Marine Geology最新文献_第6页

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 : 2025-09-04 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

Caught in the act: calcareous algae creating undescribed morphologies of mesophotic algal reef 被捕获的行为：钙质藻类创造了未描述的中囊藻礁形态

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-27 DOI: 10.1016/j.margeo.2025.107644

Sara Innangi , Valentina Alice Bracchi , Daniela Basso , Renato Tonielli

The exploration of the Linosa Island shelf (Sicily Channel, Mediterranean Sea) by remotely operated vehicle surveys revealed a previously undescribed morphotype of coralligenous algal reef. These biogenic solid substrates are characterized by planar to conical shapes, ranging from single to multilayered structures, with an elevation of 20–30 cm and a concave to convex arrangement. Such coralligenous assemblages primarily cover the seafloor at depths between 80 and 100 m, developing on a sedimentary substrate rich in biogenic components, particularly abundant rhodoliths. We document the role of crustose coralline algae as autogenic engineers, in transforming mobile biogenic sediments into stable substrates by algal reef formation, as theorized by benthic bionomics for the coralligène de plateau.

对利诺萨岛大陆架（地中海西西里岛海峡）的远程操作车辆调查揭示了一种以前未描述的珊瑚藻礁形态。这些生物源固体基质的特征是平面到圆锥形，从单层到多层结构，高程为20-30厘米，凹凸排列。这种珊瑚组合主要覆盖海底深度在80到100米之间，在富含生物成分的沉积基底上发育，特别是丰富的菱形岩。我们记录了珊瑚藻作为自生工程师的作用，在通过藻礁形成将可移动的生物沉积物转化为稳定的基质中，正如海底生物生物学对高原珊瑚藻的理论。

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 : 2025-08-27 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

Storm sediment deposit from Ko Phra Thong, Thailand 风暴沉积物在泰国的Ko Phra Thong

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-24 DOI: 10.1016/j.margeo.2025.107641

C. Gouramanis , Y.T. Yan , Z. Yang , J.L. Soria , W. Yap , K. Jankaew , A.D. Switzer

Siliciclastic storm deposits have been described from coastlines around the world over the last six decades. Most of these storm deposits are formed from storms directly or obliquely making landfall, or tangentially bypassing nearby coastal systems. In these instances, coastal water piles up on the coast as the storm approaches the coastline before breaching or overtopping the beach barrier. Seldom have storm deposits been examined from coastlines on the lee of the storm. We describe the sedimentary and stratigraphical variation of a small storm fan from three short sediment cores from Ko Phra Thong, western Thailand. The fan was formed after a tropical depression crossed the Malay-Thai peninsula in May 2007, resulting in water piling up along the coast and breaching of the small berm on the western coastline of Ko Phra Thong. Sufficient accommodation space resulted in fine to medium quartz and heavy-mineral rich sands to be deposited upon the back beach sediments. The basal contact consists of a soil horizon above beach sands with an abundance of Casuarina equisetifolia needles. Horizontal laminations of heavy minerals characterise the lowest stratigraphic unit, conformably overlain by a massive unit which is in turn overlain by a unit with vertical and sub-horizontal root structures. At the landward extremity of the fan, faint landward dipping cross beds are observed, indicative of terminal foresets. As Ko Phra Thong preserves a well-established history of past tsunami sand washover deposits, the presence of a storm overwash fan along this coast complicates the inferred overwash event history. This complication is particularly pertinent when the palaeo-shoreline was closer to the swales where smaller, lower energy events, such as storms, can overtop the palaeo-berm and deposit sandy units. This most likely occurred between 2500 and 2000 years ago when thin, structureless sandy deposits were emplaced near the palaeo-shoreline.

在过去的60年里，人们从世界各地的海岸线上描述了硅屑风暴沉积。这些风暴沉积物大多是由直接或间接登陆的风暴形成的，或者是切线绕过附近的海岸系统。在这些情况下，当风暴接近海岸线时，海岸上的水在冲破或超过海滩屏障之前堆积在海岸上。很少对风暴背风处海岸线上的风暴沉积物进行检查。我们描述了泰国西部Ko Phra Thong三个短沉积物岩心的小型风暴扇的沉积和地层变化。2007年5月，一个热带低气压穿过马来-泰国半岛，导致海水沿着海岸堆积，并破坏了Ko Phra Thong西海岸的小护堤，形成了这个扇形。充足的容纳空间使得后滩沉积物上沉积了细至中石英和富重矿物砂。基底接触层由沙滩上的土壤层组成，上面有丰富的木麻黄针叶。重矿物的水平层状是最低地层单元的特征，它被一个块状单元整合覆盖，而块状单元又被一个具有垂直和亚水平根结构的单元覆盖。在扇向陆地的末端，观察到微弱的向陆地倾斜的交叉层，表明终末林。由于Ko Phra Thong保留了过去海啸冲积砂沉积物的完善历史，因此该海岸上风暴冲积扇的存在使推断的冲积事件历史变得复杂。当古海岸线靠近峡谷时，这种复杂性尤为重要，在那里，较小的、能量较低的事件，如风暴，可以覆盖古堤岸并沉积沙质单元。这很可能发生在2500到2000年前，当时薄而无结构的沙质沉积物被安置在古海岸线附近。

