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Marine Geology
Elsevier Science B.V.
Marine Geology

Elsevier Science B.V.

0025-3227

Marine Geology/Journal Marine GeologySCIISTPAHCIEI
正式出版
收录年代

    Geochemical and heavy mineral signatures of marine incursions by a paleotsunami on the Miyazaki plain along the Nankai-Suruga trough, the Pacific coast of southwest Japan

    Kagami, SayaNiwa, MasakazuWatanabe, Takahiro
    13页
    查看更多>>摘要：Earthquakes and tsunami repeatedly occur in the coastal areas of the Japanese islands, which are located on the margin of continental plates. Paleotsunami deposits in these areas provide important clues regarding the reconstruction of past marine incursions by earthquakes and tsunami. The Miyazaki plain on the Pacific coast of southwest Japan along the Nankai-Suruga trough has been also affected by marine incursions by previous interplate earthquakes and tsunami. Tsunami deposits are usually identified by their geological, sedimentological, and geochemical characteristics. In the present work, portable energy dispersive X-ray fluorescence spectrometry (portable XRF), X-ray analytical microscopy (XGT), statistical analyses, and heavy mineral analyses were performed to characterize the paleotsunami deposits of the Kanbun Hyuganada earthquake (age, 1662 common era) in the SY03 core from the south Miyazaki plain. Our new findings can be summarized as follows: (1) Increases in the Ti-normalized values of S, Ca, Fe, and Sr, and depletions of K were observed in the deposits; (2) Accumulation of Zr and heavy minerals such as zircon, likely related with the high-energy tsunami, were found in the deposits; (3) Cluster analyses of the geochemical data acquired from the SY03 core by the portable XRF distinguished the paleotsunami deposits on the south Miyazaki plain. Furthermore, we also compiled the geochemical data of samples from the Shizuoka (central Japan), Sendai (Pacific coast of northeast Japan), and Miyazaki plains. Increases in Ti-normalized values (e.g., Sr/Ti) were found in these paleotsunami deposits. Our studies indicate that geochemical approaches are suitable for the characterization and exploration of paleotsunami deposits on the several coastal areas of Japan.
      原文链接:
    • NSTL
    • Elsevier

    A combined approach to cliff characterization: Cliff Stability index

    Fernandez-Ruiz, JesusRodriguez-Ortiz, Jose M.Iglesias, GregorioBergillos, Rafael J....
    9页
    查看更多>>摘要：In this work, a combined multidisciplinary method to characterize coastal cliff environments is presented. It combined two complementary approaches - engineering and geomorphological. The first one is represented by the wave power values along the cliff face. For that purpose, the deep-water wave climate is statistically characterized, and high-energy sea states are numerically propagated to the cliff with a state-of-the-art model. The variations in wave power at the cliff face are controlled by the varying cliff orientation and by the irregular morphology, which influences wave propagation through refraction and shoaling processes. Based on wave power, four engineering exposure levels, from low to extreme, are defined and mapped onto the cliff. The geomorphological approach is based on an index developed ad hoc for this work, the Cliff Stability (CS) index, which takes into account the cliff geometry, lithology, structure and degradation state, as well as the hydrological conditions. Based on the CS index, four geomorphological exposure levels are defined and mapped, from low to extreme. The combined approach is shown through the application to a study site in NW Spain. The two perspectives, engineering and geomorphological, are found to yield similar results in some sections of the study area, but not all. It may be inferred that, despite the importance of wave action in shaping the cliff, the additional elements included in the CS index also play a significant role. In practical terms, the significance of these results is that the two approaches, engineering and geomorphological, should be combined to properly characterize coastal cliffs. This combined approach represents a multidisciplinary tool to define and characterize the exposure levels and, thus, prevent damages in cliff environments across the world.
      原文链接:
    • NSTL
    • Elsevier

    Anatomy and dynamics of a mixed contourite sand sheet, Ryukyu Island Arc, northwestern Pacific Ocean

