Marine Geology最新文献_第6页

The impact of mangroves development and morphodynamics on channel function shift and flow asymmetry in an estuarine channel-shoal system 红树林发育和形态动力学对河口河道-浅滩系统河道功能转移和水流不对称的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-12-01 Epub Date: 2025-09-17 DOI: 10.1016/j.margeo.2025.107658

Amin Rahdarian , Karin R. Bryan , Mick Van Der Wegen

Estuarine channels convey tidal flow and sediments, while the direction and magnitude of tide-residual transports largely depends on the surrounding estuarine bathymetry, shoals and vegetation cover. This study explores the controls of historic morphodynamics, mangrove development and channels on landscape-scale tidal hydrodynamics around a mangrove-covered estuarine shoal in Whitianga estuary, Aotearoa New Zealand. A Delft3D hydrodynamic model was used to explore the impact of historic developments on spatial flow patterns and flow asymmetry based on an analysis of historical images of the site including conditions of the mangrove forest in the 1940s.

Model results clearly reveal areas of ebb and flood dominance in the model domain, where mangrove surrounded creeks are ebb dominant and shoal incising channels are flood dominant. Within the forest, the seaward part of mangroves is ebb-dominant, whereas a flood-dominance function in the back of the forest with higher elevated mangroves is mostly observed. Removing vegetation leads to a large-scale change in flow routing and flow asymmetry, whereas if creeks are infilled, local changes only around the location of the creeks are observed.

The movement of fine sediment fractions is inferred by the slack water duration at high tide. The existence of vegetation affects the cohesive fraction. Without vegetation, the slack water duration becomes shorter on the shoal close to the fringe, inside and the edge of the former forest while it becomes longer inside the river channel and on the edge of the shoal close to the river channel. In the scenario that channels were infilled, a longer (shorter) slack water duration at the mouth and head of channels and inside channels (around the channels) were observed.

Expansion of mangroves can cause a function shift of the channels. Model results suggest that the ebb-dominant modern-day mangrove creek was flood-dominant in 1940s prior to colonization of mangroves in the inner bend of the shoal.

河口河道输送潮汐流和沉积物，而潮余输运的方向和大小在很大程度上取决于河口周围的水深、浅滩和植被覆盖情况。本研究探讨了历史形态动力学、红树林发育和河道对新西兰怀特安加河口红树林覆盖浅滩景观尺度潮汐水动力学的控制作用。通过分析该遗址的历史图像，包括20世纪40年代红树林的情况，使用Delft3D水动力模型来探索历史发展对空间流动模式和流动不对称性的影响。模型结果清楚地揭示了模型域中以退潮和洪水为主的区域，其中红树林环绕的小溪以退潮为主，浅滩切入的河道以洪水为主。在森林内，红树林的临海部分以退潮为主，而在森林后部以较高的红树林为主，主要观察到洪水优势功能。去除植被会导致水流路径和水流不对称的大规模变化，而如果填充溪流，则只会观察到溪流周围的局部变化。细粒泥沙的运动由涨潮时的淡水持续时间来推断。植被的存在影响黏结分数。在无植被的情况下，靠近原森林边缘、内部和边缘的浅滩淡水持续时间变短，而靠近河道的浅滩内部和浅滩边缘的淡水持续时间变长。在河道被填满的情况下，河道口、河口和河道内（河道周围）的松弛水持续时间更长（更短）。红树林的扩张会引起河道的功能转移。模型结果表明，在20世纪40年代，在浅滩内弯的红树林殖民化之前，以退潮为主的现代红树林小溪是洪水为主的。

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引用次数: 0

Mabahiss Deep in the Northern Red Sea: New insights from high-resolution bathymetric mapping and analysis 红海北部的Mabahiss深海：来自高分辨率深海测绘和分析的新见解

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-12-01 Epub Date: 2025-09-04 DOI: 10.1016/j.margeo.2025.107645

Margherita Fittipaldi , Daniele Trippanera , Nico Augustin , Froukje M. van der Zwan , Laura Parisi , Sigurjón Jónsson

