Marine Geology最新文献_第4页

Paleo-bathymetric Evolution of Prydz Bay since the Eocene-Oligocene Boundary, East Antarctica 东南极洲始新世-渐新世交界以来Prydz湾的古水深演化

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-27 DOI: 10.1016/j.margeo.2025.107674

Zijian Xiao , Xiaoxia Huang , Katharina Hochmuth

This study used backstripping analysis, combined with a multi-proxy dataset comprising borehole logs, multi-channel seismic surveys, high-resolution bathymetric data, and regional tectonic constraints to quantitatively reconstruct the paleobathymetric evolution of Prydz Bay. As the third largest bay in Antarctica, Prydz Bay is located in front of the Lambert Glacier-Amery Ice Shelf of the East Antarctic continental margin. Prydz Bay is covered by rich multi-channel seismic lines, and Ocean Drilling Program Leg 119 and 188 provided available lithology data of 8 boreholes, establishing it as an ideal area for basin analyses and paleobathymetric evolution. Core porosity data indicated that the sedimentary strata on the continental shelf are overcompacted due to grounded glacier loading, while the slope exhibits hemipelagic sedimentary characteristics. Considering the variability of deposition history and different crustal structure, the compaction was calculated separately between the continental shelf and slope. By comparison with previous studies, our new results quantitatively infer the thickness of sediment variations, and more detailed paleobathymetric grids were produced in different stages since Eocene-Oligocene boundary. The newly reconstructed paleobathymetry contributes to the understanding of the depositional response of ice sheet dynamics and ocean circulation changes, providing critical constraints on the coupled glacial-ocean-sediment system. Furthermore, spatially explicit gridded data could be used to establish more realistic regional ice sheet, ocean circulation, and climate models in the future.

本研究采用反采分析方法，结合钻孔测井、多通道地震调查、高分辨率测深数据和区域构造约束等多代理数据，定量重建了Prydz湾的古测深演化。普莱兹湾是南极洲第三大海湾，位于南极洲东部大陆边缘的兰伯特冰川-阿莫里冰架前。Prydz Bay被丰富的多通道地震线覆盖，Ocean Drilling Program Leg 119和Leg 188提供了8个钻孔的可用岩性数据，使其成为盆地分析和古测深演化的理想区域。岩心孔隙度数据表明，陆架上沉积地层受地面冰川负荷作用过度压实，坡面呈现半深海沉积特征。考虑到沉积历史的可变性和地壳结构的差异性，陆架和陆坡之间的压实度分别计算。通过与前人研究结果的比较，定量地推断了沉积物厚度的变化，并建立了始新世-渐新世界线以来不同阶段的更详细的古水深网格。新重建的古水深测量有助于了解冰盖动力学和海洋环流变化的沉积响应，为冰川-海洋-沉积物耦合系统提供关键约束。此外，空间明确的网格数据可用于未来建立更真实的区域冰盖、海洋环流和气候模式。

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引用次数: 0

Geyser and Zélée seamounts and adjacent basin as witnesses of SW Indian Ocean tectonic and carbonate-siliciclastic-volcanoclastic sediment interplay 间歇泉和zsamlsame海山及其邻近盆地是西南印度洋构造和碳酸盐-硅质-火山碎屑沉积相互作用的见证

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-26 DOI: 10.1016/j.margeo.2025.107673

Dhishna Buljore , Stéphan J. Jorry , Gwenael Jouet , Patrick Bachèlery , Fabien Paquet

This study examines the Late Quaternary sedimentary and volcanic history of Zélée and Geyser Seamounts, carbonate platforms in the Mozambique Channel (south-west Indian Ocean). These seamounts are in a region influenced by active tectonics, glacial-interglacial sea-level cycles, and persistent volcanic activity from both local (Mayotte and Comoros Archipelago) and regional (Madagascar) sources. As a result, they display complex sedimentary and geomorphic characteristics. The research uses sediment cores and seismic profiles to identify four glacial-interglacial stages. It traces shifts in sediment provenance and documents a transition from Madagascar-derived siliciclastic inputs to volcanic sediments associated with Mayotte volcanism around 150 ka.

