【作者】 张子鹏；

【导师】 李广雪；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2013， 博士

【摘要】 渤海，由辽东湾、渤海湾、莱州湾、中央盆地和渤海海峡组成，平均水深18m，通过渤海海峡与外海进行水体交换和能量传递。末次冰消期以来，海水重新覆盖原有的渤海陆相沉积，形成：黄河、滦河、辽河等大型水下三角洲，规模宏大的辽东浅滩潮流沙脊群、辽东湾沿岸15m水深以浅规模不一的离散分布的潮流沙脊单体，北东-南西向延伸的中央盆地泥质沉积区。本文研究区域是辽东湾北部20m水深以浅、130km×100km的海域范围：北部是辽河（我国七大主要河流之一）等多条河流的入海口，发育规模可观的潮滩以及延伸至约30m等深线附近区域的水下河口三角洲，东部和西部沿岸为港湾基岩海岸，东部沿岸水下分布古滨海残留沉积区；研究区海底地形呈现自海岸向海湾中部倾斜态势，其中东、西两岸倾斜坡度较大；研究区潮差大（最大潮差超过5m）、潮流强（2-3节）、冰期长（最长180天），陆海相互作用强度极高。虽然前人已开展过相关方面的研究，但历史调查精度不高、调查区域覆盖不全面、样品测试数量不多、样品测试内容不全面不系统、关注的视角偏重陆地和海岸带，更鲜有细致研究人类活动对近海沉积的影响以及悬浮体对区域现代沉积作用及影响的研究。本文全面依托“我国近海海洋环境综合调查与评价”中CJ01区块A1调查区1:5万大比例尺调查的底质、水体、柱状样资料及辽宁省908专项中“辽宁省海岸带调查”的潮滩柱状样资料，进行了全面的粒度、碎屑矿物、常微量元素、水体（温盐密）、悬浮体（质量浓度和体积浓度）、210Pb放射性测年等测试分析，开展了区域精细的沉积分布特征、现代沉积物质来源、近代人类活动影响记录、悬浮体输运、现代河口沉积动力过程研究，获得以下五个主要方面的基本结论：（1）该区域沉积物中粉砂和砂平均含量超过80%，以砂质粉砂和粉砂质砂两种沉积物类型为主，西北部抵近小凌河口的5-10m水深之间的海底沉积物（粉砂）最细，在东南方向近岸水下沙脊区分布最粗的沉积物类型（砂）。表层沉积物的分布与区域海洋动力、海底地貌特征和物源供给密切相关，除东南沿岸砂质残留沉积受现代物质供给影响较小外，绝大多数海域沉积物来源依赖海湾周边河流输入的泥沙，尤以北部四条河流来水来沙为主。（2）表层沉积中轻矿物占97.1%，主要矿物是长石，平均含量为59.8%，石英为29.3%，矿物成熟度较低。重矿物不稳定组分含量较高，组合以角闪石-绿帘石-石榴子石-透闪石为主，钾长石和榍石是区域内的特征矿物。研究区以钾长石和角闪石含量高而区别于渤海其他海域。（3）常量成分中SiO2和Al2O3平均含量高达67.47%和12.45%，金属元素含量次之，TiO2、P2O5和MnO位居末三位，均小于0.58%。元素组合分析结果显示，陆源碎屑、生物质粗粒沉积是控制元素分布的主要因子。重金属相对含量较高，分布规律符合粒度控制律，所测各金属均与Al有较高的相关性，体现了近源陆相输入物为主的影响。（4）210Pb和137Cs测年揭示了北部潮滩的沉积速率和沉积过程。潮滩沉积对河流入海泥沙量敏感度较高，80年代以来沉积速率明显降低，局地出现淤积与侵蚀的交互作用过程。水下三角洲的沉积过程基本稳定，测试结果反映的物质供给和沉积速率未显现出大的波动，基本保持在2~6mm/a的水平。（5）悬浮体浓度分布呈现较为明显的自河口向外扩散的分布态势，底层浓度远高于表层；潮流顶托和海面风场增大了悬浮体浓度，尤其是在浅海和东南沿岸海域。盐度28‰为界，悬浮体质量浓度与浊度呈现不同程度的线性关系。现场体积浓度与质量浓度分布规律相近，海水中絮凝体和生物组分含量低，底层悬浮体浓度较高，在河口存在明显的辽河冲淡水锋面。辽河海底谷地、辽河口等水动力作用较强的海域，悬浮体现场平均粒径组成偏粗，可达1-5Φ，其它区域以5-7Φ为主。本文以前所未有的站位密度获取了均匀覆盖整个辽东湾北部的研究数据，资料充分、样品数量充足、分析测试方法可信，区域水体、底质、柱状样等载体真实反映悬浮体、粒度、碎屑矿物、地球化学、沉积速率等研究要素的分布及特征。通过全面深入研究，在三个方面有了新的认识：（1）从沉积物分布和动力分异方面，细化并更新了辽东湾北部现代沉积特征。研究区中部偏西侧海域、围绕海湾环流分布典型的粘土质粉砂细粒沉积区，海湾东西两侧残留沉积区及水下谷地区粗粒沉积特征明显，陆源碎屑矿物动力分异特征、重金属元素在细粒沉积区富集等均符合上述现代沉积特征。（2）河控作用减弱、潮控作用加强，这是辽东湾北部沉积环境改变的显著特点。河流水沙量骤降致使物质供给量减少，北部和东部区域河流冲淡水扩散方式限制了河口悬浮体的输运距离，碎屑矿物扩散能力减弱降低了重矿物分异能力，表层细粒沉积再悬浮搬运减小了原地沉积速率，原有的河流影响沉积区逐渐被潮流沉积体系所代替。（3）人类活动是改变和再塑辽东湾北部现代沉积格局和沉积作用的重要影响因素。修建水库水闸严重减少了河流水沙输入量；围填海活动重新塑造了海岸的自然形态和空间分布格局，限制了沿岸浅水区物质参与现代沉积的能力并间接影响了沉积速率变化、碎屑矿物的动力分异、重金属元素的富集和扩散。更多还原

【Abstract】 The Bohai sea, composed of Liaodong bay, Bohai bay, Laizhou bay, the central basin and Bohai strait, the average depth of18m, through the Bohai Strait interchange sea water and energy with Yellow Sea. Since the last deglaciation periods, sea water re-cover the original land of Bohai deposition to form:a large underwater delta of the Yellow River, Luan River, Liaohe, the scale of Liaodong shoal tidal sand ridge along the Liaodong Bay15m depth shallow-scale mixed the discrete distribution tidal sand ridges monomer, NE-SW extension of the central basin argillaceous sediments District. Study area is20m water depth to shallow130km X100km the waters range of northern Liaodong Bay:northern part is Liaohe (China’s seven major rivers) and other river estuaries, developmental sizable intertidal and extends to about30m deep lines near the region’s the underwater river deltas; eastern and western along the coast to the harbor bedrock coast, the eastern coast of the underwater distribution of ancient coastal residue deposition area; Seabed terrain rendering of the study area from the coast to the bay central tilt trend, which both sides of the East