共查询到20条相似文献，搜索用时 24 毫秒
1.
The petrographic and micropaleontological studies of the rocks in the sedimentary cover of the Primorye continental slope in the area of Vladimir Bay in the Sea of Japan made it possible to establish that the sedimentary cover is represented in this area by two different facial complexes of Late Miocene rocks. The first facial complex consists of terrigenous rocks (siltstones, sandstones, and conglomerates) that were accumulated under relatively shallow-water conditions of the shelf and the uppermost part of the continental slope. The second one is formed by diatomaceous-clayey rocks under more deep-water conditions, mainly in the upper part of the continental slope. The carbonate nodules that are widely distributed among the deposits of the first complex but are also recorded in the second one were formed as a result of diagenetic processes in the terrigenous or silicious-terrigenous sediments that had been formed. With respect to their age, the Late Miocene deposits are characterized by a full succession of diatomaceous zones over 10.0–5.5 mln yr. The sediments of the first facial complex accumulated during the first third of the Late Miocene (10.0–8.5 mln yr), while those of the second began to accumulate somewhat later, but their accumulation continued until the late Miocene (9.2–5.5 mln yr). 相似文献
2.
《Marine Geology》2005,216(3):145-154
The Eastern Basin in the Ross Sea (Antarctica) contains a sedimentary sequence that is a direct record of advance and retreat of the West Antarctic Ice Sheet.We analyzed a sedimentary section ranging from the upper Miocene to present.The joint tomographic inversion of refracted and reflected arrivals of pre-stack multi-channel seismic data revealed in this area the presence of layers with anomalous high velocity. These anomalies are correlated with sediments that were eroded and compacted by the load of the West Antarctic Ice Sheet during its expansion on the continental shelf.The deepest and stronger velocity anomaly correspond to a basin-wide seismic unconformity (RSU2, Late Miocene–Early Pliocene in age). This anomaly is interpreted as evidence of a major advance of the West Antarctic ice sheet on the continental shelf that resulted in high velocity and low porosity in sediment immediately above the unconformity. 相似文献
3.
对南海北部陆架坡折附近取的50个表层沉积物样品,作粒度测试,计算粒度参数。粒度分析表明研究区的沉积物主要存在4种类型:含砾砂、砾质砂、砂质砾和含砾泥质砂;沉积物组分中砾石和砂占绝对优势,基本上不含黏土。综合因子分析和聚类分析的结果把研究区划分为4类沉积区:Ⅰ类沉积区属于内陆架沉积区,Ⅱ类沉积区属于陆架坡折上部沉积区,Ⅲ类沉积区属于陆架坡折下部沉积区,Ⅳ类沉积区区属于陆架边缘沉积区,每类沉积区都代表着不同的沉积环境。研究区沉积物的粒径趋势分析结果显示,陆架坡折附近的沉积物主要向内陆架和外陆架边缘或上陆坡输运,同时存在着跨陆架输运和沿陆架坡折输运现象,这与研究区实测的底流方向相一致。本研究表明,南海北部陆架坡折附近的沉积环境和沉积物输运模式比较复杂和特殊。本研究对今后陆架和陆坡区其他相关的研究具有十分重要的指导和借鉴意义。 相似文献
4.
The Cenozoic shelf margin of the Amazon Mouth Basin is characterized by a thick prograding prism of siliciclastic sediments. This prism, composed mainly of Upper Miocene and younger sediments, overlies a Lower Tertiary carbonate shelf. Two tectonic–sedimentary models for the area were developed with the aid of new deep-reflection seismic data. Gravitational tectonics dominate the regional geological framework. Tensional stresses are created near the shelf margin, and compressional features dominate at the base of the slope. The morphology of this compressional zone is closely associated with the St. Paul Fracture Zone and the boundary between continental and oceanic crusts. 相似文献
5.