The analysis also tests a model of platform formation in general on two independently formed edifices, Zélée and Geyser. Detailed geomorphological mapping reveals steep slopes, terraces, volcanic cones, and erosional features. Seismic profiles show stratified deposits including turbidites of different origins. These turbidites highlight episodic sediment transport. Volcanoclastic layers are linked to volcanic events, while siliciclastic layers trace back to Madagascar. Calciturbidites reflect carbonate shedding from Zélée and Geyser during sea-level changes.

The findings enhance our understanding of carbonate platform evolution in tectonically active marine environments, emphasizing the influence of volcanism, tectonics, and climatic fluctuations on sediment distribution and platform morphology. This study contributes a refined perspective on sedimentary processes and sediment provenance in carbonate platforms, with broader implications for reconstructing past oceanographic conditions in similar regions.

本研究考察了莫桑比克海峡（西南印度洋）碳酸盐台地zsamuelsame和Geyser海山的晚第四纪沉积和火山历史。这些海山所处的区域受到活动构造、冰期-间冰期海平面旋回以及来自当地（马约特群岛和科摩罗群岛）和区域（马达加斯加）的持续火山活动的影响。因此，它们表现出复杂的沉积和地貌特征。该研究利用沉积物岩心和地震剖面确定了四个冰期-间冰期。它追溯了沉积物来源的变化，并记录了从马达加斯加衍生的硅碎屑输入到150 ka左右与马约特火山活动相关的火山沉积物的转变。该分析还测试了两个独立形成的大厦，zsamusame和Geyser的平台形成模型。详细的地貌地图揭示了陡峭的斜坡、阶地、火山锥和侵蚀特征。地震剖面显示层状沉积，包括不同来源的浊积岩。这些浊积岩突出了幕式沉积物搬运。火山碎屑层与火山事件有关，而硅碎屑层可以追溯到马达加斯加。钙辉石反映了海平面变化过程中z薪金和间歇泉中碳酸盐的脱落。这些发现加强了我们对构造活跃海洋环境中碳酸盐岩台地演化的认识，强调了火山作用、构造作用和气候波动对沉积物分布和台地形态的影响。该研究为研究碳酸盐岩台地的沉积过程和沉积物物源提供了一个更精确的视角，对重建类似地区过去的海洋条件具有更广泛的意义。

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引用次数: 0

Post-glacial sandy contourite drifts in the Malta-Gozo Channel (Pelagian Platform, central Mediterranean Sea): Characteristics, bottom currents and implication for shallow-water contourite systems 马尔他-戈佐海峡（地中海中部伯拉吉海台地）冰川后砂质轮廓岩漂移：特征、底流及其对浅水轮廓岩体系的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-24 DOI: 10.1016/j.margeo.2025.107672

Daniele Spatola , Aaron Micallef , Daniele Casalbore , Francesco Latino Chiocci , Eleonora Martorelli

An increasing number of studies have documented the occurrence of sandy contourites in modern systems. However, knowledge on their characteristics and links with oceanographic processes remains limited. In particular, the pattern of bottom current circulation on the Pelagian Platform (central Mediterranean Sea) and its driving mechanisms are poorly understood. To address these gaps, we analyse newly acquired very high-resolution geophysical and sedimentological data from offshore the Maltese Islands, which allow us to identify small-scale, sandy contourite drifts (named EM1–5), located in shallow water (depths between 50 and ∼ 100 m). Using a dense grid of high-resolution seismic profiles, multibeam bathymetry, and sedimentological analyses, we detail the internal and external geometry, morphology, and sedimentology of the deposits. Drifts EM1a, EM1b, EM1c, EM2, EM3, and EM5 appear as small elongated mounded deposits (separated and plastered drifts) cropping on the shelf seafloor, while EM4 is a buried mounded deposit located in the southern part of the study area. The spatial distribution of the studied drifts suggests that their formation is driven by a mesoscale anticyclonic gyre, tentatively ascribed to the Malta-Sicily Gyre, with currents enhanced by topographic interactions. Stratigraphic evidence suggests that this oceanographic dynamic has played a significant role in shaping the Maltese insular shelf since at least the Holocene, highlighting the potential of the Pelagian Platform to form carbonate sandy contourites. These findings advance the understanding of shallow-water (shelf-channelized) contourite systems and offer valuable insights to refine sedimentation models for carbonate-rich contourite deposits in temperate settings.