and West tilt steeper; tidal range in the study area (maximum tidal range more than5m), a strong trend (2-3nmail), glacial length (the longest180days), land-ocean interaction strength is very strong. Predecessors have been carried out related research, but the historical investigation precision is not high, the survey is not comprehensive regional coverage, the small number of sample tests, sample test content is not comprehensive systems perspective concern emphasis on land and in the coastal zone, and more rarely detailed study of the impact of human activities on the offshore sedimentary and the suspension of the role and impact of modern sedimentary area of research. The paper comprehensively relying on "China’s coastal marine environment, a comprehensive survey and evaluation" CJ01the blocks Al investigations District1:50,000scale investigation of sediment, water, core sample data and Liaoning Province,"908Liaoning Province Coastal Zone Survey" tidal flat core sample data, the full range of particle size, detrital minerals, macroelement and microelement, the water (temperature, salinity and density), suspension (mass concentration and volume concentration),210Pb radioactive dating test analysis, to carry out a regional fine deposition distribution characteristics of modern sedimentary material sources, modern human activities affecting record suspension transport, the modern estuarine sediment dynamic process research, the basic conclusions of the following five major areas:(1) The average compositions of silt and sand are more than80%in regional sediments, mainly sandy silt and silty sand sediment types. The northwest nearly Xiaoling River estuary, between5-10m water depth, seabed sediments (silt) is finest, while seabed sediments (sand) in the southeast direction subaqueous sand ridge is the most coarse. Marine hydrodynamics, submarine geomorphological features and matter source are closely related to the distribution of seabed sediments. In addition to the southeast coast of sandy residue deposition is less affected by the modern material supply, the vast majority of marine sediment source is dependent on input of the rivers surrounding the gulf, especially the four rivers in the northern part.(2) In the seabed surface sediments, light minerals accounted for97.1%, and as major mineral, feldspar’s average content is59.8%, quartz29.3%. Highly unstable components of heavy mineral, mineral assemblage amphibole-epidote-garnet stone-tremolite, and K-feldspar and sphene are characteristic minerals in the region. The study area is distinguished from other Bohai areas with the high content of K-feldspar and hornblende.(3) In compositions of macroelement, the average SiO2and Al2O3content are up to67.47%and12.45%, followed by metal element content, TiO2, P2O5and MnO among the last three are less than0.58%. Element composition analysis shows that terrigenous coarse clastic and biological coarse clastic are the major factor controlling the distribution of elements. Heavy metals content relative higher, and distribution law in line with the granularity control law. Each measured metal remaining higher correlation with Al, reflecting the influence that the input material is near and terrigenous.