The northern Red Sea is largely floored by evaporites, covering its basement structure and associated lithology of the lithosphere. The basement is exposed at only a few locations, called “Deeps”. Mabahiss Deep is the largest deep in the northern Red Sea. It hosts a large submarine volcano, Mabahiss Mons, and lies north of the Zabargad Fracture Zone. We use new high-resolution bathymetric data, ROV images, and basalt sample analysis to map the morphology of the Mabahiss Deep to understand the volcano-tectonic setting of this area and study its geologic evolution, providing insights into a young ocean basin that is potentially representative of other ultra-slow spreading ridges worldwide. Our results show that Mabahiss Deep is a 2360 m deep axial valley bordered by NW-SE Red Sea axis-parallel normal faults. The Mabahiss Mons has a ∼2 km summit caldera containing columnar basalts at its footwall, volcanic cones with pillow lavas, and extensive lava flows indicating Holocene activity. The basaltic submarine caldera is rare in such settings but is consistent with considerable lava flows and high melt supply due to magma focusing and elevated heat flux in the Red Sea, in spite of the slow spreading rates. The rock samples analysis shows MORB-type composition without any interaction of continental crust. Together our results show that Mabahiss Deep is a typical mid-oceanic ridge segment, confirming that oceanic spreading processes are occurring in this part of the northern Red Sea.

红海北部大部分被蒸发岩覆盖，覆盖着它的基底结构和岩石圈的相关岩性。地下室只暴露在几个被称为“深”的地方。马巴希斯深海是红海北部最大的深海。它拥有一个巨大的海底火山，Mabahiss Mons，位于Zabargad断裂带的北部。我们使用新的高分辨率测深数据、ROV图像和玄武岩样本分析来绘制Mabahiss Deep的形态图，以了解该地区的火山构造环境，并研究其地质演化，为一个年轻的海洋盆地提供见解，该盆地可能代表全球其他超慢扩张脊。结果表明，Mabahiss深是一个深2360 m的轴向谷，与北西-东南方向的红海正断层平行。Mabahiss Mons有一个2公里长的山顶火山口，下盘含有柱状玄武岩，火山锥和枕状熔岩，以及表明全新世活动的广泛熔岩流。玄武岩海底火山口在这样的环境中是罕见的，但与相当大的熔岩流和高熔体供应相一致，这是由于岩浆集中和红海热通量升高，尽管扩张速度缓慢。岩石样品分析显示为morb型成分，没有大陆地壳的相互作用。综上所述，Mabahiss深是一个典型的洋中脊段，证实了在红海北部这部分海域发生了海洋扩张过程。

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引用次数: 0

Intelligent prediction of sediment floc settling velocity: Employing explainable machine learning and quantifying the impacts of environmental factors 泥沙沉降速度的智能预测：采用可解释的机器学习和量化环境因素的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-05 DOI: 10.1016/j.margeo.2025.107631

Jinglun Huang, Zhixin Cao, Leiping Ye, Jie Ren, Jiaxue Wu

Settling velocity of flocs resulting from cohesive sediment flocculation, significantly influenced by hydrological factors (e.g., turbulence shear, salinity, suspended sediment concentration and sediment size), is a key parameter to evaluate sediment transport in estuarine and coastal ocean. Measurement and prediction of in-situ settling velocity for sediment flocs are challenging at current stage due to the complex estuarine dynamics and technique constraints. A powerful and interpretable prediction model is urgently required. To meet this requirement, we propose a new paradigm in predicting settling velocity with interpretable machine learning (ML) model by combination of ML with Shapley additive explanation (SHAP) using 4 hydrological parameters as independent input features. Eight ML algorithms (including recently proposed XGBoost, LightGBM and so on) and ensemble learning (Stacking) were employed, with Bayesian Optimization Algorithm to determine the hyper-parameters. XGBoost model was found to have the highest prediction accuracy in terms of 6 performance metrics, among the 8 base learners. Stacking of these models outperform each component model. With the powerful SHAP methods, the proposed paradigm is able to interpret/explain ML model predictions and highlight the highly influential features for the system of sediment dynamics in both local and global points of view. Additionally, the developed ML model provides transparent insights into the contribution of each feature without compromising predictive accuracy. These ML-based models outperform conventional modified Stokes law or empirical equations. Specially, physics-informed neural network (PINN) is employed for prediction of floc settling velocity, which is also a useful approach to overcome the limitations of data driven model characterized by black box. Combinations of ML with physical law and SHAP, the key of the proposed paradigm, could be very powerful tool for researchers on sediment transport.