南海北部陆缘东部中生代沉积的地震反射特征 总被引：14，自引：3，他引：14
姚伯初 《海洋地质与第四纪地质》1995,15(1):81-90
本文介绍了中美合作在南海北部陆缘进行的双船地震（合成排列剖面）工作，讨论了新生代沉积之下的中生代沉积之地震反射特征，在今日陆架新生代沉积之下的中生代沉积之地震反射表现杂乱，低振幅和不连续特性，而在今日上陆坡新生代沉积之下的中生代沉积之地震反射呈现连续，较强振幅和可和距离对比的特征。根据地球物理特征及区域地质资料，我们指出燕山运动时间广东大陆边缘的构造格架：今日东沙群岛－彭湖列岛一带火山弧，今日陆架 相似文献
6.
The continental slope south of Baltimore Canyon seaward of the coasts of Delaware and Maryland has a different morphology and sedimentary structure than adjacent portions of the continental margin. Ridges of sediment 600 m thick and transverse to the slope contain many unconformities that can be traced from ridge to ridge. The age of the sediment is inferred to be late tertiary to recent with the morphology related to a major drainage system. Physical properties of a suite of sediment cores display a pattern that varies in relationship to the morphology and depositional environment. Sedimentary structures and low shear strengths indicate instability of surficial sediments present on the upper slope and can be correlated with regions where the seismic reflection profiles show slumping has occurred. A veneer of sand overlying the general silty clay of the area is present on the upper slope and on the ridges indicating sand spillover from the shelf with a recent change in deposition pattern. 相似文献
7.
William P Dillon 《Marine Geology》1974,16(3):121-143
The structure of the continental shelf off southern Morocco was studied by means of 2,100 km of seismic reflection profiles, magnetic and bathymetric surveys, and dredge samples. The research area lies off four geologic divisions adjacent to the coast: the Atlas Mountains; the Souss Trough; the Anti-Atlas Mountains; and the Aaiun Basin. The continental shelf, along with the western Atlas Mountains, the western Souss Trough, and the entire Aaiun Basin, has subsided along a normal fault-flexure system. This system runs along the shore at the Anti-Atlas Mountains, and cuts off this cratonic block from the shelf subsidence. The shelf is narrow and characterized by out-building off the Anti-Atlas range, whereas it is broader and characterized by upbuilding to the north and south. Deposition was essentially continuous at least from Early Cretaceous through Eocene time. Published work suggests that the last cycle of sedimentation began during Permian rifting. After Eocene time, most sediments carried to the shelf must have bypassed it and gone to construct the slope and rise or to the deep sea. Tertiary orogenies caused extensive folding of Mesozoic and early Tertiary deposits off the Atlas Mountains. 相似文献
8.
冲绳海槽中南部不同环境表层沉积物质来源 总被引：1，自引：0，他引：1
对冲绳海槽中南部3种不同沉积环境(东海外陆架、东海陆坡和冲绳海槽)表层沉积物进行了稀土等元素地球化学分析,结果显示,冲绳海槽和陆坡表层沉积物具有与台湾物质来源类似的稀土元素配分模式,La/Sm-Gd/Yb散点图也显示海槽和陆坡沉积物主要分布在台湾物源端元区,表明冲绳海槽中南部海槽和陆坡表层沉积物主要来源于台湾,而外陆架... 相似文献
9.
本文根据南海深海盆地三个沉积柱样的粒度结构、地球化学、微体古生物等特征分析,深讨了南海深海盆地细粒沉积物的浊积现象。结果表明,位于南海北部陆架斜坡上KL37孔的浊流沉积现象并不明显;位于陆架斜坡和深海盆地交界处的KL29孔存在着大量的浊积层,属于浊流沉积和半远洋沉积环境;位于南海盆地中部的KL91孔虽然已属于远洋性沉积环境,但除出现火山灰沉积外,浊流沉积作用仍然是相当活跃的。 相似文献
10.
