渤海湾西侧泥质海岸带全新世岸线的变化与海洋的影响

以渤海湾泥质海岸带为例,从形态和地层证据2个方面总结了全新世岸线变化与海洋作用对该地区海岸带发育的影响。中全新世以来千年级别的岸线变迁至少以6次停顿（形成贝壳堤和泥质岭地）和岸进的交替为特征。过去130年间10年级别的岸线变化分为4个阶段,显示了＂小冰期＂结束后随气温上升而发生的岸线自然蚀退是如何逐渐被人类活动（特别是2000年以来的围海造陆）所取代的。全新世海相沉积中发现的9个峰值期和晚全新世的7次风暴驱动事件,表明了研究区泥质海岸带增强的海洋影响。这些结果提供了一条经由地质背景认识现代泥质海岸带过程的途径。     

“泥质海岸带近现代地质环境与海平面变化研讨会”将于9月份在津召开

2011年9月中下旬,天津地质调查中心将举办"泥质海岸带近现代地质环境与海平面变化研讨会"。会议内容:(1)泥质海岸带晚更新世以来地质环境演化、(2)全新世海平面变化、(3")小冰期"结束以来自然进程与人类活动共同作用下的现代地质环境变化及海岸带演化趋势。届时将邀请来自中国、英国、美国、丹麦等国的多位专家围绕以上主题做专题学术报告,欢迎有兴趣的同行们届时与会。     

中国海岸20 ka以来的演替过程及趋势分析：对现代海岸生态保护修复的启示

【研究目的】为支撑海岸带生态保护修复,提出科学修复方案,需要掌握中国海岸自然演替总体规律和趋势。【研究方法】本文在系统梳理总结中国海岸演化相关成果的基础上,采用钻孔综合研究、遥感解译和ArcGIS空间分析等手段,定量重建了末次盛冰期以来的海岸演化过程。【研究结果】结果显示,近200多万年以来海水频繁进出中国海岸带地区,其中最后一次大规模海退-海侵发生在近20 ka以来,当时,中国海岸整体经历了末次盛冰期—中全新世早期的海侵、中全新世早期—1850年的海退、～1850年以来的海侵3个阶段。【结论】基于现有器测资料分析显示,中国乃至世界海岸未来将面临海面上升加快、海岸侵蚀加剧、风暴潮威胁增大的自然过程,这些将是海岸带生态保护修复面临的核心问题。有鉴于此,针对海岸带生态保护修复建议如下：一是顺应砂质岸线整体侵蚀的自然规律,将具有重要生态和/或经济价值的岸段作为修复重点,避免大规模过度修复。二是针对海面上升和海岸侵蚀对红树林生态空间的挤压,确定科学可行的修复目标。三是加强泥质沿海低地地区的生态化海堤建设。     

渤海湾泥质海岸带近现代地质环境变化研究(Ⅱ):成果与讨论

渤海湾泥质海岸带国土资源大调查以其特有的方法、手段和要求,获得了一批带有地质调查特点的、关于全新世地层与近现代地质环境变化的阶段性成果,主要包括:1)该地区海岸带全新世地层具有4种沉积类型:(A)远离海岸的传统的"三分"型;(B)海相层与陆(海陆过渡)相层的多次交替;(C)末次冰期后期未接受沉积,全新统半咸水的海陆过渡相直接覆于历时约10～20ka的沉积间断面上,向上,进一步发育为海相层;(D)沿海低洼地区在末次盛冰期后的晚更新世晚期即已进入海侵阶段,晚更新世晚期与全新世早期的海陆过渡相沉积是连续的,向上继续发育海相层.2)从以海水影响为主的开放潮坪(及浅海区)环境转变为(陆源影响逐渐加强的)湖-盐沼环境,是研究区中晚全新世地质环境转变的重要特征,建立了表征这两种不同环境的非正式地层单位("灰色单元"与"黄色单元").3)牡蛎礁与贝壳堤的对比方案,以牡蛎礁对应潮坪的贝类繁盛期,牡蛎礁中的水平再搬运夹层和/或上覆泥质盖层(往往形成"岭地")对应贝壳堤成堤.4)大比例尺区调地质点(浅孔)揭示了中晚全新世(近现代)地质环境变化,编绘出约4500calB.P.以来小于1ka时段的二维、假三维环境系列图.一个实例是Ⅱ贝壳堤向陆侧的洼地甚至早于该堤的形成,推测洼地边缘的NNW向的埋藏线性凸起可能受同一方向的新构造活动控制.5)渤海湾沿海平原线性砂坝(障壁岛)-湖/盐沼成因假说.作为堆积贝壳堤正地形的补偿,堤前因"簸选"贝壳导致的潮坪负地形,同样可发育湖沉积.6)210pb/137Cs测年研究提供了该地区现代沉积速率的初步结果(＜0.1cm/a或＞3cm/a不等),据此将海岸带划分为不同的沉积类型区.     

