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High-resolution geophysical data unravel the post-Variscan structural history of the NW Cotentin inner shelf (Central English Channel) 高分辨率地球物理数据揭示了西北科唐内大陆架(英吉利海峡中部)瓦利斯坎时期之后的构造历史
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-06-07 DOI: 10.1016/j.margeo.2024.107333
Tassadit Kaci , Bernard Le Gall , Anne Duperret , David Graindorge , Stephane Baize , Yann Méar

The Cotentin Peninsula (CP) is one of the only area in Europe which contains records of a > 2.5 Ga-lasted geological history including three orogenic events (Archaean, Cadomian and Variscan) followed by a polyphase basin/inversion evolution during Meso-Cenozoic times. The CP area sensu lato is thus a suitable place for discussing how the structural configuration of the basement might have influenced the development of part of the southern shelf margin of the Central English Channel, even if sediments and post-Variscan tectonic records are limited at this place. This issue is addressed through an onshore/offshore structural approach combining newly-acquired high resolution bathymetric data and reflection seismic profiles, further constrained by lateral correlations onshore. The resulting Land-Sea Digital Elevation Model and corresponding geological map reveal a number of fault-bounded blocks involving a relatively thin package of Jurassic to Plio-Quaternary sequences, locally involved in slightly compressional deformations. These specific sedimentary and tectonic features typically characterize the southern shelf margin of the Central English Channel. They are discussed in terms of basin development and inversion processes in relation with basement structures and then integrated in the English Channel basin framework. Special attention is paid to three major structural features, i.e. the La Hague Offshore Fault, the La Hague Deep Fault network and the La Hague Deep, which emphasize, respectively, the role of structural inheritance and erosion/incision/deposition events during the post-Variscan tectono-sedimentary history of the southern elevated shoulder of the Central English Channel.

科唐坦半岛(CP)是欧洲唯一一个记录了长达 2.5 千兆年地质历史的地区,包括三次造山运动(太古宙、卡多米宙和瓦里斯坎宙),以及中新生代时期的多相盆地/倒转演化。因此,尽管沉积物和瓦利斯坎时期之后的构造记录在这里非常有限,但 CP 地区是讨论基底构造如何影响英吉利海峡中部南部陆架边缘发展的合适地点。我们采用陆上/近海结构方法,结合新获得的高分辨率测深数据和反射地震剖面图,并通过陆上横向关联进一步约束,解决了这一问题。由此产生的陆海数字高程模型和相应的地质图揭示了一些以断层为边界的区块,涉及相对较薄的侏罗纪至第四纪上新统序列,局部涉及轻微的压缩变形。这些特定的沉积和构造特征是英吉利海峡中部南部大陆架边缘的典型特征。本文从海盆发育和反转过程的角度,结合基底构造对其进行了讨论,然后将其纳入英吉利海峡海盆框架。特别关注了三个主要的构造特征,即拉海牙近海断层、拉海牙深海断层网和拉海牙深海,它们分别强调了构造继承和侵蚀/冲积/沉积事件在英吉利海峡中部南部隆起的肩部后瓦利斯坎构造沉积历史中的作用。
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引用次数: 0
New chronology for submerged relict paleoshorelines and associated rates of crustal vertical movements offshore the Marzamemi village, Sicily (Southern Italy) 意大利南部西西里岛马尔扎梅米村近海水下遗迹古海岸线的新年代学及相关地壳垂直运动速率
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-31 DOI: 10.1016/j.margeo.2024.107326
Andrea Giulia Varzi , Marco Meschis , Luca Fallati , Giovanni Scicchitano , Vincenzo De Santis , Giovanni Scardino , Daniela Basso , Valentina Alice Bracchi , Alessandra Savini

We investigated the Late Pleistocene-Holocene crustal vertical movements off the coast of Marzamemi village in SE Sicily, Italy. By using a Synchronous Correlation Approach (SCA), we analysed terraced landforms that characterize a submerged sector within one of Southern Italy's most seismically active regions. In this area, the emerging portion of the NE-SW oriented bulge of the African foreland structurally shapes the coastal and marine regions off Marzamemi village.

