Grain size distribution patterns of the Bay of Bengal marine sediments have the potential to provide valuable insights into the long-term variability of the Indian Summer Monsoon (ISM). The study presents a Plio-Pleistocene marine sediment grain size record from the offshore Mahanadi Basin to decipher precipitation phases and reconstruct long-term ISM variability. We have analysed the grain size distribution of 150 marine sediment core samples recovered from the Hole NGHP-01-19A in the western Bay of Bengal, covering the Plio-Pleistocene interval. Through the application of end-member Modelling Analysis of grain size distribution, the study identifies key sediment transport modes and infers monsoon-influenced depositional changes. Three dominant end-members (EM1, EM2, and EM3) were identified, with the majority (∼ 96 %) of sediments falling within the silt-size range. The temporal distribution of EM3, sand (%), and mean grain size reveals the intensified monsoon precipitation phases between 5.3 Ma – 5.2 Ma, 4.6 Ma - 3.2 Ma, at 2.7 Ma, 1.4 Ma - 1.2 Ma and 0.8 Ma - Recent. These observations are validated using published monsoonal proxies [Runoff data (IODP U1445 and U1446), Uvigerina proboscidea abundance and δ18O of Planktic foraminifera (ODP 758)]. The spectral and continuous wavelet transformation of EM3 and sand (%) indicates a strong influence of orbital forcing during the entire Pliocene epoch on the ISM precipitation phases. These findings highlight the close connection between monsoonal variability, orbital forcing, and sediment delivery to the western Bay of Bengal.
孟加拉湾海洋沉积物的粒度分布模式有可能为印度夏季风（ISM）的长期变化提供有价值的见解。本文利用Mahanadi盆地上新世-更新世海相沉积粒度记录，对降水阶段进行了解析，重建了ISM的长期变化。本文分析了孟加拉湾西部NGHP-01-19A孔150个海相沉积物岩心样品的粒度分布，样品覆盖了上新世-更新世区间。通过对粒度分布的端元模拟分析，确定了关键的输沙模式，推断了受季风影响的沉积变化。确定了三个主要的端元（EM1， EM2和EM3），大多数（~ 96%）的沉积物落在粉砂粒度范围内。EM3、沙粒（%）和平均粒径的时间分布揭示了5.3 Ma ~ 5.2 Ma、4.6 Ma ~ 3.2 Ma、2.7 Ma、1.4 Ma ~ 1.2 Ma和0.8 Ma ~近期的季风降水增强阶段。这些观测结果通过已公布的季风代用物[径流数据（IODP U1445和U1446）、长形假水蛭丰度和浮游有孔虫的δ18O (ODP 758)]得到了验证。EM3和沙（%）的光谱和连续小波变换表明，整个上新世的轨道强迫对ISM降水阶段有很强的影响。这些发现强调了季风变率、轨道强迫和向孟加拉湾西部输送沉积物之间的密切联系。
{"title":"Plio-pleistocene sediment grain size variability in the Western Bay of Bengal: Evidences of Indian Summer Monsoon intensification","authors":"Nitika Millicent Patrick, Nishant Vats , Ajoy K. Bhaumik, Satabdi Mohanty, Koustav Chattopadhyay","doi":"10.1016/j.margeo.2025.107682","DOIUrl":"10.1016/j.margeo.2025.107682","url":null,"abstract":"<div><div>Grain size distribution patterns of the Bay of Bengal marine sediments have the potential to provide valuable insights into the long-term variability of the Indian Summer Monsoon (ISM). The study presents a Plio-Pleistocene marine sediment grain size record from the offshore Mahanadi Basin to decipher precipitation phases and reconstruct long-term ISM variability. We have analysed the grain size distribution of 150 marine sediment core samples recovered from the Hole NGHP-01-19A in the western Bay of Bengal, covering the Plio-Pleistocene interval. Through the application of end-member Modelling Analysis of grain size distribution, the study identifies key sediment transport modes and infers monsoon-influenced depositional changes. Three dominant end-members (EM1, EM2, and EM3) were identified, with the majority (∼ 96 %) of sediments falling within the silt-size range. The temporal distribution of EM3, sand (%), and mean grain size reveals the intensified monsoon precipitation phases between 5.3 Ma – 5.2 Ma, 4.6 Ma - 3.2 Ma, at 2.7 Ma, 1.4 Ma - 1.2 Ma and 0.8 Ma - Recent. These observations are validated using published monsoonal proxies [Runoff data (IODP U1445 and U1446), <em>Uvigerina proboscidea</em> abundance and δ<sup>18</sup>O of Planktic foraminifera (ODP 758)]. The spectral and continuous wavelet transformation of EM3 and sand (%) indicates a strong influence of orbital forcing during the entire Pliocene epoch on the ISM precipitation phases. These findings highlight the close connection between monsoonal variability, orbital forcing, and sediment delivery to the western Bay of Bengal.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"491 ","pages":"Article 107682"},"PeriodicalIF":2.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145576506","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}
Pub Date : 2026-01-01Epub Date: 2025-11-18DOI: 10.1016/j.margeo.2025.107681
Wenjun Zeng , Zhijun Dai , Jiejun Luo , Yi Chen , Xiaowen Xie , Riming Wang
