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1.
利用2014–2017年在台湾海峡西部采集的多波束、单道地震剖面、沉积物粒度样品及海流监测资料,在厦门湾近岸陆架区识别出一系列海底沙波,并对沙波的形态特征、分布规律和沉积物组成特征进行分析,探讨水动力条件及其对沙波发育的影响。结果表明沙波发育区水深一般为10~60 m,地形较平缓开阔,坡度一般为0°~1°;平面上沙波区呈一系列NW-SE向条带状坡地,波脊呈线性或新月形,波脊轴线为SW-NE方向,沙波波长为120~800 m,波高2~12 m,沙波指数较大(>30)。地震剖面显示,波形形态主要分为三类:近对称性沙波、非对称性沙波及叠合沙波。近对称性沙纹的波高较大,沙波指数小;非对称性沙波的波长较长,沙波指数大;稳定沙波经后期水流“改造、激活”形成叠合沙波。砂含量较高,沉积物类型以砂、粉砂质砂及砂质粉砂为主,多为细砂—中砂。厦门湾口外的近岸陆架区水动力较强,流系复杂,总体受浙闽沿岸流、南海表层流和黑潮分支的影响。本区为不正规半日潮,流速为0.3~0.7 m/s,落潮流以S向为主,涨潮流向以NNE向为主,潮流作用对沙波的发育和改造起重要影响。  相似文献   

2.
北部湾东侧莺东潮流沙脊是整个琼西南沙脊群之一,沙脊从感恩角岸外发育最好,至东方岸外已趋缓和。根据海底特征,由海向岸分为深水平坦段、沙波沙脊段和近岸段共3个区段。沙波沙脊区段主要分布4条沙脊,这些沙脊大都呈NS或NW—SE走向,与主水流平行,呈不甚规则的长条状,长约45km,宽度较大。脊槽高差约20~30m,脊顶水深5~8m,沙脊槽向不对称,向海侧缓,向陆侧陡。成因上属于全新世低海面形成的连滨沙脊,受现代浪流修蚀改造而成。这些沙脊的基础部分基本稳定,只在暴风浪或强潮流情况下表面活动性泥沙做少量迁移。2003年铺设的东方1-1气田输气管线路由经过北部湾莺东沙脊。通过对中国海洋大学东方1-1海底管线多年调查资料分析认为,本区沙波沙脊海底管线被严重掏空,已发现的130余掏空悬跨点平均长达33m,深度最大可达1m。管线掏空可归因于底形特征动态变化和管线改变海底水动力环境的综合作用。  相似文献   

3.
利用多波束测深系统和浅地层剖面系统,对舟山群岛岱山后沙洋进行高精度探测,结果表明:1区内微地貌形态具有明显的分带性,依次出现岸坡区、沙脊区、缓坡区、沟槽区和深水平坦区;2海底沙波主要集中在缓坡区、沙脊区南侧及东侧边缘、沟槽区北侧及沟槽内2个小沟槽交界处的迎水流斜坡上;3海底沙波多发育于水深10.0~21.1m之间,地形相对平缓,坡度0.09°~2.8°;4区内海底沙波可分为小型、中型和大型沙波;5区内海底沙波是潮流动力形成的现代强运动型沙波。  相似文献   

4.
扬子浅滩东南海域海底潮流沙脊、沙波特征   总被引:1,自引:0,他引:1       下载免费PDF全文
利用seabat8101多波束系统对扬子浅滩东南海底地形进行了高精度探测。发现海底呈明显近乎平行排列的条带状起伏,脊谷相间,沙脊大部分呈NW-SE向排列,发育在45~50 m水深范围之内,沙脊横剖面不对称,大部分沙脊西南侧坡度大、东北坡缓。沙脊规模略有差异,沙脊宽度约0.6~9.8 km,沙脊之间间距可达8.9~22.4 km,高度约1.8~13.3 m,研究区内最长可达53 km。部分脊槽过渡区域发育成片链状海底沙波,沙波大致呈NE-SW走向,波高约0.3~1 m,波长1 km左右。研究区中西部有海底礁石孤立地突兀于相对平坦的海底之上,暂定名为扬礁,最浅水深35.9 m,位于30°59'7.4'~31°N,124°36'48.7'~124°37'40'E。扬子浅滩东南海域沙脊是介于活动沙脊和衰亡沙脊之间的准活动沙脊。该研究将为我国海洋开发和海洋经济发展、海洋行政管理以及海洋安全保障提供服务。  相似文献   

