonnegligible contribution of terrigenous sediment inputs from local small watersheds to west regions of the Pearl River Estuary, northern South China Sea shelf","authors":"","doi":"10.1016/j.margeo.2024.107369","DOIUrl":"10.1016/j.margeo.2024.107369","url":null,"abstract":"<div><p>As a crucial “sink” for terrigenous material entering the ocean, provenance of sediments within the coastal zone and continental shelf sea regions holds significant scientific importance in the investigation of global material cycling. Environmental magnetism was proved as an effective and rapid approach for sediment source identification. Detail and systematic magnetic measurements were performed for surface sediment samples collected from the mega Pearl River, local small rivers (Tan, Moyang and Jian rivers) of west Guangdong, coastal zone (CZ) and continental shelf (CS) to analyze the contribution of local small watersheds to marine sediments. The results indicate that detrital river input magnetite and hematite are coexisted in both CZ and CS sediments. Compared to CZ sediments, relatively higher concentration of hematite and finer grain size of magnetite are appeared at CS sediments. By comparing of magnetic parameters, it was inferred that magnetic minerals from the Pearl and Tan rivers are transported and deposited on the coastal zone by Guangdong longshore current. Meanwhile, sediment magnetic parameters in the Moyang and Jian Rivers are similar to the CS sediments, implying the two rivers-sourced materials were directly transported and deposited at the CS due to their narrow and restricted estuaries, and/or the CS preserves the residual deposits from the two rivers formed during the Last Glacial. Except for the Pearl River, sources of local small rivers significantly contribute to marine sediments at the coastal zone and continental shelf.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001531/pdfft?md5=017d409748fc64c8814f47132bed8a3b&pid=1-s2.0-S0025322724001531-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141944202","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":"Provenance shift of the abyssal plains in the Southwest sub-basin of the South China Sea at ∼ 8 Ma: Tectonics & climate changes implication","authors":"","doi":"10.1016/j.margeo.2024.107368","DOIUrl":"10.1016/j.margeo.2024.107368","url":null,"abstract":"<div><p>Tectonic processes and climatic changes are recognized as two major drivers of erosion along the southeastern margin of the Tibetan Plateau and consequently are the main factors controlling depositional patterns along the margins of the South China Sea. However, the role of tectonics and climate in governing the types and patterns of sedimentation in the abyssal plains is relatively little known. The results of International Ocean Discovery Program (IODP) drilling in the abyssal plains of the Southwest sub-basin of the South China Sea show that the multi-trace element and rare earth element (REE) character of sediments older than ∼8 Ma are in disorder. εNd(0) and ⁸⁷Sr/⁸⁶Sr values exhibit large fluctuations, which implies temporally variable sediment sources during the early post-spreading stage of the South China Sea. High εNd(0) and low ⁸⁷Sr/⁸⁶Sr values and abundant Cenozoic (13–35 Ma) zircon grains in the sediments suggest relatively juvenile sources for their origins, such as the Cagayan Ridge and Palawan Block in the south before ∼8 Ma. Multi-trace element and REE patterns of sediments younger than ∼8 Ma are more uniform. Low εNd(0) and high ⁸⁷Sr/⁸⁶Sr values of the sediments indicate that more continentally-derived sediments were transported to the abyssal plain. Coastal rivers in SE Vietnam, and the Mekong and Red Rivers in the west gradually became the major detrital sources of abyssal sediments in the Southwest sub-basin after ∼8 Ma. The switching of the sediment sources from the south to the west is consistent with the progressive uplift of the Vietnamese Central Highlands (VCH) and the SE Tibetan Plateau margin during the Late Miocene. The strengthened summer monsoon since ∼5 Ma affected not only the marginal basins, but also the deep abyssal basins. We argue that the regional tectonics shaped and controlled the shift of provenance and sediment routing system, whereas the East Asian monsoon affected the sediment flux to the abyssal plains of the Southwest sub-basin in the South China Sea.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141944203","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 Formation of Deflation Ridges","authors":"","doi":"10.1016/j.margeo.2024.107367","DOIUrl":"10.1016/j.margeo.2024.107367","url":null,"abstract":"<div><p>The deposition of both pumice and shell is common on beaches during calm and storm wave conditions. This paper describes an investigation of pumice and shell ridges at two sites in Australia, Dark Point in NSW, and in the Younghusband Peninsula in SE South Australia. The formation of lines of wave formed shelly and pumice rich deposits on, and above the backshore is described. The deposits are buried by dune development, but then later exhumed by aeolian deflation as deflation plains and basins evolve. Aeolian erosion of the finer sandy sediments leads to the creation of a ridge form, herein termed a deflation ridge. A new schematic model of ridge formation is also detailed whereby deflation ridges are formed by the aeolian erosion and deflation of shell or pumice concentrations and lag deposits.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001518/pdfft?md5=b0ee298bdd6a7defca66fa2e4cec0b36&pid=1-s2.0-S0025322724001518-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141847792","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":"Stable carbon and oxygen isotope signatures of mantle-derived calcite in Aitutaki lherzolite xenolith: Implications for organic carbon cycle in the oceanic mantle","authors":"","doi":"10.1016/j.margeo.2024.107363","DOIUrl":"10.1016/j.margeo.2024.107363","url":null,"abstract":"<div><p>Carbon isotope data is desired to be increased to promote the understanding of carbon cycle throughout in the Earth. Diamond is a key carbonaceous tool to study deep carbon cycle, but most diamond occurrences are limited from kimberlite pipes in the continental region. Recently, micron-sized diamonds have been discovered from the oceanic region and investigated to understand deep carbon cycle in the oceanic mantle. However, some fundamental cautions have been issued on the oceanic diamonds because some of them could be of artificial origin. Hence, alternative oceanic mantle-derived carbonaceous material is needed to increase oceanic carbon isotope data. We report micron-sized calcite vein in a lherzolite xenolith hosted by enriched mantle I (EM1)-type olivine nephelinite from Aitutaki Island, Cook Islands in the southern Pacific. With employing various techniques to determine carbon and oxygen isotope compositions from sub-micrograms of calcite, we demonstrate that carbonaceous fluid originated from EM1-type mantle source exhibited organic carbon signature based on its light carbon isotope composition along with petrographic characteristics of the calcite vein. The oceanic mantle hosts organic carbon in places due to the recycling of surface materials.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.6,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0025322724001476/pdfft?md5=5889153e298ced6e1dd4aeb97f4b34e9&pid=1-s2.0-S0025322724001476-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141852204","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}