粘性泥沙絮凝形成的絮凝体沉降速度受湍流剪切、盐度、悬沙浓度和泥沙粒径等水文因素的显著影响，是评价河口海岸带泥沙输运的关键参数。由于复杂的河口动力学和技术限制，现阶段泥沙絮凝体原位沉降速度的测量和预测具有挑战性。迫切需要一个强大的、可解释的预测模型。为了满足这一要求，我们提出了一种新的可解释机器学习（ML）模型预测沉降速度的新范式，该模型将ML与Shapley加性解释（SHAP）相结合，使用4个水文参数作为独立输入特征。采用了8种ML算法（包括最近提出的XGBoost、LightGBM等）和集成学习（Stacking），并使用贝叶斯优化算法确定超参数。在8个基本学习器中，XGBoost模型在6个性能指标方面具有最高的预测精度。这些模型的叠加优于每个组件模型。利用强大的SHAP方法，所提出的范式能够解释/解释ML模型的预测，并从局部和全局的角度突出沉积物动力学系统的高度影响特征。此外，开发的ML模型提供了对每个特征的贡献的透明见解，而不会影响预测的准确性。这些基于ml的模型优于传统的修正Stokes定律或经验方程。特别地，将物理信息神经网络（PINN）用于絮凝体沉降速度的预测，这也是克服数据驱动模型黑箱特征局限性的有效方法。将ML与物理定律和SHAP相结合，可以成为研究泥沙输运的有力工具。

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引用次数: 0

Sediment provenance shifts in the South Yellow Sea: Implications of reduced river discharges over the past 60 years 南黄海沉积物物源转移：过去60年河流流量减少的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-20 DOI: 10.1016/j.margeo.2025.107638

Jian Lu , Anchun Li , Jin Zhang , Xiaochuan Ma

The Yellow River and Yangtze River significantly influence the South Yellow Sea (SYS) through sediment discharges. Over the past several decades, sediment loads from these rivers into the sea have dramatically decreased due to climate change and intensified human activities. However, there is limited understanding of how this reduction in river discharge might affect the provenance of sediments in the SYS. To address this, surface sediment samples were collected at identical stations in the SYS during two periods: 1958 and 2012. Grain size analysis revealed notable differences: in 2012, clay content decreased, and silt increased, resulting in coarser sediments compared to 1958. Provenance analysis revealed that the fine-grained surface sediments in the SYS were primarily derived from the Yellow and Yangtze Rivers, as evidenced by clay mineral compositions (illite, smectite, kaolinite, and chlorite) and element ratios (Ti/Al vs. Ti/Zr, and Ti/Zr vs. La/Hf). Interestingly, despite reduced sediment loads, the influence of the Yellow River expanded, while the influence of the Yangtze River decreased between 1958 and 2012. These changes in provenance are attributed to differences in sediment transport mechanisms from each source to the SYS. Reduced Yangtze sediment load led to decreased deposition off the Jiangsu coast during summer, limiting Yangtze-derived sediments in the SYS during winter. Conversely, resuspended sediments from the modern and old Yellow River subaqueous deltas provided continuous supply of material to the SYS. This study provides valuable insights into source-to-sink processes in marginal seas, particularly as global rivers continue to experience reductions in sediment discharge.

黄河和长江通过输沙对南黄海有显著影响。在过去的几十年里，由于气候变化和人类活动的加剧，这些河流进入海洋的沉积物负荷急剧减少。然而，对于河流流量的减少如何影响SYS沉积物的来源，人们的理解有限。为了解决这个问题，在1958年和2012年两个时期，在SYS的相同站点收集了地表沉积物样本。粒度分析显示出显著差异：2012年黏土含量减少，粉砂含量增加，沉积物较1958年粗。从黏土矿物组成（伊利石、蒙脱石、高岭石和绿泥石）和元素比值（Ti/Al vs. Ti/Zr, Ti/Zr vs. La/Hf）来看，该地区细粒表层沉积物主要来源于黄河和长江。有趣的是，1958年至2012年间，尽管泥沙负荷减少，黄河的影响却扩大了，而长江的影响却减少了。这些物源的变化归因于各源区向南太平洋的沉积物输运机制的差异。夏季长江泥沙负荷的减少导致江苏沿海的沉积减少，冬季长江泥沙在南海的分布受到限制。与此相反，现代和古代黄河水下三角洲的重悬沉积物则为南水北调提供了持续的物质供应。这项研究为边缘海域的源-汇过程提供了有价值的见解，特别是在全球河流的沉积物排放量继续减少的情况下。