天津三河岛及其周边地区晚全新世沉积环境

坐落于永定新河-潮白新河与蓟运河汇流处的三河岛及其周边潮间带,以其独特的地理位置,记录了中全新世晚期以来直至现代的泥质海岸带变化过程。作者通过全取心浅孔钻探、全站仪高程测量和沉积学综合研究,重建了该地区中全新世晚期以来地层及沉积环境演替过程:中全新世开放潮坪沉积了“灰色单元”砂泥质层,约在2.4 ka cal BP开始转为晚全新世盐沼环境,沉积了“黄色单元”泥质层。近百余年以来,因人类活动加剧,重归开放潮坪环境,堆积了现代淤泥质层。该项研究成果可为了解现代地质环境,预测未来地质环境的变化过程提供科学依据。     

渤海湾西岸海岸带第四纪地质研究成果概述

本文简要介绍了天津地质调查中心海岸带与第四纪地质研究所(海岸带近现代地质环境变化研究小组)自1998年承担国土资源大调查任务以来,以滨海新区及渤海湾西岸海岸带为主要研究基地所取得的基本成果:(1)确立了泥质海岸带(沿海低地-潮间带-浅海区)地质环境变化(大致划分为(a)晚更新世以来-"小冰期"、(b)"小冰期"结束-现...     

“海岸带地质学基础理论与关键方法”学术讨论会在天津举行

中国地质调查局天津地质调查中心于2013年7月在天津召开了以“海岸带地质学基础理论与关键方法”为主题的学术讨论及培训会议,邀请英国普利茅斯大学的 Dr. W. A. Marshall、比利时皇家自然科学院（比利时地质调查所）的Dr. C. Baeteman和北京大学的周力平教授分别讲学,内容主要包括以下6方面：(1)晚更新世-全新世地层细分、地层单元、分类系统和海面变化的关系。(2)泥质海岸带沉积环境和沉积相,以实例展示了不同沉积环境的沉积物及特征、野外描述方法和内容,地层垂直序列的连续性及与岩相的相关性。(3)相对海面变化研究历史和基础理论,涉及众多方面,包括气候与海面变化的关系、影响相对海面变化的各种因素（构造、绝对海面升降、均衡、温度、沉积物压实、海洋虹吸作用和大陆杠杆作用等）、21世纪高分辨率测量和预测对海面变化研究的意义等。(4)海面研究的关键技术方法。盐沼沉积物中获取高精度的海面代用指标--盐沼有孔虫与海面高度的转换函数,精度可达厘米级;获得全新世沉积物高分辨率年龄的方法--14C、210Pb/137Cs/241Am、OSL测年、天然剩磁等方法和其它多种年龄替代指标（人类活动造成的Pb富集历史、孢粉标志层、火山碎屑层、球状碳质颗粒等）的应用,以及对14C年龄数据的“wiggle matching”和“bomb spike”校正等。(5)海岸带变化进程与驱动机制：介绍了比利时海岸带全新世海面上升过程（控制因素、上升速率变化等）,人类活动的影响等,重建了比利时西部沿海平原的形成演化过程（海岸进积、潮道发育过程）。(6)人类活动和湿地发展：海岸带三角洲的环境极为脆弱,其可持续发展需要建立在基础地质研究及对工程地质特征了解的基础上。通过实例展示,指出IPCC的预测只考虑了由于冰融化和热膨胀导致的海洋水体增加而引起的海面上升,而不同地区的预测模型要考虑各种因素对海面变化影响的贡献量,未来的海面上升预测应考虑在振幅和时间上的变异性,区域海面上升预测比全球上升预测更有应用价值。会议期间,两位国外学者还参与了我们的钻孔岩心编录及分样,并进行了野外实地考察。通过这次活动,使大家了解了英国和比利时泥质海岸带晚更新世全新世地层的基本情况、研究方法与现状,交流了钻孔岩心编录方法与经验、当前海岸带研究的基本理论与方法、海面标志点和海面变化研究的进展以及光释光研究的复杂性和最新动态。     

