首页期刊导航|Marine Geology
期刊信息/Journal information
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

    Cretaceous to Cenozoic controls on the genesis of the shelf-incising Perth Canyon; insights from a two-part geomorphology mapping approach

    Nanson, Rachel A.Borissova, IrinaHuang, ZhiPost, Alexandra...
    21页
    查看更多>>摘要：Perth Canyon is Australia's second largest submarine canyon, and its shelf-incising morphology contrasts with the more prolific slope-confined canyons that typify Australia's passive continental margin. The canyon has a sinuous course that extends 120 km from the shelf break (-180 m depth) to its fan at the foot of the continental slope (-4500 m). Though the canyon initiates only 50 km offshore from a major city, its genesis and geomorphic stability have not been well understood. Bathymetry data acquired in 2015 by the Schmidt Ocean Institute enabled the application of a new two-part seafloor classification approach to objectively map the complexity of the system in unprecedented detail. Part 1 used a semi-automated approach to classify the seafloor bathymetry into morphological categories, and Part 2 defined these units as geomorphological features through the inter-pretation of sub-bottom and seismic images, sediment samples and acoustic backscatter datasets. The resulting geomorphic map reveals an array of aggradational (cyclic steps and sediment waves), incisional (entrenched canyon floor and nick-points) and mass movement (slump and slab failures) features that for the first time provide detailed insights into the canyon's formative processes. Large faults and the Cretaceous palae-obathymetry appear to have strong influence on the canyon's planform, its depth of incision, and the distribution and types of mass failure that characterise its flanks. These data also reveal the Perth Canyon to be a predom-inantly relict feature; a large Late Cretaceous infilled incised valley (subaerial) beneath the canyon headwall likely initiated the canyon's development and represents its initial and most active phase. Two more infilled incised valleys are stacked above the first, and demonstrate a progressive decrease in scale, and presumably also canyon activity. Each incised valley represents lowstand incisions of the palaeo-Swan River, and their timing is linked to pronounced Late Cretaceous to Cenozoic sea level regression events, palaeoclimatic change, and onshore catchment enlargement. The disconnection of the modern Perth Canyon from the present day Swan River, and the low rates of sediment accumulation on the adjacent shelf and slope, ensure low rates of sediment supply to the canyon, and only infrequent ignition of turbidity currents. Low rates of sediment supply can similarly account for the entrenched morphology of the modern fan and only minimal headwall movement coincident with seismic events in 2018. However, additional core and bathymetry data for the lower canyon reaches are required to conclusively determine the extent of recent canyon activity.
      原文链接:
    • NSTL
    • Elsevier

    Identification, extraction and interpretation of multi-period variations of coastal suspended sediment concentration based on unevenly spaced observations

    Yu, QianWang, YunweiGao, ShuLin, Hangjie...
    13页
    查看更多>>摘要：Suspended sediment concentration (SSC) is an important indicator for coastal morphodynamics and health, exhibiting significant periodic variations at multiple timescales in response to various cyclic forcing factors. Identification of key periods and the extraction of corresponding amplitudes and phases can greatly aid effort to characterize the representative portrayal of SSC, which contributes to further physical interpretation. Remote sensing missions are intended to satisfy the retrieval of long-term SSC variations. However, the unevenly spaced characteristic and low effective sampling rates of the retrieved time series would hamper the extraction and interpretation of the feature changes. Here, we retrieved a 9-year SSC time series in a coastal tidal basin of Jiangsu coast, China, based on hourly GOCI satellite images from 2011 to 2019, and applied the Lomb-Scargle periodogram with the phase-folded method to extract their periodic information. On the basis of the unevenly spaced data with effective rate of 6.9%, the semidiurnal, diurnal, fortnightly, and seasonal cycles were successfully identified as the main periods, with amplitudes of 33.1, 23.4, 54.1, and 71.4 mg/L, respectively. In accordance with investigations into phase lags between SSC and forcing factors, we found that the unimodal SSC pattern at the semidiurnal timescale was induced by flood dominance, while the diurnal inequality of water level and wave intensity accounts for the SSC variation at the diurnal timescale. Tidal ranges vary consistently with the SSC in the fortnightly scale while background wave dominates the SSC variation in the seasonal timescale, the latter resulting in the seasonal difference in semidiurnal and fortnightly SSC cycles. The annual semidiurnal SSC variations experience a regime shift from 2014 to 2016, which is in consistency with the sequential reclamation. The research presents a typical application of long-term unevenly spaced observations into coastal SSC, and the proposed methodology can be extended to similar studies aiming at uncovering the mechanism of SSC variations at multiple timescales.
      原文链接:
    • NSTL
    • Elsevier