越来越多的研究记录了现代体系中砂质等高线的出现。然而，关于它们的特点及其与海洋学过程的联系的知识仍然有限。特别是对伯拉基平台（地中海中部）的底流环流模式及其驱动机制了解甚少。为了解决这些差距，我们分析了马耳他群岛近海新获得的高分辨率地球物理和沉积学数据，这些数据使我们能够识别位于浅水（深度在50至~ 100米之间）的小规模沙质轮廓岩漂移（命名为EM1-5）。利用高分辨率地震剖面的密集网格、多波束测深和沉积学分析，我们详细描述了矿床的内部和外部几何形状、形态和沉积学。EM1a、EM1b、EM1c、EM2、EM3和EM5漂流体在陆架海床上表现为小型细长的丘状沉积物（分离的灰泥漂流体），而EM4则为埋藏的丘状沉积物，位于研究区南部。所研究的漂移的空间分布表明，它们的形成是由一个中尺度反气旋环流驱动的，该环流初步归因于马耳他-西西里环流，地形相互作用增强了洋流。地层学证据表明，至少自全新世以来，这种海洋动力学在塑造马耳他岛陆架方面发挥了重要作用，突出了伯拉海地台形成碳酸盐砂质等高线岩的潜力。这些发现促进了对浅水（陆架河道化）廓长岩体系的理解，并为完善温带环境中富含碳酸盐的廓长岩沉积模式提供了有价值的见解。

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引用次数: 0

Multiple methane release events from Cascadia Margin sediments since 1 Ma inferred from pyrite multiproxy data 从黄铁矿多代理资料推断1 Ma以来卡斯卡迪亚边缘沉积物多次甲烷释放事件

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-23 DOI: 10.1016/j.margeo.2025.107670

Qiang Song , Jiasheng Wang , Thomas J. Algeo , Can Chen , Zhou Wang , Qin Yang , Kunlong Geng , Qing Li

Large-scale methane release events (MREs), which can trigger transient climatic hyperwarming, are associated with enhanced anaerobic oxidation of methane (AOM), generating diagnostic geochemical and petrographic signatures in authigenic pyrite. Previous studies of MREs have analyzed single proxies such as pyrite framboid size or the sulfur isotopic composition of bulk-sediment pyrite over short core intervals, providing insufficient data regarding the intensity and magnitude of such events. Here, we utilize multiple proxies (i.e., pyrite framboid content, size, and sulfur isotopic composition) to reconstruct a detailed history of paleo-MREs at Site U1329 (IODP Leg 311) on the Cascadia Margin since 1 Ma. The recovered pyrite consists mainly (>99%) of isolated framboids and framboid aggregates, some having late diagenetic overgrowths. The characteristics of these framboids reflect the intensity and magnitude of each MRE: strong events were associated with FeS₂ > 1.0 wt.%, mean framboid size >20 μm, and Δ³⁴S < 0‰ (where Δ³⁴S = δ³⁴S_CRS – δ³⁴S_SMTZ), whereas weak events were associated with FeS₂ = ∼0.5-1.0 wt.%, mean framboid size ∼10-20 μm, and Δ³⁴S > 0‰. The study core contains four MREs (one strong, three medium) with mean pyrite content of 1.27 wt.%, mean framboid diameter of 26±6 μm, and mean Δ³⁴S of 10.5‰ (cf. background interval values of 0.85 wt.% mean FeS₂ content; 12±2 μm mean framboid diameter; and 16.0‰ mean Δ³⁴S). Each MRE was associated with a glacio-eustatic lowstand, a relationship reflecting destabilization of gas hydrates through pressure release, leading to an upward flux of methane, shallowing of the sulfate-methane transition zone (SMTZ), and enhanced AOM activity. Our results indicate that the morphological and geochemical signatures of pyrite are important carriers of paleoclimate information that can be used to study the occurrence and intensity of paleo-methane events and further improve understanding of methane hydrate dynamics.