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引用次数: 0

Sea level changes and the Indian Summer Monsoon influence on chemical weathering and sediment deposition on the Ninetyeast Ridge over the past 21 ka 过去21 ka海平面变化和印度夏季风对尼尼特酵母脊化学风化和沉积的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-07-31 DOI: 10.1016/j.margeo.2025.107632

Md. Sazzad Hossen , Jianguo Liu , Yun Huang , Md Hafijur Rahaman Khan , Bin Wang

The sediment core retrieved from the Ninetyeast Ridge (NER) provides valuable insights into the interplay between chemical weathering processes and sediment deposition patterns in the marine environment. This interplay is strongly influenced by fluctuations in sea level and variations in the Indian Summer Monsoon (ISM). In this study, geochemical analyses of elemental compositions suggest that the Last Glacial Maximum (LGM) (∼21–19 ka) was a period of enhanced chemical weathering, likely driven by lowered sea levels and intensified glacial or aeolian activity. Concurrently, high surface productivity and reduction in bottom-water oxygenation favored the accumulation of organic carbon in the sedimentary record. In contrast, the deglacial period (∼17–11 ka) was characterized by rapid sea-level rise and dynamic monsoon evolution. This interval generally exhibited oxic bottom-water conditions, except for the Bølling–Allerød (B/A) interstadial. During the B/A event, increased sedimentation rates coincided with elevated paleoproductivity and suboxic marine conditions. The Holocene epoch reflects a shift, as rising sea levels and intensified ISM activity promoted enhanced chemical weathering in source regions. Notably, the Holocene Climatic Optimum (HCO) stands out as a period when increased solar insolation and strengthened monsoon circulation within the Indo-Pacific Warm Pool contributed to bottom-water deoxygenation and increased marine productivity. These findings highlight the intricate coupling between sea-level fluctuations and monsoonal forcing in modulating chemical weathering regimes and deep-sea sedimentation dynamics in the Indian Ocean basin.

从Ninetyeast Ridge （NER）获取的沉积物岩心为海洋环境中化学风化过程与沉积物沉积模式之间的相互作用提供了有价值的见解。这种相互作用受到海平面波动和印度夏季风（ISM）变化的强烈影响。在这项研究中，元素组成的地球化学分析表明，末次盛冰期（~ 21-19 ka）是一个化学风化作用增强的时期，可能是由海平面下降和冰川或风成活动加剧引起的。同时，在沉积记录中，高地表生产力和低底水氧合作用有利于有机碳的聚集。而去冰期（~ 17-11 ka）则以海平面快速上升和季风动态演化为特征。除Bølling - allero ød （B/A）层段外，该层段普遍表现为含氧底水条件。在B/A事件期间，沉积速率的增加与古生产力的提高和海洋缺氧条件相一致。全新世反映了一种转变，海平面上升和ISM活动加剧促进了源区化学风化的增强。值得注意的是，全新世气候最佳期（HCO）是一个太阳日照增加和印度洋-太平洋暖池内季风环流增强的时期，这一时期有助于海底脱氧和海洋生产力的提高。这些发现强调了海平面波动和季风强迫之间复杂的耦合，从而调节了印度洋盆地的化学风化机制和深海沉积动力学。

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引用次数: 0

Sedimentary processes in transport-limited versus weathering-limited erosional regimes: Contrasting mineralogical and geochemical signatures of sand and mud in Hainan and Taiwan islands 运输受限和风化受限侵蚀机制下的沉积过程：海南和台湾岛内砂泥的矿物学和地球化学特征对比

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-08 DOI: 10.1016/j.margeo.2025.107635

Jie He , Eduardo Garzanti , Tao Jiang , Entao Liu , Marta Barbarano , Alberto Resentini , Hua Wang

This study provides and discusses an integrated petrographic, heavy-mineral, clay-mineral, elemental-geochemistry and Sr-Nd isotope-geochemistry dataset on sand and mud transported by mountain rivers in Hainan Island, where sand composition is mainly feldspatho-quartzose to quartz-rich feldspatho-quartzose, with K-feldspar invariably prevailing over plagioclase. Illite associated with chlorite prevails in the west, whereas kaolinite prevails in the north and northeast, underscoring a gradient of eastward-increasing weathering intensity in close correspondence with the progressive eastward increase in monsoonal rainfall.

