共查询到20条相似文献，搜索用时 562 毫秒
1.
中国东部陆架边缘海发育多个全新世泥质区,是研究古海洋和古气候的理想区域。本研究从现代沉积过程和全新世沉积记录的视角,对山东半岛近岸泥质区的前人研究结果进行总结梳理,为后续相关研究提供参考。山东半岛近岸泥质区位于山东半岛沿岸,主要是来自黄河的沉积物在沿岸流、上升流、潮汐等相互作用下沉积而成,呈现独特的“Ω”形沉积模式。山东半岛近岸泥质区形成于全新世,物质来源主要是黄河,近岸侵蚀和当地小河流也贡献一定的物质来源。山东半岛近岸泥质区的形成和演化与古海洋条件、海平面升降、内陆古气候演变等多种因素有关,蕴藏着丰富的环境演化信息。山东半岛近岸泥质区沉积能够快速记录东亚季风的演变,其较高的沉积速率为研究黄河流域的古气候和古生态演化提供高分辨率的材料,可为预测未来全球变化背景下黄河流域的发展趋势提供参考。虽然前人对现代沉积过程进行了大量工作,但仍需加强现代观测和数值模拟等方面的工作,为更好地重建研究区的沉积动力过程提供数据和理论支撑。此外,该区在长时间尺度上的沉积物和有机质的沉积过程对古海洋和古气候的响应机制也亟待开展研究。 相似文献
2.
The subaerial delta of the Yellow River has undergone a notable reshaping process with drastic changes in erosion and accretion patterns both temporally and spatially. These morphological changes not only have significant impact on the long-term evolution of delta but also pose severe threat to the existing infrastructures adjacent to the eroding delta lobe. This paper presents a data-based study of waves, currents, sediments and subaqueous bedforms including the application of Principal Component Analysis (PCA) to the measured coastal profiles in order to understand qualitative and quantitative processes that are responsible for the observed changes. The results demonstrated that the Yellow River Delta has recently been dominated by recession process due to the reduced sediment supply from the Yellow River in the recent decades. A critical threshold of river sediment discharge was formulated and used to explain the observed morphodynamic processes. It was found that the coast of the Yellow River Delta could be broadly divided into three geomorphic zones: the area near abandoned delta, the estuarine area, and Laizhou Bay. At the nearshore zone of the abandoned delta, waves are the main agent for bed erosion and sediments suspension. The tidal current is effective in transporting suspended sediments and exerts the main control on the depths of the erosion–accretion balance zone on the coastal profiles. The area near the present estuary has seen rapid deposition with the progradation rate being governed by the relative intensity of fluvial and marine processes while the coasts in Laizhou Bay are stable and the particular characteristics of the tidal current field prevent the sediments supplied by the Yellow River from reaching this area. 相似文献
3.
4.
Coastal erosion and management attract much conern all around the world as coastal erosion is a problem at many coastal sites exacerbated by human activities and its adaptability through reasonable mitigation measures. This paper summarizes the main factors causing coastal erosion including reduction of sediment discharged by rivers trapped coastal structures, sand mining and reclaimation, relative sea-level rise, destruction of coastal ecosystem and weakening of coastal defenses. Mechanisms causing erosion of coastal dune, soft rock coast and muddy coast are identified and discussed. Sandy coastal erosion, soft rock coastal erosion, muddy coastal erosion, biological coastal erosion and coastal structural erosion are identified according to the characteristics of erosion in China. This study supplements the theory and methodology for coastal erosion management and provides information for managers and stakeholders. 相似文献
5.
为了探讨渤海东部和黄海北部稀土元素分布特征及其影响因素,对渤海东部和黄海北部138个表层沉积物样品进行电感耦合等离子体质谱法分析.结果表明:渤海东部和黄海北部沉积物的配分模式与中国黄土的接近,与周边的鸭绿江、黄河等河流输入物质也有相似性,表明研究区沉积物主要来自于周边大陆.沉积物物源判别结果显示:山东半岛近岸及其西南部沉积物主要来源于黄河,该区域沉积物分布受山东半岛沿岸流及近岸潮流影响;研究区东部沉积物稀土元素组成特征与鸭绿江沉积物组成相近,表明研究区东部沉积物可能由鸭绿江供应;研究区西北部沉积物主要来源于黄河及辽宁沿岸物质输入,局部有滦河、六股河物质存在;研究区东南部物质主要来源于黄河.对沉积物稀土元素百分含量及参数特征值进行了Q型聚类分析,将研究海域沉积物划分为4个不同的区域,分别为北黄海东部区域(Ⅰ)、山东半岛近岸周边区域(Ⅱ)、渤海东部中部区域(Ⅲ)及研究区的西北部与东南部分布区(Ⅳ). 相似文献
6.