    Nishida, NaohisaItaki, TakuyaAmano, AtsukoKatayama, Hajime...
    16页
    查看更多>>摘要：Contourites are well-known from many continental margins under the influence of bottom currents but have been little reported from the Pacific Ocean. This paper documents a new area of contourite-controlled sedimentation in the NW Pacific Ocean, which we call the Ryukyu Sand Sheet. This contourite sand sheet has an area of around 35,000 km2 and extends from the narrow island shelves to over 1500 m water depth. It comprises mainly moderate to well-sorted fine-grained sands, with current ripples and giant sediment waves and is also associated with small drifts. It is formed under the influence of three principal current systems - the Kuroshio Current, the Kuroshio Countercurrent and the Ryukyu Current. The interaction of these currents with each other and with a complex seafloor topography, spawns a series of meso-scale gyres, eddies and vortices that shape the seafloor and lead to deposition of an extensive sandy substrate, locally with gravels and exposed seafloor. Strong surface currents, as well as deep-water thermohaline circulation, both influence the depositional and erosional processes of deep-sea sediments. The role of the modern Kuroshio Current in this context supports earlier work that proposed an ancestral Kuroshio Current for the deposition of Miocene contourites onshore Japan. Sediment supply to the Ryukyu Sand Sheet is by a mixed process of seafloor polishing and sand spillover that involves combined oceanographic and gravitational processes.
      原文链接:
    • NSTL
    • Elsevier

    Holocene morpho-stratigraphic evolution of a compound submarine deltaic system in front of the shelf-incising Almanzora and Garrucha Canyons (Palomares margin, southeastern Iberia)

    Casalbore, D.Biancone, M.Casas, D.Mata, P....
    17页
    查看更多>>摘要：The Holocene morpho-stratigraphic evolution of a compound submarine deltaic system linked with the Antas and Almanzora Rivers on the narrow (< 5 km) shelf along the Palomares margin (southeastern Iberia) has been reconstructed from the integrated analysis of geomorphology, seismo-stratigraphy and sedimentology. The shelf morphology is characterized by a 3-4 km wide deltaic body off the Almanzora River, where seafloor undulations and gullies are present. Larger and more incised gullies, crescent-shaped bedforms and pockmarks are recognizable at or close to the head of shelf-indenting canyons associated with the Almanzora-Garrucha canyon system. The seismo-stratigraphy displays a strong and irregular basal reflector overlain by a sedimentary wedge, showing variable thicknesses (1-25 m) and seismic characteristics along and across the shelf. The main depocenter of this wedge is not located off the Almanzora River mouth (i.e., the main sedimentary input in the study area) but along the southern shelf encompassing the Almanzora and Antas Rivers. Grain-size and sand compositional analyses show that silty sand with high terrigenous content (mostly quartz and mica) is mainly found on the submarine deltaic body. In contrast, sandy silt with variable ratios between terrigenous and biogenic contents is retrieved from the canyon head and associated gullies as well as from the surrounding mid-outer shelf. The evolution of the Antas-Almanzora compound delta has been divided into three evolutionary stages, mainly driven by the interplay between paleo-topography and riverine and marine processes and modulated by sea level changes during the Holocene. The origin of the present-day morphological features is also discussed, again highlighting a complex interaction between sedimentary gravity flows (mainly flash flood-generated hyperpycnal flows), storm-waves and shelf currents, fluid seepage and retrogressive slope failures.
      原文链接:
    • NSTL
    • Elsevier

    Gravel barrier resilience to future sea level rise and storms

    Pollard, J. A.Christie, E. K.Spencer, T.Brooks, S. M....
    16页
    查看更多>>摘要：Globally, communities, ecosystems, and assets situated within the coastal zone will likely experience increased risk in the future owing to chronic and acute pressures associated with climate change and accompanying sea level rise. Gravel barrier islands represent an intermediate pathway between seaward hazards and vulnerable landward receptors and possess inherent morpho-sedimentary characteristics which allow coastal risk reduction functions. If gravel barriers are to be usefully and reliably integrated into broader coastal risk management strategies, there is a need to understand the extent to which these landforms are likely to remain resilient under future environmental conditions. Using the Blakeney Point Barrier System, southern North Sea, this study investigates the resilience of gravel barrier landforms to storm surge conditions under future sea level rise scenarios. Resilience is assessed through reference to barrier resistance, susceptibility to state change, persistence, and continued functional performance. Numerical modelling reveals that variable pre-surge barrier morphologies result in a spectrum of episodic resilience trajectories along the barrier frontage. This study also considers the role of humans in altering landscape resilience, demonstrating that previously managed barrier sections (through reprofiling to steepen and heighten the barrier) are more vulnerable to severe morphological change, and associated landward overtopping volume, compared to unmanaged barrier sections. This said, under moderate to high sea level rise, even unmanaged barrier sections failed to demonstrate resilience to storm surge forcing. Such insights help temper our expectations regarding the coastal erosion and flood risk reduction functions of gravel barriers in the face of global environmental change.
      原文链接:
    • NSTL
    • Elsevier