Mangrove wetlands play a vital role in reducing water flow and wave energy, facilitating sediment capture and accumulation, thereby stabilizing coastlines and protecting coastal zones. Nevertheless, few studies have comprehensively investigated the hydrodynamic and sedimentary processes from bare flat zone to the forest interior of mangrove wetlands. Therefore, this study collected comprehensive field data, including hydrological, sediment, and elevation measurements between 2020 and 2022, aiming to diagnosing the attenuation of hydrodynamic and sediment processes in an undisturbed mangrove wetland of the Nanliu River Estuary. Results showed both current velocity and wave height declined markedly landward, accompanied by spatial fluctuations. Specifically, mean flood velocity, mean ebb velocity, and mean significant wave height decreased by over 70 %, 40 %, and 50 %, respectively. Correspondingly, surface sediments showed a general fining trend landward, with localized variations reflecting spatial heterogeneity of hydrodynamic forces. Meanwhile, surface elevation in bare flat zone increased sharply landward at an average slope of 1.6 ‰, while vegetated zone displayed a much gentler profile, averaging around 0.3 m. Vegetated zone was in relatively stable state, typically undergoing weak erosion or strong accretion, whereas bare flat zone experienced pronounced erosion or minor deposition. Dense, mature mangroves could effectively dissipate wave energy and slowing tidal currents, reducing flood velocity, ebb velocity, and wave height by 0.42 %/m, 0.25 %/m, and 0.45 %/m, respectively. Typhoons not only triggered substantial erosion but also reshaped sediment characteristics, with their impacts modulated by water depth controlled by tidal cycle variations.
{"title":"Hydro-sedimentary processes of mangrove wetland over a meso-macrotidal estuary","authors":"Wenjun Zeng , Zhijun Dai , Jiejun Luo , Yi Chen , Xiaowen Xie , Riming Wang","doi":"10.1016/j.margeo.2025.107681","DOIUrl":"10.1016/j.margeo.2025.107681","url":null,"abstract":"<div><div>Mangrove wetlands play a vital role in reducing water flow and wave energy, facilitating sediment capture and accumulation, thereby stabilizing coastlines and protecting coastal zones. Nevertheless, few studies have comprehensively investigated the hydrodynamic and sedimentary processes from bare flat zone to the forest interior of mangrove wetlands. Therefore, this study collected comprehensive field data, including hydrological, sediment, and elevation measurements between 2020 and 2022, aiming to diagnosing the attenuation of hydrodynamic and sediment processes in an undisturbed mangrove wetland of the Nanliu River Estuary. Results showed both current velocity and wave height declined markedly landward, accompanied by spatial fluctuations. Specifically, mean flood velocity, mean ebb velocity, and mean significant wave height decreased by over 70 %, 40 %, and 50 %, respectively. Correspondingly, surface sediments showed a general fining trend landward, with localized variations reflecting spatial heterogeneity of hydrodynamic forces. Meanwhile, surface elevation in bare flat zone increased sharply landward at an average slope of 1.6 ‰, while vegetated zone displayed a much gentler profile, averaging around 0.3 m. Vegetated zone was in relatively stable state, typically undergoing weak erosion or strong accretion, whereas bare flat zone experienced pronounced erosion or minor deposition. Dense, mature mangroves could effectively dissipate wave energy and slowing tidal currents, reducing flood velocity, ebb velocity, and wave height by 0.42 %/m, 0.25 %/m, and 0.45 %/m, respectively. Typhoons not only triggered substantial erosion but also reshaped sediment characteristics, with their impacts modulated by water depth controlled by tidal cycle variations.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"491 ","pages":"Article 107681"},"PeriodicalIF":2.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145576505","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}
Pub Date : 2025-12-01Epub Date: 2025-09-11DOI: 10.1016/j.margeo.2025.107646
P.H. Adema , J.T. Eggenhuisen , R. Silva Jacinto , N. Lagunova , A.I. Alwadhakhi , R. van der Woning , E. Miramontes
Turbidity currents transport sediment, organic carbon, nutrients, and pollutants from the continental shelf to the deep sea. They can flow over hundreds of kilometers through submarine canyons and channels. Along their trajectory, these flows may interact with contour currents, creating a mixed turbidite–contourite depositional system. Examples of such systems in the oceans exhibit a variety of channel shapes that are often asymmetrical. The effect of channel shape on turbidity currents and their interaction with contour currents remains unclear, yet understanding this could link flow characteristics to seafloor morphology. To this end, purely gravity-driven flows (turbidity currents) and combined flows were simulated in five different channel shapes (three symmetrical and two asymmetrical). The experiments show that firstly, combined flows have less steep vertical velocity gradients than purely gravity-driven experiments. The contour current advects momentum of the turbidity currents out of the channel onto the overbank, reducing the downslope flow velocity in the channel. Secondly, channel asymmetry results in asymmetrically overspilling flows, even without a contour current. Specifically, the overspilling flow is thicker and faster over the steep channel margin than over the gentle margin. Lastly, two types of secondary flow cells were formed. Channel cells, which are confined to the channel, and front cells, which form near stationary fronts in combined flows. These findings suggest that channel asymmetry alone is not diagnostic for inferring paleo-contour current directions. However, channel asymmetry can help to infer velocity distributions inside channels when only bathymetric data is available.
