共查询到20条相似文献，搜索用时 15 毫秒
1.
Detailed analysis of the morphology of Bacino Bannock, a deep-sea basin filled by a hypersaline brine, shows with unusual
detail the effect on the ocean floor topography of the deformation and dissolution of a salt body under tectonic stress. Although
salt diapirism occurs in the central part of the investigated area, the major cause of basin formation is dissolution of subsurface
evaporites which creates negative relief that exceeds by about one order of magnitude the positive relief. The true shape
of the deformed salt deposit is preserved as a result of the absence of a thick post-evaporites sedimentary cover. 相似文献
2.
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
3.
N. G. Vashchenkova 《Oceanology》2008,48(6):855-863
Sedimentary rocks from the northern slope of the Kuril Deep-Water Basin are examined. Four different-age lithological units are distinguished, and inferences about the probable conditions of their formation are made. The Paleogene-Lower Miocene deposits (lithological units I and II) are represented by the purest varieties of siliceous rocks, which implies their accumulation far away from the source areas under quiet hydrodynamical conditions of the waters. The composition of the microfossils suggests a relatively shallow-water marine basin. The Pliocene-Pleistocene deposits of lithological units III and IV were formed in an active hydrodynamical environment under conditions of synchronous explosive volcanism at bathyal depths. The presence of porcelanite outcrops on the continental slope of the basin, together with the micropaleontological data about the paleodepths of the sedimentation, allows us to assume that, in the region studied, the continental slope was formed as a result of vertical motions in the post-Middle Miocene time. 相似文献
4.
《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(23):2169-2182
The Congo deep-sea fan is one of the largest fans in the world still affected by presently active turbidity currents. The present activity of deep-sea sedimentary processes is linked to the existence of a direct connection between the Congo River estuary and the Congo canyon head that allows relatively continuous sediment feeding of the deep-sea environment, in spite of a wide continental shelf (150 km). Because of this important activity in terms of sedimentary processes, the deep-sea environment of the Congo–Angola margin presents major interests concerning physical, chemical and biological studies near the seafloor.The main aim of this paper is to present the initial geological context of the BioZaire Program, showing a synthesis of the major results of the ZaïAngo Project including (1) the brief geological setting of the Congo–Angola margin, (2) the structure of the modern Congo deep-sea fan, (3) the sedimentary architecture of the recent Congo turbidite system (from the canyon to the distal lobes) and (4) the recent and present turbidite sedimentation. In order to provide useful information and advice relevant to biological and geochemical studies across the Congo sedimentary system, this article is particularly focused on the present sedimentary processes and the present activity of turbidity current along the Congo canyon and channel. 相似文献
5.
O. N. Zezina 《Oceanology》2006,46(3):396-400
The obligate (missing from different settings) species and genera of recent marine fauna dwelling in extreme (high-latitudinal, deep-sea, hydrothermal) and isolated (around islands, on mid-oceanic rises, in underwater caves) biotopes were never found in pre-Cenozoic sediments even tough they belong to ancient families. The prevalence of Pliocene-Pleistocene species and Miocene genera among these taxa suggests that they originated worldwide in the Cenozoic after stabilization of the Circum-Antarctic Current, when the Cenozoic thermohaline circulation pattern and the contrasting climatic regime were established on the planet. 相似文献
6.
This paper presents the results of geological studies carried out during the two marine expeditions of the R/V Akademik M.A. Lavrent’ev (cruises 37 and 41) in 2005 and 2006 at the underwater Vityaz Ridge. Dredging has yielded various rocks from the basement
and sedimentary cover of the ridge within the limits of three polygons. On the basis of the radioisotope age determinations,
petrochemical, and paleontological data, all the rocks have been subdivided into the following complexes: the volcanic ones
include the Paleocene, Eocene, Late Oligocene, Middle Miocene, and Pliocene-Pleistocene; the volcanogenic-sedimentary ones
include the Late Cretaceous-Early Paleocene, Paleogene undifferentiated, Oligocene-Early Miocene, and Pliocene-Pleistocene.
The determination of the age and chemical composition of the rocks has enabled us to specify the formation conditions of the
extracted complexes and to trace the geological evolution of the Vityaz Ridge. The presence of young Pliocene-Pleistocene
volcanites allows one to come to a conclusion about the modern tectono-magmatic activity of the central part of the Pacific
slope of the Kuril Islands. 相似文献
7.