    New multibeam mapping of the unique Ikaite columns in Ikka Fjord, SW Greenland

    Seaman, PaulSturkell, ErikGyllencreutz, RichardStockmann, Gabrielle J....
    14页
    查看更多>>摘要：Ikka Fjord in SW Greenland is world famous for its submarine, cold-water craving ikaite (CaCO3.6H2O) tufa columns. Due to the uniqueness of the columns, Ikka Fjord is declared a protected area by the Greenlandic authorities. In the summers of 2018-19, multibeam sonar bathymetry and aerial drone photogrammetric surveys were made in Ikka Fjord mapping and counting the columns and comparing the results to data from geophysical surveys of the fjord in 1995-96. The new surveys provide highly detailed maps of the fjord bathymetry and its columns, their height and position, and several hitherto unknown pockmarks in the seabed. A total of 938 individual columns and structures ranging 0.5-20 m in height from the sea floor were identified: a number surpassing the 678 taller columns (> 1 m) known from previous mapping. Our results support previous observations that the columns are restricted to the spatial extents of the Gronnedal-I ' ka igneous complex. The new survey data show that column distribution exhibits lineations and variable density over the fjord floor, notably that the innermost central deep part is free of columns. The tallest columns are observed to grow up to the halocline at approximately 2-4 m water depth. The majority of columns have reached only 15-50% of their growth potential. The -60 columns of maximum growth stand in clusters, interpreted as representing exceptionally favourable growth settings. New seawater data collected in 2019 shows a worrying increase in temperature since the previous measurements in 1995 and 2007-2009, which could potentially affect the stability of the delicate columns of Ikka Fjord.
      原文链接:
    • NSTL
    • Elsevier

    A direct evidence for disturbance of whole sediment layer in the subducting Pacific plate by petit-spot magma-water/sediment interaction

    Danhara, TohruHirata, TakafumiAkizawa, NorikatsuHirano, Naoto...
    6页
    查看更多>>摘要：Recently, small volcanic knolls known as petit-spot are highlighted from seismic viewpoint for a functional necessity to suppress the coseismic displacement during the 2011 Tohoku-Oki earthquake. To better understand physical mechanism of shallow oceanic plate disturbance by the petit-spot magma intrusion, we aim at elucidating the interaction of petit-spot magma and wet sediment in subseafloor volcanic environment. We used petitspot peperites that are mixtures generated by mingling of magma and wet sediment. The peperites were collected at a petit-spot knoll located east of the outer trench swell in the northwestern Pacific (offshore of northern Japan). The sedimentary portions in the peperites are hardly to poorly consolidated due to heat supply from the magma body, and in places include radiolarian microfossils and zircon grains. Mineral phases of the sedimentary portions were identified to illite, quartz and hydrated sodium aluminum silicate. The radiolarian species and zircon grains were dated at ca. 10.6 to 15.6 Ma and ca. 1 to 108 Ma, respectively. The wide age range can be interpreted that whole sediments on the Early Cretaceous basaltic basement were entirely disturbed and transported to the surface via recent (younger than 1 million years) violate petit-spot magmatism. The subduction of petit-spot with annealed sediment "armor" functioned to prevent coseismic tsunamigenic slip propagation during the 2011 Tohoku-Oki earthquake as the seismic data predicted.
      原文链接:
    • NSTL
    • Elsevier

    Composition of volatiles of sulfide deposits and carbonate structures in submarine hydrothermal fields of the Mid-Atlantic Ridge

    Tomilenko, A. A.Bul'bak, T. A.Timina, T. YuShaparenko, E. O....
    15页
    查看更多>>摘要：In this study, the composition of fluid inclusions in minerals from polymetallic sulfide deposits Ashadze-1, Semenov-2, Krasnov, Rainbow and from the Lost City carbonate structures of hydrothermal fields in the Atlantic Ocean was determined using pyrolysis-free gas chromatography-mass spectrometry. It was found out that sulfides and anhydrite from the hydrothermal ore crystallized in reducing conditions with the active participation of hydrocarbons, including high-molecular, sulfonated, nitrogenated and halogenated compounds as well as water and carbon dioxide. On the other hand, carbonate structures formed in considerably more oxidizing conditions, for which the main components of volatiles were CO2 and H2O. The amount of detected hydrocarbons, including sulfonated, nitrogenated and halogenated compounds is significantly smaller compared to sulfides of ore vent structures.
      原文链接:
    • NSTL
    • Elsevier

