共查询到20条相似文献，搜索用时 15 毫秒
1.
K. Solli B. Kuvaas Y. Kristoffersen G. Leitchenkov J. Guseva V. Gandjukhin 《Marine Geophysical Researches》2007,28(1):43-57
Multichannel seismic data from the eastern parts of the Riiser-Larsen Sea have been analyzed with a sequence stratigraphic
approach. The data set covers a wide bathymetric range from the lower continental slope to the abyssal plain. Four different
sequences (termed RLS-A to RLS-D, from deepest to shallowest) are recognized within the sedimentary section. The RLS-A sequence
encompasses the inferred pre-glacial part of the deposits. Initial phases of ice sheet arrival at the eastern Riiser-Larsen
Sea margin resulted in the deposition of multiple debris flow units and/or slumps on the upper part of the continental rise
(RLS-B). The nature and distribution of these deposits indicate sediment supply from a line or a multi-point source. The subsequent
stage of downslope sediment transport activity was dominated by turbidity currents, depositing mainly as distal turbidite
sheets on the lower rise/abyssal plain (RLS-C). We attribute this to margin progradation and/or a more focussed sediment delivery
to the continental shelf edge. As the accommodation space on the lower rise/abyssal plain declined and the base level was
raised, the turbidite channels started to backstep and develop large channel–levee complexes on the upper parts of the continental
rise (RLS-D). The deposition of various drift deposits on the lower rise/abyssal plain and along the western margin of the
Gunnerus Ridge indicates that the RLS-D sequence is also associated with increased activity of contour currents. The drift
deposits overlie a distinct regional unconformity which is considered to reflect a major paleoceanographic event, probably
related to a Middle Miocene intensification of the Antarctic Circumpolar Current. 相似文献
2.
Bauxitic red-mud slurry, discharged by an aluminium processing factory on the shelf of the Gulf of Corinth, Greece, is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin.
The Gulf of Corinth is a silled elongate basin with a maximum depth of 860 m; it is characterised by high seismicity. The red mud is discharged through a pipeline at a depth of 100 m, where it forms an extensive deposit.
Grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline. It forms small scattered sheet-like deposits of up to 3 cm in thickness. The structures observed in the scattered patches of the red mud, which in some places are overlain by a thin veneer of grey/olive green (natural) sediments, suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows. The flows are triggered by earthquakes.
Granulometric and geochemical analyses of the red-mud samples show that the red mud, during its transport from the shelf to the abyssal plain, is subjected to mixing with the surrounding sediments. A different mixing ratio is determined, however, by reference to the various trace metals (Fe, Ni, Co, Pb). 相似文献
3.
Sedimentary processes related to turbidity current interaction with bathymetric obstacles were studied in the area of the
Lametini Seamounts and Stromboli Canyon. Four types of turbidite were identified on the basis of their compositional and sedimentological
characteristics, and they were interpreted in terms of provenance, transport, and depositional processes. At the bend of the
Stromboli Canyon, south of the Lametini Seamounts, the fine fraction of large turbidity currents can spill over and either
(1) expand within the canyon embayment; (2) cross the saddle that divides the two volcanic cones of the Lametini Seamounts;
or (3) be reflected by the steep slopes of the seamounts. 相似文献
4.
K. T. Pickering 《Geo-Marine Letters》1982,2(1-2):41-46
Deep-water siliciclastic systems are classified primarily on their shape as: submarine fans with well developed or poorly
developed morphology, slope drapes, for example, over relatively stable basin margins, fault-scarp aprons, canyons and large
channels, under-supplied sheet systems such as abyssal plains, non-fan ponded systems such as over-supplied perched basins,
and fan deltas. Collectively, or separately, these systems may form sedimentary basin fills that can be over or under-supplied
with respect to the sediment input although most systems will tend toward over-supply/overflow with time. Finally, the sum
total of the siliciclastic systems and basins can be used to define the tectonic milieux such as passive, strike-slip and
convergent margins. 相似文献
5.