黄东海陆架和朝鲜海峡等5个泥质沉积区全新世中期以来(自约6kaB.P.至今)的细粒沉积物主要是黄河、长江和朝鲜半岛的河流入海物质在复杂的海洋动力系统中的沉积产物.对取自山东半岛北部近岸泥质区和长江口以南的闽浙沿岸泥质区(舟山群岛近岸海区)的表层细粒沉积物(粘土质粉砂和粉砂质粘土)开展了详细的岩石磁学测试,包括磁化率、等温剩磁和样品磁化率随温度的变化等分析,并将实验数据与以往研究过的济州岛西南陆架区、南黄海东南部陆架区和朝鲜海峡西岸等3个泥质沉积区细粒沉积物的磁学特征进行比较研究.结果表明,上述5处细粒沉积物的磁性矿物主要组分为磁铁矿、磁赤铁矿和赤铁矿,其中低矫顽力磁性矿物为主,平均粒度为准单畴(PSD).根据磁性矿物的粒度和低矫顽力组分的相对含量,这5处细粒沉积物可以划分为3种类型:第1种类型是朝鲜海峡西岸细粒沉积物,其磁性矿物的粒度最粗,低矫顽力组分的相对含量为中等;第2种类型是南黄海东南部陆架细粒沉积物,其磁性矿物的粒度为中等,低矫顽力组分的相对含量最大;第3种类型是山东半岛北部近岸、闽浙沿岸(舟山群岛近岸)和济州岛西南陆架区的细粒沉积物,其磁性矿物的粒度最细,低矫顽力组分的相对含量最低.在这5处细粒沉积物中,闽浙沿岸(舟山群岛近岸)细粒沉积物的磁性矿物含量最高,其他4处细粒沉积物的磁性矿物含量都较低且大体相当.这种磁学特征的差异反映了物源的不同.从磁学特征来分析,济州岛西南陆架区的泥质沉积物主要来自黄河和长江;南黄海东南部泥质区的主要物源是朝鲜半岛进入黄海的河流,黄河和长江对其没有重要贡献. 相似文献
7.
进入20世纪50年代以来,我国海岸侵蚀日趋明显,一些海岸带资源或油田设施遭到破坏。针对我国黄河三角洲和长江三角洲海岸线的侵蚀现状,分析了我国海岸线侵蚀的主要因素:河流泥沙减少;海平面的上升或海洋动力因素增强以及人为因素的影响。并对目前我国所采用的海岸防护措施进行了分析。提出了我国海岸防护工程类型较多,应根据海岸侵蚀的特点采用不同的措施或多种形式组合,因势利导,使工程达到最好的防护效果。 相似文献
8.