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引用次数: 0

Observations of oscillatory and unidirectional flow dynamics over a limestone reef 石灰岩礁上振荡和单向流动动力学的观测

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-24 DOI: 10.1016/j.margeo.2025.107640

Freya Barr , Charlotte F.K. Uphues , Graziela Miot da Silva , Patrick A. Hesp

Natural and human made reef structures provide effective coastal protection by attenuating incident wave and current energy. Anticipated effects of climate change, such as sea level rise, threaten coastal zones and are predicted to reduce the protection provided to coastlines by reef structures. This study aims to investigate wave and current dynamics at a limestone reef site at Robe, South Australia, to improve our understanding of how limestone reefs act as protective reef structures in present-day and in changing climate conditions. Pressure sensors and acoustic doppler current profilers were deployed on a cross-reef transect to investigate rates of wave attenuation, shifts in spectral wave energy, and changes to current speed and direction. Field measurements indicate that the Town Beach reef acts as a tidally modulated low-pass filter, attenuating more wave energy at lower water levels compared to higher water levels. Despite attenuating less wave energy than other reported studies, the Town Beach reef effectively dissipates approximately 42 % of gravity wave energy, resulting in a domination of lower frequency, infragravity wave energy within the landward reef-protected lagoon. Current speeds landward of the reef are approximately one third lower than those observed seaward of the reef. Bidirectional flows (north-south and east-west, respectively) occur at higher water levels, changing to unidirectional flows (south and west, respectively) at lower water levels. Potential reasons for these observed dynamics are discussed, and future research is proposed to address key limitations, such as unknown ecological, geometric, and morphologic aspects of the reef.

天然和人工造礁结构通过衰减入射波和电流能量提供有效的海岸保护。气候变化的预期影响，如海平面上升，威胁到沿海地区，预计将减少珊瑚礁结构对海岸线的保护。本研究旨在调查南澳大利亚罗布的石灰岩珊瑚礁遗址的波浪和洋流动力学，以提高我们对石灰岩珊瑚礁在当今和不断变化的气候条件下如何作为保护性珊瑚礁结构的理解。压力传感器和声学多普勒电流剖面仪部署在跨礁样带上，以研究波浪衰减率，频谱波能量的变化以及电流速度和方向的变化。实地测量表明，镇滩礁作为一个潮汐调制低通滤波器，在较低的水位比较高的水位衰减更多的波浪能量。尽管衰减的波能比其他报告的研究少，但镇滩礁有效地耗散了大约42%的重力波能量，导致低频、次重力波能量在向陆地珊瑚礁保护的泻湖中占主导地位。珊瑚礁向陆地方向的水流速度大约比珊瑚礁向海方向的水流速度低三分之一。双向流动（分别为南北和东西）出现在高水位，在低水位转变为单向流动（分别为南和西）。讨论了这些观察到的动态的潜在原因，并提出了未来的研究，以解决关键的限制，如未知的生态，几何和形态方面的珊瑚礁。

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引用次数: 0

Application potential of UK′37 and TEX86H palaeothermometers in high-energy strait-type marginal seas: a case study in the Taiwan Strait UK’37和TEX86H古地温计在高能海峡型边缘海的应用潜力——以台湾海峡为例

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-22 DOI: 10.1016/j.margeo.2025.107639

Chang Ran , Shuqin Tao , Mengyuan Wang , Zhen Jiang , Xiang Ye , Aijun Wang

U^K’₃₇ and TEX₈₆^H palaeothermometers are widely applied to sea surface temperature (SST) reconstructions in global oceans. However, their applications in marginal seas often yields biased results due to regional environmental factors. This study investigated the applicability and controlling factors of these proxies in the subtropical, high-energy Taiwan Strait (TS). Utilizing a 35-year dataset (1982–2016) of AVHRR and MODIS-derived annual and seasonal average SST archives, we conducted regression analyses on U^K’₃₇ and TEX₈₆^H proxies of 58 surface sediment samples from the study area. Additionally, we employed Empirical Orthogonal Function (EOF) analysis to elucidate the physical processes influencing the index reliability. TEX₈₆^H-reconstructed SSTs exhibit a cold bias of −5.5–0.3 °C compared to observed SSTs, largely due to seasonal upwelling and terrestrial inputs. Conversely, U^K’₃₇-reconstructed SST in the muddy sediment zone of the northern TS shows a warm bias of 1.8–6.3 °C, relative to observed SST, attributable to lateral transport processes in the said environment. By accounting for terrestrial influences as the main non-temperature factor, we developed an improved regional calibration equation for TEX₈₆^H-SST in the TS. These results highlight the necessity of considering hydrodynamic effects when applying U^K’₃₇ index in such marginal seas. Through modern calibration using surface suspended particulate matter (SPM) and hydrodynamic correction, this study effectively mitigates lateral transport interference, providing a robust framework for palaeotemperature reconstruction in strong hydrodynamic strait-type marginal sea environments.

