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1.
Laboratory analysis of core samples from the western Alboran Sea slope reveal a large variability in texture and geotechnical properties. Stability analysis suggests that the sediment is stable under static gravitational loading but potentially unstable under seismic loading. Slope failures may occur if horizontal ground accelerations greater than 0.16g are seismically induced. The, Alboran Sea is an active region, on which earthquakes inducing accelerations big enough to exceed the shear strength of the soft soil may occur. Test results contrast with the apparent stability deduced from seismic profiles. 相似文献
2.
Five depositional bodies occur within the Quaternary deposits of the northwestern Alboran Sea: Guadalmedina-Guadalhorce prodelta, shelf-edge wedges, progradational packages, Guadiaro channel-levee complex, and debris flow deposits. The sedimentary structure reflects two styles of margin growth characterized: 1) by an essentially sediment-starved outer, shelf and upper slope and by divergent slope seismic facies; 2) by a prograding sediment outer shelf, and parallel slope seismic facies. Eustatic oscillations, sediment supply, and tectonic tilting have controlled the type of growth pattern, and the occurrence of the depositional bodies. Debris flows were also controlled locally by diapirism. 相似文献
3.
Recent structures in the Alboran Ridge and Yusuf fault zones based on swath bathymetry and sub-bottom profiling: evidence of active tectonics 总被引：2，自引：2，他引：0
The seafloor of the Alboran Sea in the western Mediterranean is disrupted by deformations resulting from convergence between
the African and Eurasian plates. Based on a compilation of existing and new multibeam bathymetry data and high-resolution
seismic profiles, our main objective was to characterize the most recent structures in the central sector, which depicts an
abrupt morphology and was chosen to investigate how active tectonic processes are shaping the seafloor. The Alboran Ridge
is the most prominent feature in the Alboran Sea (>130 km in length), and a key element in the Gibraltar Arc System. Recent
uplift and deformation in this ridge have been caused by sub-vertical, strike-slip and reverse faults with associated folding
in the most recent sediments, their trend shifting progressively from SW–NE to WNW–ESE towards the Yusuf Lineament. Present-day
transtensive deformation induces faulting and subsidence in the Yusuf pull-apart basin. The Alboran Ridge and Yusuf fault
zones are connected, and both constitute a wide zone of deformation reaching tens of kilometres in width and showing a complex
geometry, including different active fault segments and in-relay folds. These findings demonstrate that Recent deformation
is more heterogeneously distributed than commonly considered. A narrow SSW–NNE zone with folding and reverse faulting cuts
across the western end of the Alboran Ridge and concentrates most of the upper crustal seismicity in the region. This zone
of deformation defines a seismogenic, left-lateral fault zone connected to the south with the Al Hoceima seismic swarm, and
representing a potential seismic hazard. Newly detected buried and active submarine slides along the Alboran Ridge and the
Yusuf Lineament are clear signs of submarine slope instability in this seismically active region. 相似文献
4.
Aaron Micallef Christian Berndt Douglas G. Masson Dorrik A.V. Stow 《Marine Geology》2008,247(1-2):46-60
This study documents the fractal characteristics of submarine mass movement statistics and morphology within the Storegga Slide. Geomorphometric mapping is used to identify one hundred and fifteen mass movements from within the Storegga Slide scar and to extract morphological information about their headwalls. Analyses of this morphological information reveal the occurrence of spatial scale invariance within the Storegga Slide. Non-cumulative frequency-area distribution of mass movements within the Storegga Slide satisfies an inverse power law with an exponent of 1.52. The headwalls exhibit geometric similarity at a wide range of scales and the lengths of headwalls scale with mass movement areas. Composite headwalls are self-similar.One of the explanations of the observed spatial scale invariance is that the Storegga Slide is a geomorphological system that may exhibit self-organized criticality. In such a system, the input of sediment is in the form of hemipelagic sedimentation and glacial sediment deposition, and the output is represented by mass movements that are spatially scale invariant. In comparison to subaerial mass movements, the aggregate behavior of the Storegga Slide mass movements is more comparable to that of the theoretical ‘sandpile’ model. The origin of spatial scale invariance may also be linked to the retrogressive nature of the Storegga Slide. The geometric similarity in headwall morphology implies that the slope failure processes are active on a range of scales, and that modeling of slope failures and geohazard assessment can extrapolate the properties of small landslides to those of larger landslides, within the limits of power law behavior. The results also have implications for the morphological classification of submarine mass movements, because headwall shape can be used as a proxy for the type of mass movement, which can otherwise only be detected with very high resolution acoustic data that are not commonly available. 相似文献
5.