Duncan M. Fitzgerald Mark Kulp† Shea Penland† James Flocks‡ Jack Kindinger‡ 《Sedimentology》2004,51(6):1157-1178
The Barataria barrier coast formed between two major distributaries of the Mississippi River delta: the Plaquemines deltaic headland to the east and the Lafourche deltaic headland to the west. Rapid relative sea‐level rise (1·03 cm year?1) and other erosional processes within Barataria Bay have led to substantial increases in the area of open water (> 775 km2 since 1956) and the attendant bay tidal prism. Historically, the increase in tidal discharge at inlets has produced larger channel cross‐sections and prograding ebb‐tidal deltas. For example, the ebb delta at Barataria Pass has built seaward > 2·2 km since the 1880s. Shoreline erosion and an increasing bay tidal prism also facilitated the formation of new inlets. Four major lithofacies characterize the Barataria coast ebb‐tidal deltas and associated sedimentary environments. These include a proximal delta facies composed of massive to laminated, fine grey‐brown to pale yellow sand and a distal delta facies consisting of thinly laminated, grey to pale yellow sand and silty sand with mud layers. The higher energy proximal delta deposits contain a greater percentage of sand (75–100%) compared with the distal delta sediments (60–80%). Associated sedimentary units include a nearshore facies consisting of horizontally laminated, fine to very fine grey sand with mud layers and an offshore facies that is composed of grey to dark grey, laminated sandy silt to silty clay. All facies coarsen upwards except the offshore facies, which fines upwards. An evolutionary model is presented for the stratigraphic development of the ebb‐tidal deltas in a regime of increasing tidal energy resulting from coastal land loss and tidal prism growth. Ebb‐tidal delta facies prograde over nearshore sediments, which interfinger with offshore facies. The seaward decrease in tidal current velocity of the ebb discharge produces a gradational contact between proximal and distal tidal delta facies. As the tidal discharge increases and the inlet grows in dimensions, the proximal and distal tidal delta facies prograde seawards. Owing to the relatively low gradient of the inner continental shelf, the ebb‐tidal delta lithosome is presently no more than 5 m thick and is generally only 2–3 m in thickness. The ebb delta sediment is sourced from deepening of the inlet and the associated channels and from the longshore sediment transport system. The final stage in the model envisages erosion and segmentation of the barrier chain, leading to a decrease in tidal discharge through the former major inlets. This process ultimately results in fine‐grained sedimentation seaward of the inlets and the encasement of the ebb‐tidal delta lithosome in mud. The ebb‐tidal deltas along the Barataria coast are distinguished from most other ebb deltas along sand‐rich coasts by their muddy content and lack of large‐scale stratification produced by channel cut‐and‐fills and bar migration. 相似文献
9.
Neelima Thankappan Noujas Varangalil Thomas Kachapally Varghese Kurian Njaliplackil Philipose 《Natural Hazards》2018,90(3):1177-1199
Shoreline changes are largely dependent on coastal morphology. South-west coast of India is a high energy coast characterised by monsoon high waves, steep beach face and medium-sized beach sand. Waves are generally from west and west south-west during rough monsoon season and from south-west during fair weather season. Shoreline change along this coast is studied with reference to coastal morphological features. Various morphological features, modifications and chronological positions of shoreline are analysed with the information derived from multidated satellite imageries, toposheets and GPS shoreline mapping along with extended field survey. Image processing and GIS techniques have been used for the analysis of data and presentation of results. Sediment accumulation on the leeward side of artificial structures such as harbour breakwaters and groynes is used as a sediment transport indicator. Artificial structures such as seawalls, groynes and harbour breakwaters modify morphology. Shoreline south of headlands/promontories and breakwaters are stable or accreting due to net northerly longshore sediment transport while erosion tendency is observed on the north side. Lateritic cliffs fronting the sea or with seasonal beach undergo slumping and cliff edge retreat as episodic events. Spits adjoining tidal inlets are prone to shoreline variations due to oscillations of inlet mouth. Interventions in the form of inlet stabilization and construction of coastal protection structures trigger erosion along adjoining coasts. Seawalls constructed along highly eroding coasts get damaged, whereas those constructed along monsoon berm crest with frontal beaches for protection against monsoon wave attack are retained. Fishing gaps within seawalls are areas of severe temporary erosion during rough monsoon season. Accretion or erosion accompanies construction of harbour breakwaters in a stable coastal plain. Close dependence of shoreline changes on morphology necessitates detailed understanding of impacts on morphology prior to introducing any intervention in the coastal zone. 相似文献
10.
The coastal zone of the Sagar island has been studied. The island has been subjected to erosion by natural processes and to
a little extent by anthropogenic activities over a long period. Major landforms identified in the coastal area of the Sagar
island are the mud flats/salt marshes, sandy beaches/dunes and mangroves. The foreshore sediments are characterized by silty,
slightly sandy mud, slightly silty sand and silty sand. Samples 500 m inland from high waterline are silty slightly sandy
mud, and by clayey slightly sandy mud. The extent of coastline changes are made by comparing the topographic maps of 1967
and satellite imageries of 1996, 1998 and 1999. Between 1967 and 1999 about 29.8 km2 of the island has been eroded and the accreted area is only 6.03 km2. Between 1996 and 1998 the area underwent erosion of 13.64 km2 while accretion was 0.48 km2. From 1998 to 1999, 3.26 km2 additional area was eroded with meager accretion. Erosion from 1997 to 1999 was estimated at 0.74 km2 /year; however, from 1996 to 1999, the erosion rate was calculated as 5.47 km2/year. The areas severely affected by erosion are the northeastern, southwestern and southeastern faces of the island. As
a consequence of coastal erosion, the mud flats/salt marshes, sandy beaches/dunes and mangroves have been eroded considerably.