为探索印度洋深海沉积物中纯培养细菌的多样性,本文对采自印度洋12个沉积物样品进行细菌纯培养分离,共获得343株细菌.所有细菌采用16S?rRNA基因进行比对分析,鉴定为4个门:厚壁菌门(Firmicutes)、变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroi... 相似文献
8.
We analyse tectonic and sedimentary field and subsurface data for the Angola onshore margin together with free-air gravity anomaly data for the offshore margin. This enables us to characterize the mode of syn-rift tectonism inherited from the Precambrian and its impact on the segmentation of the Angola margin. We illustrate that segmentation by the progressive transition from the Benguela transform-rifted margin segment to the oblique-rifted South Kwanza and orthogonal-rifted North Kwanza margin segments. The spatial variation in the intensity of post-rift uplift is demonstrated by the study of a set of geomorphic markers detected in the post-rift succession of the coastal Benguela and Kwanza Basins: Upper Cretaceous to Cenozoic uplifted palaeodeltas, erosional unconformities, palaeovalleys, Quaternary marine terraces and perched Gilbert deltas. The onshore Benguela transform margin has a distinctive, mainly progradational stratigraphic architecture with long-term sedimentary gaps and high-elevation marine terraces resulting from moderate Upper Cretaceous–Cenozoic to major Quaternary uplifting (i.e. 775–1775 mm/ky or m/Ma). By contrast, repeated synchronous episodes of minor Cenozoic to Quaternary uplift occurred along the orthogonal-rifted North Kwanza segment with its Cenozoic aggradational architecture, short-term sedimentary gaps and low-elevation Pleistocene terraces. Margin style likewise governs spatial variations in the volume of offshore sediment dispersed in the associated deep-sea fans. Along the low-lying North Kwanza margin, sedimentation of the broad Cenozoic to Pleistocene Kwanza submarine fan was probably governed by the width of the Kwanza interior palaeodrainage basin combined with the wet tropical Neogene climate. Along the high-rising Benguela margin, the small size of the Benguela deep-sea fan is related to the interplay between moderate continental sediment dispersal from long-lived small catchments and a warm, very arid Neogene climate. However, the driving forces behind the epeirogenic post-rift uplift of the Angola coastal bulge remain a matter of speculation. 相似文献
9.
Seamounts are ubiquitous topographic units in global oceans, and their influences on local oceanic circulation have attracted great attention in physical oceanography; however, previous efforts were less made in paleoclimatology and paleoceanography. The Caiwei Guyot in the Magellan Seamounts of the western Pacific is a typical seamount, and in this study, we investigate a well-dated sediment core by magnetic properties to reveal the relationship between deep-sea sedimentary processes and global climate changes. The principal results are as follows: (1) the dominant magnetic minerals in the sediments are low-coercivity magnetite in pseudo-single domain range, probably including a biogenic contribution; (2) the variabilities of magnetic parameters can be clustered into two sections at ～500 ka, and the differences between the two units are evident in amplitudes and means; (3) changes in the grainsize-dependent magnetic parameters can be well correlated to records of global ice volume and atmospheric CO2 in the middle Pleistocene. Based on these results, a close linkage was proposed between deep-sea sedimentary processes in the Caiwei Guyot and global climate changes. This linkage likely involves different roles of biogenic magnetite in the sediments between interglacial and glacial intervals, responding to changes in marine productivity and deep-sea circulation and displaying a major change in the Mid-Brunhes climate event. Therefore, we proposed that the sedimentary archives at the bottom of the Caiwei Guyot record some key signals of global climate changes, providing a unique window to observe interactions between various environmental systems on glacial-interglacial timescales. 相似文献
10.
This article discusses an effective way to study deep-water current activity with the sedimentary features of seabed sediments. In the paper, we have processed a seismic survey line crossing the Northwest sub-basin of the South China Sea (SCS). In the seismic profile, we can clearly distinguish the contourite sediment waves and find the erosion scope formed by the deep-water bottom current. Combining the analytic result of piston cores sediments in the research area, we can conclude that the deep-water current is the contour current. It enters the SCS through the narrow Bashi Channel and then it flows to the southwest direction along the isobaths of Dongsha uplift and Southern uplift, but there isn't direct evidence to explain that bottom current flows to the direction of the deep-sea basin. The conclusion confirms former speculation about the passage of deep-water current and provides an important foundation to construct the whole structure of deep-water circulation for the SCS. 相似文献
11.