UK ' 37和TEX86H古温度计被广泛应用于全球海洋的海表温度重建。然而，由于区域环境因素，它们在边缘海域的应用往往产生有偏差的结果。研究了这些指标在副热带高能台湾海峡的适用性及其控制因素。利用35年（1982-2016）AVHRR和modis衍生的年平均和季节平均海温数据，对研究区58个表层沉积物样本的UK ' 37和TEX86H代理进行了回归分析。此外，我们采用经验正交函数（EOF）分析来阐明影响指标信度的物理过程。与观测到的海温相比，tex86h重建的海温表现出−5.5-0.3°C的冷偏，这主要是由于季节性上升流和陆地输入。相反，UK’37重建的北TS泥质沉积带海温相对于观测海温偏暖1.8 ~ 6.3°C，这是由于该环境的侧向输运过程所致。通过考虑陆地影响作为主要的非温度因素，我们建立了改进的TS中TEX86H-SST区域定标方程，这些结果突出了在边缘海应用UK ' 37指数时考虑水动力效应的必要性。通过海面悬浮颗粒物（SPM）的现代定标和水动力校正，有效减轻了横向输运干扰，为强水动力海峡型边缘海环境的古温度重建提供了强有力的框架。

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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 : 2025-08-21 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

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 : 2025-08-20 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

Micro-Erosion Meter derived downwearing rates on inter-tidal shore platforms at Māhia Peninsula, New Zealand: Implications for uplifted rock coasts 微侵蚀仪在Māhia半岛潮汐间海岸平台上得出的下降速率，新西兰：对隆起的岩石海岸的影响

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-11 DOI: 10.1016/j.margeo.2025.107636

Jokotola Omidiji , Wayne Stephenson , Mark Dickson , Kevin Norton

Downwearing rates obtained from tectonically active coasts provide evidence of rapid rock breakdown following coseismic uplift. These measurements help solve puzzles about ‘missing' marine terraces and have implications for accurate reconstruction of past sea levels, earthquakes and rock coast evolution. However, very few detailed erosion datasets exist for uplifted shore platforms, making it uncertain if erosion records from one coast can be extrapolated to other regions with similar tectonic, geologic, or geomorphic characteristics. Here we present new downwearing rates from an inter-tidal mudstone shore platform at Kahutara Point, Māhia Peninsula, New Zealand that was uplifted likely by ∼3 m within the last 300 years. Downwearing rates were measured over 49 months/4.05 years using the Micro-Erosion Meter (MEM) and Structure-from-Motion photogrammetry: the mean annual downwearing rate was 1.08 mm yr⁻¹, while the total erosion at individual MEM stations ranged from 0.44 to 14.37 mm (equivalent to mean downwearing rates of 0.11 to 3.54 mm yr⁻¹). Orthophotographs of the eroded rock surfaces indicate the combined role of marine processes (waves and tides), sub-aerial weathering processes, salt weathering and biological activity in the erosion of the mudstone platform surface. The downwearing rates from Kahutara Point, Māhia Peninsula are statistically similar to previously published downwearing rates (1.23 mm yr⁻¹) from mudstone platforms at Kaikōura Peninsula, New Zealand, that were obtained prior to the 2016 Kaikōura earthquake, but are significantly different from perturbed post-uplift downwearing rates (2.25 mm yr⁻¹) obtained from the same MEM stations following coseismic uplift of ∼1 m. This work provides valuable data to support comparison of the development of shore platforms and marine terraces at Kaikōura and Māhia at different stages of their tectonic evolution.