Deposition is experienced mainly on the western and southern part of the island. The island is built primarily by silt and
clay, which can more easily be eroded by the waves, tides and cyclonic activities than a sandy coast. Historic sea level rises
accompanied by land subsidence lead to differing rates of erosion at several pockets, thus periodically establishing new erosion
planes. 相似文献
11.
MIS 3晚期以来江苏中部海岸的层序地层 总被引：6，自引：0，他引：6
通过对苏北岸外西洋潮流通道内钻孔和地震剖面的地层沉积学、年代地层学、地震地层学和层序地层学等多学科再研究,以及区域钻孔再对比,本文确定该海域约从35kaBP(14C惯用年龄)开始经历了滨岸砂坝、淡水湖沼、河流泛滥平原、滨岸沼泽、潮流沙脊和潮流通道一系列的环境演变,主要受控于MIS3晚期以来的海平面旋回以及古河流入海沉积物供给,而构造沉降是相对次要的,由此形成了五级层序地层中的末次冰期晚间冰阶准层序和冰后期准层序,以及前者的高水位体系域和强制海退楔体系域、后者的海侵体系域和高水位体系域。海域中潮流沙脊可能开始发育于冰后期海侵淹没本区(约9calkaBP)之后,但一直只是水下暗沙且处在不断调整之中,直到1128～1855AD间黄河夺淮从苏北入黄海,大量泥沙充填潮道,部分水下暗沙出露海面成为明沙。西洋潮流通道并非是晚全新世期间通过沙脊的蚀低而形成,而在全新世高海面前后就已具雏形并持续至1128AD,1128～1855AD和1855AD至今分别经历了充填淤浅与冲刷成型的过程,且今后具有进一步展宽刷深的趋势。 相似文献
12.
In this study, on the basis of 3,200 km shallow stratigraphic section and side-scan sonar data of the coastal area of the Yellow River Delta, we delineated and interpreted a total of seven types of typical hazardous geologies, including the hazardous geology in the shallow strata (buried ancient channel and strata disturbance) and hazardous geology in the seabed surface strata (pit, erosive residual body, sand patch, sand wave and scour channel). We selected eight parameters representing the development scale of the hazardous geology as the zoning indexes, including the number of hazardous geology types, pit depth, height of erosive residual body, length of scour channel, area of sand patch, length of sand wave, width of the buried ancient channel and depth of strata disturbance, and implemented the grid processing of the research area to calculate the arithmetic sum of the zoning indexes of each unit grid one by one. We then adopted the clustering analysis method to divide the near-shore waters of the Yellow River Delta into five hazardous geology areas, namely the serious erosion disaster area controlled by Diaokou lobe waves, hazardous geology area of multi-disasters under the combined action of the Shenxiangou lobe river wave flow, accumulation type hazardous geology area controlled by the current estuary river, hazardous geology area of single disaster in the deep water area and potential hazardous geology area of the Chengdao Oilfield. All four of the main factors affecting the development of hazardous geology, namely the diffusion and movement of sediment flux of the Yellow River water entering the sea, seabed stability, bottom sediment type and distribution, as well as the marine hydrodynamic characteristics, show significant regional differentiation characteristics and laws. These characteristics and laws are consistent with the above-mentioned zoning results, in which the distribution, scale and genetic mechanism of hazardous geology are considered comprehensively. This indicates that the hazardous geology zoning based on the cluster analysis is a new attempt in research regarding the hazardous geology zoning of the near-shore waters of the modern Yellow River Delta and that this type of zoning has a high level of reasonability. 相似文献
13.