山东半岛东北部全新统研究新进展

全新世以来山东半岛东北部沿岸的相对海面（基准面）变化控制了入海河流河谷内全新统的发育,并通过影响进入海岸带碎屑物质的类型与数量,深刻影响了海岸带全新统的发育。全新世早期（１０～６ｋａ Ｂ． Ｐ．）快速的相对海面上升导致河谷溯源堆积,河流输沙中的推移质均堆积于河谷中,仅有悬移质进入海岸带堆积,因而海岸全新统下部均为细粒的海湾、湖、沼泽相沉积。全新世中期（６～４ｋａ Ｂ．Ｐ．）时海面虽已相对稳定,但早期基准面上升导致的河谷堆积作用仍在进行,因而中全新统的粗碎屑海岸沉积均为源于基岩海岸侵蚀的含贝壳砂砾石。从全新世后期（４ｋａ Ｂ．Ｐ．以来）开始有较丰富的河流推移质输沙进入海岸带,但由于不同规模河流对相对海面变化的地貌响应有显著差别,不同河流对海岸全新统发育的影响各不相同。上述结论为精确地解释低序列、小尺度地层层序提供了理论依据     

渤海湾泥质海岸带近现代地质环境变化研究(Ⅰ):意义、目标与方法

渤海湾泥质海岸带的近现代地质环境变化研究,是通过两种形式(大比例尺区域地质调查和综合研究)在两个方面即垂向的浅表沉积物和平面上的地表形态变化同时展开的.(1)海岸带深覆盖区区域地质调查(1:50000)分为4个层次:基底(前第四纪)研究、早中更新世研究、晚更新世-全新世多学科综合研究、中晚全新世-现代多学科高分辨率综合研究.(2)海岸带综合研究采用多期图形对比、短半衰期同位素示踪与测年等方法,围绕近百年来地表形态、沉积速率变化及海岸线变迁展开.(3)正在形成的系统工作方法:包括Eijkelkamp槽型取样器获取浅表地层的无扰动岩心、岩心编录、手持GPS定位;少量辅助性机械钻孔岩心(30～100m,全取心)研究;地质点水准(与国家高程联网的)测量;有孔虫、介形虫、孢粉、OSL、14C测年(加速器质谱法与液体闪烁计数器法)、磁学研究和210Pb/137Cs测年,以及多期图形(历史地图、地形图、航片与卫星遥感影像)的计算机处理与对比、假三维表达的综合研究等.     

全新世渤海泥质沉积物地球化学特征

对渤海泥质区柱状沉积物的粒度与化学成分的分析及AMS 14C测年数据表明,全新世以来本区泥质沉积物的物质来源与沉积环境较为稳定.R型因子分析得出三种主要组合类型,以Ca、Ti和Mn为代表,分别对应黄河物质影响、陆源细粒物质输入和海洋自生作用.其中西南部与中部泥形成于约6000 a B.P.以来,黄河物质影响较强,主要在潮余流的作用下搬运后沉积下来.北部泥自早全新世之前便已开始形成,且主要沉积于高海面之前,受滦河物质作用相对较强.南部和北部泥质沉积年代存在明显差异,受水深、离岸距离、海平面高度等多种因素影响.尽管距黄河口较近,但区内沉积速率远低于中国近海其他泥质体,这与渤海环流状况及泥沙运移方向关系密切.     

