长江三角洲地区的相对海平面上升与地面沉降

在有关学者以往研究工作的基础上,对长江三角洲地区的相对海平面上升和地面沉降问题作了分析探讨。认为相对海平面上升已经在并将继续在该区造成多种危害,地面沉降是影响相对海平面上升诸多因子中贡献率最大的因子,它主要由人类活动引起,同相对海平面上升一样．也是该区不容忽视的地质灾害之一。然而,由于采取了积极的控制措施,上海地区人为引起地面沉降在相对海平面上升中的贡献率已从20世纪50、60年代的90％以上降至目前的60％以下,但预计在未来几十年中仍将占相当大的比例,必须引起人们的高度警觉,采取更为积极的防治对策。     

新世纪上海地区相对海平面变化影响因素及预测方法

针对传统相对海平面变化分析方法均将理论海平面变化和地面沉降进行的叠加分析,本文讨论和分析了近20年来全球理论海平面上升速率加快背景下的区域海平面变化速率,利用灰色线性回归组合模型预测上海地区海平面变化趋势。考虑了上海地面沉降发展的新特点,以及长江流域来沙显著减少和河口大型工程建设对上海地区相对海平面变化的影响。在流域来沙量显著减少但来水量变化不大情况下,流域大坝的坝下冲刷使得河槽刷深,河口水位降低,同时长江口深水航道整治工程和促淤围垦工程束狭入海口,使得潮位站水位发生变化,两者的综合效应是目前研究长江口相对海平面变化时必须考虑的重要因素。     

关于海平面上升及其环境效应

沿海地区地质环境复杂。由于国民经济的迅速发展,人类活动日益增多,对地质环境进一步造成严重的不利影响。特别是“温室效应”引发的海平面上升,使各种地质灾害更加激化。文章详细探讨了海平面上升的影响因素,理论海平面与相对海平面升降幅度的评估,以及海平面上升所造成的地质环境效应与相应的防治对策,特别强调控制沿海城市地面沉降,以减轻海平面相对上升造成的危害,具有特殊而重要的意义。     

论中国现代海平面变化

本文根据对大量实际观测资料的统计分析,总结了现今阶段中国东部沿海海平面变化的基本规律,分析了主要控制因素,预测了未来变化趋势。认为,目前和今后数十年,气候和海平面变化的自然趋势是继续向相对寒冷的低海面阶段缓慢发展;温室效应虽然干扰了这一进程,但不会引起大幅度海平面上升;受地壳和地面升降控制,差异性海面升降活动剧烈,部分滨海地区因此相对海面急剧上升,面临严重的海水侵袭威胁。     

未来上海地区海平面上升激化土层液化的探讨

未来上海地区海平面上升引起地下水位抬升,将会激化土层液化,本文就土层液化问题从理论上进行了分析探讨,并对未来工作提出了设想。     

未来海平面上升激化的地基变形的研究

未来上海地区海平面上升将引起地下水位招升,将会对多层建筑地基产生影响。文章在研究探讨地基变形激化程度的同时,也进行了土压缩模量Ｅｓ的预测分析工作,并提供分析结果。     

未来海平面上升激化地基变形的研究

未来上海地区海平面上升将引起地下水位抬升,将会对多层建筑地基产生影响。文章在研究探讨地基变形激化程度的同时,也进行了土压缩模量Es的预测分析工作,并提供分析结果。     

应对海平面上升与地面沉降迭加引发的地质灾害与生态环境问题

海平面上升已引起各国政府和科技界的高度关注。预计未来30年,浙江沿海海平面将比2009年升高88~140 mm。海平面上升与浙江沿海平原地面沉降迭加将进一步恶化地质与生态系统,引发许多灾害问题,制约沿海区域经济社会的可持续发展。本文主要就如何应对海平面上升与地面沉降迭加引发的地质灾害链与生态环境问题进行了探讨,认为要从地球系统科学角度,重视对陆-海相互作用机制与生态环境效应的研究,着手考虑建立陆海(包括入海河流)统筹的海岸带地质与生态环境监测评价系统。     