All sand samples are enriched in SiO₂ relative to the upper continental crust and consequently depleted in most other chemical elements. The order of element mobility indicated by α^Al values is Mg > Ca > Na > Sr > K ≈ Ba ≈ Rb. The ⁸⁷Sr/⁸⁶Sr ratio varies between 0.717 and 0.721, and εNd ranges from −6.7 to −9.6. Moderately negative εNd and relatively high ⁸⁷Sr/⁸⁶Sr point at a significant contribution from old crystalline basement, directly or through recycling of siliciclastic strata.

Two endmember types of short river systems can be distinguished in eastern Asia, one dominated by chemical weathering controlled by tropical monsoonal climate under a tectonically stable background and gentle topography (transport-limited regime, dominant in Hainan Island) and another dominated by provenance-controlled physical erosion under a tectonically active background and rugged topography (weathering-limited regime, dominant in Taiwan Island). Mineralogical and geochemical information obtained from river sediments in these contrasting regimes can be profitably used in paleo-climatic inferences and reconstructions.

本研究提供并讨论了海南岛山地河流搬运砂泥的岩石学、重矿物、粘土矿物、元素地球化学和Sr-Nd同位素地球化学综合数据集，其中砂的组成主要为长石-石英到富石英的长石-石英，钾长石始终优于斜长石。西部以伊利石和绿泥石为主，北部和东北部以高岭石为主，风化强度呈东向递增的梯度，与季风降水的东向递增密切相关。相对于上大陆地壳，所有的砂样都富含SiO2，因此大多数其他化学元素都是贫乏的。αAl值表示元素迁移率的顺序为Mg >；Ca比;Na在老的在K≈Ba≈Rb。87Sr/86Sr比值在0.717 ~ 0.721之间，εNd在−6.7 ~−9.6之间。相对负的εNd和较高的87Sr/86Sr点主要来自旧结晶基底，直接或通过硅塑性地层的再循环。东亚地区的短河系可划分为两种端元类型，一种是构造稳定背景和平缓地形下受热带季风气候控制的化学风化作用主导（运输受限型，以海南岛为主），另一种是构造活跃背景和崎岖地形下受物源控制的物理侵蚀作用主导（风化受限型，以台湾岛为主）。从这些对比制度的河流沉积物中获得的矿物学和地球化学信息可以有益地用于古气候推断和重建。

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引用次数: 0

A thousand-year journey of lithification: CT-analysis and radiocarbon dating of algal reef from Central Mediterranean 一千年的岩化之旅：地中海中部藻礁的ct分析和放射性碳定年

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-21 DOI: 10.1016/j.margeo.2025.107637

Pietro Bazzicalupo , Valentina Alice Bracchi , Mara Cipriani , Adriano Guido , Antonietta Rosso , Rossana Sanfilippo , Francesco Maspero , Anna Galli , Elena de Ponti , Daniela Basso

Calcareous algal reefs are Mediterranean carbonate structures, formed by coralline red algae, that display early lithification and preserve key geobiological records. These structures exhibit complex three-dimensional frameworks influenced by environmental conditions and biological interactions, but their lithification processes, porosity evolution, and long-term growth patterns remain poorly understood. In this study, we use Computed Tomography (CT) scanning and radiocarbon dating on four coralligenous build-ups collected along a depth gradient offshore Marzamemi, SE Sicily, to investigate internal skeletal density, porosity distribution, and age profiles. Our findings reveal that lithification progresses gradually from High-Density (HD) to Ultra-High-Density (UHD) material, correlating inversely with porosity. Radiocarbon dating indicates a lithification timeline of roughly 1000 years, with the oldest, densest material dating back over 5000 years. The structures demonstrate a depth-density and age-depth gradient: deeper and older build-ups exhibited higher quantity of UHD material, whereas younger, shallower build-ups contain a higher proportion of HD material. Additionally, evidence suggests that specific build-ups may have been fragmented and relocated due to environmental or anthropogenic factors, further influencing growth patterns. The CT-analysis contributes to improving knowledge on coralligenous reef formation and evolution, underscoring the role of lithification in maintaining structural stability over millennia and providing insights applicable to the study of fossil reef systems.

