Marine Geology最新文献_第10页

The role of exposure on the vertical variation of mudflat sediment erodibility 暴露对泥滩沉积物可蚀性垂直变化的影响

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-05-14 DOI: 10.1016/j.margeo.2025.107579

Chuning Dong , Yongping Chen , Ian Townend , Yiming Wu , Zichao Guo , Qin Jiang , Giovanni Coco , Karin R. Bryan , Zeng Zhou

Variations in meteorological conditions are known to influence the erodibility of sediments on tidal flats. However, there is limited understanding of how evaporation during exposure affects the stability of mudflats. In this study, we conducted field tests spanning 5 days in January 2021 and 14 days in August 2022 in the intertidal zone along the Yancheng coast in Jiangsu Province, China. We selected critical shear stress for erosion (τ_cr) and shear strength (SS) as erosion parameters, and analyzed the variations in hydrodynamic and meteorological parameters, and vertical sediment properties. Our results indicate that bed exposure in summer significantly enhances sediment stability, an effect that extends below the surface layer and even to deeper layers. As exposure duration increases, the differences with depth become more pronounced, leading to increased variability in τ_cr. This vertical gradient increases with exposure duration and atmospheric evaporation intensity, with both the values of vertical τ_cr and SS in summer showing a nearly 2 times increase compared to that in winter. The primary controlling parameter for changes in sediment erodibility during summer exposure is water content, while in winter, the mean grain size (D50) and salinity are more significant. The causal relationship between summer and winter exposure and resistance to vertical erosion of mudflats, shown in this study, underscores the need to pay greater attention to the seasonal influence of atmospheric processes on the spatial heterogeneity of sediments that arises from tidal exposure.

众所周知，气象条件的变化会影响潮滩沉积物的可蚀性。然而，人们对暴露期间的蒸发如何影响泥滩稳定性的了解有限。在这项研究中，我们于2021年1月和2022年8月在中国江苏省盐城沿海的潮间带进行了为期5天和14天的现场试验。选取侵蚀临界剪应力τcr和抗剪强度SS作为侵蚀参数，分析了水动力、气象参数和垂直泥沙特性的变化规律。我们的研究结果表明，夏季的河床暴露显著提高了沉积物的稳定性，这种影响延伸到表层以下甚至更深的层。随着曝光时间的增加，随深度的差异变得更加明显，导致τcr的变异性增加。垂直梯度随暴露时间和大气蒸发强度的增大而增大，夏季垂直τcr和SS值均比冬季增大近2倍。夏季暴露时泥沙可蚀性变化的主要控制参数是含水量，冬季暴露时平均粒径（D50）和盐度变化更为显著。本研究表明，夏季和冬季暴露与泥滩抵抗垂直侵蚀之间的因果关系，强调需要更多地注意大气过程对潮汐暴露引起的沉积物空间异质性的季节性影响。

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引用次数: 0

Sources and transport-sedimentation processes of surficial detrital sediments in the southwest Arabian Sea: Insights from grain-size end-member component analysis 阿拉伯海西南部表层碎屑沉积物的来源和搬运-沉积过程：来自粒度端元组分分析的见解

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-05-11 DOI: 10.1016/j.margeo.2025.107578

Dongyi Li, Yonghang Xu, Jian Chen, Yunhai Li, Liang Wang

The Arabian Sea is an ideal region for exploring the sources and transport-sedimentation processes of surficial detrital sediments. Notably, grain-size end-member component (EMC) separation methods are powerful tools for this exploration. Through integration of this method with mineralogical and morphological characterization analyses, we identified four EMCs (EMC1-EMC4) suitable for the study area and elucidated the role of multiple forcings in controlling sources and transport-sedimentation processes. The findings revealed that variations in sources and diverse transport mechanisms govern the grain-size distribution patterns of surficial detrital sediments in the study area. The EMC1 ultrafine end-member is dominated by basalt weathering products from the Deccan Plateau and the west Indian Ocean, and is slightly influenced by aeolian dust from the interior of the Arabian Peninsula and northeast Africa. EMC2, EMC3, and EMC4 represent fine, coarse, and ultra-coarse fractions of aeolian dust primarily from different regions of the Arabian Peninsula, respectively. Monsoon circulation transports smectite-rich ultrafine sediments eastward across the Indian shelf, while Lower Circumpolar Deep Water (LCDW) carries them northward over long distances. Furthermore, the LCDW flows anticlockwise in the north Somali Basin, hindered by the Carlsberg Ridge, leading to the deposition of the ultrafine sediments it carries. Various wind systems interactions enable size-selective transport: fine EMCs traverse via mid-tropospheric pathways, whereas coarse EMCs are confined to the lower troposphere. The southwest monsoon facilitating the transport of fine EMC southward while impeding the transport-sedimentation of coarse EMCs.