J. Galindo-Zaldívar F. González-Lodeiro A. Jabaloy A. Maldonado A. A. Schreider 《Geo-Marine Letters》1998,18(1):10-18
Magnetic and gravimetric data from the central Alboran Sea allow identification of two axes of crustal thinning, which were
probably active during the Oligocene–Early Miocene. The western Alboran basin axis is subparallel and may be related in origin
to the Gibraltar Arc. The ENE–WSW trending Alboran Channel axis is probably intruded by basic igneous rocks and may represent
the western end of the Algerian–Balearic basin rift. Present-day small areas with high heat flow may well be related to volcanism
and an anomalous mantle. Areas of active deformation in the Alboran Sea accommodate the present Eurasia-Africa convergence.
Received: 17 May 1996 / Revision received: 19 April 1997 相似文献
6.
Seismic stratigraphic and main lithological features of the sedimentary cover overlying the basement of the Alboran Sea were established via the analysis of commercial multichannel seismic surveys, geophysical well logs, and well data. Six seismic stratigraphics units (VI to I), bounded by unconformities, form the marine sediments that range in age from early Miocene to Quaternary. They are dated by extrapolation of commercial drilling results from the northern Alboran Sea. Volcanic activity is recorded within sedimentary sequences of units V to II. Undercompaction features are detected in the two basal units. 相似文献
7.
Shallow-seismic surveys around the Storegga Slide off western Norway have allowed greater understanding of the development of this part of the European margin. The northern flank of the scarp is formed of seismically well-layered, hemipelagic and distal-glaciomarine deposits in which a variety of luid-escape structures, probably due to gas, are locally abundant. There is evidence of slides that substantially pre-date the earliest slide previously recognized. Surveying on the North Sea Fan to the southwest of the Storegga Slide shows the markedly different nature of the autochthonous sediments on the southern flank of the Storegga Slide; there is a predominance of glacigenic debris flows in the upper part of the sequence, lesser maximum slopes, and an apparent absence of interstitial gas and/or hydrates. This contrast has had considerable effect on slope stability and has influenced the position of the southwestern Storegga Slide boundary. The North Sea Fan succession includes at least three major buried slides, termed the Vigra, Møre and Tampen slides, all of which substantially pre-date the Storegga event and probably pre-date predominantly glacigenic margin sedimentation. Post-late Weichselian slope failure is locally significant. The region has a long, but as yet chronologically poorly defined history of instability in which seismic triggering is considered to have been important. 相似文献
8.
南海西北部晚第四纪典型地震相—沉积相特征 总被引：1，自引：0，他引：1
南海西北部地形变化大,水深由近岸几十米变化至深海盆区的3 500m,跨越了陆架、陆坡、深海盆、岛礁等地貌单元。南海西北部也是深水油气的重要勘探地区。利用高分辨率单道地震资料,采用地震相分析方法,对研究区晚第四纪典型地震相—沉积相分布特征开展深入分析。研究区内的主要地震相包括：①席状、亚平行、强振幅、低连续、中频地震相;②披盖状、波状、中振幅、中—低连续、中低频地震相;③披盖状、平行—亚平行、中—弱振幅、中连续、中—低频地震相;④披盖状、平行、强振幅、高连续、中—高频地震相;⑤席状、平行、中—弱振幅、高连续、中—低频地震相;⑥披盖状、波状、弱振幅、低连续、低频地震相;⑦前积相;⑧下切充填地震相;⑨杂乱地震相;⑩条带状、波状、中—弱振幅、中—低连续、低频地震相;瑏瑡披盖状、平行、强振幅、高频、高连续地震相共11种。对地震相—沉积相及其分布特征的分析结果认为,区内晚第四纪主要发育有三角洲相、河道相、滨浅海相、浅海相、半深海相、深海相、滑塌相、斜坡相、浊流相、生物礁相等沉积相,其分布主要受海底地形地貌、构造运动等多种因素所控制。 相似文献
9.