大规模甲烷释放事件（MREs）可引发短暂的气候过热，与甲烷厌氧氧化（AOM）增强有关，产生自生黄铁矿的诊断地球化学和岩石学特征。以前的MREs研究分析了单一的指标，如黄铁矿的草莓状大小或短岩心间隔内块状沉积物黄铁矿的硫同位素组成，提供的有关此类事件的强度和量级的数据不足。在这里，我们利用多种代理（即黄铁矿的含量、大小和硫同位素组成）重建了Cascadia边缘U1329遗址（IODP Leg 311）自1ma以来的古mres详细历史。回收的黄铁矿主要由（>99%）孤立的草莓状和草莓状团聚体组成，部分有晚成岩过度生长。这些frboids的特征反映了每个MRE的强度和大小：强事件与FeS2 >； 1.0 wt.%，平均frboid尺寸>；20 μm和Δ34S <； 0‰（其中Δ34S = δ34SCRS - δ34SSMTZ）相关，而弱事件与FeS2 = ~ 0.5-1.0 wt.%，平均frboid尺寸~ 10-20 μm和Δ34S >； 0‰相关。研究岩心包含4个MREs（1个强、3个中），平均黄铁矿含量为1.27 wt.%，平均树状直径为26±6 μm，平均Δ34S为10.5‰（cf.背景区间值为0.85 wt.%，平均FeS2含量为12±2 μm，平均Δ34S为16.0‰）。每个MRE都与一个冰川-上升低潮相关联，这种关系反映了通过压力释放导致天然气水合物不稳定，导致甲烷通量上升，硫酸盐-甲烷过渡带（SMTZ）变浅，AOM活动增强。结果表明，黄铁矿的形态和地球化学特征是古气候信息的重要载体，可用于研究古甲烷事件的产状和强度，进一步提高对甲烷水合物动力学的认识。

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引用次数: 0

Buried Middle Miocene cyclic steps on the northwestern slope of the Xisha carbonate platform, South China Sea 南海西沙碳酸盐岩台地西北坡中中新世隐伏旋回台阶

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-22 DOI: 10.1016/j.margeo.2025.107671

Biwen Wang , Jinfeng Ren , Zenggui Kuang , Guangfa Zhong

High-amplitude undulating seismic reflections within the Middle Miocene strata on the northwestern slope of the Xisha carbonate platform, located on the northwestern continental margin of the South China Sea, have drawn significant research interest over the past decade. Several conflicting genetic models have been proposed, including those suggesting carbonate reefs, turbidity-current or bottom-current channels, and fault-related features. This study examines the morphology, internal structures, and distribution of these undulations using 3D seismic data, combined with 2D seismic and drilling data. These undulations are characterized by long wavelength (0.5–2.3 km), low wave height (15–80 m), large aspect ratios (20–60), upslope-migrating waveforms, upslope-asymmetric cross-sectional morphology, typical stoss-side backset beddings and truncated lee sides, and are therefore identified as cyclic steps associated with supercritical flows. The slope-parallel crestlines of the cyclic steps further indicate their turbidity-current origin. Some coexisting downslope extending linear depressions are attributed to turbidity-current channels. Development of the cyclic steps is closely associated with the evolution of the Xisha carbonate platform. During the early Middle Miocene, when the carbonate platform productivity was high, abundant calcareous sediments were delivered from the platform margin to the study area, contributing to the formation of the cyclic steps in the lower slope off the platform. As the platform was drowning in the late Mid-Late Miocene, sediment supply from the platform was reduced, leading to the abandonment of the bedforms, with the bedform troughs being infilled by interbedded hemipelagites and turbidites. Our findings are significant for a better understanding of 3D morpho-sedimentary architecture of buried supercritical-flow bedforms that have been rarely reported, with implications for regional paleogeographic reconstructions and carbonate platform evolution.