阿拉伯海是研究表层碎屑沉积物来源和搬运-沉积过程的理想区域。值得注意的是，粒度端元组分（EMC）分离方法是这一探索的有力工具。通过将该方法与矿物学和形态学特征分析相结合，我们确定了适合研究区域的4种EMCs (EMC1-EMC4)，并阐明了多种强迫在控制物源和运输-沉积过程中的作用。研究结果表明，研究区表层碎屑沉积物的来源变化和不同的输运机制决定了其粒度分布格局。EMC1超细端元以来自德干高原和西印度洋的玄武岩风化产物为主，受阿拉伯半岛内部和非洲东北部风沙的影响较小。EMC2、EMC3和EMC4分别代表主要来自阿拉伯半岛不同地区的细粒、粗粒和超粗粒风沙组分。季风环流将富含蒙脱石的超细沉积物向东穿过印度陆架，而环极深水（LCDW）则将它们向北长距离输送。此外，LCDW在索马里盆地北部逆时针流动，受到嘉士伯山脊的阻碍，导致其携带的超细沉积物沉积。各种风系统的相互作用使大小选择性输送成为可能：细EMCs通过对流层中层路径穿越，而粗EMCs则局限于对流层下层。西南季风有利于细粒状电磁干扰南移，阻碍粗粒状电磁干扰南移沉降。

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引用次数: 0

Submerged bedrock shore platforms, Orkney Islands, UK: A new record of significant, though chronologically uncertain sea-level change and coastal erosion 淹没的基岩海岸平台，奥克尼群岛，英国：一个重要的新记录，尽管在年代上不确定海平面变化和海岸侵蚀

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-05-08 DOI: 10.1016/j.margeo.2025.107577

Dayton Dove , Tom Bradwell , Natasha L.M. Barlow

Reconstructions of sea level change in NW Europe are primarily based on records of relative sea level (RSL) recovered from terrestrial environments, above modern sea level. This deficit in marine-based records results from the highly limited number of sea level indicators observed in modern submarine settings, as well as the often-limited absolute chronology information available. This sampling bias introduces significant uncertainty in former RSL predictions, negatively impacting efforts to accurately model ice-sheet histories and isostatic response. Here we present new seabed mapping data (i.e. high-resolution multibeam bathymetry) from northern Scotland to address this data gap. Encircling the Orkney Islands we identify an exceptional sequence of submerged terraces ranging from -5 to -95 m below modern sea level, carved in bedrock. We interpret these bedrock terraces as relict shore platforms, based on their spatial distribution and a range of geomorphological characteristics. Shore platform development was linked to contemporaneous landward coastline erosion and cliff formation, and each landform pair (i.e. terrace = shore platform and accompanying seacliff / escarpment) likely represents a single sea-level stillstand event of considerable duration (possibly millennia). These wide and well-preserved shore platforms attest to formation during multiple, separate periods of RSL stillstand, and we estimate that 5–7 RSL stillstands are recorded offshore Orkney. We discuss their potential age – spanning more than the last glacial cycle (i.e. Middle - Late Pleistocene) – and explore the wider implications for Quaternary coastal erosion and sea-level change in the region. This study shows how marine geological data and geomorphological analysis can be used to identify palaeo-sea-level indicators within a glacio-isostatically complex region. Despite a current lack of absolute chronological constraint, we believe these observations may provide crucial information towards understanding sea level change within the NW European region.