5.
北部湾东南海域海底发育大量沙波,利用最新获得的多波束测深、沉积物和水动力数据对沙波形态和分布特征进行综合分析,探讨沉积物特征、水动力条件,海平面变化等不同控制因素对海底沙波发育及分布的影响。结果表明研究区沙波广泛分布于沙脊顶部、沙脊槽中线附近及沙脊槽北端,沙波呈现远岸区尺度较小、对称性较好,近岸区尺度较大、多不对称的分布特征。海底沙波的发育和分布受现代潮流作用和沉积物特征的共同控制。潮流通道及流速的分布情况与沙波形态、规模的差异性分布一致。表层沉积物具有"远岸细、近岸粗"的特点,与沙波远岸尺度小、近岸尺度大的分布规律有较好的对应关系。此外,研究区出现有近对称形态的沙波,可能为海平面变化期间多期潮流共同作用形成的残余沙波。  相似文献   

6.
海南岛西南海底沙波活动及底床冲淤变化   总被引:17,自引:0,他引:17  
为了研究沙波迁移对底床稳定性的影响,通过对比分析2004—2006年连续3年的多波束海底地貌扫描数据,得出研究区域海底沙波的波长为5.8~91.8 m,波高0.1~4.3 m,陡峭度0.013~0.12,对称指数0.32~6.52。沙波的移动速率最大48.8 m/a,移动方向在研究区域西部为SE向,中部呈往复迁移,东部为NW向;沙波不同部位的迁移速率不同,一般的沙波尾翼迁移速率较大;同一组沙波存在反向扭转迁移的现象,反向扭转迁移的轴线位于研究区域沙脊的脊线附近,这种反向迁移不仅与底层流作用有关,还与海底地形关系密切;西部海底底床处于侵蚀状态,局部最大侵蚀量可达1.3 m,东部处于堆积状态,最大堆积量达2.8 m。  相似文献   

7.
南海北部陆架陆坡沙波底形   总被引:2,自引:0,他引:2  
南海北部珠江口—台湾岛南端一线以南、东沙岛以东海区的水深变化较大,地形起伏亦较大,海底水流动力较强,沙源丰富,发育大片海底沙波底形。按成因可分成A、B、C 3个海底沙波区:A区在珠江口外的内陆架上,水深80和200~250m,在陆架底流(潮、浪、洋流)作用下,海底沙波波高数十厘米至2~3m,属于两坡强烈不对称、现代仍然运动的正常沙波;B区在陆坡上部,水深200~600m,在斜坡间局部平台上发育大片波高数米至数十米、波长相应较短的特大型砂质沙波,一些专家认为是不同密度水层间的偶发性内波能通量强烈集中并突然释放而塑造的底形;C区在陆坡下部水深3 200~3 400m的数条海底峡谷交汇处,峡谷西和南侧有粉砂泥质沉积物波,波高数十米,波长数十千米,是深水细粒浊流形成的非正常沙波。陆架底流变化、沙波迁移、陆坡上部偶发性内波塑造的巨型沙波和陆坡下部的细粒浊流沉积物波均对油气勘探海底管线和平台的稳定性构成威胁。  相似文献   

8.
台风对北部湾南部海底地形地貌及海底管线的影响   总被引:7,自引:0,他引:7  
利用旁侧声纳和多波束在不同时间段内对琼西南近岸海域进行了探测,并对台风前后的旁侧声纳资料进行了对比和分析。研究表明,琼西南近岸海域主要存在沙脊区和沙波区两种地貌类型,其中,沙波波高在1~5.5m,波长3~60m,沙脊波高在6~20m,波长2~4km。在不同年份和台风期间,沙波和沙脊存在明显的活动性,对铺设于此的海底管线构成了严重的影响。台风对小沙波起夷平作用,对较大沙波、沙脊增高加宽,并且可以使海底出现冲刷沟槽和凹坑。  相似文献   