The western South Korea Plateau in the East Sea (Sea of Japan) is occupied by rifted continental fragments formed in association
with the early phase of back-arc opening. The present study focuses on the seismic stratigraphy of the sedimentary succession
and the underlying acoustic basement in this region, based on closely spaced multichannel seismic reflection profiles. The
sedimentary succession occurs mainly within a series of subparallel basement troughs (grabens or half grabens) bounded by
faulted continental blocks (horsts) or volcanic ridges, and commonly floored by extrusive volcanic rocks showing hyperbolic
reflectors. These features are strongly suggestive of continental rifting accompanied by normal faulting, volcanic activity
and high rates of basin subsidence. The sedimentary succession can be subdivided into four seismic units. Unit 1 is characterized
by short and irregular high-amplitude reflectors and interpreted as a syn-rift deposit consisting of a non-marine volcanics/sediment
complex in topographic lows. Units 2 and 3 formed in an open marine environment during the Middle Miocene to Early Pliocene,
characterized by an onlap-fill and later draping marine sedimentary succession dominantly composed of hemipelagic sediments
and turbidites with frequent intercalation of mass-flow deposits. Along the western margin of the plateau, these units were
deformed under a compressional regime in the Early Pliocene, associated with the back-arc closing phase. Unit 4 (deposited
since the Early Pliocene) comprises hemipelagic sediments and turbidites with evidence of sporadic slides/slumps. 相似文献
10.
根据浅地层地震剖面的解译结果,对南黄海西部滨浅海区灾害地质要素进行了识别。结果表明,研究区存在多种灾害地质要素,包括海岸侵蚀与淤积、水下浅滩、浅层气、埋藏古河道和古三角洲、沙脊、陡坡、沙层液化、冲蚀沟槽、滑坡、差异性压实断层等等。探讨了灾害地质要素的特征和分布规律,并绘制了主要灾害地质要素分布图。 相似文献
11.
天然气水合物作为现今乃至未来的重要清洁能源之一,其沉积环境和成矿条件的研究一直是国内外地质学家关注的热点问题,我国2007年、2013年及2015年已先后在神狐、和东沙海域多次成功钻获了天然气水合物实物样品。由此南海北部陆坡成为探讨天然气水合物沉积成因与成矿条件的重要试验区。然而,南海北部陆坡区的神狐、东沙及琼东南三个海域均有不同程度的天然气水合物发现,其各自的水深、沉积特征、气源成因及水合物成矿条件各有特点。本文利用地震沉积学原理,结合不同沉积相和沉积演化和古地貌、海平面变化和构造运动等因素,识别出不同类型的地震相。通过对比南海北部陆坡区域的水道系统的MTDs,认为其发育位置、展布和控制因素的不同影响了沉积展布。其中东沙区域位于近物源的上陆坡,神狐区域位于正常的缓陆坡区域,琼东南区域位于远离物源的海底平原区域。并且,水道系统可以分成侵蚀型,侵蚀-加积型和加积型,MTDs也可以分成头部拉张型,中部过渡型和趾部挤压型。 相似文献
12.
Four main seismic sequences of Plio-Quaternary age identified in the northeastern Alboran Sea record the main phases of margin and basin development. The geometry and thickness of these sequences reveal that the Motril and Almeria basins contain the main sediment depocenters. Sea level fluctuations and sediment input were probably the most significant factors controlling growth patterns, but the presence of structural barriers and the active tectonism influenced sediment traps and downslope gravity processes. 相似文献
13.