钙质藻礁是地中海的碳酸盐岩结构，由珊瑚红藻形成，显示了早期的岩化作用，并保存了重要的地球生物学记录。这些结构受到环境条件和生物相互作用的影响，呈现出复杂的三维框架，但它们的岩化过程、孔隙演化和长期生长模式仍然知之甚少。在这项研究中，我们使用计算机断层扫描（CT）和放射性碳定年技术对西西里岛东南部Marzamemi近海沿深度梯度收集的四个珊瑚堆积进行了研究，以调查内部骨骼密度、孔隙度分布和年龄分布。研究结果表明，岩石化过程由高密度（HD）向超高密度（UHD）逐渐发展，与孔隙度呈负相关。放射性碳定年法表明，石化时间大约为1000年，最古老、密度最大的物质可以追溯到5000多年前。这些结构表现出深度-密度和年龄-深度梯度：较深和较老的建筑物显示出较多的超高清物质，而较年轻、较浅的建筑物含有较高比例的超高清物质。此外，有证据表明，由于环境或人为因素，特定的堆积物可能已被分散和重新安置，从而进一步影响了增长模式。ct分析有助于提高对珊瑚礁形成和演化的认识，强调了岩化作用在维持数千年结构稳定性方面的作用，并提供了适用于化石礁系统研究的见解。

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引用次数: 0

Dating ‘Zebra’: A subaerial to ultra-shallow marine Lomonosov Ridge at the end of the Oligocene? “斑马”测年：渐新世末期陆基到超浅海罗蒙诺索夫海岭？

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-07-19 DOI: 10.1016/j.margeo.2025.107618

Francesca Sangiorgi , Evi Wubben , Suning Hou , Henk Brinkhuis

Twenty years after the pioneering IODP Expedition 302 (ACEX) to the Lomonosov Ridge, central Arctic Ocean, a robust age model was still lacking. This was foremost due to the overall poor core recovery, and frequent lack of age diagnostic features including (micro)fossils, notably in the likely Neogene succession. Interestingly, one of the few intervals that were relatively well-recovered was interpreted to span the Paleogene-Neogene transition. On board and follow up marine palynological studies indicated that within this interval, a potential ∼26 Myr long hiatus separated the local top of the Paleogene (∼44 Ma) from the Neogene (∼18 Ma), occurring between local lithological subunits 1/6 and 1/5. The latter was informally also referred to as the ‘Zebra’ interval, owing to its characteristic black/white alternations in the colour of the sediments. This hiatus would possibly imply a subaerial or ultra-shallow marine Lomonosov Ridge during late Oligocene to early Miocene times. A Neogene, (late) Early Miocene age for the base of ‘Zebra’ subunit 1/5 was tentatively provided by the finding of a new, later formally described, organic walled dinoflagellate cyst (dinocyst) genus we named Arcticacysta, which included two species, A. backmanii and A. moraniae. Subsequent work challenged the presence of a hiatus and the age of the ‘Zebra’ subunit.

Here we present recent palynological (dinocyst) findings from Miocene sediments retrieved from the Pennell Basin during IODP Expedition 374 (Ross Sea, Antarctica) that contain the first appearance at 17.7 Ma of specimens of the same dinocyst genus, Arcticacysta, and species, and a more continuous presence between 17.0 and 15.9 Ma. Providing that the (first) occurrence of this dinocyst genus is synchronous in both (polar) records, these findings confirm the assignment of the Arctic Ocean ‘Zebra’ interval to the (late) Early Miocene, adding evidence for a large hiatus characterizing the Paleogene/Neogene transition on the Lomonosov Ridge.