欧洲西北部海平面变化的重建主要基于从现代海平面以上的陆地环境中恢复的相对海平面（RSL）记录。这种海洋记录的不足是由于在现代潜艇环境中观测到的海平面指标数量非常有限，以及通常有限的绝对年代学资料。这种抽样偏差给以前的RSL预测带来了很大的不确定性，对准确模拟冰盖历史和均衡响应的努力产生了负面影响。在这里，我们提出了来自苏格兰北部的新的海底测绘数据（即高分辨率多波束测深），以解决这一数据差距。围绕奥克尼群岛，我们确定了一个特殊的淹没梯田序列，范围从现代海平面以下-5到-95米，雕刻在基岩上。根据其空间分布和一系列地貌特征，我们将这些基岩阶地解释为遗留的海岸平台。海岸平台的发展与同期的陆地海岸线侵蚀和悬崖形成有关，每个地貌对（即阶地=海岸平台和伴随的海崖/悬崖）可能代表了一个相当长时间（可能是几千年）的单一海平面静止事件。这些宽阔且保存完好的海岸平台证明了在多个不同时期的RSL仍然存在，我们估计在奥克尼近海记录了5-7个RSL仍然存在。我们讨论了它们的潜在年龄-跨越超过最后一个冰期旋回（即中-晚更新世）-并探索了该地区第四纪海岸侵蚀和海平面变化的更广泛含义。这项研究显示了如何利用海洋地质数据和地貌分析来确定冰川-均衡复杂区域内的古海平面指标。尽管目前缺乏绝对的时间限制，但我们相信这些观测结果可能为了解西北欧洲地区的海平面变化提供重要信息。

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引用次数: 0

Evidence for mixing of migrated hydrocarbons and indigenous organic matter in the Paleocene deepest core in IODP Expedition 378 Hole U1553D, Campbell Plateau, New Zealand 新西兰坎贝尔高原378孔U1553D古新世最深处运移烃与原生有机质混合的证据

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-05-07 DOI: 10.1016/j.margeo.2025.107576

Simon C. George , Lian Jiang , Blanca Ausín , Eleni Anagnostou , Ann G. Dunlea , Laurel B. Childress , Ursula Röhl , Deborah J. Thomas

International Ocean Discovery Program (IODP) Expedition 378 recovered a continuous, > 580 m thick Paleogene sedimentary sequence at Site U1553 on the Campbell Plateau, south of the South Island of New Zealand. Oil stain samples are rarely recovered during scientific ocean drilling, but one was recovered from the deepest Paleocene core in Hole U1553D (579.94 m CSF-A), associated with high amounts of methane and wet gases detected by on-board instrumentation, that led to drilling any deeper being prevented. This oil stain was analysed by gas chromatography–mass spectrometry and gas chromatography–triple quadrupole mass spectrometry, and compared with the indigenous Paleocene organic matter.

The n-alkane distribution of the oil stain sample is bimodal, suggesting mixing of a thermogenic migrated oil with a signal from the indigenous Paleocene sediments. This is confirmed by the ≥C₂₇ hopanoid and steroid biomarkers in the oil stain sample which are very similar to the immature Unit Vb early Paleocene sediments, including the presence of neohop-13(18)-enes, ββ hopanes, and βαα steranes. The C₁₀–C₂₀ aromatic compound distributions are in the molecular weight range where there is a mixed signal. The migrated thermogenic oil and gas were derived from a marine source rock containing a significant contribution from terrigenous and probably coniferous organic matter, deposited in a dysoxic depositional environment. Vertical migration of thermogenic oil and gas penetrated the early Paleocene sediments, but did not reach into the Eocene section due a significant permeability barrier associated with a middle–late Paleocene unconformity. Deeper drilling and geophysical investigation are required to understand the putative Cretaceous or older strata in this region.