H. O. Woodbury 《Marine Georesources & Geotechnology》2013,31(1-4):263-273
Abstract Grain size, coarse fraction analyses, and depositional environment as interpreted from microfauna are related to the character of sparker reflections at the location of core holes drilled by Exxon, Chevron, Gulf, and Mobil on the continental slope of the northern Gulf of Mexico. Continuous sparker reflections are correlated with slowly deposited, evenly bedded sediments containing bathyal faunas. The coarse fraction is dominated by the tests of foraminifera. Discontinuous, discordant reflections and diffractions are correlated with sediments more rapidly emplaced in the bathyal environment of the continental slope by slumping and sliding from the continental shelf. Their coarse fraction is dominated by terrigenous sand grains. A large portion of the volume of continental slope sediments appears to consist of these “displaced”; sediments, including an area 3–24 km wide and 80 km long, southeast of Corpus Christi, Texas. Comparable processes of movement of sediments are interpreted on the continental shelf south of the Southwest Pass of the Mississippi River. Bathymetry in this area is characterized by a series of subaqueous “gullies”; radiating from the river mouth and leading to terraces at their southern extremities. Side‐scan sonar and PDR surveys show a rough bottom in these “gullies”; and terraces, as contrasted with a relatively smooth bottom elsewhere. The rough bottom is interpreted as indicative of slump and creep of the sediments from shallower water. Some foundation soil borings in this area south of Southwest Pass find a low‐strength material gradually increasing in strength with depth. Other borings find a “crust”; of anomalously strong material 8–15 m below the mudline. The microfauna recovered from the “crust”; has moved to its present position by slump or creep from shallower water along a pattern comparable to the gullies shown in the present‐day bathymetry. 相似文献
11.
B. Kuvaas Y. Kristoffersen J. Guseva G. Leitchenkov V. Gandjukhin G. Kudryavtsev 《Marine Geophysical Researches》2004,25(3-4):247-263
Multichannel seismic reflection data from the Cosmonaut Sea margin of East Antarctica have been interpreted in terms of depositional
processes in the continental slope and rise area. A major sediment lens is present below the upper continental rise along
the entire Cosmonaut Sea margin. The lens probably consists of sediments supplied from the shelf and slope, being constantly
reworked by westward flowing bottom currents, which redeposited the sediments into a large scale drift deposit prior to the
main glaciogenic input along the margin. High-relief semicircular or elongated depositional structures are also found on the
upper continental rise stratigraphically above the regional sediment lens, and were deposited by the combined influence of
downslope and alongslope sediment transport. On the lower continental rise, large-scale sediment bodies extend perpendicular
to the continental margin and were deposited as a result of downslope turbidity transport and westward flowing bottom currents
after initiation of glacigenic input to the slope and rise. We compare the seismostratigraphic signatures along the continental
margin segments of the adjacent Riiser Larsen Sea, the Weddell Sea and the Prydz Bay/Cooperation Sea, focussing on indications
that may be interpreted as a preglacial-glaciomarine transition in the depositional environment. We suggest that earliest
glaciogenic input to the continental slope and rise occurred in the Prydz Bay and possibly in the Weddell Sea. At a later
stage, an intensification of the oceanic circulation pattern occurred, resulting in the deposition of the regional plastered
drift deposit along the Cosmonaut Sea margin, as well as the initiation of large drift deposits in the Cooperation Sea. At
an even later stage, possibly in the middle Miocene, glacial advances across the continental shelf were initiated along the
Cosmonaut Sea and the Riiser Larsen Sea continental margins. 相似文献
12.
The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000–20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin. 相似文献
13.