Based on a newly created 17 km2 high-resolution bathymetric map generated from a Multibeam Echosounder (MBES) survey conducted in June 2021, we identified and examined four main paleo-shorelines identifying four submerged terraces. Terraced landforms play a crucial role in reconstructing Quaternary glacial and interglacial stages, offering insights into associated sea level fluctuations. Through the application of the SCA, our goal is to refine the chronology of these recently mapped and submerged marine terraces off the Marzamemi village, thereby contributing to the calculation of associated rates of crustal vertical movements. We demonstrate that these rates persist constantly throughout the Late Pleistocene-Holocene epoch, suggesting overall tectonic stability, with a slight and likely local fault-related subsidence. We explore a few chronology scenarios, raising questions about whether these submerged marine terraces are indeed recording the Late Pleistocene-Holocene limit or not. This research contributes to a better understanding of the geological dynamics in this region and sheds light on the potential factors influencing coastal landscape development over time.

我们研究了意大利西西里岛东南部 Marzamemi 村沿海的晚更新世-全新世地壳垂直运动。通过使用同步相关方法(SCA),我们分析了意大利南部地震最活跃地区之一淹没区的阶地地貌特征。根据 2021 年 6 月进行的多波束回声测深仪(MBES)勘测新绘制的 17 平方公里高分辨率测深图,我们确定并研究了四条主要的古海岸线,确定了四个水下阶地。阶地地貌在重建第四纪冰川和间冰期方面发挥着至关重要的作用,有助于深入了解相关的海平面波动。通过应用 SCA,我们的目标是完善 Marzamemi 村外最近绘制和淹没的这些海洋阶地的年代学,从而有助于计算相关的地壳垂直运动速率。我们证明,这些速率在整个晚更新世-全新世时期持续存在,表明总体构造稳定,但局部可能有轻微的与断层有关的下沉。我们探讨了几种年代学方案,提出了这些淹没的海洋阶地是否确实记录了晚更新世-全新世界限的问题。这项研究有助于更好地了解该地区的地质动态,并揭示了影响海岸景观随时间发展的潜在因素。
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引用次数: 0
Daily timescale analysis of sediment transport and topographic changes on a mesotidal sandy beach under low to moderate wave conditions 中低浪条件下潮间带沙滩沉积物迁移和地形变化的日时间尺度分析
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-27 DOI: 10.1016/j.margeo.2024.107323
Isaac Rodríguez-Padilla , Ismael Mariño-Tapia , Amaia Ruiz de Alegría-Arzaburu

Understanding sediment transport processes on natural sandy beaches is essential for gaining insights into beach recovery and making effective coastal management decisions. This study examines surfzone sediment transport rates related to beachface morphological variations on an embayed mesotidal sandy beach located on the northwestern coast of the Baja California Peninsula in Mexico. Data were collected during a week-long field experiment conducted in June 2016 under low-to-moderate wave energy conditions (Hs=0.41.3m). Daily topographical surveys and continuous measurements of near-bottom suspended sediment fluxes were conducted alongside the application of an extended energetics-based model that accounted for velocity and acceleration skewness. Results reveal contrasting accretionary and erosive patterns in the inner surfzone, along with consistent sediment deposition in the swash zone throughout the study period. Onshore sediment transport is found to be related to short-period calm wave conditions (Hs<0.7 m; Tp<10 s) and a weak undertow (<0.2 ms−1). Alongshore nonuniform wave breaking, influenced by irregular bathymetry and moderate-energetic oblique waves from the northwest, contributes to an alongshore gradient in sediment transport rate, leading to erosion in the northern part of the intertidal beach and accretion in the southern part. Suspended sediment flux measurements at 0.2 m above the bed suggest offshore mean transport predominates over oscillatory transport throughout the field experiment. Nevertheless, this observation should be interpreted with caution, as the flux is not vertically integrated across the water column and does not consider fluid acceleration. The model predictions effectively replicate sediment transport rates and consequent volumetric changes (Accuracy = 55–63%; RMSE = 44–69 m3; Bias=2 to −61 m3), although they underestimate observed accretion by a factor of three and overestimate erosion by a factor of two. Overall, this research highlights the complexities of natural sandy beach recovery processes in mesotidal environments and emphasizes the importance of considering both cross-shore and longshore components in sediment transport assessments.