{"title":"Submarine channel shape controls combined turbidity current–contour current flow","authors":"P.H. Adema , J.T. Eggenhuisen , R. Silva Jacinto , N. Lagunova , A.I. Alwadhakhi , R. van der Woning , E. Miramontes","doi":"10.1016/j.margeo.2025.107646","DOIUrl":"10.1016/j.margeo.2025.107646","url":null,"abstract":"<div><div>Turbidity currents transport sediment, organic carbon, nutrients, and pollutants from the continental shelf to the deep sea. They can flow over hundreds of kilometers through submarine canyons and channels. Along their trajectory, these flows may interact with contour currents, creating a mixed turbidite–contourite depositional system. Examples of such systems in the oceans exhibit a variety of channel shapes that are often asymmetrical. The effect of channel shape on turbidity currents and their interaction with contour currents remains unclear, yet understanding this could link flow characteristics to seafloor morphology. To this end, purely gravity-driven flows (turbidity currents) and combined flows were simulated in five different channel shapes (three symmetrical and two asymmetrical). The experiments show that firstly, combined flows have less steep vertical velocity gradients than purely gravity-driven experiments. The contour current advects momentum of the turbidity currents out of the channel onto the overbank, reducing the downslope flow velocity in the channel. Secondly, channel asymmetry results in asymmetrically overspilling flows, even without a contour current. Specifically, the overspilling flow is thicker and faster over the steep channel margin than over the gentle margin. Lastly, two types of secondary flow cells were formed. Channel cells, which are confined to the channel, and front cells, which form near stationary fronts in combined flows. These findings suggest that channel asymmetry alone is not diagnostic for inferring paleo-contour current directions. However, channel asymmetry can help to infer velocity distributions inside channels when only bathymetric data is available.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107646"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154936","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}
Pub Date : 2025-12-01Epub Date: 2025-09-05DOI: 10.1016/j.margeo.2025.107647
Jianfeng Su , Yijing Wu , Daidu Fan
Coastal wetlands are essential yet vulnerable carbon sinks; however, the impacts of vegetation replacement on carbon dynamics remain less understood. This study investigates the sources, burial rates, and historical trends of sedimentary organic carbon (OC) across various wetland types, including mangroves, Spartina alterniflora (S. A.), and barren tidal flats in Sansha Bay, Fujian Province, Southeast China. We analyzed sediment cores for geochemical (TOC, TN, δ13C) and radionuclide (210Pb, 137Cs) proxies. Our results reveal that riverine inputs are the primary sources of OC, contributing 51–75 % of the total. The mangrove ecosystem exhibits the highest OC burial rate at163 ± 49 g/m2/yr, followed by the S. A. marshland at 115 ± 16 g/m2/yr, and barren flats at 69 ± 13 g/m2/yr. However, human interventions, particularly land reclamation and the invasion of S. A., have resulted in a 13.64 % decrease in the bay-wide OC burial rate from 1999 to 2018. While S. A. enhances local carbon sequestration, its invasion disrupts mangrove ecosystems and destabilizes existing carbon pools. This study underscores the dual impact of vegetation changes on coastal carbon dynamics: invasive species may temporarily enhance OC burial rates but ultimately undermine long-term ecosystem resilience. To maintain blue carbon functions, we advocate prioritizing mangrove conservation, restoring degraded wetlands, and curbing the spread of S. A. These findings provide valuable insights for balancing carbon mitigation efforts and biodiversity conservation in rapidly changing coastal environments.
{"title":"Impacts of vegetation replacement on organic carbon burial in coastal wetlands of Sansha Bay, Southeast China","authors":"Jianfeng Su , Yijing Wu , Daidu Fan","doi":"10.1016/j.margeo.2025.107647","DOIUrl":"10.1016/j.margeo.2025.107647","url":null,"abstract":"<div><div>Coastal wetlands are essential yet vulnerable carbon sinks; however, the impacts of vegetation replacement on carbon dynamics remain less understood. This study investigates the sources, burial rates, and historical trends of sedimentary organic carbon (OC) across various wetland types, including mangroves, <em>Spartina alterniflora</em> (<em>S. A.</em>), and barren tidal flats in Sansha Bay, Fujian Province, Southeast China. We analyzed sediment cores for geochemical (TOC, TN, δ<sup>13</sup>C) and radionuclide (<sup>210</sup>Pb, <sup>137</sup>Cs) proxies. Our results reveal that riverine inputs are the primary sources of OC, contributing 51–75 % of the total. The mangrove ecosystem exhibits the highest OC burial rate at163 ± 49 g/m<sup>2</sup>/yr, followed by the <em>S. A.</em> marshland at 115 ± 16 g/m<sup>2</sup>/yr, and barren flats at 69 ± 13 g/m<sup>2</sup>/yr. However, human interventions, particularly land reclamation and the invasion of <em>S. A.</em>, have resulted in a 13.64 % decrease in the bay-wide OC burial rate from 1999 to 2018. While <em>S. A.</em> enhances local carbon sequestration, its invasion disrupts mangrove ecosystems and destabilizes existing carbon pools. This study underscores the dual impact of vegetation changes on coastal carbon dynamics: invasive species may temporarily enhance OC burial rates but ultimately undermine long-term ecosystem resilience. To maintain blue carbon functions, we advocate prioritizing mangrove conservation, restoring degraded wetlands, and curbing the spread of <em>S. A.</em> These findings provide valuable insights for balancing carbon mitigation efforts and biodiversity conservation in rapidly changing coastal environments.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107647"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047016","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}