    On the distribution of sand banks in the southwestern North Sea and an approach of predicting them

    Albers, Aike Elias
    10页
    查看更多>>摘要：The morphology of the southwestern North Sea is greatly influenced by sand banks. With this paper these features have been identified by analysing bathymetric data and estimating their geometric properties. This allowed an assessment of the dimensions of the structures and enabled an economical evaluation of the associated sand resources. In fact, there are several aspects that are of economic interest, which include the sand as a potential exploitable resource and the interaction of the sand banks with submarine infrastructures, such as cables, pipelines and shipping channels. Therefore, this study aimed to evaluate and compare several oceanographic and sedimentary factors on the formation and distribution of the sand banks in the southwestern North Sea to create a prediction model for the bank occurance. The main focus was on the relation between critical shear stress of the bedload and the shear stress of currents and waves and it's effects on the sand bank formation. It has been figured out that the maximum bed shear stress needs to exceed the critical shear stress by a factor of nine to allow sand bank formation to a greater extend. Thus, this study contributes new knowledge about sand banks in the southern North Sea.
      原文链接:
    • NSTL
    • Elsevier

    The bioprotective properties of the blue mussel (Mytilus edulis) on intertidal rocky shore platforms

    Baxter, Timothy I. I.Coombes, Martin A. A.Viles, Heather A. A.
    12页
    查看更多>>摘要：Biogeomorphological processes are an important component in the geomorphic evolution of rocky coasts. Sessile organisms, including those which form dense biological covers, enhance and/or retard weathering and erosion. The common blue mussel (Mytilus edulis) is found on rocky shores in many parts of the world, typically forming extensive beds several centimetres thick. Yet, unlike other canopy forming marine organisms (e.g., seaweeds), the influences of mussels on processes of rock breakdown lack quantitative analysis. This study assesses the potential of M. edulis to act as a biogeomorphic agent through weathering experiments and field trials on a mudstone shore platform in Wales, UK.Monitoring on the shore platform showed that daily near-surface temperature maxima, range and short-term variability were lower on surfaces colonised by M. edulis compared to those that were bare. This was supported by laboratory simulations which showed that (artificial) mussel beds consistently reduced the internal (subsurface) temperature of rock samples during 'low-tide' periods. As mechanical rock weathering processes are influenced by surface and subsurface temperature regimes, it is inferred that these stabilising effects may translate to a reduction in the efficiency of particular rock breakdown processes. Rock hardness (Equotip Piccolo) measurements collected from the shore platform support this assertion as mussel-colonised surfaces were found to be significantly harder than bare surfaces, indicating they had experienced less breakdown during exposure to intertidal weathering and erosion. A supplementary field experiment based on the disintegration of gypsum 'domes' as an indirect measure of water/wave motion both within and outside of mussel beds further indicates that mussels may act as bioprotective agents by reducing turbulence at the rock surface.Overall, this study presents the first empirical evidence of mechanisms by which mussels may protect intertidal rocks from weathering and erosional processes through the moderation of near-surface microclimate regimes and water motion in temperate environments. Importantly, compared to other canopy forming species, such as seaweeds, the observed dampening effects of M. edulis are likely only small in magnitude. However, as mussels can dominate the surfaces of rocky shores at certain tidal heights, they may act as locally important geomorphic agents that warrant further consideration as one component of the collective effect of bioprotective and bioerosive species in these environments. Further work is now needed to examine the geomorphic roles of mussel beds on a variety of other rock types, and the extent to which their impacts vary in time and space in relation to other biological, chemical and physical agents of change.
      原文链接:
    • NSTL
    • Elsevier

    On the paleo footprint of Cape Darnley Bottom Water off MacRobertson Land Shelf, East Antarctica