了解天然沙滩的沉积物运移过程,对于深入了解沙滩恢复和做出有效的海岸管理决策 至关重要。本研究考察了位于墨西哥下加利福尼亚半岛西北海岸的一个筑堤潮间带沙滩上与滩面形态变化有关的表层沉积物迁移率。数据是在 2016 年 6 月进行的为期一周的实地实验中收集的,实验条件为中低浪能(Hs=0.4-1.3 米)。在进行每日地形勘测和近底悬浮沉积通量连续测量的同时,还应用了基于能量学的扩展模型,该模型考虑了速度和加速度偏度。研究结果表明,在整个研究期间,内冲浪区的吸积和侵蚀模式截然不同,而斜冲区的沉积物沉积则始终如一。研究发现,沿岸沉积物迁移与短周期平静波浪条件(Hs<0.7 m; Tp<10s)和微弱暗流(<0.2 ms-1)有关。受不规则水深和来自西北方向的中等能量斜波的影响,沿岸的不均匀破浪造成了沉积物迁移率的沿岸梯度,导致潮间带海滩北部的侵蚀和南部的增生。海床上方 0.2 米处的悬浮泥沙通量测量结果表明,在整个现场实验过程中,离岸平均运移比振荡运移更占优势。尽管如此,由于通量没有在整个水体中进行垂直整合,也没有考虑流体加速度,因此在解释这一观测结果时应谨慎。模型预测有效地复制了沉积物运移速率和随之而来的体积变化(准确率 = 55-63%;均方根误差 = 44-69 立方米;偏差 =-2 至 -61 立方米),尽管模型预测低估了观测到的增殖量三倍,高估了侵蚀量两倍。总之,这项研究强调了潮间带环境中天然沙滩恢复过程的复杂性,并强调了在沉积物运移评估中同时考虑跨岸和长岸部分的重要性。
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引用次数: 0
High-resolution seismic record of the Quaternary palaeoenvironments along a Dalmatian-type coast (Lošinj Channel, Adriatic Sea) 沿达尔马提亚型海岸(亚得里亚海,洛希尼海峡)第四纪古环境的高分辨率地震记录
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-25 DOI: 10.1016/j.margeo.2024.107325
Dea Brunović , Ozren Hasan , Slobodan Miko , Nikos Georgiou , Maria Geraga , Dimitris Christodoulou , Xenofon Dimas , Nikolina Ilijanić , George Papatheodorou

Coastal systems have changed considerably in response to Quaternary glacial–interglacial variability. Here, we offer the first detailed assessment of geomorphic features and late Quaternary sedimentation dynamics in the Lošinj Channel in the Adriatic Sea. The present study attempts to resolve the complex evolution of the environments by applying high-resolution seismic records that build upon sediment core data. Within this coastal karst basin, a significant amount of sediment accumulated during the Quaternary. Notably, the existence of several prominent erosional and depositional environments was revealed. We distinguished recurrent episodes of fluvio-lacustrine and marine sedimentation that probably occurred since Marine Isotope Stage (MIS) 6. The preserved record consists of erosional features and subparallel and oblique reflectors attributed to glacial periods (Seismic Units SU-II, SU-IV, and SU-V). Interglacial units are acoustically semitransparent and generally reflection-free (Seismic Units SU-I and SU-III). The mutual influence of sea level and climate change, sill depth, and karst hydrology enabled environmental changes in the Lošinj Channel. The area proves to be important for Quaternary studies because it contains a long sediment succession spanning at least the middle and late Pleistocene and Holocene. Our study has implications for the assessment of the long-term palaeoenvironmental evolution of similar coastal settings and reconstruction of the regional palaeogeography which is in turn crucial for understanding prehistoric human occupation and/or dispersal. This is one of the few well-preserved records in the Adriatic Sea that provides insight into submerged landscapes and sea levels since the penultimate glacial.