In this study we provide evidence for methane hydrates in the Taranaki Basin, occurring a considerable distance from New Zealand's convergent margins, where they are well documented. We describe and reconstruct a unique example of gas migration and leakage at the edge of the continental shelf, linking shallow gas hydrate occurrence to a deeper petroleum system. The Taranaki Basin is a well investigated petroleum province with numerous fields producing oil and gas. Industry standard seismic reflection data show amplitude anomalies that are here interpreted as discontinuous BSRs, locally mimicking the channelized sea-floor and pinching out up-slope. Strong reverse polarity anomalies indicate the presence of gas pockets and gas-charged sediments. PetroMod™ petroleum systems modelling predicts that the gas is sourced from elevated microbial gas generation in the thick slope sediment succession with additional migration of thermogenic gas from buried Cretaceous petroleum source rocks. Cretaceous–Paleogene extensional faults underneath the present-day slope are interpreted to provide pathways for focussed gas migration and leakage, which may explain two dry petroleum wells drilled at the Taranaki shelf margin. PetroMod™ modelling predicts concentrated gas hydrate formation on the Taranaki continental slope consistent with the anomalies observed in the seismic data. We propose that a semi-continuous hydrate layer is present in the down-dip wall of incised canyons. Canyon incision is interpreted to cause the base of gas hydrate stability to bulge downward and thereby trap gas migrating up-slope in permeable beds due to the permeability decrease caused by hydrate formation in the pore space. Elsewhere, hydrate occurrence is likely patchy and may be controlled by focussed leakage of thermogenic gas. The proposed presence of hydrates in slope sediments in Taranaki Basin likely affects the stability of the Taranaki shelf margin. While hydrate presence can be a drilling hazard for oil and gas exploration, the proposed presence of gas hydrates opens up a new frontier for exploration of hydrates as an energy source. 相似文献
14.
The Cenozoic shelf margin of the Amazon Mouth Basin is characterized by a thick prograding prism of siliciclastic sediments.
This prism, composed mainly of Upper Miocene and younger sediments, overlies a Lower Tertiary carbonate shelf. Two tectonic–sedimentary
models for the area were developed with the aid of new deep-reflection seismic data. Gravitational tectonics dominate the
regional geological framework. Tensional stresses are created near the shelf margin, and compressional features dominate at
the base of the slope. The morphology of this compressional zone is closely associated with the St. Paul Fracture Zone and
the boundary between continental and oceanic crusts.
Received: 20 August 1996 / Revision received: 11 June 1998 相似文献
15.
Shallow 3D seismic data show contrasting depositional patterns in Pleistocene deepwater slopes of offshore East Kalimantan, Indonesia. The northern East Kalimantan slope is dominated by valleys and canyons, while the central slope is dominated by unconfined channel–levee complexes. The Mahakam delta is immediately landward of the central slope and provided large amounts of sediments to the central slope during Pleistocene lowstands of sea level. In the central area, the upper slope contains relatively straight and deep channels. Sinuous channel–levee complexes occur on the middle and lower slope, where channels migrated laterally, then aggraded and avulsed. Younger channel–levee complexes avoided bathymetric highs created by previous channel–levee complexes. Levees decrease in thickness down slope. Relief between channels and levees also decreases down slope.North of the Mahakam delta, siliciclastic sediment supply was limited during the Pleistocene, and the slope is dominated by valleys and canyons. Late Pleistocene rivers and deltas were generally not present on the northern outer shelf. Only one lowstand delta was present on the northern shelf margin during the upper Pleistocene, and sediments from that lowstand delta filled a pre-existing slope valley complex and formed a basin-floor fan. Except for that basin-floor fan, the northern basin floor shows no evidence of sand-rich channels or fans, but contains broad areas with chaotic reflectors interpreted as mass transport complexes. This suggests that slope valleys and canyons formed by slope failures, not by erosion associated with turbidite sands from rivers or deltas. In summary, amount of sediment coming onto the slope determines slope morphology. Large, relatively steady input of sediment from the Pleistocene paleo-Mahakam delta apparently prevented large valleys and canyons from developing on the central slope. In contrast, deep valleys and canyons developed on the northern slope that was relatively “starved” for siliciclastic sediment. 相似文献
16.
冲绳海槽北端表层沉积物过渡元素地球化学特征 总被引：4，自引：0，他引：4
利用原子吸收和等离子发射光谱等方法,对冲绳海槽北端184个表层沉积物中的Al和过渡元素(Ti、Cr、Mn、Fe、Co、Ni、Cu、Zn和Zr)进行了化学分析。结果表明,由于受生源碎屑稀释作用的影响,过渡元素在陆架砂质区含量较低,其分布呈北西-南东向舌状延伸;由于细粒组分的增加,在陆架细粒沉积区和海槽区过渡元素含量较高。Mn主要在海槽区富集,在陆架和陆坡区变化不大。除了Mn之外,Al和其他过渡元素均呈明显正相关。Al/Ti比值与陆壳平均值接近,说明二者主要来源于陆源碎屑。Mn/Fe比值与邻近海区沉积物类似,但在陆架区CaO含量大于20%的沉积物和海槽区沉积物中相对较高,这分别是生物富集作用和自生沉积的结果。过渡元素富集因子分析结果表明,研究区过渡元素部分来自于黄河、部分来自于长江物质。 相似文献
17.