Morphotectonics and evolutionary controls on the Pearl River Canyon system, South China Sea 总被引：2，自引：0，他引：2
Weiwei Ding Jiabiao Li Jun Li Yinxia Fang Yong Tang 《Marine Geophysical Researches》2013,34(3-4):221-238
The Pearl River Canyon system is a typical canyon system on the northern continental slope of the South China Sea, which has significant implications for hydrocarbon exploration. Through swath bathymetry in the canyon area combined with different types of seismic data, we have studied the morphotectonics and controlling factors of the canyon by analyzing its morphology and sedimentary structure, as well as the main features of the continental slope around the canyon. Results show that the Pearl River Canyon can be separated into three segments with different orientations. The upper reach is NW-oriented with a shallowly incised course, whereas the middle and lower reaches, that are located mainly in the Baiyun Sag, have a broad U-shape and have experienced consistent deposition. Seventeen deeply-cut canyons have developed in the slope north of the Baiyun Sag, playing an important role in the sedimentary processes of the middle and lower reaches of the Pearl River Canyon. These canyons display both asymmetrical V- and U-shapes along their lengths. Numerous buried channels can be identified below the modern canyons with unidirectionally migrating stacking patterns, suggesting that the canyons have experienced a cyclic evolution with several cut and fill phases of varying magnitude. These long established canyons, rather than the upper reach of the Pearl River Canyon, are the main conduits for the transport of terrigenous materials to the lower slope and abyssal basin during lowstand stage, and have contributed to the formation of vertically stacked deep-water fans in the middle reach. Canyon morphology is interpreted as a result of erosive sediment flows. The Pearl River Canyon and the 17 canyons in the slope area north of the Baiyun Sag probably have developed since the Miocene. Cenozoic tectonics, sea level change and sediment supply jointly control the morphology and sedimentary structure. The middle and lower reaches of the Pearl River Canyon developed on the paleo-terrain of the Baiyun Sag, which has been a persistently rapid depositional environment, receiving most of the materials transported via the canyons. 相似文献
6.
The petrophysical properties of sediment drill core samples recovered from the Sardinian margin and the abyssal plain of the
Southern Tyrrhenian Basin were used to estimate the downhole change in porosity and rates of deposition and mass accumulation.
We calculated how the deposited material has changed its thickness as a function of depth, and corrected the thickness for
the compaction. The corresponding porosity variation with depth for terrigenous and pelagic sediments and evaporites was modelled
according to an exponential law. The mass accumulation rate for the Plio-Quaternary is on average 4.8×104 kg m−2 my−1 on the Sardinian margin and for the Pliocene in the abyssal plain. In the latter area, the Quaternary attains its greatest
thickness and a mass accumulation rate of 11–40×104 kg m−2 my−1. The basement response to sediment loading was calculated with Airy-type backstripping. On the lower part of the Sardinian
margin, the basement subsidence rate due to sediment loading has decreased from a value of 300 m my−1 in the Tortonian and during the Messinian salinity crisis (7.0–5.33 Ma) to about 5 m my−1 in the Plio-Quaternary. In contrast, on the abyssal plain this rate has changed from 8–50 m my−1 during the period 3.6–0.46 Ma, to 95–130 m my−1 since 0.46 Ma, with the largest values in the Marsili Basin. The correlation between age and the depth to the basement corrected
for the loading of the sediment in the ocean domain of the Tyrrhenian Basin argues for a young age of basin formation. 相似文献
7.
The Zenisu deep-sea channel originates on the Izu-Ogasawara island arc, and disappears in the Shikoku Basin of the Philippine Sea. The geomorphology, sedimentary processes, and the development of the Zenisu deep-sea channel were investigated on the basis of swath bathymetry, side-scan sonar imagery, submersible observations, and seismic data. The deep-sea channel can be divided into three segments according to the downslope gradient and channel orientation. They are the Zenisu Canyon, the E–W fan channel, and the trough-axis channel. The sediment fill is characterized by turbidite and debrite deposition and blocky–hummocky avalanche deposits on the flanks of the Zenisu Ridge. In the Zenisu Canyon and the Zenisu deep-sea channel, sediment transport by turbidity currents generates sediment waves (dunes) observed during the Shinkai 6500 dive 371. The development of the Zenisu Canyon is controlled by a N–S shear fault, whereas the trough-axis channel is controlled by basin subsidence associated with the Zenisu Ridge. The E–W fan channel was probably affected by the E–W fault and the basement morphology. 相似文献
8.