沿海系统因第四纪冰川-间冰期的变化而发生了巨大变化。在此,我们首次对亚得里亚海洛希尼海峡的地貌特征和第四纪晚期沉积动力学进行了详细评估。本研究试图在沉积岩芯数据的基础上,利用高分辨率地震记录来解析复杂的环境演变。在这个沿海岩溶盆地内,第四纪期间积累了大量沉积物。值得注意的是,我们发现了几种突出的侵蚀和沉积环境。我们区分了可能自海洋同位素阶段(MIS)6 以来反复出现的河流-湖泊沉积和海洋沉积。保存下来的记录包括冰川期的侵蚀特征和近平行及斜反射体(地震单元 SU-II、SU-IV 和 SU-V)。间冰期单元在声学上是半透明的,一般没有反射(地震单元 SU-I 和 SU-III)。海平面和气候变化、岩屑深度和岩溶水文的相互影响促成了 Lošinj 海峡的环境变化。事实证明,该地区对第四纪研究非常重要,因为它包含至少跨越中更新世和晚更新世以及全新世的漫长沉积物演替。我们的研究对评估类似海岸环境的长期古环境演变和重建区域古地理学具有重要意义,而区域古地理学又对了解史前人类的占领和/或迁移至关重要。这是亚得里亚海为数不多的保存完好的记录之一,有助于深入了解自倒数第二个冰期以来的水下地貌和海平面。
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引用次数: 0
The application of carbonate and sediment budgets to assess the stability of marginal reef systems 应用碳酸盐和沉积物预算评估边缘珊瑚礁系统的稳定性
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-23 DOI: 10.1016/j.margeo.2024.107324
Shannon Dee , Adi Zweifler , Michael Cuttler , Jake Nilsen , Joshua Bonesso , Michael O'Leary , Nicola K. Browne

Coral reefs and their associated landforms (carbonate islands and shorelines) are under increasing threat from the effects of anthropogenic climate change, including sea level rise (SLR). The ability of a reef to keep up with SLR depends on the rate of calcium carbonate accretion. Census-based carbonate budgets quantify rates of net calcium carbonate production on a reef and facilitate estimations of vertical reef accretion potential (RAP). To date, most carbonate budget studies have been undertaken in clear-water settings resulting in a limited understanding of how inshore reefs situated in more marginal environmental settings are functioning now and under future climate change. Here, we applied census-based carbonate framework across two inshore island reefs exposed to episodes of high turbidity within the Pilbara, Western Australia. Low net carbonate production (mean = 1.11 and 0.62 kg m−2 yr−1) was predominantly driven by low coral cover (<10%) and low calcification rates. Importantly, bioerosion rates were also low (<0.1 kg m−2 yr−1), maintaining positive carbonate budgetary states. Net sediment production rates were also low (mean = 0.06 kg m−2 yr−1) and were found to be mostly derived from coral, or mollusc material produced by invertivores. Calculated RAP estimates are below current and predicted rates of SLR, suggesting that these turbid reefs will soon struggle to keep up with increasing water depth and shoreline inundation.

珊瑚礁及其相关地貌(碳酸盐岛屿和海岸线)正日益受到人为气候变化影响的威胁,包括海平面上升(SLR)。珊瑚礁能否跟上海平面上升的速度取决于碳酸钙的增殖速度。基于普查的碳酸盐预算可量化珊瑚礁上碳酸钙的净生产率,并有助于估算珊瑚礁的垂直增殖潜力(RAP)。迄今为止,大多数碳酸盐预算研究都是在清水环境中进行的,因此对位于更边缘环境中的近岸珊瑚礁现在和未来气候变化下的功能了解有限。在此,我们在西澳大利亚皮尔巴拉地区暴露于高浊度事件的两个近岸岛礁上应用了基于普查的碳酸盐框架。低净碳酸盐产量(平均 = 1.11 和 0.62 kg m-2 yr-1)主要是由低珊瑚覆盖率(<10%)和低钙化率造成的。重要的是,生物侵蚀率也很低(0.1 kg m-2 yr-1),从而维持了正的碳酸盐预算状态。沉积物的净生产率也很低(平均 = 0.06 kg m-2 yr-1),且主要来自珊瑚或无脊椎动物产生的软体物质。计算得出的 RAP 估计值低于当前和预测的可持续土地退化速率,这表明这些浑浊的珊瑚礁将很快难以跟上水深增加和海岸线淹没的速度。
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引用次数: 0
Unveiling coastal dynamics: Investigating beach sediment distribution patterns along the Lithuanian Baltic Sea coast through heavy mineral analysis 揭示海岸动态:通过重矿物分析调查立陶宛波罗的海沿岸海滩沉积物的分布模式
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-23 DOI: 10.1016/j.margeo.2024.107320
Dovilė Karlonienė , Luca Caracciolo , Donatas Pupienis