近十年来，南海西北陆缘西沙碳酸盐岩台地西北坡中中新世地层的高振幅波动地震反射引起了人们的广泛关注。人们提出了几种相互矛盾的成因模式，包括碳酸盐岩礁、浊流或底流通道以及断层相关特征。本研究利用三维地震数据，结合二维地震和钻井数据，研究了这些波动的形态、内部结构和分布。这些波动具有波长长（0.5-2.3 km）、波高低（15-80 m）、宽高比大（20-60）、上坡迁移波形、上坡不对称横截面形态、典型的应力侧背向层序和背风侧截短等特征，因此被认为是与超临界流动相关的循环阶跃。旋回台阶的斜平行顶线进一步表明其浊流成因。一些同时存在的下坡扩展线性凹陷归因于浊流通道。旋回阶的发育与西沙碳酸盐岩台地的演化密切相关。中中新世早期，碳酸盐岩台地生产力较高，大量钙质沉积物从台地边缘向研究区输送，形成了台地下斜坡旋回台阶。中-晚中新世晚期台地淹水，台地输沙量减少，导致床型废弃，床型槽被互层半玄武岩和浊积岩填满。我们的发现对于更好地理解埋藏的超临界流层的三维形态-沉积结构具有重要意义，这对区域古地理重建和碳酸盐岩台地演化具有重要意义。

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引用次数: 0

Sedimentary dynamics in the subaqueous delta of the abandoned estuary: Effects of strong wave activity and riverine re-supply 废弃河口水下三角洲的沉积动力学：强波活动和河流补给的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-08 DOI: 10.1016/j.margeo.2025.107662

Chaoran Lin , Longhai Zhu , Yaping Wang , Rui Bao , Rijun Hu , Lingpeng Meng

Global climate change and the decline in riverine sediment supply are profoundly reshaping the fate and trajectory of numerous river deltas around the world. Notably, subaqueous deltas of abandoned estuaries (SDAEs) resulting from river diversion represent an extreme example of zero riverine sediment supply, yet studies of these environments remain scarce. Based on in-situ bottom boundary layer observations in both spring and summer in the SDAE of the Yellow River, we examined the variation patterns and controlling mechanisms of sediment dynamics —under the effect of strong wave activity and the new secondary distribution. Strong wave events exhibited a pronounced dual influence on SSC; alongshore wave substantially increase SSC (>21.28 g/L) by enhancing sediment resuspension and liquefaction, whereas onshore wave significantly reduce nearshore SSC through water mass replacement (with values rapidly dropping from 13.11 g/L to 1.14 g/L). Riverine re-supply due to the new secondary course of the Yellow River has altered sediment transport pathways, enabling SSC in the SDAE to reach as high as 22.34 g/L under calm weather conditions, and resulting in a net alongshore sediment flux of 117 kg/m². We identified and established three conceptual models of fluid mud formation mechanisms: wave-supported, wave-current coupled fluid mud (WCFM), and river advection. We identified and established three conceptual models of fluid mud formation: wave-supported, wave-current coupled fluid mud (WCFM), and river advection. Identification of the WCFM highlights the sustained impact of strong wave activity on sediment transport within the SDAE. These findings advance our understanding of sediment dynamics in the SDAEs and provide valuable theoretical references and comparative examples for the studying the global evolution of abandoned or sediment-starved delta.