国际海洋发现计划（IODP）的378号探险队发现了一个连续的，>；新西兰南岛南部坎贝尔高原U1553遗址上580米厚的古近系沉积层。在科学海洋钻探过程中很少回收油渍样本，但在U1553D孔（579.94 m CSF-A）最深的古新世岩心中回收了一个油渍样本，与船上仪器检测到的大量甲烷和湿气有关，导致钻探更深的钻探被阻止。采用气相色谱-质谱联用、气相色谱-三重四极杆质谱联用对油样进行了分析，并与当地古新世有机质进行了对比。油渍样品的正构烷烃分布呈双峰型，表明热源运移油与古新世原生沉积物的信号混合。油斑样品中的≥C27类藿烷和甾类生物标志物与早古新世未成熟的Vb单元沉积物非常相似，包括新藿烷-13(18)-烯、ββ藿烷和βαα甾烷的存在，证实了这一点。C10-C20芳香族化合物分布在分子量范围内，存在混合信号。运移的热生油气来自海相烃源岩，其中陆源有机质占很大比重，可能有针叶有机质，沉积于欠氧沉积环境。热生油气垂直运移穿透了早古新世沉积层，但由于中晚古新世不整合相关的显著渗透率障碍，未进入始新世剖面。需要进行更深入的钻探和地球物理调查，以了解该地区假定的白垩纪或更古老的地层。

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引用次数: 0

Morphology and Holocene activity of a high-latitude Canyon – Channel system: The proximal Lofoten Basin channel system (Norwegian Sea) 高纬度峡谷-水道系统的形态与全新世活动：挪威海罗弗敦盆地近端水道系统

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-30 DOI: 10.1016/j.margeo.2025.107574

Hilde B. Amundsen , Jan Sverre Laberg, Daniel H. Wiberg , Tom Arne Rydningen, Amando P.E. Lasabuda , Stine Bjordal-Olsen, Matthias Forwick

Canyon – channel systems have the potential to be biological and marine litter “hotspots”, and they can act as important carbon sinks. However, knowledge about the modern (Holocene) activity of many of these systems remains poor. This includes the high-latitude Andøya Canyon - Lofoten Basin Channel located in the Norwegian Sea (∼69^oN). This study focuses on the proximal Lofoten Basin Channel and associated deposits (the Andøya Canyon is previously reported). The Lofoten Basin Channel includes two channel branches representing the canyon continuation beyond the foot of the continental slope, terminating in an area resembling a braidplain including braided channels, bars, as well as MTDs. Sediment cores included sandy turbidites. Based on their age and Ca/Fe ratios, we infer that the youngest sandy turbidites were deposited during the same event, suggesting that the event covered an area of c. 120 km × 20 km. Assuming an average thickness of ∼10 cm, this result in a volume of ∼0,24 km³ of terrigenous sand deposited in the basin over an area of ∼2400 km² sometime during the period from 3.7 to 2.4 kyrs BP. This equals a sand thickness of 4.8 m in the c. 50 km long and 1 km wide thalweg part of the Andøya Canyon, here considered to be the source area. The sand could derive from failure of sandy accumulations within the canyon and/or from sand piracy. Another aspect of this Holocene turbidite event is that it represented a substantial export of inorganic carbon into the deep sea which in this way got buried, representing a carbon sink removing carbon from the carbon cycle (a carbon draw-down effect). These results shows that the canyon is a potential source and route for sediments that may cover ∼2400 km² of the sea floor, large deep-sea areas that also represent carbon sinks so far not well accounted for.

峡谷-水道系统有可能成为生物和海洋垃圾的“热点”，它们可以作为重要的碳汇。然而，关于这些系统的现代（全新世）活动的知识仍然很贫乏。这包括位于挪威海（~ 69oN）的高纬度Andøya峡谷-罗弗敦盆地海峡。本研究的重点是罗浮敦盆地近端水道及其伴生矿床（先前报道了Andøya峡谷）。罗浮敦盆地海峡包括两个分支，代表了大陆斜坡脚下以外的峡谷延伸，终止于一个类似辫状平原的区域，包括辫状海峡、沙洲和mtd。沉积物岩心包括砂质浊积岩。根据它们的年龄和Ca/Fe比值，我们推断最年轻的砂质浊积岩是在同一事件中沉积的，表明该事件覆盖面积约为120 km × 20 km。假设平均厚度为~ 10 cm，这导致在3.7至2.4 kyrs BP的某个时间内，在盆地约2400 km2的面积上沉积了约0.24 km3的陆源砂。这相当于在50公里长、1公里宽的Andøya峡谷中部的4.8米厚的沙子，这里被认为是源区。这些沙子可能来自于峡谷内的沙质堆积的破坏和/或沙的掠夺。全新世浊积岩事件的另一个方面是，它代表了大量无机碳出口到深海，这些无机碳以这种方式被埋藏，代表了碳汇从碳循环中去除碳（碳下降效应）。这些结果表明，峡谷是沉积物的潜在来源和路径，可能覆盖约2400平方公里的海底，大型深海区域也代表碳汇，迄今尚未得到很好的解释。