Effective coastal management requires an understanding of sediment dynamics. This study examines the distribution of heavy minerals (HMs) in two distinct coastal regions: the mainland and spit, each with unique sediment deposition patterns. The spit accumulates sediment through alongshore sediment transport (AST), while the mainland experiences erosive processes and significant human impacts. The hydrodynamic behaviour and weathering resistance of HMs enables source identification. This has helped to reveal differences between the two regions, with apatite being characteristic of spit sediments and garnet of mainland beaches. Coastal processes, such as erosion, sediment transport, and accumulation, significantly shape the distribution of the HMs, with garnets dominating erosive shores and amphiboles dominating accumulative shores. Furthermore, the study found that human-made coastal infrastructure also affects the composition of HMs and the sediment distribution through AST. This research has implications beyond the local level, providing global insights into the complexities of coastal dynamics. The study emphasises the importance of using HM analysis in conjunction with grain size analysis to understand the distribution of beach sediment composition. It also highlights the significant role of coastal processes, including anthropogenic impacts such as jetty construction or deepening port entrance canals on AST.

有效的海岸管理需要了解沉积物动力学。这项研究考察了重矿物 (HMs) 在两个不同沿海地区的分布情况:大陆和海湾,每个地区都有独特的沉积物沉积模式。海湾通过沿岸沉积物输运(AST)积累沉积物,而大陆则经历侵蚀过程和巨大的人为影响。HMs 的流体力学行为和抗风化能力有助于确定来源。这有助于揭示两个地区的差异,磷灰石是海湾沉积物的特征,而石榴石则是大陆海滩的特征。侵蚀、沉积物迁移和堆积等海岸过程在很大程度上决定了 HMs 的分布,侵蚀海岸以石榴石为主,堆积海岸以闪石为主。此外,研究还发现,人造海岸基础设施也会通过 AST 影响 HMs 的组成和沉积物的分布。这项研究的意义超出了地方层面,为全球提供了有关海岸动力学复杂性的见解。该研究强调了将 HM 分析与粒度分析结合使用,以了解海滩沉积物组成分布的重要性。它还强调了沿岸过程的重要作用,包括对 AST 的人为影响,如修建码头或加深港口入口运河。
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引用次数: 0
TC activity affected the northern sea of the Shandong Peninsula over the past 1500 years and its driving mechanism 过去 1500 年影响山东半岛北部海域的 TC 活动及其驱动机制
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-22 DOI: 10.1016/j.margeo.2024.107311
Wenzhe Lyu , Tengfei Fu , Zhen Cui , Yancheng Wang , Wenquan Liu , Xingyong Xu , Hongjun Yu

Modern observational records indicate that the activity of tropical cyclone (TC) has been influenced by changes in tropical sea surface temperatures over the past century. However, due to a lack of direct observational records and the low resolution of current TC reconstructions, further investigation is needed to understand the driving factors behind TC activity. Additionally, key parameters such as TC paths and the extent of their impact remain unclear, with limited research on the characteristics of TC impacts in the northern sea of the Shandong Peninsula. In this study, we utilized sedimentary records from the muddy area to reconstruct the TC impact history in the northern sea of the Shandong Peninsula over the past 1500 years. Our reconstruction results indicate that TC activity affected the north China Sea region during the intervals 1000–1600 CE and 1850–2000 CE, TC activity showed an increasing and decreasing trend before and after 1300 CE, respectively. Research suggests that on a centennial scale, TCs affecting the northern sea of the Shandong Peninsula are mainly controlled by ENSO. A stronger ENSO led to increased TC activity in the region of genesis, resulting TC tracks shifting northward, which result in higher TC activity affected the BS.