江苏沿海辐射沙脊群在国内潮成沙体中较为罕见,有关辐射沙脊形成的动力机制已有定论,但对其形成时间和物质来源说法不一。运用长时间尺度动力地貌过程数学模型复演了辐射沙脊群形成演变过程,结果表明:江苏岸外辐聚辐散的流场不依赖于局部海底地形而独立存在;不同初始地形下只要泥沙供给充足,经过150年左右潮流动力对地形不断塑造,辐射状"水道-沙脊"相间的地貌格局都能基本形成;辐射沙脊群是废黄河北归约150年后,随着废黄河水下三角洲不断被侵蚀,辐聚辐散的潮流对不同来源物质重新塑造的结果,是动力-泥沙-地形相互作用的产物。 相似文献
14.
A sea-survey was carried out along the Chinese coast from the Bohai Sea to South China Sea, and 15 surficial samples were
taken from major coastal estuaries, i.e., from north to south, the Yellow, abandoned Yellow, Yangtze, Qiantang, Ou, Min, Han,
and Pearl River estuaries. On the basis of clay mineral analysis and published data collection, this paper discusses the characteristics
of clay minerals of each coastal river and potentials of implications of sediment sources. The results show that the change
of diagnostic clay minerals from smectite to kaolinite from the Yellow to the Pearl River estuaries is southward, as clearly
shown by the ratios of smectite to chlorite (S/Ch) and kaolinite to illite (K/I). S/Ch decreases southward, while K/I moves
reversely, implying change in climate setting from cool/dry to humid/hot with intensified weathering processes. Besides, these
two indicators in the estuaries are also linked with the derivation of parent-rock of each river-basin and coastal hydrodynamics.
The disproportional higher ratio of K/I in the Yellow and abandoned Yellow River estuaries is ascribed to their sediment sources
with abundant loess component in the north-central China. The K/I decrease offshore from the Pearl River estuary is primarily
due to hydrodynamic sorting. Therefore, the S/Ch and K/I of the present study comprehensively reflect the controls of climate,
parent-rock, and sediment transport along the coast. 相似文献
15.
《China Geology》2018,1(4):505-511
The coastal cities are the most advanced regions in China. In the past few decades, the environment changed very significantly due to large scale human activities in the coastal regions. Polycyclic aromatic hydrocarbons (PAHs) in three dated sediment cores from the west coast of the Yellow Sea (core A01), the Yangtze River estuary (YRE; core A02) and the Oujiang River estuary (ORE; core A03) were analyzed to reconstruct the environmental evolutionary process of the east China coastal region over the past century. In the three cores, PAHs concentrations were increased rapidly. Lower concentrations of PAHs were measured in core A02 than in cores A01 and A03. The vertical variation of PAHs in the YRE was dominated by the petrogenic sources. Historical records of PAHs in the ORE were controlled by pyrolytic sources. PAHs on the west coast of the Yellow Sea were contributed by the two sources. 相似文献
16.
河北省沙质岸滩存在海岸侵蚀现象,对沙滩旅游、海滩工程建设造成严重威胁,制约河北省海洋经济社会发展。海岸侵蚀监测结果显示,区域海滩滩面受波浪、潮流影响较大,时冲时淤,摆动频繁,沙质岸滩整体处于侵蚀状态,各区段蚀淤情况有所差异,高潮线以上有所淤高,海滩坡度开始变陡,呈下蚀状态。海岸侵蚀灾害已引起沙滩沙质粗化、滩肩变窄、滩坡变陡及基岩裸露比率增多等问题。针对这一突出问题,通过定点测量与遥感监测相结合的方式,研究了河北省海岸线动态演变特征,经计算,河北省各侵蚀岸段海岸侵蚀速率达1.0~4.0m/a,单宽体积侵蚀量-1.42~-19.08m~3/m·a。综合分析显示,人类海岸工程建设、区域海洋水文条件及输砂量减少,是河北省发生海岸侵蚀发生的主要原因。 相似文献
17.