Sediment delivery to the abyssal regions of the oceans is an integral process in the source to sink cycle of material derived from adjacent continents and islands. The Zambezi River, the largest in southern Africa, delivers vast amounts of material to the inner continental shelf of central Mozambique. The aim of this contribution is to better constrain sediment transport pathways to the abyssal plains using the latest, regional, high-resolution multibeam bathymetry data available, taking into account the effects of bottom water circulation, antecedent basin morphology and sea-level change. Results show that sediment transport and delivery to the abyssal plains is partitioned into three distinct domains; southern, central and northern. Sediment partitioning is primarily controlled by changes in continental shelf and shelf-break morphology under the influence of a clockwise rotating shelf circulation system. However, changes in sea-level have an overarching control on sediment delivery to particular domains. During highstand conditions, such as today, limited sediment delivery to the submarine Zambezi Valley and Channel is proposed, with increased sediment delivery to the deepwater basin being envisaged during regression and lowstand conditions. However, there is a pronounced along-strike variation in sediment transport during the sea-level cycle due to changes in the width, depth and orientation of the shelf. This combination of features outlines a sequence stratigraphic concept not generally considered in the strike-aligned shelf-slope-abyssal continuum. 相似文献
9.
Franco Ricci Lucchi 《Geo-Marine Letters》1984,3(2-4):203-210
Submarine fans of different sizes, geometry, and petrology were built in the Marnoso-arenacea Basin, a migrating foredeep
within an active continental margin. In an initial depositional stage, a well-developed basin plain received sediment from
flows that by-passed restricted fan systems, now buried, located near the north end of an elongated basin. Minor fans grew
near the steeper, tectonically deformed side of the basin. In the later stage, turbidite deposition was stopped in the former
basin plain. Sediment sources and feeder channels shifted and fed fan lobes that prograded in a narrower trough and were distored
(choked). The tectonic control on development of megasequence and sand bodies is stressed here in contrast with previous emphasis
on “inner” or “autocyclic” mechanisms.
Margin setting represents fan and/or source area 相似文献
10.
Using bathymetry and reflection seismic profiles this study reveals the nature of the modern ponded Fangliao Fan within a framework of sediment infilling of an intra-slope basin on a tectonically active margin off southwestern Taiwan. The Fangliao Fan begins at the mouth of Fangliao Canyon at a water depth of 900 m and terminates down-slope at the escarpment of a linear ridge north of the Kaoping Slope Valley at a water depth of about 1,100 m, sediment gravity flows being prevented from farther down-slope transport due to ponding against this bathymetric high. The fan appears as a distinct basinward-opening triangular depocenter confined by ridges on both sides and the NW–SE trending ridge aligned normal to the elongation of the fan. These topographic ridges were formed by mud-diapiric intrusions. The external form of the ponded Fangliao Fan is characterized by a fan-valley fill pattern that has a concave cross-sectional morphology, in contrast to typical mounded fans deposited on slope-basin plains having a smooth topography. Sediment episodically funneled through the Fangliao Canyon from upslope areas and derived from the flanks of the mud-diapiric ridges are mainly transported by mass movement before being re-dispersed by unconfined channels to infill the intra-slope basin, thereby building up channelized fan complexes with poorly developed levees. The sediment flows from the mouth of Fangliao Canyon flow down-slope along the west flank of the Fangliao Ridge. In the process, a feeder channel has been eroded into the seafloor along which sediment is transported to the distal parts of the fan. Sediment west of the feeder channel is mainly redistributed by mass movement and/or fan channels to fill up the irregular topographic low in the slope. Due to a very low sediment supply, Fangliao Fan represents a starved ponded slope fan. As such it provides insights into the processes by which ponded fans develop and can therefore serve as an analog for similar fans developed on topographically complex slopes elsewhere. The morpho-structural features of the Fangliao Fan resulted from the interplay between sediment supply, uplift of the mud-diapiric ridge, mass movements, and alternating incision and deposition. 相似文献
11.