现代观测记录表明,热带气旋(TC)的活动受到过去一个世纪热带海洋表面温度变化的影响。然而,由于缺乏直接观测记录,而且目前的热带气旋重建分辨率较低,因此需要进一步调查,以了解热带气旋活动背后的驱动因素。此外,TC路径及其影响范围等关键参数仍不清楚,对山东半岛北部海域TC影响特征的研究也很有限。在本研究中,我们利用泥质地区的沉积记录重建了山东半岛北部海域过去1500年的TC影响历史。重建结果表明,在公元1000-1600年和公元1850-2000年期间,TC活动影响了中国北部海域,TC活动在公元1300年之前和之后分别呈上升和下降趋势。研究表明,在百年尺度上,影响山东半岛北部海域的热带气旋主要受厄尔尼诺/南方涛动控制。强烈的厄尔尼诺/南方涛动导致成因区的TC活动增加,导致TC轨迹北移,从而使影响BS的TC活动增加。
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引用次数: 0
Imprints of washover sediments by tropical storm Pabuk 2019 along the coast of the Gulf of Thailand; insight into coastal geomorphological response to storm surge 热带风暴 "帕布2019 "在泰国湾沿岸造成的冲刷沉积物的印迹;对风暴潮的沿海地貌响应的深入研究
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-22 DOI: 10.1016/j.margeo.2024.107321
Chanakan Ketthong , Sumet Phantuwongraj , Montri Choowong , Vichai Chutakositkanon

Tropical storm Pabuk (4th January 2019) struck southern Thailand, causing damage to the low-lying coastal area. The combination of waves, storm surge, and high tide resulted overwash and inundation of regions on the West coast of the Gulf of Thailand (GOT) side. After the event, we conducted a field survey from January 7–10 and 15–20, 2019 to investigate the effect of storm surges and the degree of damage from the site under the eye of storm affected area up to the north 500 km from the landfall sites. This paper investigates how variations in coastal geomorphological features respond to the storm surge generated by tropical storm Pabuk at a regional scale. Coastal damage was observed along the beach from the presence of the scour, beach scarp, knocked down trees, and destroyed buildings and infrastructure. The most damaged area was at Nakhon Si Thammarat (NST), where the tropical storm made landfall with maximum wind speeds of almost 100 km/h and a storm surge height of 5 m. At NST site, the washover deposits extended as far as 80 m from the coastline with a maximum inundation of 330 m. From this study, two types of washover deposits including perched fan and washover terrace were identified. The thickest washover sediment, 60 cm thick, was discovered in a relatively low-lying area adjacent to a small estuary. Mud rip-up clasts, planar stratification, cross stratification, foreset bedding, scouring at base, and sharp and erosional contact are characteristics of sedimentary structures found in storm sediments. Bedform surfaces, such as current ripples with indicated storm surge direction, were well-preserved at several sites. We suggest that the local geomorphological controlling factors, especially coastal elevation have played important roles in the difference of coastal geomorphological responses as well as the type of washover deposits.

热带风暴帕布(2019 年 1 月 4 日)袭击了泰国南部,对低洼沿海地区造成了破坏。海浪、风暴潮和高潮的共同作用导致泰国湾(GOT)西海岸一侧的地区被冲刷和淹没。事件发生后,我们于 2019 年 1 月 7-10 日和 15-20 日进行了实地调查,以调查风暴潮的影响以及从风暴眼下的受灾地区到距离登陆点以北 500 公里的受灾程度。本文研究了沿海地貌特征的变化如何在区域范围内对热带风暴帕布所产生的风暴潮做出反应。在海滩沿岸观察到了冲刷、海滩疤痕、被撞倒的树木以及被摧毁的建筑物和基础设施造成的海岸破坏。受破坏最严重的地区位于那空沙马拉府(Nakhon Si Thammarat,NST),热带风暴登陆时的最大风速接近 100 公里/小时,风暴潮高度达 5 米。最厚的冲积沉积物(60 厘米厚)是在一个小河口附近相对低洼的地区发现的。泥质裂隙碎屑、平面分层、交叉分层、前置层理、底部冲刷、尖锐和侵蚀接触是风暴沉积物中沉积结构的特征。在一些地点,床形表面(如显示风暴潮方向的水流波纹)保存完好。我们认为,当地的地貌控制因素,特别是海岸高程,对沿岸地貌反应的差异以及冲刷沉积物的类型起了重要作用。
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引用次数: 0
Molecular and radiocarbon constraints on the fate of sedimentary organic carbon in a human-impacted river-dominated ocean margin 受人类影响的以河流为主的海洋边缘沉积有机碳命运的分子和放射性碳制约因素
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-22 DOI: 10.1016/j.margeo.2024.107322
Chenglong Wang , Chuchu Zhang , Zhuoyue Zhang , Qihang Liao , Yang Zhang , Ning Wang , Yaping Wang , Xinqing Zou