Pub Date : 2025-12-01Epub Date: 2025-09-19DOI: 10.1016/j.margeo.2025.107659
Bei Song , Shihui Lv , Xin Su , Xuan Ding , Chunhui Tao , Chonghan Yu , Jie Zhang , Xuezhen Li
Hydrothermal plumes play a critical role in chemical fluxes and element transport in the oceans. However, the impact on the sediments along mid-ocean ridge flanks is not well constrained. In this study, samples from three sediment cores (MC03/04/05) were analyzed for their geochemical records located at the Southwest Indian Ridge (SWIR) flanks over the past 40 ka. In addition to the dominant CaO content, these flank sediments show elevated concentrations of Fe, Mn, Cu, Zn, and REEs with positive Y anomalies. We also constructed two geochemical diagrams (Cu/Zn-Mn/Fe-REE/Fe and REE/Fe vs. Mn/Fe) to identify hydrothermal plume inputs. Based on these results, we revealed four distal plume events at 32–30 ka (MC04), 16–14 ka (MC05), 10–8 ka (MC05), and 7.5–6.5 ka (MC03). Furthermore, cluster analysis indicates that these plume events originated from the Yuhuang Hydrothermal Field (YHF), and they correspond temporally to periods of sulfide formation within the field. Finally, we propose that the YHF plume dispersion was coupled with the Agulhas Return Current (ARC) migration, resulting in the following processes: (1) 32–30 ka southward ARC transported plume material to MC04; (2) 16–14 ka and 10–8 ka northward shifts deposited plume fallout at MC05; (3) 7.5–6.5 ka southward ARC movement led to MC03 deposition. Our findings reveal metal (Fe, Mn, REE) transport mechanisms from the SWIR axial zones to distal flanks, highlighting plume-ARC interactions over millennial timescales.
热液柱在海洋的化学通量和元素运输中起着关键作用。然而，对洋中脊两侧沉积物的影响并没有得到很好的限制。本文分析了西南印度洋脊（SWIR）侧翼3个沉积物岩心（MC03/04/05）过去40ka的地球化学记录。除了主要的CaO含量外，这些侧翼沉积物中Fe、Mn、Cu、Zn和ree浓度升高，Y呈阳性异常。我们还构建了Cu/Zn-Mn/Fe-REE/Fe和REE/Fe vs. Mn/Fe地球化学图来识别热液柱输入。基于这些结果，我们揭示了32-30 ka （MC04）、16-14 ka （MC05）、10-8 ka （MC05）和7.5-6.5 ka （MC03）的4次远端羽流事件。聚类分析表明，这些羽流事件起源于玉黄热液田，与该热液田内硫化物形成的时间相对应。最后，我们认为YHF羽流弥散与阿古拉斯回流（Agulhas Return Current， ARC）迁移耦合，导致以下过程：(1)32-30 ka南向ARC将羽流物质输送到MC04；(2) 16-14 ka和10-8 ka向北移动的MC05沉积羽流沉降物；(3) 7.5 ~ 6.5 ka南向弧运动导致MC03沉积。我们的发现揭示了金属（Fe, Mn， REE）从SWIR轴向区到远侧翼的运输机制，突出了千年时间尺度上羽-弧的相互作用。
{"title":"Hydrothermal plume events in a 40 kyr sediment record from the flanks of the Southwest Indian Ridge","authors":"Bei Song , Shihui Lv , Xin Su , Xuan Ding , Chunhui Tao , Chonghan Yu , Jie Zhang , Xuezhen Li","doi":"10.1016/j.margeo.2025.107659","DOIUrl":"10.1016/j.margeo.2025.107659","url":null,"abstract":"<div><div>Hydrothermal plumes play a critical role in chemical fluxes and element transport in the oceans. However, the impact on the sediments along mid-ocean ridge flanks is not well constrained. In this study, samples from three sediment cores (MC03/04/05) were analyzed for their geochemical records located at the Southwest Indian Ridge (SWIR) flanks over the past 40 ka. In addition to the dominant CaO content, these flank sediments show elevated concentrations of Fe, Mn, Cu, Zn, and REEs with positive Y anomalies. We also constructed two geochemical diagrams (Cu/Zn-Mn/Fe-REE/Fe and REE/Fe vs. Mn/Fe) to identify hydrothermal plume inputs. Based on these results, we revealed four distal plume events at 32–30 ka (MC04), 16–14 ka (MC05), 10–8 ka (MC05), and 7.5–6.5 ka (MC03). Furthermore, cluster analysis indicates that these plume events originated from the Yuhuang Hydrothermal Field (YHF), and they correspond temporally to periods of sulfide formation within the field. Finally, we propose that the YHF plume dispersion was coupled with the Agulhas Return Current (ARC) migration, resulting in the following processes: (1) 32–30 ka southward ARC transported plume material to MC04; (2) 16–14 ka and 10–8 ka northward shifts deposited plume fallout at MC05; (3) 7.5–6.5 ka southward ARC movement led to MC03 deposition. Our findings reveal metal (Fe, Mn, REE) transport mechanisms from the SWIR axial zones to distal flanks, highlighting plume-ARC interactions over millennial timescales.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107659"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154930","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}
Pub Date : 2025-12-01Epub Date: 2025-09-12DOI: 10.1016/j.margeo.2025.107656
Ammoose K. Jayan , A.V. Sijinkumar , Kaustubh Thirumalai , Lael Vetter , P. John Kurian , A. Prajith , Rajveer Sharma