18.
Late Cenozoic seismic stratigraphy of the Vøring continental margin has been studied in detail, with emphasis on the geological development of the Naust Formation deposited during the last 3 million years. The Kai Formation (15–3 Ma) comprises mainly biogenic ooze deposited in the Møre and Vøring Basins. In Naust time, there was a marked increase in supply of sediments from the inner shelf areas and the western part of the Scandinavian mountain range, and glaciers expanded to the shelf and reached the shelf edge several times during the last 1.5–2 million years. During early to mid Naust time the shelf was widened by westerly prograding sediment units, but for a long period the shallowest part of the Helland-Hansen Arch (HHA) formed a barrier preventing glacially derived debris from being distributed farther west. West of the HHA, mainly stratified marine and glacimarine sediments were deposited. A substantial part of these sediments were transported by the north-flowing Norwegian Atlantic Current, which redistributed suspended particles from ice streams, rivers, coastal erosion and seabed winnowing. After burial of the crest of the HHA at c. 0.5 Ma, glacial debris and slide deposits were also deposited west of this high. In the north, massive units of glacial debris were distributed beyond the crest of the HHA, also in mid Naust time, thinning westwards and interfingering with fine-grained sediments on the lower slope. The Sklinnadjupet Slide, inferred to be c. 250,000 years old, corresponds in age with an earlier huge slide in the Storegga area. An elongated area of uneven seabed topography previously interpreted as diapirs (Vigrid diapirs) on the slope west of the HHA is shown to be formed by ooze eruption from the crest of the arch and submarine sliding. 相似文献
19.
Eirik Sundvor 《Marine Geophysical Researches》1971,1(3):303-313
A seismic refraction survey along nine profiles has been carried out on the Norwegian continental shelf in the area between Andøya and Fugløybanken (69°–71°N). In all but one of the profiles the shelf is found to be covered with layered sediments. Average velocities are 1.85, 2.20, 2,55, 3.25, and 3.90 km/s probably representing sediments of Cenozoic and Mesozoic ages. An average velocity of 5.25 km/s represents a basement, which probably is the seaward continuation of the onshore Caledonian rocks. Except for an apparent depressional area just north of Andøya the sedimentary layers appear to dip towards the shelf edge. On the outer part of the shelf the 2.20 km/s layer appears at the sea-floor while more complex structures are found on the inner part of the shelf.Publication No. 3 in NTNF's Continental Shelf Project. 相似文献
20.
The results of continuous seismic profiling thermodynamics performed in the northern part of the Japan Basin in the region of the Tarasov Rise and the data of a micropaleontological examination of the diatom remains encountered in the sediment samples from the rise and continental slope are presented. In the area studied, the topography of the acoustic basement features a vast rise (plateau) buried under the sedimentary cover outlined by the depth contour 5.8 s. The plateau has a relatively smooth top surface crossed by a series of rises of the acoustic basement. The two largest rises are represented by the ridges of the Tarasov Rise. The plateau is separated from the continental slope by a depression in the acoustic basement with a depth up to 6.8 s. From the end of the Middle Miocene up to the beginning of the Paleocene, the region of the plateau represented an area of active volcanism; it coincided in time with the stage of subsidence of the floor of the acoustic basement depression. At the end of the Late Miocene, the ridges of the Tarasov Rise started to sink. In the Pliocene, this process accelerated, and, at the beginning of the Pleistocene, it stopped. In the Middle Miocene-Early Pleistocene time, the portion of the continental slope adjacent to the plateau remained stable and suffered no significant vertical movements. 相似文献