    Nielsen, RicardaUenzelmann-Neben, Gabriele
    17页
    查看更多>>摘要：Cape Darnley Bottom Water (CDBW) is a major contributor to Antarctic Bottom Water (AABW) formation in the MacRobertson Land continental shelf area, East Antarctica. As the production of CDBW is dependent on intense sea ice formation in the Cape Darnley Polynya Region, it is sensitive to climatic changes, such as global warming. Studying paleo-conditions of CDBW during Antarctica's transition from coolhouse to icehouse during the middle to late Miocene allows to gain knowledge about the onset of bottom water production in the Cosmonaut/Prydz Bay region as well as changes in the strength and outflow path of the CDBW.In order to study the paleo-conditions of the CDBW, we have investigated the formation history of a 200 km long, 70 km wide sediment drift (Darnley Drift herein) at the western flank of Wild Canyon. In the early Miocene, the upper rise was dominated by turbiditic channel-levee growth and large continental sediment supply off the MacRobertson Land continental shelf. Therefore, no indications of CDBW formation were observed. During the middle Miocene, the dominant sediment transport regime transformed from turbiditic to contouritic mode, mirroring Antarctica's climatic transition into an icehouse world. This climatic transformation caused the initiation of CDBW, which is inferred from the onset of Darnley Drift formation as a levee-drift and its growth to a maximum areal extent of 60,000 km(2), four times the size of today. Since the late Miocene/early Pliocene the sedimentation rate has been strongly reduced and bottom current controlled deposition dominated. The growth of mixed levee-drifts along the continental slope-rise transition parallel to Darnley Drift suggests an intensifi-cation of paleo CDBW generation and outflow to be comparable to observations of recent CDBW, in addition to an intensification of the Antarctic Slope Front and Circumpolar Deep Water.
      原文链接:
    • NSTL
    • Elsevier

    Influence of sediment sources, water mass, and physical processes on the dynamics of flocs at a location between the mouth of a river and the head of a submarine canyon

    Du, XiaoqinLiu, James T.Lee, JayHuang, Peter S....
    15页
    查看更多>>摘要：A field experiment was conducted in the summer of 2011 to obtain detailed process-response data to understand the dynamics of suspended sediment off the Gaoping River mouth near the head of the Gaoping Submarine Canyon in Southern Taiwan. An instrumented tetrapod and a collocated floating platform were used to record the temperature, salinity, current and wave fields. Additionally, the volume concentration (VC) and mass concentration (SSC) of suspended sediments were recorded. Temperature and salinity signals over a tidal cycle distinguished water masses originating from the river plume and the canyon, which alternately dominated the surface dynamics of suspended sediment at the study area. Terrestrial-sourced suspended sediments aggregated into larger flocs, characterized by high VC, SSC, and low effective density values. Conversely, marine-sourced suspended sediments generally had smaller grain sizes, characterized by lower VC, SSC, and high effective densities. In the surface water, the effective density of suspended sediments decreased exponentially with size. In the bottom water, values of VC and SSC were higher under energetic wave conditions and lower under non energetic wave conditions, whereas mean size of suspended sediments showed an opposite trend. The hydrodynamics also affected the sediment-water interface, which was reflected in the grain size composition of surficial sediments. The silt and clay content on the seabed was lower under energetic wave conditions and higher under nonenergetic conditions. According to process-responses characteristics, suspended sediments in the bottom water were associated with two regimes: smaller mean size with lower effective densities formed under energetic wave conditions and larger mean size with higher effective densities formed under nonenergetic wave conditions. In the former regime, waves-induced turbulence dominated suspended sediment dynamics by entraining seafloor sediments into the bottom water and aggregating them into microflocs (<~125 mu m) and macroflocs (> ~ 125 mu m). However, the size distribution of suspended sediment showed a bimodal distribution, and the larger peak is close to the Kolmogorov microscale (around 250 mu m). It suggests that strong turbulence associated with significant sediment suspension and flocculation also resulted in disaggregation of macroflocs. As the wave energy dissipated, most of suspended sediments including all fine ones were removed from the bottom water, via flocculation and deposition. Under nonenergetic wave conditions, suspended sediments in the bottom water were contributed from upcanyon water and river plumes, controlled by semidiurnal tidal currents. The size distributions of suspended sediment under nonenergetic conditions were mostly unimodal, with peaks around 100-300 mu m, less than the Kolmogorov microscales of turbulence flow (350 mu m). Therefore, it could be concluded that turbulence strength plays a key role in flocculation of suspended sediment in the bottom water.
      原文链接:
    • NSTL
    • Elsevier