Extant since the Miocene, Globigerinoides ruber is a mixed-layer planktic foraminiferal species, cosmopolitan to the tropical–subtropical oceans. Globigerinoides ruber has multiple morphotypical variants with distinctive white and pink chromotypes. Today, the pink variety is exclusively found in the Atlantic Ocean and its nearby basins. For the past few decades, it was believed that pink-pigmented G. ruber disappeared from the Indo-Pacific Oceans at about 120 kyr BP. However, a recent study from the northwestern Bay of Bengal documented the presence of G. ruber (pink) in surface sediments. Hitherto, there was no evidence of G. ruber (pink) in downcore sediments from the Indian Ocean since 120 kyr BP. In this study, for the first time, we document the re-appearance of G. ruber (pink) from 30 to 8 kyr BP in gravity core MGS30/GC-03. The core was retrieved from the eastern BoB from a water depth of 1883 m, and its chronology was established using eight AMS radiocarbon dates. We observed high abundances of G. ruber (pink) during the Last Glacial Maximum (LGM) and Heinrich Event 1 and 2 (H1 and H2) compared to the Holocene Epoch. Higher abundances of G. ruber (pink) during the LGM were followed by a gradual decrease during the deglaciation and the early Holocene until it disappeared after around 8 kyr BP. Variability in the relative abundance of G. ruber (pink) was compared with mixed-layer and thermocline-dwelling species. The high abundance of G. ruber (pink), N. dutertrei and G. menardii during H2 and LGM in the eastern BoB suggests enhanced NE monsoon-driven vertical mixing, which may have facilitated nutrient transport from deeper layers to the thermocline and photic zone. The presence of G. ruber (pink) during glacial stages and the early Holocene demonstrates that it has not entirely disappeared from the Indian Ocean since 120 kyr BP and that its turnover may be driven by changing hydrographic conditions.
{"title":"Did Globigerinoides ruber (pink) disappear entirely from the Indian Ocean after 120 kyr BP?","authors":"Ammoose K. Jayan , A.V. Sijinkumar , Kaustubh Thirumalai , Lael Vetter , P. John Kurian , A. Prajith , Rajveer Sharma","doi":"10.1016/j.margeo.2025.107656","DOIUrl":"10.1016/j.margeo.2025.107656","url":null,"abstract":"<div><div>Extant since the Miocene, <em>Globigerinoides ruber</em> is a mixed-layer planktic foraminiferal species, cosmopolitan to the tropical–subtropical oceans. <em>Globigerinoides ruber</em> has multiple morphotypical variants with distinctive white and pink chromotypes. Today, the pink variety is exclusively found in the Atlantic Ocean and its nearby basins. For the past few decades, it was believed that pink-pigmented <em>G. ruber</em> disappeared from the Indo-Pacific Oceans at about 120 kyr BP. However, a recent study from the northwestern Bay of Bengal documented the presence of <em>G. ruber</em> (pink) in surface sediments. Hitherto, there was no evidence of <em>G. ruber</em> (pink) in downcore sediments from the Indian Ocean since 120 kyr BP. In this study, for the first time, we document the re-appearance of <em>G. ruber</em> (pink) from 30 to 8 kyr BP in gravity core MGS30/GC-03. The core was retrieved from the eastern BoB from a water depth of 1883 m, and its chronology was established using eight AMS radiocarbon dates. We observed high abundances of <em>G. ruber</em> (pink) during the Last Glacial Maximum (LGM) and Heinrich Event 1 and 2 (H1 and H2) compared to the Holocene Epoch. Higher abundances of <em>G. ruber</em> (pink) during the LGM were followed by a gradual decrease during the deglaciation and the early Holocene until it disappeared after around 8 kyr BP. Variability in the relative abundance of <em>G. ruber</em> (pink) was compared with mixed-layer and thermocline-dwelling species. The high abundance of <em>G. ruber</em> (pink), <em>N. dutertrei</em> and <em>G. menardii</em> during H2 and LGM in the eastern BoB suggests enhanced NE monsoon-driven vertical mixing, which may have facilitated nutrient transport from deeper layers to the thermocline and photic zone. The presence of <em>G. ruber</em> (pink) during glacial stages and the early Holocene demonstrates that it has not entirely disappeared from the Indian Ocean since 120 kyr BP and that its turnover may be driven by changing hydrographic conditions.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107656"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096740","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}
Pub Date : 2025-12-01Epub Date: 2025-09-06DOI: 10.1016/j.margeo.2025.107655
Karol Zglinicki , Michał Pilaszkiewicz , Agnieszka Wrzosek , Krzysztof Szamałek , Szymon Uścinowicz , Kazimierz Szefler , Jarosław Nowak , Paweł Bylina
Studies of polymetallic nodules in oceans and shelf seas, including the Baltic Sea, have a long history. However, detailed mineralogical and geochemical data for nodules from the southern Polish Baltic region are limited in comparison to data from oceans and other regions of the Baltic Sea. This study fills gaps in knowledge regarding the mineralogical and chemical composition of nodules from the southern Baltic. The research concerned nodules sampled from two locations in the Polish Exclusive Economic Zone (EEZ), namely seabed elevations between the Słupsk Furrow and Gdańsk Basin (P1) and between Bornholm Basin and Słupsk Furrow (P2), areas known for their abundance of nodules. The following analytical methods were used: X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), inductively coupled plasma emission spectroscopy/optical emission spectroscopy (ICP-MS/OES) and electron probe microanalysis (EPMA). The nodules comprise a mixture of terrigenous minerals and autochthonous