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引用次数: 0

Testing spatial interpolation methods for deep-time organic carbon burial in epicontinental seas by taking Sunda Shelf as an example 以巽他陆架为例，对陆表海深时间有机碳埋藏空间插值方法进行了验证

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-25 DOI: 10.1016/j.margeo.2025.107566

Yida Yang , Pengfei Ma , Xiumian Hu , Yuan Gao , Chengshan Wang

Quantifying the burial of organic carbon (OC) in epicontinental seas is crucial for understanding its role in regulating global long-term carbon cycle and climate. Utilizing spatial interpolation methods, prior works have quantified OC burial globally or regionally based on limited, unevenly distributed measurements. However, there remains a notable lack of comparative studies and assessments regarding their applicability and uncertainty in deep-time research. Taking the middle Miocene Sunda Shelf OC burial estimation as an example, four popular spatial interpolation methods are assessed quantitatively and qualitatively, including Thiessen polygons, Inverse Distance Weighting (IDW), Ordinary Kriging (OK) and Random Forests (RF). Based on quantitative and qualitative evaluation, the data-driven RF method demonstrates superior performance due to fewer assumptions, effectively capturing nonlinear relationships and complex spatial patterns in heterogeneous, non-Gaussian deep-time data, and demonstrating strong generalizability and robustness. High-resolution RF-based reassessment reveals significant spatial-temporal heterogeneity of OC burial on the Sunda Shelf between the Miocene Climatic Optimum (MCO) and Middle Miocene Climate Transition (MMCT). Although the overall OC burial and sediment accumulation rates (SAR) increase during the MMCT, notable spatial discrepancies emerge, with OC burial rates elevated near basin margins but decreased in distal regions. These variations primarily reflect the combined influences of eustatic sea-level fall and enhanced terrigenous input, highlighting the complex interplay of factors modulating OC burial efficiency. Machine learning methods such as RF prove highly effective in handling deep-time spatial data, but their application should be adapted to specific objectives, geological conditions, and data characteristics.

陆表海洋有机碳埋藏量的量化对于理解其在全球长期碳循环和气候调节中的作用至关重要。利用空间插值方法，以前的工作是基于有限的、不均匀分布的测量来量化全球或区域的碳埋藏。然而，对于它们在深度时间研究中的适用性和不确定性，目前还缺乏比较研究和评估。以中新世中巽他陆架OC埋藏估算为例，定量和定性地评价了四种常用的空间插值方法：Thiessen多边形、逆距离加权（IDW）、普通克里格（OK）和随机森林（RF）。基于定量和定性评价，数据驱动射频方法由于较少的假设，能够有效捕获异构非高斯深度时间数据中的非线性关系和复杂空间模式，并且具有较强的泛化性和鲁棒性。基于高分辨率rf的重新评估揭示了中新世气候最佳期（MCO）和中中新世气候过渡期（MMCT）之间巽他陆架OC埋藏的时空异质性。在MMCT期间，尽管总体的OC埋藏率和沉积物堆积率（SAR）增加，但存在显著的空间差异，盆地边缘附近的OC埋藏率升高，而远端区域的OC埋藏率降低。这些变化主要反映了海平面上升和陆源输入增强的综合影响，突出了调节OC埋藏效率的因素的复杂相互作用。像RF这样的机器学习方法在处理深时空间数据方面被证明是非常有效的，但它们的应用应该适应特定的目标、地质条件和数据特征。