Geomorphology and sedimentary/biosedimentary structures of the intertidal environment along the coast of Kuwait,north-western Arabian Gulf

The coast of Kuwait can be divided into nine intertidal geomorphological subunits, of which four are found along the northern muddy shoreline and five along the southern sandy shoreline. In the north the coast is characterized by wide intertidal mudflats, bounded landward by an extensive coastal sabkha which is partly covered by sand drifts. The upper part of the intertidal environment is covered with a mixture of aeolian sands and muddy sediments of marine origin. A number of shallow tidal channels dissect the intertidal flats and small sand bars occur near the low water line. In contrast, the southern shore is characterized by relatively steep sandy beaches fronted by narrow to moderately wide rocky intertidal platforms which are partly covered by sand, bioherms, skeletal debris and algal mats. In some areas the rocky surface is dissected by numerous small gulleys and shallow channels. Multiple sand bars lying either parallel or diagonal to the shoreline are developed near the low water line. This southern intertidal environment is bounded landward by a sandy berm and a wave-cut cliff.Ripple marks are developed almost parallel to the shoreline, showing different flow directions. Energy levels are moderate to high along the southern shore, but low along the northern shore. In the south, waves induced by winds blowing mostly from the north-east and south-east form the dominant energy source, whereas tidal and wind-driven currents are the only tangible process acting along the northern shore.     

渤海湾海岸带近现代地质环境变化

淤泥质海岸带地区10～10²a级别的相对快速的“缓变型地质环境变化”,主要包括水体、湿地和盐沼-湖退化或消失、贝壳堤和牡蛎礁被破坏、村镇和城市面积剧增、海岸线(平均大潮高潮线)被侵蚀后退、潮间带和近海河道被淤积、潮间带变宽变缓等。这些变化,已对我国东部沿海地区的经济和社会发展造成不利影响,并将对该类地区的可持续发展构成潜在威胁。在该类地区正在进行的1∶50000区域地质调查,充分发挥其高精度和规范化的优势,并辅以对近百年来不同时期的地形图、航空照片和遥感影像的数字化处理和对比研究,试图对这些变化做出形象、直观和定量的二维(2D)表达。本文介绍的是正在渤海湾海岸带进行的工作,充分显示出地质调查服务社会的公益性、基础性和战略性特点。对这一研究方向所显示的巨大潜力的进一步开发,将可能形成供政府决策部门和各方面用户广泛利用的、可二次开发的平台,从而使该类地区的可持续发展建立在对近现代地质环境变化详细了解的扎实基础之上。     

Coastal progradation in response to the recent sea level rise: a case study of El Grine coast, Gulf of Gabes (Southeastern Tunisia)

Over the last 30 years El Grine coast recorded significant morphological changes leading to the shoreline progradation. Diachronic coastal evolution, through a set of satellite images data, supported by sedimentologic analysis of five sand cores have been applied to elucidate tidal flat reaction following the recent sea level rise. We found that an emerging sandy barrier and salt marsh domain were shaped by the local hydro-sedimentary processes. The marine sediments, mobilised by wave and tide currents, have been the sole sedimentary source. Recent sandy accumulations, occurred around 1987, have been able to balance a recent sea level rise. While during a mid-Holocene period, El Grine coast was governed by net erosion tendency inducing cliff recession.     

Potential impacts of extreme storm surges on a low-lying densely populated coastline: the case of Dunkirk area, Northern France

Along the southern coast of the North Sea, a large proportion of the Flemish coastal plain consists of densely populated reclaimed land, much of which lying below mean high tide level. This is particularly the case along the northern coast of France, from Dunkirk to the Belgium border, where the shoreline consists of coastal dunes that protect low-lying reclaimed lands from marine flooding. This area is vulnerable and subject to several risks. Extreme weather conditions could induce strong surges that could cause (1) a shoreline retreat, (2) marine submersion and (3) land and/or urban flooding due to drainage problems of the polders. Highly energetic events such as the November 2007 storm could have had much more severe consequences especially if they occurred at high tide and/or during a spring tide. In the current context of global change and projected sea-level rise, it is then important for the local authorities to take into account the potential impacts and return periods of such events, in order to implement coastal risk policies prevention and management, to reinforce sea defense, increase pumping station efficiency and plan warning systems against marine submersion and polder flooding, which is not the case yet in Northern France.     