(4)210Pb and137Cs dating reveals the northern intertidal deposition rate and deposition process. Tidal flat sedimentation is sensitive highly to the loads from river. Since the1980s, the deposition rate decreased significantly, and even some parts appear deposition and erosion interactions. The subaqueous delta deposition process is basically stable, and material supply and deposition rate of the test results reflect not show large fluctuations, remained at the level of2～6mm/a.(5) The suspension concentration distribution since estuary outward diffusion presents more obviously, and the underlying concentration is much higher than the surface. Tidal current and sea surface wind field increases the concentration of the suspension, especially in shallow water and the southeast coastal waters. Salinity28‰for the sector, the mass concentration of the suspension and turbidity showed varying degrees of linear relationship. Site volume concentration and mass concentration distribution are similar, flocs and biological components in seawater relative lower, the underlying suspension higher, and Liaohe diluted water front in the estuary obviously. In Liaohe undersea valley and Liaohe estury, site average particle size is coarse, about1-5Φ, the other area to5-7Φ.At an unprecedented density of stations, obtain research data uniform coverage throughout the northern Liaodong Bay, with full information, an adequate number of samples, credible analytical test methods, then the water, sediment and cores can reflect truly on the distribution and characteristics of suspensions, particle size, detrital minerals, geochemistry, deposition rate. By comprehensive in-depth study, there is a newer understanding in three aspects:(1) In the differentiation from the sediment distribution and power, refine and update the modern sedimentary characteristics of northern Liaodong Bay. Around the gulf circulation, in the central part of western study area, is typical clayey silt fine-grained sedimentary distribution area. Residual deposition area in eastern and western bay, and underwater valley remain coarse-grained sedimentary characteristics. The terrigenous detrital mineral power differentiation characteristics, and heavy metal enriched in the fine sediment are in line with the modern sedimentary characteristics.(2) River control weakened and influx control enhanced is notable features of sedimentary environment change in northern Liaodong Bay. Sudden drop in the amount of river water and sediment resulting decrease in material supply, and rivers in northern and eastern regions diluted water diffusion limit of suspended transport distance, the proliferation of detrital minerals diminished capacity to reduce the heavy mineral fractionation capacity, surface fine sediment again suspension handling reducing in situ deposition rate, and the original river affective deposition zone gradually trend by tidal deposits.(3) Human activity is an important factor of change and remodeling northern Liaodong Bay the modern deposition pattern and deposition. Severe reduction of river water and sediment input to build a reservoir sluice; reclamation activities to reshape the coast’s natural shape and spatial distribution pattern, limits the ability of shallow coastal waters during the modern sedimentary, indirect effects of the changes in deposition rate, detrital minerals dynamic fractionation and enrichment and diffusion of heavy metal elements.更多还原