manganese oxides, represented by birnessite, vernadite (7 Å and 10 Å varieties) and iron oxyhydroxides, mainly goethite. Depending on the location, the samples reveal varying chemical compositions. Nodules from sampling site P1 are characterized by a moderate Fe content, averaging 10.68 wt%, and low Mn content, averaging 3.04 wt%, with an Mn/Fe ratio ranging from 0.12 to 0.43. These nodules have low concentrations of ∑Ni + Co + Cu (104.5 to 238.6 ppm) and other economically significant metals such as Zn (78.0–140 ppm), Mo (14.9–77.8 ppm), and V (80.0–187.0 ppm). These nodules exhibit pronounced lithium enrichment, with concentrations ranging from 72.1 to 444.6 ppm. On the other hand, at sampling site P2, the average parameters are higher, i.e., Fe content 12.30 wt%, Mn 10.50 wt%, and a Mn/Fe ratio of 0.50 to 1.25. The concentration of ∑Ni + Co + Cu ranges from 159.0 to 530.0 ppm, with elevated contents of Zn (104.0–238.0 ppm), Mo (26.0–174.0 ppm), and V (118.0–249.0 ppm). Lithium content is low (max. 145.4 ppm). In field P1, the growth rates ranged from 2.21 to 3.47 mm/1000 years, while in field P2, the growth rates ranged from 6.50 to 21.00 mm/1000 years. The genesis of the nodules indicates mixed diagenetic‑hydrogenetic processes probably influenced by hydrothermal activity. Although classical hydrothermal processes do not occur in the Baltic Sea, the impact of deep-seated fluids may significantly shape the formation of the nodules.
{"title":"Fe-nodules from the southern Baltic Sea: Morphology, mineralogy and geochemistry","authors":"Karol Zglinicki , Michał Pilaszkiewicz , Agnieszka Wrzosek , Krzysztof Szamałek , Szymon Uścinowicz , Kazimierz Szefler , Jarosław Nowak , Paweł Bylina","doi":"10.1016/j.margeo.2025.107655","DOIUrl":"10.1016/j.margeo.2025.107655","url":null,"abstract":"<div><div>Studies of polymetallic nodules in oceans and shelf seas, including the Baltic Sea, have a long history. However, detailed mineralogical and geochemical data for nodules from the southern Polish Baltic region are limited in comparison to data from oceans and other regions of the Baltic Sea. This study fills gaps in knowledge regarding the mineralogical and chemical composition of nodules from the southern Baltic. The research concerned nodules sampled from two locations in the Polish Exclusive Economic Zone (EEZ), namely seabed elevations between the Słupsk Furrow and Gdańsk Basin (P1) and between Bornholm Basin and Słupsk Furrow (P2), areas known for their abundance of nodules. The following analytical methods were used: X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), inductively coupled plasma emission spectroscopy/optical emission spectroscopy (ICP-MS/OES) and electron probe microanalysis (EPMA). The nodules comprise a mixture of terrigenous minerals and autochthonous manganese oxides, represented by birnessite, vernadite (7 Å and 10 Å varieties) and iron oxyhydroxides, mainly goethite. Depending on the location, the samples reveal varying chemical compositions. Nodules from sampling site P1 are characterized by a moderate Fe content, averaging 10.68 wt%, and low Mn content, averaging 3.04 wt%, with an Mn/Fe ratio ranging from 0.12 to 0.43. These nodules have low concentrations of ∑Ni + Co + Cu (104.5 to 238.6 ppm) and other economically significant metals such as Zn (78.0–140 ppm), Mo (14.9–77.8 ppm), and V (80.0–187.0 ppm). These nodules exhibit pronounced lithium enrichment, with concentrations ranging from 72.1 to 444.6 ppm. On the other hand, at sampling site P2, the average parameters are higher, i.e., Fe content 12.30 wt%, Mn 10.50 wt%, and a Mn/Fe ratio of 0.50 to 1.25. The concentration of ∑Ni + Co + Cu ranges from 159.0 to 530.0 ppm, with elevated contents of Zn (104.0–238.0 ppm), Mo (26.0–174.0 ppm), and V (118.0–249.0 ppm). Lithium content is low (max. 145.4 ppm). In field P1, the growth rates ranged from 2.21 to 3.47 mm/1000 years, while in field P2, the growth rates ranged from 6.50 to 21.00 mm/1000 years. The genesis of the nodules indicates mixed diagenetic‑hydrogenetic processes probably influenced by hydrothermal activity. Although classical hydrothermal processes do not occur in the Baltic Sea, the impact of deep-seated fluids may significantly shape the formation of the nodules.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107655"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096741","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}
Pub Date : 2025-12-01Epub Date: 2025-08-27DOI: 10.1016/j.margeo.2025.107644
Sara Innangi , Valentina Alice Bracchi , Daniela Basso , Renato Tonielli
The exploration of the Linosa Island shelf (Sicily Channel, Mediterranean Sea) by remotely operated vehicle surveys revealed a previously undescribed morphotype of coralligenous algal reef. These biogenic solid substrates are characterized by planar to conical shapes, ranging from single to multilayered structures, with an elevation of 20–30 cm and a concave to convex arrangement. Such coralligenous assemblages primarily cover the seafloor at depths between 80 and 100 m, developing on a sedimentary substrate rich in biogenic components, particularly abundant rhodoliths. We document the role of crustose coralline algae as autogenic engineers, in transforming mobile biogenic sediments into stable substrates by algal reef formation, as theorized by benthic bionomics for the coralligène de plateau.