研究源-汇系统对于理解岩石风化、河流输砂、泥砂沉积以及陆地和海洋沉积过程具有重要意义。我国江苏省东海岸具有丰富的沉积物供应,在某些沿海地段形成了一系列沙脊,是进行沉积物源-汇过程研究的理想沉积记录之一。但目前对其物源区来自哪里还未达成共识。我们利用已发表的碎屑锆石U-Pb年龄和钾长石Pb同位素数据,结合江苏沙脊及其周缘区域的数据结果,详细厘定江苏沙脊的物源区,并运用蒙特卡罗反演模型定量评估江苏沙脊潜在物源区对其物质贡献率。结果表明江苏沙脊北部的碎屑物质主要受大别山(45%)和鲁中山区(24%)的共同影响;黄河(29%)、古黄河(27%)和长江(25%)的碎屑物质对江苏沙脊中部的物质组成起重要影响。江苏沙脊南部的物源主要来自长江(68%)。江苏沙脊的出现得益于黄河和长江这样的大陆尺度的大河搬运了丰富的碎屑物质到下游,南黄海西海岸的平坦地貌有利于保存这些碎屑物质,末次冰期后东亚陆架海动力过程(潮汐、海浪和沿岸流等)持续对其改造,这体现了河流-海洋在塑造河口-海岸地貌中的交互作用。 相似文献
18.
Beach erosion has advanced in many countries of the world, especially in Japan, because of a decrease in sediment sources from rivers and a lack of longshore sediment transport from the adjacent coasts due to coastal structures. The former cause concerns the reduction of river deltas due to a decrease in sediment input from the river. Two timescales important in beach erosion, a longer timescale which concerns a change in the location of the river mouth, and a shorter one which is due to a decrease in longshore sediment transport, are discussed in the formation and reduction of the delta of the Kurobe River. Based on these timescales, beach erosion control is considered. 相似文献
19.
《China Geology》2020,3(3):445-454
This study is about the reconstruction of fluvial origins based on the grain size distribution of sediment deposits in the western Laizhou Bay, Bohai Sea, China. Thirteen sediment cores were selected to research sediment characteristics using the Sahu discriminant formula, C-M diagram, and Folk method. The results showed: (1) Bounded by the Guangli River estuary, the north sediment was affected by the water and sand flowing from the Yellow River during different periods. The south sediment came from multi-source rivers under the influence of the Xiaoqing River, Mihe River, and other coastal rivers; (2) the deposited sediments were dated by a clear historical record of the branched channel oscillation combined with the characteristics of the diversion channel, erosion, and regression. The subaqueous delta overlapped during several Yellow River channel runs (1897–1904, 1929–1934, 1938–1947, 1947–1953, 1976–1996) and the deposited sediment facies changed (the north tidal flat-abandoned subaqueous delta-lateral delta-delta front); (3) the deposited sediment characteristics can be revealed by studying the branched diversions of the Yellow River and coastal multi-rivers of the past one hundred years. 相似文献
20.
近岸强海流切变锋作用下悬浮沉积物的输送和沉积--以山东半岛东端外海为例 总被引：4，自引：1，他引：3
利用2007年国家908专项ST02区块（渤海海峡及北黄海）水体专项夏季和冬季两个航次调查的温度、浊度和悬浮体浓度数据,选取了跨越山东半岛东端外海泥质沉积体的B1和B2两个断面,结合该区浅地层剖面资料,辅以研究海域的冬季环流数值模拟,着重分析了山东半岛东端外海强海流切变锋作用下的悬浮体输送和沉积特征。结果表明山东半岛东端外海悬浮体向外海输送存在类似“夏储冬输”的规律:夏季,北黄海海水浊度普遍小,不仅北黄海温跃层抑制了底层悬浮体向中上层水体扩散,而且北黄海冷水团在中底层与山东半岛东部沿岸水也形成了显著的温度和悬浮体锋面,阻碍了悬浮物的纬向输送,故夏季应是悬浮体沉积的主要时节;冬季,温跃层消亡,在强风的作用下,山东半岛东部悬浮体浓度高且垂向混合较好,然而在泥质沉积体顶积层两侧,山东半岛东部沿岸中下层北上的逆风补偿流和北上的黄海暖流与位于顶积层上方表中层南下的沿岸流构成了两道显著的强海流切变锋,使得底积层上大量的再悬浮沉积物不能越过山东半岛东部陆架末梢,从而有助于形成山东半岛东端外海特有的Ω状泥质沉积体。 相似文献