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引用次数: 0

Longitudinal transport of net suspended sediment in the river-dominated Modaomen Estuary of the Pearl River: Effects of river, tide, and mouth bar 珠江口磨道门净悬沙纵向输移：河流、潮汐和河口坝的影响

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-24 DOI: 10.1016/j.margeo.2025.107575

Xinran Li , Feng Liu , Hao Zou , Chao Tan , Jie Huang , Sihao Mo , Haiwei Li , Rongyao Xie , Heng Wang

The suspended sediment dynamics in estuaries are strongly affected by the interaction of rivers, tides, and morphological factors. However, little is known about the combined impact of these driving factors on longitudinal net sediment transport. A field investigation of current velocity, salinity, and suspended sediment concentration (SSC) was conducted in the Modaomen Estuary of the Pearl River. Hydrological data were simultaneously measured at three mooring stations in the longitudinal direction on July 31, and August 8, 2017, covering a neap tide and a spring tide. Net suspended sediment transport patterns were also analyzed. Current velocity, SSC, and salinity exhibited spatial and temporal variations during the spring–neap tides. Seaward net sediment transport was dominant during the observation period and, vertically, double patterns of net sediment transport inside and outside the mouth bar appeared to occur in the longitudinal profile. The net sediment flux can be divided into three major components—advection sediment transport, tidal-pumping, and vertical circulation. Of these, seaward sediment advection was the dominant component, which generally conformed to the dynamic characteristics in a river-dominated estuary. Salinity intrusion into the bottom layer caused stratification, inhibited vertical diffusion, and enhanced sediment settling, resulting in an elevated SSC in the bottom layer at the mouth bar. Eulerian residual flow primarily contributed to the seaward advection transport. Tidal asymmetries during the ebb–flood tidal cycle enhanced tidal-pumping sediment transport, and the main driving factor, SSC asymmetry, corresponded well with sediment flux. The mouth bar exerted a significant morphological effect on salinity intrusion and promoted longitudinal estuarine circulation, thus affecting longitudinal sediment transport. Our results contribute to a better understanding of the underlying mechanism of suspended sediment transport in complex dynamic environments as well as the feedback between the hydrodynamic structure and morphology in estuaries, facilitating the development of evidence-based guidelines for estuarine and coastal engineering and management.

河口悬沙动力学受河流、潮汐和地貌因素的相互作用的强烈影响。然而，这些驱动因素对纵向净输沙的综合影响知之甚少。在珠江口磨道门进行了流速、盐度和悬浮沙浓度（SSC）的野外调查。2017年7月31日和8月8日在三个系泊站纵向同步测量水文数据，包括小潮和大潮。同时分析了净悬沙输运模式。大潮小潮期间，海流流速、海温和盐度呈现时空变化特征。观测期间以向海净输沙为主，纵向上呈现河口坝内外双重净输沙格局。净输沙通量可分为平流输沙、潮汐抽沙和垂直环流三个主要组成部分。其中，向海沉积物平流为主导成分，基本符合河流主导型河口的动力特征。盐度侵入底层引起分层，抑制垂向扩散，增强沉积物沉降，导致河口沙洲底层SSC升高。欧拉残余流对向海平流输送起主要作用。退潮-涨潮周期的潮汐不对称增强了抽潮输沙，主要驱动因子SSC不对称与输沙通量有较好的对应关系。河口坝对盐度入侵具有显著的形态影响，促进河口纵向环流，从而影响纵向输沙。我们的研究结果有助于更好地理解复杂动力环境下悬沙运移的潜在机制，以及河口水动力结构与形态之间的反馈，促进河口和海岸工程与管理的循证指南的发展。

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引用次数: 0

Discovery of the world's largest cliff-top boulder: Initial insights and numerical simulation of its transport on a 30–40 m high cliff on Tongatapu (Tonga) 发现世界上最大的悬崖顶部巨石：在汤加30-40米高的悬崖上对其运输的初步见解和数值模拟

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-21 DOI: 10.1016/j.margeo.2025.107567

Martin Köhler , Annie Lau , Koki Nakata , Kazuhisa Goto , James Goff , Daniel Köhler , Mafoa Penisoni