对从南海东沙群岛近海陆坡（水深约500-3100m）采集到的二维地震剖面提取地形数据后进行统计学分析,结合地震相研究,发现研究区陆坡形态的变化与火成岩体,以及与火成岩体相关联的沉积过程存在着紧密地联系。共识别出了3种陆坡类型：（a）发育多个火成岩体的粗糙、陡的陆坡（类型1）;（b）发育单个火成岩体的较为光滑、平缓的陆坡（类型2）;（c）无火成岩体发育的光滑并且平缓的陆坡（类型3）。这些火成岩体形成于南海海底扩张之后,具有较为复杂的形态,在地震剖面上多表现为强振幅的杂乱反射。在类型1中,多个火成岩体将陆坡分为上部的两个或者多个次凹和下部的一个主凹,这些凹陷可以同时被沿坡流带来的沉积物充填。然而在类型2中,单个火成岩体将陆坡为一个上部的次凹和一个下部的主凹,只有当上部的次凹被沉积物填满后,沉积物才可以开始充填主凹。类型3为发育斜坡沉积的正常陆坡。研究区现今的陆坡形态是由于火成岩体的侵入和与火成岩体相关的沉积过程所共同导致的陆坡形态调整的结果。三种陆坡类型现今陆坡形态间的差异指示不同的沉积条件和陆坡形态调整。 相似文献
14.
Ingrid Marie Hasle Amundsen Maria Blinova Berit Oline Hjelstuen Rolf Mjelde Haflidi Haflidason 《Marine Geophysical Researches》2011,32(4):441-453
The northeastern high-latitude North Atlantic is characterised by the Bellsund and Isfjorden fans on the continental slope
off west Svalbard, the asymmetrical ultraslow Knipovich spreading ridge and a 1,000 m deep rift valley. Recently collected
multichannel seismic profiles and bathymetric records now provide a more complete picture of sedimentary processes and depositional
environments within this region. Both downslope and alongslope sedimentary processes are identified in the study area. Turbidity
currents and deposition of glacigenic debris flows are the dominating downslope processes, whereas mass failures, which are
a common process on glaciated margins, appear to have been less significant. The slide debrite observed on the Bellsund Fan
is most likely related to a 2.5–1.7 Ma old failure on the northwestern Barents Sea margin. The seismic records further reveal
that alongslope current processes played a major role in shaping the sediment packages in the study area. Within the Knipovich
rift valley and at the western rift flank accumulations as thick as 950–1,000 m are deposited. We note that oceanic basement
is locally exposed within the rift valley, and that seismostratigraphic relationships indicate that fault activity along the
eastern rift flank lasted until at least as recently as 1.5 Ma. A purely hemipelagic origin of the sediments in the rift valley
and on the western rift flank is unlikely. We suggest that these sediments, partly, have been sourced from the western Svalbard—northwestern
Barents Sea margin and into the Knipovich Ridge rift valley before continuous spreading and tectonic activity caused the sediments
to be transported out of the valley and westward. 相似文献
15.