Neslihan Ocako?lu 《Geo-Marine Letters》2012,32(1):17-28
New (2009) multi-beam bathymetric and previously published seismic reflection data from the NE-SW-oriented Fethiye Bay and
the neighboring N-S-oriented Marmaris Bay off SW Anatolia were evaluated in order to interpret the seafloor morphology in
terms of the currently still active regional tectonic setting. This area lies between the Pliny Trench, which constitutes
the eastern sector of the subduction zone between the African and Eurasian plates in the Eastern Mediterranean, and the Fethiye-Burdur
Fault Zone of the Anatolian Plate. The bathymetric data document the very narrow shelf of the Anatolian coast, a submarine
plain between the island of Rhodes and Marmaris Bay, and a large canyon connecting the abyssal floor of the Rhodes Basin with
Fethiye Bay. The latter are here referred to as the Marmaris Plain and Fethiye Canyon, respectively. Several active and inactive
faults have been identified. Inactive faults (faults f1) delineate a buried basin beneath the Marmaris Plain, here referred
to as the Marmaris Basin. Other faults that affect all stratigraphic units are interpreted as being active. Of these, the
NE-SW-oriented Marmaris Fault Zone located on the Marmaris Plain is interpreted as a transtensional fault zone in the seismic
and bathymetric data. The transtensional character of this fault zone and associated normal faults (faults f3) on the Marmaris
Plain correlates well with the Fethiye-Burdur Fault Zone on land. Another important fault zone (f4) occurs along the Fethiye
Canyon, forming the northeastern extension of the Pliny Trench. The transpressional character of faults f4 inferred from the
seismic data is well correlated with the compressional structures along the Pliny Trench in the Rhodes Basin and its vicinity.
These observations suggest that the Marmaris Fault Zone and faults f3 have evolved independently of faults f4. The evidence
for this missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone implies possible kinematic problems in this
tectonic zone that deserve further detailed studies. Notably, several active channels and submarine landslides interpreted
as having been triggered by ongoing faulting attest to substantial present-day sediment transport from the coast into the
Rhodes Basin. 相似文献
12.
海底峡谷在全球陆缘广泛分布，是浅海沉积物向深海运移的主要通道，对于理解深海浊流触发机制、深海沉积物的搬运模式、深海扇的发育历史和深海油气资源勘探等均具有重要意义。本文基于高分辨率高精度的多波束测深数据，首次对南海东北部海底峡谷体系进行了研究，精细刻画了高屏海底峡谷、澎湖海底峡谷、台湾浅滩南海底峡谷和东沙海底峡谷等4条大型海底峡谷的地貌特征并分析其发育控制因素。海底坡度、构造运动、海山与海丘是影响南海东北部峡谷群走向与特征的重要因素，其中，海底坡度对于峡谷上游多分支与“V”字特征有显著的控制作用；构造运动是控制高屏海底峡谷走向的因素，澎湖海底峡谷的走向则与菲律宾海板块与欧亚板块碰撞有关，东沙海底峡谷的走向则与东沙运动相关，台湾浅滩南海底峡谷上段受NW向断裂构造的控制；海山的阻挡作用造成峡谷局部走向和特征改变。海底峡谷群输送大量陆源沉积物到深海盆并形成大面积的沉积物波，海山和沉积物波的发育导致东沙海底峡谷下段“回春”和转向。 相似文献
13.
High-resolution sub-bottom (3.5 kHz) traverses of the southwestern portion of the Balearic Abyssal Plain between North Africa and the Balearic block show an irregular topography where rates of deformation appear to locally exceed those of sedimentation. The basin is underlain by salt of Messinian age, and diapirism has disturbed post-Messinian sediments. The 3.5 kHz records, augmented by 30,000 Joule seismic reflection profiles, indicate that this diapirism is continuing at present and is even now significantly deforming the uppermost sediment sequences.A high concentration of structural features including doming and the development of rim synclines within the 35–60 m of section penetrated are associated with diapirism. Over 70% of the domes have penetrated the surface in the studied area; of these, most display a relief of 10 m or more. In some instances, domes apparently act as dams behind which sediment is ponded. Non-faulted relief averages 3–4 m/km, notable for an abyssal plain surface. Frequently, the uppermost Holocene strata are offset several meters as a result of normal faults and grabens. This concentration of sea-floor irregularities necessarily modifies the present-day sediment dispersal pattern and rules out the uniform flow of turbidity currents and lateral continuity of sedimentation units across this basin plain. 相似文献
14.