This study provides the first scientific investigation of the Maka Lahi boulder, a large limestone cliff-top boulder, measuring 14 × 12 × 6.7 m and weighing approximately 1180 t, located 200 m inland at 39 m elevation on the southern coast of Tongatapu, Tonga. The boulder is one of the largest known wave-transported boulders worldwide. Fieldwork conducted in 2024 revealed its presence, geomorphic setting, and karstification features. Utilizing numerical modelling, we established that wave heights of approximately 50 m and periods of 90 s were required to transport the boulder from its cliff-edge origin, suggesting that its emplacement likely resulted from a landslide-triggered tsunami event. U/Th dating of flowstone on the surface is indicative of a minimum age of 6891 cal yr BP and contributes critical evidence of a significant early Holocene tsunami event in Tonga. Notably, this represents the earliest known Holocene tsunami in the Pacific, offering new insights into the long-term history of extreme wave events in the region. This research strengthens the understanding of megaclast transport mechanisms and their implications for coastal hazard assessments in tsunami-prone regions.

这项研究首次对Maka Lahi巨石进行了科学调查，这是一块巨大的石灰岩悬崖顶部巨石，尺寸为14 × 12 × 6.7米，重约1180吨，位于汤加汤加塔普南部海岸，海拔39米，内陆200米。这块巨石是世界上已知的最大的波浪搬运巨石之一。2024年的野外考察揭示了它的存在、地貌环境和岩溶特征。利用数值模拟，我们确定需要大约50米的波浪高度和90秒的周期才能将巨石从悬崖边缘的起源移动，这表明它的就位可能是由山体滑坡引发的海啸事件造成的。表面流石测年表明其最小年龄为6891 calyr BP，为汤加早全新世重大海啸事件提供了重要证据。值得注意的是，这代表了太平洋已知最早的全新世海啸，为该地区极端海浪事件的长期历史提供了新的见解。这项研究加强了对巨碎岩运输机制的理解及其对海啸易发地区沿海灾害评估的影响。

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引用次数: 0

A coral microatoll record of sea-level rise, interseismic deformation, and El Niño in La Union, Philippines since 1906 CE 自公元1906年以来，菲律宾La Union的海平面上升，地震间变形和El Niño的珊瑚微环礁记录

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-19 DOI: 10.1016/j.margeo.2025.107565

Gina M. Sarkawi , Aron J. Meltzner , Dongju Peng , Joanne T.Y. Lim , Xinnan Li , Rohan Gautam , Anandh Gopal , Andrew Mitchell , Loraine Faye Sarmiento , Jennifer Weil-Accardo , Kathrine V. Maxwell , Junki Komori , Noelynna T. Ramos

Relative sea level (RSL) along western Luzon is influenced by climate change, tectonic deformation, and the El Niño–Southern Oscillation. Long, high-resolution records of past changes in sea level and land level are crucial to distinguish these contributions for forecasting future RSL or identifying tectonic hazards. Coral microatolls are invaluable proxies for reconstructing RSL, but their interpretation relies on understanding how short- and long-term changes are recorded in the coral skeleton. We analyzed growth bands from 1906 to 2018 CE of a Porites microatoll from Balaoan, La Union, Philippines, using X-rays of vertical cross sections. The microatoll's surface morphology, annual banding, and growth history reveal RSL rise during its lifetime punctuated by 17 diedowns. Coral diedowns generally coincide with low water near the site, often resulting from El Niño events. Excluding eroded sections, 10 of the 11 strongest El Niños since 1918 produced a diedown. Similarly, excluding a diedown caused by the coral tilting, 10 of the 12 preserved diedowns exceeding 3 mm in amplitude occurred during strong El Niños. Between 1948 and 2018 CE, RSL rose at 1.3 ± 1.8 mm/yr (2σ). Comparing sea-level rates from satellite altimetry and RSL from the coral, we estimate vertical land motion at −0.1 ± 12.1 mm/yr between 1995 and 2018 CE. The indicative meaning at Balaoan, defined as the relationship between local water levels and the highest level of growth of a coral microatoll before its most recent diedown, is estimated at 31.5 ± 10.0 cm (2σ) above lowest astronomical tide.