在IODP第302远征队（ACEX）前往北冰洋中部罗蒙诺索夫海脊20年后，一个可靠的年龄模型仍然缺乏。这主要是由于整体上较差的岩心恢复，以及经常缺乏年龄诊断特征，包括（微）化石，特别是在可能的新近纪演取中。有趣的是，为数不多的几个相对较好的恢复区间之一被解释为跨越古近系-新近系过渡。船上和后续的海洋孢粉学研究表明，在这段时间内，古近纪（~ 44 Ma）的局部顶部与新近纪（~ 18 Ma）之间可能存在~ 26 Myr长的间隙，发生在局部岩性亚单位1/6和1/5之间。后者也被非正式地称为“斑马”间隔，因为其特征是沉积物颜色的黑/白交替。这一断裂带可能暗示渐新世晚期至中新世早期存在陆基或超浅海罗蒙诺索夫海岭。“斑马”亚基1/5的新发现（晚）中新世早期，我们将其命名为Arcticacysta，其中包括A. backmanii和A. moraniae两种，这初步提供了一个新的、后来正式描述的有机壁甲藻囊（dinocyst）属。随后的工作挑战了中断的存在和“斑马”亚单位的年龄。本文介绍了IODP 374考察（南极洲罗斯海）期间从Pennell盆地中新世沉积物中获得的孢粉学（dinocyst）发现，在17.7 Ma时首次出现了相同的dinocyst属、arcacysta和物种的标本，并在17.0至15.9 Ma之间持续存在。考虑到该恐龙属的首次出现在两个极地记录中是同步的，这些发现证实了北冰洋“斑马”间隔的定位是早中新世（晚），并为罗蒙诺索夫海岭古近纪/新近纪过渡的大间断提供了证据。

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引用次数: 0

Tracking coccolithophore productivity trends over the last 22,000 years: insights from sediments of IODP Expedition 385 in a high-productivity oceanic basin (Guaymas Basin) 跟踪过去22000年的球石藻生产力趋势：来自高生产力海洋盆地（瓜伊马斯盆地）IODP 385考察沉积物的见解

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-05 DOI: 10.1016/j.margeo.2025.107629

María-Carmen Álvarez , Ligia Pérez-Cruz , Jaime Urrutia-Fucugauchi , Alejandro Aldama-Cervantes , Mauricio Velázquez-Aguilar , Mariem Saavedra-Pellitero , Miguel-Ángel Díaz-Flores

We study sediment cores retrieved during International Ocean Discovery Program (IODP) Expedition 385 to gain a deeper understanding of the Guaymas Basin's (GB) response to climate fluctuations over the past 22,400 years by analyzing coccolithophore assemblages and estimating net primary productivity (NPP). Coccolithophore-based data and the NPP at IODP Hole 1549 A reveal that the GB consistently remained an area of high productivity throughout the studied time interval, with an average productivity value of 1288.25 mgC m⁻² day⁻¹, with a gradually declining trend towards the present.

Three main intervals are defined: (I) Cold, high productivity and vertically mixed surface waters during the Last Glacial Maximum and Heinrich Event 1 (22,400–15,320 cal yr BP), suggested by elevated net primary productivity (NPP), high abundance of Gephyrocapsa oceanica, and the presence of Coccolithus pelagicus subsp. braarudii. These conditions may be related to the incursion of the California Current Water into the GB. (II) Intermittent stratification with a deep position of the nutricline and thermocline during Bølling-Allerød, Younger Dryas, and broadly, the beginning of the Holocene (15,320–11,200 cal yr BP) indicated by an increase in relative abundance of Florisphaera profunda and the decrease in key coccolithophore taxa (notably G. oceanica and C. pelagicus subsp. braarudii). (III) Recurrent events of low productivity, warm surface water conditions with stratification since the beginning of the Holocene Climatic Optimum (11,200 cal yr BP-present), as suggested by the dominance of warm and oligo-mesotrophic water taxa (Helicosphaera spp., Calcidiscus leptoporus, Syracosphaera spp. and Umbilicosphaera sibogae) alongside a rise in F. profunda. From approximately 4900 cal yr BP to the present sustained stratification and declining NPP suggest the onset and intensification of modern monsoonal dynamics in the GB.