Examining bathymetric and seismic reflection data collected from the deep-sea region between Taiwan and Luzon in 2006 and
2008, we identified a connection between a submarine canyon, a deep-sea channel, and an oceanic trench in the northern South
China Sea. The seafloor of the South China Sea north of 21°N is characterized by two broad slopes: the South China Sea Slope
to the west, and the Kaoping Slope to the east, intersected by the prominent Penghu Canyon. This negative relief axis parallels
the strike of the Taiwan orogen, extends downslope in an approx. N–S direction, and eventually merges with the northern Manila
Trench via a hitherto unidentified channel. The discovery of this channel is pivotal, because it allows connecting the Penghu
Canyon to the Manila Trench. This channel is 80 km long and 20–30 km wide, with water depths of 3,500–4,000 m. The progressive
morphological changes recorded in the aligned canyon, channel, and trench suggest that they represent three distinct segments
of the same longitudinal sediment conduit from southern Taiwan to the northern Manila Trench. Major sediment input would be
via the Kaoping Canyon and Kaoping Slope, with a smaller contribution from the South China Sea Slope. We determined the northern
end of the Manila Trench to be located at about 20°15′N, 120°15′E, where sediment accumulation has produced a bathymetry shallower
than 4,000 m, thereby abruptly terminating the trench morphology. Comparison with existing data reveals a similarity with,
for example, the Papua New Guinea–Solomon Sea Plate convergent zone, another modern analog of a mountain source to oceanic
sink longitudinal sediment transport system comprising canyon–channel–trench interconnections. 相似文献
15.
A corridor 315 km wide centered along the southeast projection of the Atlantis fracture zone between 21°W and 29°W was investigated with seismic reflection, bathymetric, gravity, and magnetic profiles. Six sub-parallel, sediment-filled troughs in acoustic basement trend about 106° across the abyssal hills and lower continental rise off northwest Africa. Where the southernmost structural lineations cross the abyssal plain, they are interrupted by a ridge trending 080° surmounted by volcanic peaks.The structural lineations become less distinct landward of the western margin of the abyssal plain coincident with a decrease in topographic relief on acoustic basement and increasing sediment thickness. This transition is coincident with a reduction in the amplitude of gravity and magnetic anomalies. 相似文献
16.
Patrick S. Ditty Carol J. Harmon Orrin H. Pilkey Mahlon M. Ball Evan S. Richardson 《Marine Geology》1977,24(1):1-20
Sedimentation in the 9500 km2, 4100 m deep Hispaniòla—Caicos Basin is dominated by turbidity currents. Carbonate turbidites originate from the Bahama Islands, Great Inagua and Caicos at the north end of the basin. Mixed carbonate—non-carbonate flows come from Hispaniola and perhaps Cuba. Most flows originate on insular slopes rather than in shallow water. The relatively low CaCO3 content of hemipelagic sequences throughout the entire basin reveals that the influence of non-carbonate Hispaniola—Cuba sources is widespread.The basin was sampled with closely spaced piston cores. Sand-layer isopach and frequency maps reveal four or five major basin entry points for turbidity currents. Flow size is proportional to the size of source areas. Average volumes of flows originating from Hispaniola—Cuba, the largest source, are 109 m3. This compares to an average flow volume of 106 m3 for flows derived from the smallest source area, the Southeastern Caicos Bank. Measures of turbidity-current activity, such as thickness and frequency, change in a regular fashion away from each entry point. Average lutite thickness (combining hemipelagic and turbiditic lutite) are greatest near the basin entry points. On the abyssal plain occupying the south half of the basin, Bouma turbidite sedimentary structure sequences tend to be complete. However, on the Caicos Fan, the sedimentary structure sequences in turbidites are characterized by missing or repeated units. Six radiocarbon dates of two widespread presumed pelagic units in the basin yielded younger dates in stratigraphically older positions. The reversed dates are assumed to reflect storm erosion of older sediment on adjacent insular shelves.Consideration of a north—south reflection seismic profile over the basin indicates that the present sediment regimen has pertained through much of the Neogene. The coherence, convergence and termination of reflections in the seismic section are consistent with and tend to confirm conclusions based on the core study regarding the greater extent and volume of sediment deposits derived from the Hispaniola source area. 相似文献
17.