12.
A. Zabanbark 《Oceanology》2012,52(4):513-525
The North Sea basin occupies a spacious depression almost isometric in shape. In the west and northwest, the basin is bordered by the continental crust consolidated during the Precambrian, Caledonian, and Hercynian orogenic epochs, which now forms epiplatformal orogenic structures. They are represented by the London-Brabant uplift and the Arden massif in the southwest and south and the Baltic Shield in the east and northeast. The North Sea basin may be considered as an ancient aulacogen that was transformed in the Early Mesozoic into a complex system of continental rifts and grabens. The sedimentary cover of the basin is represented by a thick (8.5?C12.5 km) Ordovician-Quaternary sequence. Oil and gas generation in the sedimentary cover of the basin is likely connected with four main productive sequences: the coaliferous Upper Carboniferous (Westphalian), the subsalt Zechstein, the Jurassic-Lower Cretaceous (Lotharingian, Toarcian, Kimmeridgian, and Weldian bituminose shales), and the shaly Cenozoic. The large oil and gas reserves in the North Sea??s sedimentary cover (over 280 fields) implies that the above-mentioned sequences have realized their oil-generating potential. The present-day position of the main oil and gas generation zones in the sedimentary section of the North Sea explains the distribution of the oil and gas fields through the basin from the genetic standpoint. The petroleum resource potential of the basin is still significant. In this regard, most promising are the spacious shelf areas, turbidite sediments, deep Paleozoic sequences, and continental slopes in the northern part of the basin, which remains insufficiently investigated. 相似文献
13.
位于马来盆地与西纳土纳盆地交汇处的研究区上新统?更新统发育复杂的浅海、海陆过渡相水下分支河道体系,常规的地震资料无法进行精细识别刻画。通过对叠后地震资料进行希尔伯特?黄变换,提取了地震资料高频分量,提高了地震资料的分辨率,有效识别了薄层砂泥岩交互特征和细微沉积体。通过对高频分量进行瞬时属性提取,明确了目的层段水下分支河道的平面展布特征。与常规叠后地震属性相比,经过希尔伯特?黄变换后的叠后地震资料提取的瞬时属性显示了更多沉积体系的细节特征,为水下分支河道的内部结构、发育期次、切割关系等时空演化研究提供了更高分辨率的地震数据。 相似文献
14.
Cheong Kee Park Wonnyon Kim Youngtak Ko Hyun-Bok Lee Jai-Woon Moon Seong-Jae Doh 《Ocean Science Journal》2012,47(4):497-508
The paleomagnetic records and mineral-magnetic properties of unconsolidated core sediment from the east Mariana Basin of the western Pacific have been analyzed to trace the time-dependent variations in sedimentary environments. Progressive alternating field demagnetization effectively extracts a stable remanent magnetization showing both normal and reverse polarities. Comparison of successive polarity changes, recorded in the sediment core, with reference magnetic polarity time-scale, reveals that the recovered sediment column was deposited since the late Pliocene. From the sediment age model, calculated sedimentation rate during the late Pliocene was 9.8 times higher than that during the Pleistocene. Considering the oceanic environments and geologic setting in the study area, the anomalous high sediment flux during the late Pliocene was probably caused by enhanced current flows, such as North Equatorial Current, associated with atmospheric circulation as well as by debris flows from adjacent sea mounts. In addition, the systematic variation of mineral-magnetic properties indicates periodical fluxes of coarse and magnetically stable particles, on the fine-grained dominant sedimentary environments. Such influxes, however, would not be related to syn-volcanic activities, because the summits of seamounts were totally blanketed by biogenic Pliocene-Pleistocene sediments. It is, hence, reasonable to interpret that paleomagnetic and mineral-magnetic data probably reflect drastic paleoenvironmental changes at the boundary between the Pliocene and Pleistocene, where strong current and atmospheric circulations decreased. 相似文献
15.