Organic carbon (OC) burial in river-dominated ocean margins plays a pivotal role in the global carbon cycle, impacting atmospheric CO2 levels over the long term. Despite its significance, uncertainties persist regarding the influence of external environmental factors and intrinsic properties on sedimentary OC. In this study, we conducted a comprehensive analysis of surface sediments from the East China Sea, examining geochemical properties (including total OC content [TOC], Δ14C, δ13C, and C/N ratio), terrestrial biomarkers (n-alkanes), and mineral properties (such as specific surface area, Al/Si ratio, and mineral composition). Our aim was to shed light on the fate of sedimentary OC.

The surface sediment's Δ14C values displayed significant spatial heterogeneity, delineating four distinct sub-regions. Strong positive correlations (all p < 0.01) were found between the ∆14C values and fine-grained sediments, specific surface area, and clay minerals, suggesting the potentially pivotal role of mineral protection in shaping the fate of sedimentary OC. The proportion of terrestrial OC gradually decreased towards the south, while marine OC proportion increased, corresponding to the enrichment of Δ14C. The co-variation of Δ14C values, mineral properties, and OC source proportions suggests that terrestrial OC may undergo progressive replacement by marine OC during southward transport. Temporal variations in ∆14C values indicated that seabed erosion led to a significant increase in ∆14C values (p < 0.01) in the coastal mud belt, a phenomenon likely common in river-dominated ocean margins globally due to the new sediment cycle during the Anthropocene.

有机碳(OC)埋藏在以河流为主的海洋边缘地区,在全球碳循环中发挥着关键作用,长期影响着大气中的二氧化碳水平。尽管其意义重大,但外部环境因素和内在特性对沉积 OC 的影响仍存在不确定性。在本研究中,我们对东海表层沉积物进行了全面分析,考察了地球化学性质(包括总 OC 含量 [TOC]、Δ14C、Δ13C 和 C/N 比值)、陆地生物标志物(正烷烃)和矿物性质(如比表面积、铝/硅比和矿物组成)。表层沉积物的Δ14C值显示出显著的空间异质性,划分出四个不同的子区域。Δ14C值与细粒沉积物、比表面积和粘土矿物之间存在很强的正相关性(均为p <0.01),表明矿物保护在影响沉积OC命运方面可能起着关键作用。陆相 OC 的比例向南逐渐降低,而海洋 OC 的比例则逐渐升高,与 Δ14C 的富集相对应。Δ14C值、矿物性质和OC来源比例的共同变化表明,陆相OC在向南迁移的过程中可能逐渐被海相OC所取代。Δ14C值的时间变化表明,海床侵蚀导致沿岸泥带的Δ14C值显著增加(p < 0.01),由于人类世期间新的沉积物循环,这种现象可能在全球以河流为主的海洋边缘地区普遍存在。
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引用次数: 0
Sediment dynamics on a subtidal reef flat of an atoll in the South China Sea 中国南海环礁潮下礁盘的沉积动力学
IF 2.9 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2024-05-21 DOI: 10.1016/j.margeo.2024.107310
Jin Li , Andrew D. Ashton , Ya Ping Wang , Xiaomei Xu , Shu Gao