    Linking oceanographic processes to contourite features: Numerical modelling of currents influencing a contourite depositional system on the northern South China Sea margin

    Chen, HuiZhang, WenyanXie, XinongGao, Ya...
    18页
    查看更多>>摘要：Combining high-resolution bathymetry and 2-D seismic data with 3-D hydrodynamic numerical simulation results to identify Quaternary plastered contourite drifts in the South China Sea northern margin (i.e., the Jianfeng and Yitong slopes), this study aims to disentangle the impacts of bottom currents associated with the intermediate and deep water masses. Upslope parts of plastered drifts (similar to 1000-1200 mwd) are smooth and gentle (up to 1 degrees) surfaces, which can also be classified as contourite terraces. They are characterised by non-deposition and sheeted deposition that indicate dominant flow conditions capable of transporting sediments. The responsible hydrodynamic forcing here is the anticyclonic South China Sea Intermediate Water currents, which flow eastward with a mean velocity of 2-3 cm/s. These are sporadically enhanced and can exceed 6 cm/s during high-energy intermittent events such as deep-reaching eddies. The central parts of the plastered drifts, located seaward of the terraces, present a subtle mounded morphology (1 degrees-2 degrees, similar to 1200-1500 mwd) partly perturbated by wavy bedforms. The downslope parts of the plastered drifts feature step-forming slides/slumps with steep slope gradients (1 degrees-5 degrees, similar to 1500-2000 mwd). According to our simulation results, the depth range of the plastered drifts overlaps the transition zone between the intermediate and deep water masses, wherein the simulated mean current velocity is 0-2 cm/s with variable directions, suggesting its deposition-favourable environment. Steep (>2 degrees) slopes beneath the plastered drifts (below similar to 2000 mwd) present along-slope truncations, including contourite channels and moats that indicate enforced currents capable of erosion. Responsible hydrodynamic forcing is the cyclonic South China Sea Deep Water currents, which flow westward with a mean velocity of 3-5 cm/s and exceed 15 cm/s during high-energy intermittent events. The results of this study show a clear link between bottom currents' behaviours (e.g., mean flow condition and variability) and contouritic depositional patterns, which suggest that continental slopes can be effectively shaped by large-scale ocean circulations through the topography-current interaction. The weakest hydrodynamic condition and highest sediment accumulation rate, occurring in the similar to 800 m thick transition domain between two water masses in the study area, facilitate the development of plastered drifts at the seaward side of contourite terraces. The outcomes of our study may have broad implications for understanding the relationship between processes and products in continental margins.
      原文链接:
    • NSTL
    • Elsevier

    Geomorphological imprint of opposing ocean bottom currents, a case study from the southeastern Brazilian Atlantic margin

    de Mahiques, M. M.Lobo, F. J.Schattner, U.Lopez-Quiros, A....
    13页
    查看更多>>摘要：The combination of oceanographic processes and a negligible fluvial terrestrial sediment contribution makes the Santos Basin margin (southwestern Brazil) a unique environment for studying thew morphological imprint of bottom currents on the seafloor morphology. We divide the seafloor into four domains: outer shelf, upper, middle, and lower slope, based on an analysis of sub-bottom Chirp profiles, multichannel seismic data, hydro graphic data, numerical simulation outputs, and a seismic-derived bathymetry map. A clinoform at the outer shelf and upper slope, topped by erosional morphologies, developed below the SW-flowing Brazil Current (BC). At the bottom of the upper slope, a rugged and mounded surface around 600 mbsl coincides with the current flow reversal to the underlying NE-flowing Intermediate Western Boundary Current (IWBC). The smooth middle slope exhibits sheeted contourites interrupted by occasional channel-and-mound complexes. From the middle slope base, salt tectonics becomes a major player in setting the seafloor morphology. The slope-parallel Santos Channel develops above a subsurface diapir and the Cabo Frio Fault. The latter divides between the landward gap in subsurface Albian salt and the basinward rich diapir realm. Hence, the lower slope is reworked by the SW-flowing Deep Western Boundary Current (DWBC); however, salt tectonics dictates its morphology. Our study consists of a unique example for studying the morpho-sedimentary imprint of a countercurrent flowing on the continental slope and also for exploring the interaction between bottom flows with a suite of endogenic processes, such as salt tectonics, fluid flows, and mass movements.
      原文链接:
    • NSTL
    • Elsevier