全球气候变化和河流沉积物供应的减少正在深刻地重塑世界各地众多河流三角洲的命运和轨迹。值得注意的是，河流改道导致的废弃河口水下三角洲（SDAEs）是河流沉积物零供应的一个极端例子，但对这些环境的研究仍然很少。基于黄河南岸河段春夏两季底边界层观测资料，探讨了强波活动和新的二次分布作用下泥沙动力的变化规律和控制机制。强波事件对SSC具有明显的双重影响；近岸波通过加强沉积物再悬浮和液化作用显著增加SSC (21.28 g/L)，而近岸波通过水体质量替代作用显著减少SSC（从13.11 g/L迅速下降到1.14 g/L）。黄河新次河道的河道再补给改变了输沙路径，使SDAE的SSC在平静天气条件下高达22.34 g/L，导致净岸沙通量为117 kg/m2。我们确定并建立了三种流体泥浆形成机制的概念模型：波支撑、波流耦合流体泥浆（WCFM）和河流平流。我们确定并建立了三种流体泥浆形成的概念模型：波支撑、波流耦合流体泥浆（WCFM）和河流平流。WCFM的确定强调了强波活动对SDAE内沉积物输运的持续影响。这些发现促进了我们对SDAEs沉积动力学的认识，并为研究遗弃或缺沙三角洲的全球演化提供了有价值的理论参考和比较实例。

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引用次数: 0

From impact to extinction to recovery: Discoveries of IODP-ICDP Expedition 364 to the Chicxulub impact structure 从撞击到灭绝再到恢复：364号探险队对希克苏鲁伯撞击结构的发现

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-10-01 DOI: 10.1016/j.margeo.2025.107661

S.P.S. Gulick , P. Kaskes , C.M. Lowery , A.S.P. Rae , S.M. Tikoo

In 2016, International Ocean Discovery Program Expedition 364, with support from the International Continental Scientific Drilling Program, drilled into the peak ring of the Chicxulub impact structure, famous for its causal link to the mass extinction at the end of the Cretaceous. In this summary paper, we discuss key findings from Site M0077 on the cratering processes, marine ecosystem recovery after the mass extinction, and the post-impact hydrothermal system and habitability of the impact structure. Important results include (1) the confirmation of the dynamic collapse model of peak ring formation, (2) insights into impactite emplacement processes on Earth, where water is a key component, (3) discovery of the iridium anomaly within the impact basin, unequivocally linking the Chicxulub impact basin to the global Cretaceous-Paleogene (K-Pg) boundary layer, (4) evidence for key atmospheric inputs of dust, sulfate aerosols, and soot, all likely contributing to global cooling and reduction of photosynthesis as drivers for extinction, (5) rapid recovery of life within the ocean overlying the crater, including a primary succession driven by in part by picoplankton before a transition over 100 s kyr to diversifying planktic communities, and (6) the presence of a long-lived hydrothermal system with extant thermophilic life in the buried peak ring 66 Myr later. The Chicxulub crater represents exceptional scientific opportunity in that it bridges planetary science, impact dynamics, and astrobiology; the integration of such findings continue to reveal the transformative power of asteroid impacts as a major geologic and biologic process.

2016年，在国际大陆科学钻探计划（International Continental Scientific Drilling Program）的支持下，国际海洋发现计划（International Ocean Discovery Program）第364次远征队（Expedition 364）钻进了希克苏鲁伯撞击构造的峰环，该构造因与白垩纪末期的大灭绝有因果关系而闻名。本文综述了M0077站点在陨石坑形成过程、大灭绝后海洋生态系统恢复、撞击后热液系统和撞击结构可居住性等方面的重要发现。重要成果包括：(1)确认了峰环形成的动态崩塌模型；(2)深入了解了地球上的撞击物侵位过程，其中水是关键成分；(3)发现了撞击盆地内的铱异常，明确地将希克苏鲁伯撞击盆地与全球白垩纪-古近纪（K-Pg）边界层联系起来；(4)尘埃、硫酸盐气溶胶和烟尘的关键大气输入证据；所有这些都可能导致全球变冷和光合作用的减少，从而导致物种灭绝；(5)陨石坑上海洋生物的迅速恢复，包括在100万年以前向多样化的浮游生物群落过渡之前部分由微小浮游生物驱动的初级演替；(6)66万年以后埋藏的峰环中存在一个长期存在的热液系统，其中存在现存的嗜热生物。希克苏鲁伯陨石坑代表了非凡的科学机遇，因为它连接了行星科学、撞击动力学和天体生物学；综合这些发现，继续揭示小行星撞击作为一个主要的地质和生物过程的变革力量。