9.
海南东方近岸海底发育有大量沙波,利用多波束测深、侧扫声呐、浅地层剖面、单道地震资料综合分析了活动沙波的地球物理特征,探讨了沙波的分布特征、迁移机制、活动性及形态演变特征。结果表明,研究区海底沙波分布和规模具有显著空间差异性,大中型沙波主要发育于沙脊上,小型沙波主要发育于沙脊两侧,坑槽区发育近对称沙波,研究区西南部沙波不发育。受潮流和科氏力约束,在海底沙脊西侧沙波迁移方向主要为向北(略偏东),在沙脊东侧主要为向南(略偏西);受地形制约,坑槽区近对称沙波迁移可能停止或方向发生改变。沙波活动性强的标志主要包括:(1)形态呈不对称的"脊尖槽缓",(2)叠置小沙波与沙纹发育,(3)浅部有透明层,(4)陡坡面反射模糊,(5)内部斜交前积结构。分析认为,沙波活动性与其形态密切相关,包括弱运动、强运动、不运动3个演变阶段。  相似文献   

10.
台湾浅滩海底沙波精细特征、分类与分布规律   总被引:2,自引:2,他引:0  
迄今由于缺乏高精度的实测水深数据,对台湾浅滩沙波的精细结构缺乏详细的阐述。本文基于多波束实测资料研究台湾浅滩沙波形态的精细特征及其分布规律。多波束探测结果显示:研究区沙波的平均波高达到13.5m,沙波波峰处水深为20.42m,沙波平均波高约为水深的2/3,沙波的波长大多数处于500~700m之间。研究区内主要发育3种类型的沙波,即摆线型沙波、余弦型沙波和双峰型沙波。研究区西部主要发育双峰型沙波,中部则主要发育余弦型和摆线型沙波,而东部主要发育摆线型沙波,整个区域以摆线型沙波为主。海平面波动、台湾海峡复杂的水动力条件以及台湾岛丰富的山溪河流携带的大量沉积物进入海峡,对浅滩区的沙波具有强烈的改造作用。  相似文献   

11.
南黄海辐射沙洲附近海域悬浮体的研究   总被引:4,自引:0,他引:4  
对2003年春季(3—4月)和秋季(9月)南黄海辐射沙洲附近海域的悬浮体样品进行了空间分布特征、有机无机组成、粒度特征及其季节变化分析。结果表明:(1)2003年春季研究区内悬浮体浓度要普遍高于秋季的悬浮体浓度。悬浮体浓度最高值区位于长江口-老黄河口之间的近岸区。陆源物质为主的无机组分是悬浮体的主体成分,特别是在近岸浅水区和接近海底的底层水中尤为突出;(2)研究区海水中的悬浮体主要来源于辐射沙脊区(老黄河-长江复合三角洲)沉积物再悬浮;(3)悬浮体分布是风浪、潮流及沿岸流等多种因素综合作用的结果,而风浪和潮流是影响本区悬浮体分布的主要因素,巨大的风浪和强大的潮流造成辐射沙洲海底的沉积物再悬浮、搬运和再沉积,并在苏北沿岸流的作用下向沙洲外缘输运。  相似文献   

12.
西地中海加的斯湾、埃布罗湾、巴塞罗那岸外和利翁湾等外陆架和陆坡上部分布大片的砂质水下沙丘、沙带、沙脊以及沙席等砂质底形。沙丘长为150~760m,最长为3km;高一般为0.1~5.0m,最高为20m。背流坡指向SW,丘长与丘高相关斜率为H=0.934L0.006 3,低于1978年世界标准的F氏斜率线;沙脊长为4~24km,宽为1~2.3km,高出海底10~30m。砂层厚约12~30m,其成因与冰消期古岸线相关。以水深350m的直布罗陀海峡为中心,大西洋低盐水团和地中海高盐水团相交换而形成的地中海环流是导致海底砂质底形发育的主要动力,陆架外侧普遍分布的垂岸沟谷及顺谷流也起一定作用。据14C年代测定,大型沙丘沙脊形成于距今13~11ka的冰消期,当时海面波动式趋稳。现代洋流只能在暴风浪期间、底流速较大时才能带动泥沙运动且进行局部修饰、破坏和蚀低原砂质底形。  相似文献   