{"title":"Caught in the act: calcareous algae creating undescribed morphologies of mesophotic algal reef","authors":"Sara Innangi , Valentina Alice Bracchi , Daniela Basso , Renato Tonielli","doi":"10.1016/j.margeo.2025.107644","DOIUrl":"10.1016/j.margeo.2025.107644","url":null,"abstract":"<div><div>The exploration of the Linosa Island shelf (Sicily Channel, Mediterranean Sea) by remotely operated vehicle surveys revealed a previously undescribed morphotype of coralligenous algal reef. These biogenic solid substrates are characterized by planar to conical shapes, ranging from single to multilayered structures, with an elevation of 20–30 cm and a concave to convex arrangement. Such coralligenous assemblages primarily cover the seafloor at depths between 80 and 100 m, developing on a sedimentary substrate rich in biogenic components, particularly abundant rhodoliths. We document the role of crustose coralline algae as autogenic engineers, in transforming mobile biogenic sediments into stable substrates by algal reef formation, as theorized by benthic bionomics for the <em>coralligène de plateau</em>.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107644"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144989508","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}
Pub Date : 2025-12-01Epub Date: 2025-09-12DOI: 10.1016/j.margeo.2025.107657
Eleonora M. Fernández , Carla V. Spetter , Mariana Gentile , Diana M. Villagrán , Ana M. Martínez , Natalia S. Buzzi
Coastal wetlands, particularly tidal flats, play a crucial role in carbon sequestration and nutrient cycling in temperate environments. This study investigates the biochemical composition of sedimentary organic matter (SOM) in the tidal flats of Puerto Rosales (Bahía Blanca Estuary, Argentina), emphasizing the dual influences of natural processes and anthropogenic activities. Sampling was conducted seasonally (2014–2015) at two sites: ST1, an intertidal zone affected by untreated sewage discharge, and ST2, a supratidal zone dominated by microbial mats. Surface (0–5 mm) and subsurface (5–10 mm) sediment layers were analyzed to assess early diagenetic processes, SOM component and trophic status. Results indicated that the organic carbon (OC) in sediments was predominantly non-biogenic, with proteins as the major component of the labile fraction, influenced by seasonal phytoplankton blooms and urban discharges. While the tidal flat exhibited meso-oligotrophic to eutrophic conditions, refractory material dominated over labile fractions (proteins and carbohydrates). Additionally, distinct spatial and seasonal variations in SOM quality and composition, linked to redox conditions and organic detrital quality were observed.These findings underscore the ecological importance of Puerto Rosales tidal flats as dynamic systems for carbon storage and nutrient recycling. They highlight the need for sustainable management strategies to mitigate anthropogenic pressures and preserve the critical ecosystem functions of these coastal wetlands.