Anna Sanchez-Vidal Robert W. Collier Antoni Calafat Joan Fabres Miquel Canals 《Marine Chemistry》2005,93(2-4):105-117
Particulate biogenic barium (bio-Ba) fluxes obtained from three instrumented arrays moored in the Alboran Sea, the westernmost basin in the Mediterranean Sea, are presented in this study. The mooring lines were deployed over almost 1 year, from July 1997 to May 1998, and were equipped with sediment traps at 500–700 m depth, 1000–1200 m depth and 30 m above the seafloor (1000–2200 m). The results obtained support the growing body of evidence that the relationship between particulate bio-Ba and Corg throughout the water column in margin systems is clearly different from this relation in the open ocean. In the Alboran Sea, the annual averaged bio-Ba fluxes range from 0.39 to 1.07 μmol m−2 day−1, with mean concentrations of 1.31–1.69 μmol g−1 and bio-Ba/Corg ratios lower than in the open ocean. The low bio-Ba values obtained also indicate that calculating bio-Ba is extremely sensitive to the detrital Ba/Al ratio of each sample. The lithogenic Ba fraction in the Alboran Sea continental margin area contributes between 24% and 85% of the total Ba. Increased bio-Ba export efficiency was observed after periods of high primary productivity and suggests that the processes limiting the bio-Ba formation in the study area relate to settling dynamics of organic matter aggregates. Furthermore, the ballasting effect of the abundant lithogenic and carbonate particles may limit decomposition of organic matter aggregates and enhance the transfer of particles rich in Corg and relatively poor in bio-Ba to the deep seafloor. Lateral input of freshly sedimented biogenic material, including particulate bio-Ba, has been observed on the lower continental slope in the western Alboran Sea. These observations emphasize that the use of the bio-Ba as a proxy of export productivity from the surface ocean must be used cautiously in highly dynamic environments such as those in the Alboran Sea. 相似文献
16.
Slope-confined submarine canyons in the Baiyun deep-water area,northern South China Sea: variation in their modern morphology 总被引：1，自引：0，他引：1
X. S. Li Q. J. Zhou T. Y. Su L. J. Liu S. Gao S. W. Zhou 《Marine Geophysical Researches》2016,37(2):95-112
On the basis of newly collected multibeam bathymetric data, chirp profiles and existing seismic data, we presented a detailed morphological interpretation of a series of slope-confined canyons in water depths of 300–2000 m in the Baiyun deep-water area, northern margin of the South China Sea. Although these canyons are commonly characterized by regular spacing and a straight-line shape, they vary in their lengths, starting and ending water depths, canyon relief, slope gradients, wall slope gradients and depth profiles along the axis. The eastern canyons (C1–C8) have complex surface features, low values in their slope gradient, canyon relief and wall slope gradient and high values in their length and starting and ending depth contrasting to the western ones (C9–C17). From the bathymetric data and chirp profiles, we interpret two main processes that have controlled the morphology and evolution of the canyons: axial incision and landsliding. The western part of the shelf margin where there were at least four stages of submerged reefs differs from the eastern part of the shelf margin where sedimentary undulations occurred at a water depth of ~650 m. We consider that the variation in morphology of submarine canyons in the study area is the result of multiple causes, with the leading cause being the difference in stability of the upper slope which is related to the submerged reefs and sedimentary undulations. 相似文献
17.
南黄海盆地属于下扬子地块海域部分,是我国海相中—古生界发育最齐全,保存相对较完整的地区之一。该区具双层基底结构及复杂的深部构造体系,经历了多旋回的盆地成生、改造及叠加过程。海相中—古生界则经历了印支、燕山、喜山等构造运动的改造,以往由于缺少深部地震资料,无法对海相中—古生界进行构造区划。通过该区沉积盆地原型的分析,结合深部地震资料的解释划分了南黄海盆地海相中—古生界的构造格局。 相似文献
18.
The post-Calabrian sedimentary column of the northwestern Alboran Sea comprises three depositional sequences. The two older depositional sequences are defined by lowstand systems tracts (shelf-margin deltas, slope, base-of-slope, and basin deposits, and the Guadiaro channel-levee complex). In contrast, the most recent depositional sequence also includes transgressive (relict shelf facies) and high-stand (the Guadalmedina-Guadalhorce prodelta and hemipelagic facies) systems tracts. The stratigraphic architecture of these depositional sequences is controlled by the synchronism between high frequency sea-level changes, variations in sediment supply, and sedimentary processes. The configuration of the depositional sequences is variable and their distribution is complex, as a result of the relative importance played by sea-level changes and tectonism through the area.