    Tectonic control on sedimentary dynamics in intraplate oceanic settings: A geomorphological image of the eastern Canary Basin and insights on its middle-upper Miocene to quaternary volcano-tectonic-sedimentary evolution

    Leon, R.Palomino, D.Sanchez-Guillamon, O.Fernandez-Salas, L. M....
    24页
    查看更多>>摘要：This paper integrates sedimentary, tectonic and volcanic geological processes inside a model of volcano-tectonic activity in oceanic intraplate domains related to rifted continental margins. The study case, the eastern Canary Basin (NE Atlantic), is one of the few places in the world where giant MDTs and Quaternary volcanic and hy-drothermal edifices take place in intraplate domains. In this paper, we analyse how two structural systems (WNW-ESE and NNE-SSW) matching with the oceanic fabric control the location of volcanic systems, seafloor tectonic reliefs and subsequently the distribution of main sedimentary systems. Linear turbidite channels, debris flow lobes and the lateral continuity of structural and volcanic reliefs follow a WNW-ESE trend matching the tracks of the oceanic fracture zones. Furthermore, escarpments, anticline axes and volcanic ridges follow a NNE-SSW trend matching normal faults delimiting blocks of oceanic basement. The morpho-structural analysis of all the above geomorphological features shows evidence of a volcanic and tectonic activity from the middle-upper Miocene to the Lower-Middle Pleistocene spread over the whole of the eastern Canary Basin that reached the western Canary Islands. This reactivation changes the paradigm in the seamount province of Canary Islands reported inactive since Cretaceous. A tecto-sedimentary model is proposed for this period of time that can be applied in other intraplate domains of the world. A tectonic uplift in the study area with a thermal anomaly triggered volcanic and hydrothermal activity and the subsequent flank collapse and emplacement of mass transport deposits on the Western Canary Slope. Furthermore, this uplift reactivated the normal basement faults, both trending WNW-ESE and NNE-SSW, generating folds and faults that control the location of turbidite chan-nels, escarpments, mass transport deposits and volcanic edifices.
      原文链接:
    • NSTL
    • Elsevier

    Turbidity currents on the open slope of the Fraser Delta

    Hill, Philip R.Lintern, D. Gwyn
    13页
    查看更多>>摘要：Turbidity currents have been observed and measured in submarine channels and canyons where the flows are confined, but with the exception of one serendipitous direct measurement, are only inferred to occur on unconfined delta slopes. In this paper, direct measurement of turbidity currents on the Fraser delta slope are reported and their dynamics compared to turbidity currents in channelized settings. Twelve turbidity current events occurring between May 2014 and June 2018 were identified from Acoustic Doppler Current Profiler instruments deployed at two sites (109 and 159 m water depth). All the events occurred in the months of May and June, in association with high spring river flow. Five of the events were recorded at both sites and the timing of first arrivals gives estimates of the current speed ranging from 0.4 to 3.6 m s(-1). Direct current measurements confirm that most flow speeds exceed 1.5 m s(-1), although one weak event did not exceed 0.4 m s(-1). Current profiles indicate that the flows are of variable thickness, ranging from less than 3 m to 15 m. The turbidity current events varied in duration from 5 to 66 min and, in the cases where transit speeds were available, the durations were proportionally shorter when the transit speed was high. In stronger flows, the initial stage of the flow is highly variable, suggesting extreme turbulence, and the velocity structure of the flow is similar to previous experimental and field observations, with a distinctive relatively thin, high speed lower region being evident at times. Downslope translation of the instrument platform during two of the events suggest the presence of a dense basal layer up to 2.75 m thick, as suggested in the travelling wave model of Heerema et al. (2020). The fact that only approximately half the flows measured at the shallower site are observed at the deeper site suggest that the runout distances of open slope flows are limited. Weaker flows are barely distinguishable in speed and direction from ambient tidal velocities. Flow directions suggest that the open slope flows are unconfined and initiate in the upper slope area that is approximately the same as the area of upslope sediment waves. It is hypothesized that shallow gullies in the same area may be important for initiation and ignition of the flows that become unconfined on the lower part of the slope.
      原文链接:
    • NSTL
    • Elsevier