OSL and 14C chronologies of a Holocene sedimentary record (Garding‐2 core) from the German North Sea coast

The history of sea‐level change and sediment accumulation since the last deglaciation along the German North Sea coast is still controversial because of a limitation in the quantity and quality of chronological data. In the current study, the chronology of a 16‐ka coastal sedimentary record from the Garding‐2 core, retrieved from the Eiderstedt Peninsula in Schleswig‐Holstein, northern Germany, was established using OSL and AMS ¹⁴C dating techniques. The robust chronology using 14 radiocarbon and 25 OSL dates from the Garding‐2 core is the first long‐term record that covers the Holocene as well as the last deglaciation period in one succession in the German North Sea area. It provides a new insight into understanding the Holocene transgression and coastal accumulation histories. The combined evidence from the sedimentology and chronology investigations indicates that an estuarine environment dominated in Eiderstedt Peninsula from 16 to 13 ka, followed by a depositional hiatus between 13 and 8.3 ka, attributed to erosion caused by the Holocene transgression; the onset of the Holocene transgression at the core site occurred at around 8.3 ka. The sea level continued to rise with a decelerated rate until around 3 ka. Since 3 ka, the shoreline has begun to prograde. Foreshore (tidal flat) sediments have been deposited at the drilling site with a very high sedimentation rate of about 10 m ka^?1. At around 2 ka, a sandy beach deposit accumulated in the sedimentary succession, indicating that the coastline shifted landward, which may represent a small‐scale transgression in the late Holocene. At around 1.5 ka, terrestrial clastic sediment started to accumulate, indicating a retreat of the relative sea level in this area, which may be related to local diking activities undertaken since the 11th century.     

大凌河河口地区中更新世晚期以来沉积环境演化

大凌河河口地区LZK06孔40m以浅岩心的沉积学、古生物学和年代学等综合研究以及该地区LZK02-04钻孔资料,揭示了研究区中更新世晚期以来经历了两次海侵-海退旋回,依次形成了中更新世晚期湖相/河流相→晚更新世海相-湖相/河流相→全新世海相-河流相地层。全新世早中期由于物源供给很少,研究区处于长达约10ka的饥饿滞留相沉积环境,平均沉积速率仅约0.02～0.05cm/a。全新世晚期约1500a cal BP以来,由于人类活动导致水土流失,河流输砂量增加,研究区开始了快速加积过程,平均沉积速率约0.9～1.2cm/a,下辽河平原被快速充填,开始成陆。与全球海面变化时空分布特征的对比,推断辽东湾的第II海相层发育于MIS 5-MIS 3早期,第I海相层发育于MIS 1阶段高海面时期。晚更新世以来频繁的海面升降是辽东湾泥质海岸带地层和环境演化的主要控制因素。     

Sea-level rise and shoreline retreat of the Nile Delta promontories, Egypt

Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively.Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers.     

Sea-level rise and shoreline retreat of the Nile Delta promontories,Egypt

Studies of the Nile Delta coast have indicated wide values of local subsidence, ranging from 0.4 to 5 mm/yr. Trend analysis of sea-level rise and shoreline retreat at two Nile Delta promontories have been studied. Records from tide gauges at Alexandria (1944–1989) and Port Said (1926–1987), north of the Nile delta coast, indicate a submergence of the land and/or a rise of the sea-level of 2 and 2.4 mm/yr, respectively. Dramatic erosion has occurred on some beaches of the Nile Delta. This is greatest at the tips of the Rosetta and Damietta promontories, with shoreline retreat up to 58 m/yr. Relationship between the shoreline retreat and sea level trends in terms of correlation analysis and application of the Bruun Rule indicates that the sea level rise has, by itself, a relatively minor effect on coastal erosion. The sea-level trend at the Nile delta coast is found to be only one of several effects on shoreline retreat. Major recent effects include a combination of cut-off of sediment supply to the coast by damming the River Nile and local hydrodynamic forces of waves and currents. Estimates of local future sea-level rise by the year 2100 at Alexandria and Port Said, respectively, is expected to be 37.9 and 44.2 cm. These expectations, combined with other factors, could accelerate coastal erosion, inundate wetlands and lowlands, and increase the salinity of lakes and aquifers.