《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1305-1315
Activities of dissolved, particulate, and sedimentary 210Pb were measured in the shelf-slope region of the Chukchi Sea. Samples were collected as part of the Shelf–Basin Interactions (SBI) Phase II process study (6 May–15 June, 2002) along three shelf–basin transects identified as West Hanna Shoal, East Hanna Shoal, and Barrow Canyon. Distributions of 210Pb and suspended particulate matter indicate efficient removal of 210Pb over the shelf by particle scavenging. Low 210Pb activities measured throughout the halocline of the Canada Basin are attributed to shelf scavenging and subsequent advective transport into the interior basin. Additionally, 210Pb inventories were used to construct a water-column-sediment budget of 210Pb and determine regions of particle export and deposition on the continental shelf and slope. Sediment focusing calculated with this 210Pb budget was observed throughout the shelf-slope region, particularly in shallow (∼100 m) shelf waters at Barrow Canyon. Despite elevated concentrations of suspended particulate matter in Barrow Canyon, the 210Pb budget does not indicate that sediment transport occurred from the West and East Hanna Shoals into Barrow Canyon. 相似文献
18.
Abstract It is clear from morphology alone that distinctly different dynamic and sedimentary processes can be expected to be associated with the Greater Antilles Outer Ridge relative to those of the adjacent Nares Abyssal Plain. This difference is further substantiated by seismic reflection data which show the ridge to be a very large prism of acoustically transparent sediment in contrast to the stratified deposits of the abyssal plain. An examination of the geotechnical properties of the near‐surface (0 to 2.4m) deposits of the two areas also reveals distinct differences in their sedimentological characteristics. The outer ridge sediments, of more or less homogenous clay‐size material, display much higher water contents, porosities, sensitivities, plasticity, and organic carbon contents in contrast to the abyssal plain deposits which are much less homogenous owing to the presence of turbidite sequences. The turbidites themselves are uniquely contrasted to the other abyssal plain sediments by their higher silt content, wet bulk density, shear strength, and sensitivity. 相似文献
19.
南海北部陆坡发育众多海底峡谷,其形成、发育、演化过程都存在较大差异。本文选取南海北部陆坡典型的珠江口外海底峡谷群、东沙海底峡谷、台湾浅滩南海底峡谷和澎湖海底峡谷进行研究,通过高分辨率多道地震数据和多波束测深数据,结合前人研究成果,对4条典型海底峡谷的形态特征、沉积充填特征及结构、形成发育过程及控制因素进行研究。结果表明,南海北部陆缘各个海底峡谷的形成受多个控制因素的影响,其影响程度及方式都有差别。构造活动、海平面变化及沉积物重力流与海底峡谷的演化密切相关,而陆地河流和局部构造因素也以不同方式影响着海底峡谷的发育。对于发育在主动大陆边缘的台湾岛东南侧的澎湖海底峡谷,其板块运动和岩浆活动活跃,其上发育的海底峡谷的控制因素以内营力地质作用为主。而具有被动大陆边缘属性的其他3条峡谷,由于构造运动较少或停止,其上发育的海底峡谷的控制因素以外营力地质作用为主。 相似文献
20.
远海孤立碳酸盐台地周缘发育了碳酸盐岩峡谷, 对其开展研究有助于深刻理解碳酸盐碎屑沉积物的“源-汇”体系及深水油气成藏等方面。文章利用多波束测深、高分辨率二维多道地震等数据, 精细刻画南海西沙海域永乐海底峡谷的地貌形态及内部充填特征, 揭示该峡谷沉积演化过程, 分析峡谷成因控制因素及稳定性。永乐海底峡谷形成演化可分为萌芽、汇聚和拓展3个阶段, 随着演化过程的发展, 峡谷规模及对沉积物输运作用增加。永乐海底峡谷形成及演化主要受古地貌隆起形成的负地形和沉积物重力流侵蚀作用影响。峡谷在第四纪以后仍有较明显的活动迹象。分析显示永乐海底峡谷是西北次海盆的重要物质输送通道, 其沉积演化过程及稳定性对研究碳酸盐台地沉积物输运等深水沉积过程及岛礁工程建设具有一定参考意义。 相似文献