Atolls in the South China Sea comprise 15% of the world's total in area. In contrast to most reef flats in the Indo-Pacific region, which typically develop up to contemporary sea level, a significant portion of their reef flats in the South China Sea are inundated at depths of 5–20 m. To gain insights into modern processes and determine whether these subtidal reef flats are actively shaped by hydrodynamics, we carried out an in situ observation on a 12 m-deep southwest-facing reef flat over a period of 8 months. The measurements revealed a prevalence of seasonally varying waves and stable tidal currents. While the reef flat remained sheltered from the northeast monsoon (January–May), the southwest monsoon (June–September) led to prolonged reef exposure to substantial waves (mean significant wave height of 1.3 m, with an orbital velocity of 0.22 m/s on average). Such an exposure resulted in the formation of mobile bed ripples and entrainment of coarse-grained coral sands. Estimates of potential bedload transport rate indicated that the combined action of waves and currents caused material loss from the reef flat, with movement into the lagoon or down the fore-reef slope of the atoll. This sediment loss was equivalent to reef bed erosion of up to 28 mm during the observation period. As these potential losses may be compensated by coral reef growth, our measurements implied that modern sediment budgeting has played a significant role in the maintenance of subtidal reef flats, in terms of bed elevation. Hence, the deep reef flat does not necessarily belong to the previously identified give-up pattern; a balance of coral sediment supply and transport-induced loss may result in an equilibrium morphology, or a “lock-up” pattern.

中国南海的环礁面积占世界总面积的 15%。印度洋-太平洋地区的大多数礁滩通常发育到当代海平面,与此不同的是,中国南海的礁滩有相当一部分淹没在 5-20 米深处。为了深入了解现代过程,确定这些潮下礁滩是否由水动力积极塑造,我们对一个 12 米深的西南向礁滩进行了为期 8 个月的现场观测。测量结果表明,海浪的季节性变化和稳定的潮汐流十分普遍。东北季风(1 月至 5 月)对礁石平地的影响不大,而西南季风(6 月至 9 月)则使礁石长期暴露在大浪中(平均显著波高 1.3 米,平均轨道速度 0.22 米/秒)。这种暴露导致形成移动的海床波纹和粗粒珊瑚沙的夹带。对潜在床面负载迁移率的估算表明,海浪和海流的共同作用导致礁石平地的物质流失,进入环礁湖或沿着环礁的前礁斜坡向下移动。在观测期间,这种沉积物损失相当于礁床被侵蚀 28 毫米。由于这些潜在的损失可能会被珊瑚礁的生长所补偿,我们的测量结果表明,就礁床海拔而言,现代沉积物预算在潮下礁坪的维护方面发挥了重要作用。因此,深礁平地并不一定属于先前确定的放弃模式;珊瑚沉积物的供应和运输引起的流失之间的平衡可能会导致一种平衡形态,或一种 "锁定 "模式。
{"title":"Sediment dynamics on a subtidal reef flat of an atoll in the South China Sea","authors":"Jin Li ,&nbsp;Andrew D. Ashton ,&nbsp;Ya Ping Wang ,&nbsp;Xiaomei Xu ,&nbsp;Shu Gao","doi":"10.1016/j.margeo.2024.107310","DOIUrl":"https://doi.org/10.1016/j.margeo.2024.107310","url":null,"abstract":"<div><p>Atolls in the South China Sea comprise 15% of the world's total in area. In contrast to most reef flats in the Indo-Pacific region, which typically develop up to contemporary sea level, a significant portion of their reef flats in the South China Sea are inundated at depths of 5–20 m. To gain insights into modern processes and determine whether these subtidal reef flats are actively shaped by hydrodynamics, we carried out an in situ observation on a 12 m-deep southwest-facing reef flat over a period of 8 months. The measurements revealed a prevalence of seasonally varying waves and stable tidal currents. While the reef flat remained sheltered from the northeast monsoon (January–May), the southwest monsoon (June–September) led to prolonged reef exposure to substantial waves (mean significant wave height of 1.3 m, with an orbital velocity of 0.22 m/s on average). Such an exposure resulted in the formation of mobile bed ripples and entrainment of coarse-grained coral sands. Estimates of potential bedload transport rate indicated that the combined action of waves and currents caused material loss from the reef flat, with movement into the lagoon or down the fore-reef slope of the atoll. This sediment loss was equivalent to reef bed erosion of up to 28 mm during the observation period. As these potential losses may be compensated by coral reef growth, our measurements implied that modern sediment budgeting has played a significant role in the maintenance of subtidal reef flats, in terms of bed elevation. Hence, the deep reef flat does not necessarily belong to the previously identified give-up pattern; a balance of coral sediment supply and transport-induced loss may result in an equilibrium morphology, or a “lock-up” pattern.</p></div>","PeriodicalId":18229,"journal":{"name":"Marine Geology","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141097394","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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Marine Geology
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