{"title":"Distribution of biochemical components in sedimentary organic matter of a Coastal Wetland: Anthropogenic and detrital influences","authors":"Eleonora M. Fernández , Carla V. Spetter , Mariana Gentile , Diana M. Villagrán , Ana M. Martínez , Natalia S. Buzzi","doi":"10.1016/j.margeo.2025.107657","DOIUrl":"10.1016/j.margeo.2025.107657","url":null,"abstract":"<div><div>Coastal wetlands, particularly tidal flats, play a crucial role in carbon sequestration and nutrient cycling in temperate environments. This study investigates the biochemical composition of sedimentary organic matter (SOM) in the tidal flats of Puerto Rosales (Bahía Blanca Estuary, Argentina), emphasizing the dual influences of natural processes and anthropogenic activities. Sampling was conducted seasonally (2014–2015) at two sites: ST1, an intertidal zone affected by untreated sewage discharge, and ST2, a supratidal zone dominated by microbial mats. Surface (0–5 mm) and subsurface (5–10 mm) sediment layers were analyzed to assess early diagenetic processes, SOM component and trophic status. Results indicated that the organic carbon (OC) in sediments was predominantly non-biogenic, with proteins as the major component of the labile fraction, influenced by seasonal phytoplankton blooms and urban discharges. While the tidal flat exhibited meso-oligotrophic to eutrophic conditions, refractory material dominated over labile fractions (proteins and carbohydrates). Additionally, distinct spatial and seasonal variations in SOM quality and composition, linked to redox conditions and organic detrital quality were observed.These findings underscore the ecological importance of Puerto Rosales tidal flats as dynamic systems for carbon storage and nutrient recycling. They highlight the need for sustainable management strategies to mitigate anthropogenic pressures and preserve the critical ecosystem functions of these coastal wetlands.</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107657"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096742","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}
Pub Date : 2025-12-01Epub Date: 2025-09-15DOI: 10.1016/j.margeo.2025.107642
Karen Araya , Práxedes Muñoz , Antonio Maldonado , Laurent Dezileau , Lorena Rebolledo , Gloria Sanchez , Gabriel Cantarutti
The upwelling system off Coquimbo (30°S) is strongly influenced by interannual variability driven by the El Niño-Southern Oscillation (ENSO), which decreases primary productivity and increases precipitation during the warm phase (El Niño events). This study examined the historical variations in the primary oceanographic and climatic characteristics of the region based on recent sedimentary records from Coquimbo Bay. In a sediment core (BC117; 83 cm), nine sedimentary units were identified and categorized into two groups: u1, u3, u5, and u9 represent marine sedimentation, as indicated by the major contribution of marine diatoms and higher δ13C and δ15N values reflecting marine conditions. In contrast, u4, u6 and u7 exhibited more depleted δ13C values and an increase in freshwater diatom valves, suggesting a significant continental influence, likely from alluvial events. These units showed elevated concentrations of Fe, K, and Cu and an increase in fine sediment content, likely associated with El Niño-induced heavy rainfall around 1700–1730 CE. This period was followed by a decrease in continental input owing to reduced pluviosity. Spanning from 1403 CE to 1850 CE, the core reflects a period dominated by La Niña-like conditions, sustained by an intensified Southern Oscillation Index (SOI) and diminished Interdecadal Pacific Oscillation (IPO). During this period, the seafloor experienced an increase in reduced conditions, likely leading to anoxic environments, which were subsequently followed by less reduced conditions encompassing the Current Warm Period (CWP) due to enhanced ventilation processes. Nevertheless, increasing proxies for primary productivity have suggested an intensification of upwelling in recent times. Based on the characteristics of the units, three tsunami events were characterized by a significant reduction in total diatom counts contingent on the energy of the event and a sharp basal contact between the lower undisturbed unit and the very disturbed overlying layer (1420, 1471, and 1751 CE).
{"title":"Reconstruction of oceanographic and climatic changes over the past ∼ 600 years over Coquimbo Bay, Chile (30°S)","authors":"Karen Araya , Práxedes Muñoz , Antonio Maldonado , Laurent Dezileau , Lorena Rebolledo , Gloria Sanchez , Gabriel Cantarutti","doi":"10.1016/j.margeo.2025.107642","DOIUrl":"10.1016/j.margeo.2025.107642","url":null,"abstract":"<div><div>The upwelling system off Coquimbo (30°S) is strongly influenced by interannual variability driven by the El Niño-Southern Oscillation (ENSO), which decreases primary productivity and increases precipitation during the warm phase (El Niño events). This study examined the historical variations in the primary oceanographic and climatic characteristics of the region based on recent sedimentary records from Coquimbo Bay. In a sediment core (BC117; 83 cm), nine sedimentary units were identified and categorized into two groups: u1, u3, u5, and u9 represent marine sedimentation, as indicated by the major contribution of marine diatoms and higher δ<sup>13</sup>C and δ<sup>15</sup>N values reflecting marine conditions. In contrast, u4, u6 and u7 exhibited more depleted δ<sup>13</sup>C values and an increase in freshwater diatom valves, suggesting a significant continental influence, likely from alluvial events. These units showed elevated concentrations of Fe, K, and Cu and an increase in fine sediment content, likely associated with El Niño-induced heavy rainfall around 1700–1730 CE. This period was followed by a decrease in continental input owing to reduced pluviosity. Spanning from 1403 CE to 1850 CE, the core reflects a period dominated by La Niña-like conditions, sustained by an intensified Southern Oscillation Index (SOI) and diminished Interdecadal Pacific Oscillation (IPO). During this period, the seafloor experienced an increase in reduced conditions, likely leading to anoxic environments, which were subsequently followed by less reduced conditions encompassing the Current Warm Period (CWP) due to enhanced ventilation processes. Nevertheless, increasing proxies for primary productivity have suggested an intensification of upwelling in recent times. Based on the characteristics of the units, three tsunami events were characterized by a significant reduction in total diatom counts contingent on the energy of the event and a sharp basal contact between the lower undisturbed unit and the very disturbed overlying layer (1420, 1471, and 1751 CE).</div></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":"490 ","pages":"Article 107642"},"PeriodicalIF":2.2,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220425","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}
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