    Distribution and origin of submarine landslides in the active margin of the southern Alboran Sea (Western Mediterranean Sea)

    Lopez-Gonzalez, N.Rodriguez, M.Migeon, S.El Moumni, B....
    19页
    查看更多>>摘要：Earthquakes are the most commonly cited cause of offshore slope failure, followed by high sedimentation rates and ensuing pore pressure build-up. In the South Alboran Sea, the moderate seismicity (Mw = 6.4) of the strike -slip Al Idrissi Fault Zone does not appear to control directly the landslides distribution. To provide a preliminary geohazard assessment, we characterized the spatial distribution, the volume and the ages of the submarine landslides from multibeam and seismic reflection data in the southern part of the Alboran Sea. Since the Qua-ternary numerous submarine landslide processes have affected the marine sedimentary cover with volumes of the mass transport deposits (MTD) estimated between 0.01 and 15 km(3). West of the Al Idrissi Fault Zone, along the South Alboran Ridge's northern flank, the distribution of the MTD follows the SW-NE bank and ridge trend that correlates with blind thrusts and folds covered by a plastered contourite drift. A pockmark field, related to fluid escape, is visible near landslide scars where the contourite drift is relatively thicker. In this area, landslide scars occur on variable slopes (2-24?degrees) and their associated MTDs show variable decompacted volumes (0.01-10 km(3)). East of the Al Idrissi Fault Zone, between the Alboran Ridge and the Pytheas Bank, the mapped MTDs have uneven volume. The smaller ones (< 1 km(3)) have their slide scars on steep slopes (> 10 degrees), whereas those of the largest ones (3-15 km(3)) occur on gentler slopes (< 5?degrees).These observations and a slope stability analysis suggest that the combination of seismic shaking, blind thrusts activity, relatively high sedimentation rate of contourite deposits with potential weak layers, and fluid escape dynamics are likely the main controlling mechanisms.& nbsp;These causal factors would explain the concentration of landslide head scarps at the edge of the thickest parts of the contourite drifts (i.e. crest). Slides may have been controlled locally by fluid overpressures in line with blind thrusts. Additionally, low to moderate seismicity potentially triggered by nearby faults might regionally have played a role in destabilising the landslides since 1.12 Ma (Q2 unit), which coincides with the propagation of the Al Idrissi Fault Zone in the southern Alboran Sea.
      原文链接:
    • NSTL
    • Elsevier

    Seismic stratigraphy of the north-westernmost area of the Malta Plateau (Sicily Channel): The Middle Pleistocene-Holocene sedimentation in a tidally influenced shelf

    Spatola, DanieleBasilone, GualtieroAronica, SalvatoreTodaro, Simona...
    11页
    查看更多>>摘要：In this study we present the results of a seismic-stratigraphic analysis of sub-bottom profiles in the northwesternmost area of the Malta Plateau in order to define the depositional mechanisms for the upper Quaternary sequences. During this interval the morphology of the Malta Plateau was characterized by a ramp and bathymetries not exceeding 200 m. Two major unconformities, related to MIS 6 and MIS 2 (the latter corresponding to the Last Glacial Maximum, LGM), characterize the upper Quaternary sequences. The geometries of the recognized seismic units indicate as depositional mechanisms were controlled by subsidence and sea-level fluctuations. In detail, deposits related to the last glacial event were recognized through their seismic pattern and have been interpreted as formed by the interaction between tide and wave dynamics. Contrary to the northern Sicilian continental margin, in the Malta Plateau ramp no LGM-related lowstand prograding wedge was recognized due to the absence of an effective shelf edge. It is considered as a consequence of the morphology and the dominant deposition processes in the Malta Plateau. Afterwards the ramp morphology allowed a rapid drowning of the Malta Plateau instead with the formation and preservation of transgressive deposits revealed as bedforms. The highstand deposits appear as prograding bodies and have been classified as infralittoral prograding wedge.
      原文链接:
    • NSTL
    • Elsevier