The sequence boundaries are represented by polygenetic surfaces in the proximal margin, and by monogenetic surfaces in the distal margin and basin. Each polygenetic surface results from the interaction between the sequence boundary with the lowstand erosional truncation surface and the transgressive surface, both developed during the previous sea-level cycle. The monogenetic surfaces correspond to unconformities and their correlative conformities, formed during sea-level lowstands. This pattern of depositional sequences developed in the margin and basin of the northwestern Alboran Sea shows differences with the Exxon Sequence Stratigraphy Model as traditionally applied: sea-level change control is essentially recognized through lowstand systems tracts, and sequence boundary coincides with lowstand erosional truncation surface and transgressive surface, both developed during the previous sea-level cycle. 相似文献
19.
Mehmet Sinan Özeren M. Namık Çağatay Nazmi Postacıoğlu A. M. Celal Şengör Naci Görür Kadir Eriş 《Geo-Marine Letters》2010,30(5):523-539
Potential tsunami waves were modelled on the basis of the morphology and geological setting of a late glacial submarine landslide localized in the north-eastern sector of the Sea of Marmara, using a three-dimensional algorithm with the purpose of assessing the future risk of tsunamogenic landslides in the region. The landslide occurred off the Tuzla Peninsula on the north-eastern slope of the Ç?narc?k Basin, the easternmost of the three deep Marmara basins. The mass movement appears to be related to the Main Marmara Fault that passes below the toe of the failed mass. Observations from earlier manned submersible dives suggest that the initiation of the slide was facilitated by secondary faults associated with the Hercynian orogeny and involved Palaeozoic shales dipping southwards towards the deep basin. Radiocarbon dating of core material, together with the well-dated Marmara sapropel above the chaotically mixed landslide surface, reveal that the latest landslide event occurred about 17 14C ka b.p. The uppermost scar of the landslide is found at 250 m and its toe at about 1,200 m below the present sea level. At the time of the slide, the Marmara Sea Basin was lacustrine, with its water level at ?85 m. In plan view the landslide has a distinctively triangular shape and the lateral extent of its toe is about 10 km. Multibeam bathymetric data indicate that the sliding motion probably occurred in two phases: a slower phase affecting the eastern part, characterized by an undulating surface, and a more rapid phase affecting the western part that possibly created tsunami waves. In the seismic sections, older failed slide masses can be clearly identified; these were probably displaced during marine isotopic stage 6 (～127–160 ka b.p.). The front of this buried material is located more than 1.5 km further south of the fault. We used a three-dimensional, Green’s function-based potential theory approach, rather than shallow-water equations commonly used in conventional tsunami simulations. The solution algorithm is based on a source-sink formulation and an integral equation. The results indicate that the maximum height of the tsunami in the Ç?narc?k Basin could have reached about half the average thickness of the sliding mass over a lateral extent of 7 km. Assuming an average thickness of 30 m for the landslide, and considering that the water level at 17 ka b.p. was at about ?85 m, the modelling shows that the maximum wave height generated by the slide would have been about 15–17 m. 相似文献
20.
The Pacific-type orogeny in the Tohoku Island Arc is discussed using marine geological and geophysical data from both Pacific and Japan Sea along the Tohoku region. The Tohoku Arc is divided into three belts; inner volcanic and sedimentary belt, intermediate uplifted belt and outer sedimentary trench belt. Thick Neogene sediments which are distinguished in several layers by continuous seismic reflection profiling occur on both sides of the intermediate belt. The dominant structural trend of the Neogene layers is approximately parallel to the coast line and to the axis of the Japan Trench and has a extension of approximately 100 km in each unit on the Pacific side. The trench slope break is an uplifted zone of Neogene layers. The structural trend of the upper continental slope and outer shelf is relative uplift of the landward side. Tilted block movement toward the west is the dominant structural trend on the Japan Sea side. Structural trends which can be seen in both the inner and outer belts may suggest horizontal compressional stress of east to west. Orogenesis and tectogenesis in the Tohoku Arc has been active since early Miocene or latest Oligocene. It may be implied that the Japan Trench was not present during Late Cretaceous to Paleogene, as is suggested by the volcanism of the Tohoku Arc. The basic framework of the present structure was formed during late Miocene to early Pliocene in both the inner and outer belts. Structural movements were reactivated during late Pleistocene. 相似文献