从构造活跃的海岸得到的下降速率提供了同震隆起后岩石快速破碎的证据。这些测量有助于解决关于“失踪”的海洋梯田的难题，并对精确重建过去的海平面、地震和岩石海岸演变具有重要意义。然而，对于隆起的海岸平台，很少有详细的侵蚀数据集，因此不确定一个海岸的侵蚀记录是否可以外推到具有类似构造、地质或地貌特征的其他地区。在这里，我们展示了新西兰Māhia半岛Kahutara Point的潮间带泥岩海岸平台的新下降速率，该平台在过去300年中可能上升了约3米。使用微侵蚀仪（MEM）和动态结构摄影测量法测量了49个月/4.05年的侵蚀率：平均年侵蚀率为1.08毫米/年，而各个MEM站点的总侵蚀率为0.44至14.37毫米（相当于平均侵蚀率为0.11至3.54毫米/年）。侵蚀岩石表面的正射影片显示了海洋作用（波浪和潮汐）、空中风化作用、盐风化作用和生物活动在泥岩台地表面侵蚀中的综合作用。Māhia半岛Kahutara Point的下降速率与之前公布的2016年Kaikōura地震前在新西兰Kaikōura半岛泥岩平台上获得的下降速率（1.23 mm yr - 1）在统计上相似，但与同一MEM台站在同震隆起~ 1 m后获得的扰动后下降速率（2.25 mm yr - 1）有显著差异。这项工作为比较Kaikōura和Māhia不同构造演化阶段的海岸台地和海相台地的发育提供了有价值的资料。

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引用次数: 0

Geochemistry of surface sediments from ultra-slow spreading eastern SWIR 63°E–69°E: Inferences on hydrothermal signatures 超慢扩张SWIR东部63°E - 69°E表层沉积物地球化学：热液特征的推断

IF 2.2 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology

Pub Date : 2025-08-09 DOI: 10.1016/j.margeo.2025.107633

Deepak K. Agarwal , Parijat Roy , Esha Gadekar , John Kurian Palayil

The seawater precipitation, hydrothermal input (plume-derived or weathered sulfide), and weathering of nearby rock outcrops constrain the dominant end-member components in the mid-ocean ridge (MOR) sediments. We have conducted mineralogical, geochemical, and statistical studies of surface sediments from the eastern part of the ultra-slow spreading Southwest Indian Ridge (SWIR) 63°E–69°E. Further, we combined factor analysis and linear regression to demonstrate how relative enrichment/depletion of certain elements compared to the general regional sediment composition can constrain the local seafloor processes. Mineralogy and factor analysis of the carbonate-free geochemical data reveal that the sediments consist of three main end-members with respect to Al, Ti, Mg, Fe, Mn, K, Rb, Cu, Zn, V, Cr, Ni, and As; the end-members are mixed in different proportions in the sediments. The three endmember components, authigenic hydrothermal minerals – Fe-Mn-(oxyhydr)oxides, bernessite, and hematite; basaltic detritus – Labradorite and alteration products (montmorillonite, vermiculite, and illite); and ultramafic detritus – antigorite, account for 62.3 %, 21.8 %, and 10.2 % of the elemental variance, respectively. We also used Ti/Al vs Cr/Al and Ni/Al proxies to show that some samples consist of ultramafic and serpentinized detritus. The sediment sample C-GC-16(0-1 cm) at 67.260° E, 26.574° S, consists of relatively high conservative and redox-sensitive elements (U, Mo, V, As), alkali metals (K, Rb, Cs), and Cu, reflecting the presence of a hydrothermal source in the near vicinity. Moreover, linear relations reveal the relative scavenging of REEs from the seawater by Fe-Mn-(oxyhydr)oxides, which are recorded by Ce anomaly and REE fractionation values relative to Fe and Mn content.

海水降水、热液输入（岩柱衍生或风化硫化物）以及附近岩石露头的风化作用限制了洋中脊（MOR）沉积物的主要端元成分。我们对西南印度海岭（SWIR）东部63°E - 69°E超缓慢扩张的表层沉积物进行了矿物学、地球化学和统计学研究。此外，我们将因子分析和线性回归相结合，以证明与一般区域沉积物组成相比，某些元素的相对富集/耗尽如何约束局部海底过程。无碳酸盐地球化学数据的矿物学和因子分析表明，沉积物由Al、Ti、Mg、Fe、Mn、K、Rb、Cu、Zn、V、Cr、Ni和As 3个主要端元组成；端元在沉积物中以不同比例混合。三种端元组分为自生热液矿物铁锰氧氧化物、伯恩黑石和赤铁矿；玄武质碎屑-拉布拉多石和蚀变产物（蒙脱石、蛭石和伊利石）；超镁质碎屑—反长花岗岩分别占元素方差的62.3%、21.8%和10.2%。我们还使用Ti/Al对比Cr/Al和Ni/Al来表明一些样品由超镁质和蛇纹石化碎屑组成。沉积物样品C-GC-16（0 ~ 1 cm）位于67.260°E, 26.574°S，由较高的保守性和氧化还原敏感性元素（U、Mo、V、As）、碱金属（K、Rb、Cs）和Cu组成，反映了附近存在热液源。此外，Fe-Mn-（氧合）氧化物对海水中稀土元素的相对清除作用与Ce异常和稀土元素相对于Fe和Mn含量的分馏值呈线性关系。

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