我们研究了国际海洋发现计划（IODP） 385号考察期间获取的沉积物岩心，通过分析球岩石组合和估算净初级生产力（NPP），深入了解瓜伊马斯盆地（GB）过去22400年对气候波动的响应。球石藻数据和1549 A孔的NPP表明，在整个研究时间间隔内，GB始终是一个高生产力区域，平均生产力值为1288.25 mgC m−2 day−1，并逐渐下降。(1)末次盛冰期和海因里希事件1 （22,400-15,320 cal yr BP）期间，净初级生产力（NPP）升高，Gephyrocapsa oceanica丰度高，cocolithus pelagicus亚种存在，表明表层水冷、高生产力和垂直混合。braarudii。这些情况可能与加利福尼亚水流侵入英国有关。（II）新仙女木期（b øllin - allero ød）和全新世初期（15320 - 11200 cal yr BP）营养线和温跃层处于较深位置的间歇分层，表明Florisphaera profunda的相对丰度增加，而主要的球石藻类群（特别是G. oceanica和C. pelagicus亚种）的相对丰度减少。braarudii)。（III）自全新世气候最适期（距今11200 cal yr）开始以来，低生产力、温暖的地表水条件和分层反复发生，这表明温暖和少中营养水分类群（Helicosphaera spp., Calcidiscus leptoporus, Syracosphaera spp.和脐带osphaera sibogae）的优势以及F. profunda的增加。从大约4900 calyr BP到现在的持续分层和NPP的下降表明现代季风动力学在GB的开始和加强。

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引用次数: 0

Geological, geophysical, and geobiological investigation of the inactive Nawaay`as hydrothermal vent field at West Valley, Juan de Fuca Ridge 对Juan de Fuca Ridge West Valley不活跃的Nawaay 'as热液喷口进行地质、地球物理和地质生物学调查

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-11-01 Epub Date: 2025-08-27 DOI: 10.1016/j.margeo.2025.107643

Sarah N. Moriarty , Monika Neufeld , Zoe Krauss , John W. Jamieson

In 2022, an area of now-inactive hydrothermal venting, named the Nawaay`as field, was discovered on a sediment-covered volcanic mound within the axial valley of the West Valley segment of the Juan de Fuca Ridge, northeast Pacific Ocean. Analysis of multibeam backscatter imagery of the ridge segment indicates that volcanic activity along the ridge has resulted in, at minimum, two distinct eruptive events along the valley floor. Younger lava flows emanated from a volcano located near the southern end of the valley, then flowed north, paving over areas of bathymetric lows, but flowing around and thus preserving areas of relative bathymetric highs, including the volcanic mound that hosts the Nawaay`as field. Geochemical and petrographic analysis of Nawaay`as hydrothermal rock samples indicate that the deposit formed over venting temperatures ranging from ∼100 to 300 °C. Although the valley floor is generally sediment-free, trace metal concentrations within the sulfide-rich rock samples suggest that hydrothermal fluids interacted with buried sediments. Distinct differences in deep-sea sponge communities were observed between basaltic and inactive sulfidic substrates at West Valley, indicating that inactive hydrothermal deposits are unique seafloor habitats. Observations of shimmering water, vent-associated fauna, and recent seismic activity suggest the presence of active hydrothermal venting to both the north and south of Nawaay`as. With recent increased interest in the mineral resource potential of the seafloor, studies of inactive vent sites such as Nawaay`as are critical to ensure informed, risk-mitigating marine policy decisions are made in the future.

2022年，在太平洋东北部Juan de Fuca山脊西谷段轴向山谷内的沉积物覆盖的火山丘上发现了一个现已不活跃的热液喷口区域，名为Nawaay 'as田。对山脊段的多波束后向散射图像的分析表明，沿山脊的火山活动至少导致了沿谷底的两次不同的喷发事件。年轻的熔岩流从山谷南端附近的一座火山喷发出来，然后向北流动，覆盖了水深较低的地区，但在周围流动，从而保留了相对水深较高的地区，包括拥有纳威亚斯油田的火山丘。Nawaay’as热液岩石样品的地球化学和岩石学分析表明，该矿床形成于喷口温度为~ 100 ~ 300°C。虽然谷底通常没有沉积物，但富含硫化物的岩石样品中的微量金属浓度表明，热液流体与埋藏的沉积物相互作用。在西谷的玄武岩和不活跃的硫化物基质中，深海海绵群落存在明显差异，表明不活跃的热液沉积物是独特的海底栖息地。对闪闪发光的水、与喷口相关的动物群和最近的地震活动的观察表明，在纳威亚斯的北部和南部都存在活跃的热液喷口。随着最近人们对海底矿产资源潜力的兴趣日益浓厚，对Nawaay 'as等不活跃喷口的研究对于确保未来做出明智的、降低风险的海洋政策决定至关重要。

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引用次数: 0