13.
美国东岸,自纽约长岛经马里兰、新泽西直至弗罗里达基本属于沙坝渴湖岸,岸外的内、外陆架上分布一系列水下沙脊及脊间沙带、沙丘和沙波等次一级底形。按新泽西岸外20-80m水深处35个沙脊的统计,脊长约2~11km,宽约1~4km,长宽比界于2:1~3:1之间,与世界典型沙脊长宽比40:1比较,本区沙脊属于短轴浪控型,脊高约1~3m,或者更高。向NE10°~30°伸展,两坡不对称,上游坡平缓,下游坡较陡,约2.5°~7.0°。按34-48m水深处的“黄金沙脊”上的20余钻孔岩心分析和HC年龄测试,划分沙脊自下而上3层地层:9~11kaBP以前的平原陆相层;9—5kaBP的下部沙脊沙层;5kaBP以来的上部沙脊沙层。上部沙脊层不断向下游SE侧超越迁移,局部定位观测的沙脊迁移率为1~2m/a。  相似文献   

14.
江苏北部(下称苏北)岸外辐射沙洲形态特殊,面积广大,是我国唯一、世界罕见的沉积动力地貌特征类型区。开展该区的调査和研究对苏北海岸带开发和海洋沉积动力学理论研究都具有非常重要的意义。近年来我国学者通过大量海洋水文、泥沙、海底地形和地貌调查研究,对苏北海岸的成因和岸外沙洲的演变提出了许多新的看法(王文清等,1982)。本文通过对历史资料和1958-1993年苏北海岸带调査资料、卫星照片等的对比分析,以及利用数值模拟方法的诊断,指出水动力是苏北海岸和岸外沙洲形成和演变的主要作用力。  相似文献   

15.
An investigation undertaken recently by the Division of Regional Geoecology and Marine Geology of the Karpinsky All-Russian Research Geological Institute in the coastal zones of the Eastern Gulf of Finland allowed finding some specific relief forms of both near-shore bottom topography and shoreline shape. First of all, among the most interesting objects, the sand ridges on the surface of submarine terrace (between Repino locality and Cape Lautaranta) should be mentioned. These ridges are elongated at an angle to the shoreline and are located beyond the limits of wave action. The other interesting morphological type is represented by longshore sand waves up to some hundreds of meters long and some tens of meters wide near the Bol’shaya Izhora locality. Longshore sand waves move along the southern coast of the gulf, this causing alteration of erosion and accretion zones and leading to formation and degradation of the sand spits. Shore-face-connected ridges are believed to develop under the action of drift currents generated during the passage of deep west cyclones. It is shown that the ridge turned toward the current gives rise to a convergence of the cross-shore flows over the crest and provokes a shift of the maximum velocity toward the front side of the structure. Associated changes in sediment discharges result in accumulation and growth of the ridge. The origin of wavelike features in the shoreline contour (longshore sand waves) is due to a very oblique wave approach caused by predominance of the west winds blowing along the axis of the gulf. Under these conditions a small perturbation of the shoreline contour is shown to manifest a trend to increase with time.  相似文献   

16.
El Hamra mooring pier was constructed on the northwestern Mediterranean coast of Egypt to provide shipping services for offshore oil terminals. Although the pier was built on cylindrical piles to avoid the interruption of sediment transport towards the south, unexpected sedimentation has affected navigation and the attached fire-fighting system. To provide a basis for evaluating the sedimentation problem and to provide possible mitigation strategies, a 23-month measurement program was conducted, including measurements of hydrographic surveying, nearshore waves, longshore currents, longshore littoral transport, currents seawards of the breaker zone, and offshore currents. The results confirm that carbonate sediments are transported southwards to the pier embayment from adjacent up-coast ridges by wave-induced currents. These sediments result from extensive civil engineering works (recreational development) up-coast of the El Hamra region, involving leveling of subaerial carbonate ridges and onshore sediment disposal.  相似文献   

17.
刘涛 《海洋与湖沼》2014,45(1):32-38
基于大量的悬浮体现场粒度和浓度数据,借助细颗粒悬浮体作为示踪物,分析了潮流作用下南黄海辐射沙脊群海底沉积物的再悬浮和扩散特征,并探讨了沙辐射沙脊群以北泥质区的形成机制。研究结果表明:(1)在辐射沙脊群以北,近岸悬沙在离岸方向上的扩散受到限制,向南又被辐射沙脊群中心浅滩所阻挡,只能在辐射沙脊群与废黄河口之间形成沿岸分布的高浓度浑水团。(2)辐射沙脊群以北的往复潮流对海底沉积物有分选作用,倾向于把海底沉积物中的粗颗粒分选搬运至沙脊群,把细颗粒沉积物向北输送,从而在沙脊群以北形成泥质区。(3)在正常海况下,沙脊表层沉积物再悬浮作用十分微弱,沙脊上覆水体中的悬沙主要来自于临近沟槽海底沉积物的水平扩散。  相似文献   