The analysis of 2D deep-seismic-reflection profiles across the slope and abyssal plain of the Angola oceanic basin reveals the existence of a significant and formerly unknown depocentre beneath the giant Cenozoic Congo deep-sea fan, between 7000 m and 9000 m depth, deposited directly onto the Aptian oceanic crust. The unit, which is up to 2.5 km thick and extends for more than 200 km basinwards of the Continent-Ocean boundary, is probably aged Albian–Turonian. Its radial fan-shaped depocentre is centred on the present-day Congo River outlet and contains at least 0.2 Mio km3 of sediments. These observations and the results from flexural modelling indicate that (1) the location of the Congo River's outlet has remained fairly stable since the Late Cretaceous, and (2) the basal unit was indeed sourced by a palaeo-Congo River probably located nearby the present-day one. Thus, the Atlantic sedimentary system related to the exoreism of the Congo River is much older than previously thought. Thermal modelling indicates that the maturation history of this upper-Cretaceous deposits is highly influenced by the interaction between the initial high heat flow of the young oceanic crust and further increase in sediment supply due to the progradation of the overlying Tertiary deep-sea fan during the Miocene. Hence, despite low present-day heat-flow values, should the unit have source rock potential, its basal section may be currently generating hydrocarbons. 相似文献
16.
北极深海沉积物中细菌和古菌群落结构研究 总被引：3，自引：0，他引：3
在北极深海沉积物生态系统中,微生物的群落结构由有机质输入、能量的可用性及其他环境因素决定.然而,全球气候变暖及其导致的冰盖提前融化正在影响微生物的多样性.为描述北极深海沉积物中的微生物群落结构及其与环境因素的相关性,我们利用罗氏454对北极深海沉积物样品的16S rDNA扩增子进行了测序,对细菌和古菌群落的丰富度、成分、结构及其系统发育分类地位进行了描述.硫还原和化能有机营养类是细菌群落中的主要类群;而古细菌群落主要是由微生物的关系最为密切的氨氧化奇古菌门(96.66%)和产甲烷古生菌界(3.21%).这项研究描述了北极极点附近深海沉积物(> 3500米)中的微生物多样性,将为以后研究类似环境中微生物代谢过程和途径等功能分析奠定基础. 相似文献
17.
东亚和南亚典型大河三角洲晚第四纪地层结构及成因对比 总被引：1，自引：0，他引：1
通过整理东亚、南亚典型河口三角洲末次冰消期以来演化历史的研究进展,对比各河口晚第四纪地层结构、沉积体系演替和三角洲开始建造的时间,分析其沉积历史的主要控制因素。结果显示,末次冰消期以来各河口具相似的地层结构和演变过程,即早全新世下切古河谷充填和河口湾发育,中—晚全新世三角洲建造,该过程主要受海平面变化的控制。但是各河口地层结构和沉积历史也存在差异,其中以三角洲开始建造的时间差别最为明显。对比发现这种差异与流域地貌、基岩以及河口沉积盆地的差别有关。流程短、流域基岩易侵蚀的河流,入海泥沙量大,其三角洲开始建造的时间显著早于其他河流,其中以恒河三角洲最为典型。另外,以珠江三角洲为典型,其半封闭、基底浅的河口沉积盆地特征,也有助于中全新世湾顶三角洲的建造。 相似文献
18.
琼东南盆地古近纪沉积充填演化及其区域构造意义 总被引：21，自引：1，他引：21
琼东南盆地是发育于南海西北部的新生代张性断陷盆地。始新统和早渐新统崖城组属过充填型或平衡充填类型，在盆地各个断陷内均具有砂岩-泥岩-砂岩三重沉积充填结构；晚渐新统陵水组在北部坳陷带属过充填及平衡充填类型，发育砂岩-泥岩-砂岩三重沉积充填结构，而在中央坳陷带则属由砂岩-泥岩二重沉积充填结构组成的欠充填型。古近纪盆地的沉积充填结构演化反映了始新世-早渐新世断陷阶段与晚渐新世断拗阶段的盆地演化历史，其中，晚渐新世盆地断拗阶段的发育是南海海底单期扩张过程的结果。 相似文献
19.
20.
The Upper Cretaceous and Paleocene Gottero Sandstone was deposited as a small deep-sea fan on ophiolitic crust in a trench-slope basin. It was thrust northeastward as an allochthonous sheet in Early and Middle Cenozoic time. The Gottero, as thick as 1500 m, was probably derived from erosion of Hercynian granites and associated metamorphic rocks in northern Corsica. Outcrops of inner-fan channel, middle-fan channel and interchannel, outer-fan lobe, fan-fringe, and basin-plain facies associations indicate that the depositional model of Mutti and Ricci Lucchi for mixed-sediment deep-sea fans can be used. The original fan had a radius of 30 to 50 km. 相似文献