吕宋岛西部相对海平面（RSL）受气候变化、构造变形和El Niño-Southern涛动的影响。长期、高分辨率的过去海平面和陆地水平变化记录对于预测未来的RSL或识别构造危险至关重要。珊瑚微环礁是重建RSL的宝贵替代品，但它们的解释依赖于对珊瑚骨架中记录的短期和长期变化的理解。我们使用垂直截面的x射线分析了菲律宾La Union Balaoan的Porites微环礁1906年至2018年的生长带。微环礁的表面形态、年带状带和生长历史显示，RSL在其一生中呈上升趋势，其间有17次衰减。珊瑚凋零通常与该地点附近的低潮同时发生，通常是由El Niño事件造成的。除去被侵蚀的部分，自1918年以来11次最强的厄尔尼诺Niños中有10次出现了减弱。同样，排除珊瑚倾斜引起的衰减，12个保存下来的振幅超过3毫米的衰减中有10个发生在强厄尔尼诺Niños期间。1948年至2018年，RSL以1.3±1.8 mm/年（2σ）的速度上升。通过比较卫星测高数据的海平面速率和珊瑚的RSL，我们估计1995年至2018年期间陆地垂直运动为−0.1±12.1毫米/年。巴罗安的指示意义是指当地水位与珊瑚微环礁最近一次消亡前的最高生长水平之间的关系，估计在最低天文潮以上31.5±10.0 cm （2σ）。

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引用次数: 0

Sediment source - sink processes in a typical tidal inlet bay system under intense human activities, Dingzi Bay, China 人类活动强烈影响下典型潮湾系统泥沙源汇过程

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-04-19 DOI: 10.1016/j.margeo.2025.107564

Yang Wang , Rijun Hu , Xiaodong Zhang , Jiandong Qiu , Naishuang Bi , Longhai Zhu , Yongchen Xu , Jingrui Li , Zhaohan Yi

Tidal inlet bays are regions of intense material and energy exchange between the land and the sea. In this study, based on surface sediment grain size, geochemistry, bathymetric topography, and 1354 satellite images from 1984 to 2022, we used numerical modeling, bathymetric comparison methods to examine the sediment transport, sediment provenance, and relative contributions in the Dingzi Bay area. It summarizes the source-sink patterns under intense human activities. Dingzi Bay is predominantly erosive, with differences in the erosion and deposition of tidal flats on both sides of the bay, characterized by erosion on the north tidal flat and deposition on the south tidal flat. The main sources of bay sediments are river sediment transport and erosion from the north coast. The south tidal flat inside the bay and the south beach outside the bay are the few sink areas in the bay. The sediment transport path in the study area is from river sediments transported into the bay, with some bay sediments being moved out of the bay with the ebb current. Eroded sediments from the north beach are transported along the coast to the bay mouth, and some sediments are moved into the bay with the flood current. Intense human activities in the river basin leading to a reduction in terrestrial sediment supply are the main cause of bay erosion, and the ebb current-dominated tidal current further exacerbates the erosion of the bay.

潮湾是海陆之间物质和能量交换强烈的区域。基于1984 - 2022年1354幅卫星影像，利用地表沉积物粒度、地球化学、水深地形等资料，采用数值模拟、水深比较法对定子湾地区沉积物输运、沉积物物源及其相对贡献进行了研究。总结了强烈人类活动下的源汇模式。鼎子湾以侵蚀为主，两岸潮滩的侵蚀和沉积存在差异，北潮滩为侵蚀，南潮滩为沉积。海湾沉积物的主要来源是北海岸的河流输沙和侵蚀。湾内南部滩涂和湾外南部滩涂是湾内为数不多的下沉区。研究区输沙路径主要为河流泥沙向湾内输沙，部分海湾泥沙随退潮向湾外输沙。北滩的侵蚀沉积物沿海岸被输送到海湾口，部分沉积物随洪流进入海湾。流域人类活动剧烈导致陆源泥沙供给减少是海湾侵蚀的主要原因，以退潮为主的潮流进一步加剧了海湾的侵蚀。

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引用次数: 0