18.
为研究内孤立波与沙波的相互作用,本文对基于OpenFOAM的SedWaveFoam求解器进行改进,建立了内孤立波-泥沙运动欧拉两相流模型。在利用试验资料对模型进行验证的基础上,在南海北部典型代表性条件下,模拟分析了500 m水深位置沙波床面上内孤立波作用下的水动力变化和泥沙运动。结果表明,内孤立波逐渐离开沙波时,海底沙波背流面处出现与内孤立波背景流速反向的流速,在内孤立波导致的流场作用下,沙波床面上的泥沙悬起并运动到床面以上的水体中。振幅100 m的内孤立波可以导致床面以上14 m高的位置处出现约0.07 kg/m3的悬沙浓度。  相似文献   

19.
The continental margin of northern Sinai and Israel, up to Haifa Bay, is the northeastern limb of the submarine Nile Delta Cone. It is made up predominantly of clastics from the Nile and its predecessors. The continental shelf and coastal plain of Israel are built of a series of shore-parallel ridges composed of carbonate-cemented quartz sandstone (locally named kurkar), a lithification product of windblown sands that were piled up into dunes during the Pleistocene. The drop in global sea level and regression during the last glacial period exposed the continental shelf to subaerial erosion and created a widespread regional erosional unconformity which is expressed as a prominent seismic reflector at the top of the kurkar layers. The subsequent Holocene transgression abraded much of the westernmost kurkar ridges, drowned their cores, and covered the previous lowstand deposits with marine sands, which were in turn covered by a sequence of sub-Recent clayey silts. The Mediterranean coasts of Sinai and Israel are part of the Nile littoral cell. Since the building of the Aswan dams the sand supplied to Israel's coastal system is derived mainly from erosion of the Nile Delta and from sands offshore Egypt that are stirred up by storm waves. The sands are transported by longshore and offshore currents along the coasts of northern Sinai and Israel. Their volume gradually declines northward with distance from their Nile source. The longshore transport terminates in Haifa Bay where some sand is trapped, and the test escapes to deeper water by bottom currents and through submarine canyons, thus denying Nile-derived sand supply to the 40-km-long 'Akko-Rosh Haniqra shelf. The sand balance along Israel's coastal zone is a product of natural processes and human intervention. Losses due to the outgoing longshore transport, seaward escape, and landward wind transport exceed the natural gains from the incoming longshore transport and the abrasion of the coastal cliffs. The deficit is aggravated by the construction of (1) seaward-projecting structures that trap sands on the upstream side and (2) offshore detached breakwaters that trap sands between themselves and the coast. The negative sand balance is manifested by the removal of sand from the seabed and the consequent exposure of archaeological remains that were hitherto protected by it. The sediments that escape seaward from the longshore transport system form a 2.5- to 4-km-wide sandy apron adjacent to the shore that extends to where the water is 30 - 40 m deep. The apron's slope (0.5 - 0.8) is steeper than the theoretical equilibrium slope for the median grain-size diameter in this zone (0.1 - 0.3 mm). The beach sands and the apron's surficial sands are well sorted. Their grain size decreases with distance from shore, from 0.2 - 0.3 mm nearshore to 0.11 - 0.16 mm by the drowned ridge. The coarse-grained fraction consists of skeletal debris (commonly 5 - 12% carbonate matter) and wave-milled kurkar grains (locally named zifzif). In deeper water, the basal sands underlying the fine-grained sediment cover consist of 1- to 30-cm layers whose composition ranges from silty sands to various types of sands (fine, medium, coarse, and gravelly) to zifzif. For the most part, they contain large amounts of skeletal debris (20 - 60%) and small fragments of kurkar. Two types of kurkar rock were encountered offshore: a well-sorted, fine- to medium-grained (0.074 - 0.300 mm) lithified dune sand with variable amounts of carbonate cement, ranging from hard rock of low permeability to loose sand; and a porous sandstone made up predominantly of algal grains and skeletal debris (calcarenite).  相似文献   

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