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引用次数: 0

The incompleteness of turbidite records: Comparing direct monitoring of turbidity currents to deposits preserved in submarine fans (Pointe-des-Monts, eastern Canada) 浊积岩记录的不完整性：浊积流的直接监测与海底扇中保存的沉积物的比较（加拿大东部蒙特角）

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-09-26 DOI: 10.1016/j.margeo.2025.107660

Florian Jacques , Alexandre Normandeau , Jean-Carlos Montero-Serrano , Guillaume St-Onge , Audrey Limoges , André Rochon , Urs Neumeier , Patrick Lajeunesse , Daniel Bourgault

The recurrence of turbidity currents in submarine canyons is often assessed using sediment core records from submarine fans, which are generally assumed to reflect canyon processes. However, this assumption has rarely been tested. Here, we assess the completeness of modern sedimentary records in the Pointe-des-Monts submarine fan, located in the Lower St. Lawrence Estuary, eastern Canada, by comparing turbidity current activity derived from repeat multibeam bathymetry, direct monitoring observations, and short sediment cores. The timelapse bathymetry and monitoring results revealed that turbidity current activity over the last 15 years was primarily driven by storms, especially during ice-free winters. Since 2007, a minimum of nine turbidity currents were recorded by timelapse multibeam bathymetry and direct observations in the canyon system, many of which have led to the migration of cyclic steps within the canyon axis. However, turbidites recorded in the short sediment cores on the lobe predate all monitoring efforts, indicating a largely incomplete record of canyon processes preserved on the seafloor. The absence of modern turbidites (≤15 years) in the submarine fan is interpreted to result from bottom current reworking, bioturbation, and the dilution of turbidity currents as they become unconfined on the submarine fan. This study highlights that bottom currents can extensively remobilize turbidites, resulting in a largely incomplete record of turbidity currents on submarine fans. Consequently, caution is needed when reconstructing their recurrence and sediment dynamics using sediment cores, particularly in such dynamic nearshore systems.

通常利用海底扇沉积岩心记录来评估海底峡谷浊度流的重现，这些记录通常被认为反映了峡谷过程。然而，这种假设很少得到验证。在这里，我们通过比较重复多波束测深、直接监测观测和短沉积物岩心得出的浊流活动，评估了位于加拿大东部下圣劳伦斯河口的Pointe-des-Monts海底扇现代沉积记录的完整性。时间间隔测深和监测结果显示，过去15年的浊流活动主要是由风暴驱动的，特别是在无冰的冬季。自2007年以来，通过时间间隔多波束测深和直接观测，在峡谷系统中记录了至少9个浊度流，其中许多浊度流导致了峡谷轴内循环阶跃的迁移。然而，在裂片上的短沉积物岩心中记录的浊积物比所有的监测工作都要早，这表明海底保存的峡谷过程记录基本上是不完整的。海底风扇中没有现代浊积物（≤15年）被解释为由于海底电流的重新工作，生物扰动和浊积流在海底风扇上变得不受限制时的稀释。本研究强调，海底水流可以广泛地调动浊积物，导致海底扇上的浊积流记录在很大程度上不完整。因此，在使用沉积物岩心重建其重现性和沉积物动力学时需要谨慎，特别是在这种动态近岸系统中。

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引用次数: 0

Hydrothermal plume events in a 40 kyr sediment record from the flanks of the Southwest Indian Ridge 西南印度洋脊两侧40 kyr沉积物记录中的热液羽流事件

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-09-19 DOI: 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。

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引用次数: 0

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 : 2025-09-17 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