多维动态GIS在海平面变化中的应用

随着空间对地观测技术的发展和集成,三维地理空间信息获取与更新的能力有了飞速的进步,海洋、环境等应用领域已逐步形成多维空间信息源。介绍了多维动态GIS的相关概念,多维数据、可视化在海平面变化中的研究现状,研究的主要方向等。我国沿海城市相对集中,人口密集,地势低洼,地面沉降严重,海平面上升给沿海城市和人民生活带来深远的影响。而多维动态GIS可以动态、可视化地演示海平面的变化,并对可能造成的危害进行预测和分析。因此,多维动态GIS对海平面上升变化过程的研究具有十分重要的意义。     

相对海平面变化对腕足动物群落取代的影响——以吐哈盆地北缘桃西沟上石炭统祁家沟组—奥尔土组剖面为例

相对海平面的升降变化引起的相对水深及相关生态条件的改变对腕足动物群具有影响。相对海平面变化的速度和幅度是引起腕足动物群面貌变化的重要因素。相对海平面的持续缓慢上升有利于腕足动物丰度的增加和分异度的提高,海平面的大幅度快速变化对腕足动物群落则是一个不利的因素,是造成腕足动物物种丰度下降、新种增加量减少乃至彻底死亡的重要原因。吐哈盆地北缘晚石炭世发育的5个腕足动物群落全部与相对海平面上升期有关。在海平面的持续缓慢上升期,腕足动物的丰度不断增加,分异度迅速提高;而在相对海平面下降期,本区陆源粗碎屑物大量注入,不适合腕足动物的生存。     

末次冰消期以来海平面变化研究进展

本文综述了末次冰消期特别是全新世以来全球海平面变化的研究成果。文章先介绍了海平面的变化成因,阐述了海平面变化带来的影响,总结了海平面变化的研究方法。分析总结了国内外学者研究所得的不同阶段的海平面变化数值及海平面变化曲线,并简要总结了海平面变化研究中存在的问题。     

渤海湾西岸CZ01钻孔沉积物粒度端元分析及其气候—海平面变化响应*

沧州地区位于海陆交互的渤海湾西岸,易受到海平面变化和极端气候事件的影响,对于全球气候变化的响应十分敏感。应用非参数化端元分析模型将沧州地区CZ01钻孔中更新世晚期以来的沉积物粒度划分出6个端元并分析其物源,结合已有地质记录,揭示不同时间尺度下各端元对气候—海平面变化的响应。结果表明: (1)EM1(5.01 μm)主要为远源的风尘输入,EM2(13.18 μm)和EM3(39.81 μm)为古黄河所携带的沉积物,EM4(69.18 μm)和EM5(138.04 μm)为海相沉积物,EM6(275.42 μm)可能指示古洪水等极端气候事件。(2)深海氧同位素(MIS)Ⅰ 阶段,气候温暖湿润,EM4+5含量指示渤海海平面整体呈波动上升的趋势并逐渐接近现代海平面。该阶段内由于11.5 ka BP左右的新仙女木事件以及5.1 ka BP左右冷干事件的发生,渤海海平面在稳定上升状态后出现停滞或小幅下降的现象; 而在9.5 ka BP、7.5 ka BP、5.8 ka BP和1.7 ka BP左右,东亚夏季风增强导致降水增加,渤海海平面升高。(3)MIS Ⅵ 阶段北半球气候冷干,150~132 ka BP左右因喜马拉雅运动减弱造成的区域沉降中心转移致使渤海海面升高。MIS Ⅴ 阶段气候波动剧烈: 在间冰期暖期(5a、5c和5e)气候暖湿,渤海海平面上升; 而MIS5b和5d时期渤海海面高度较低。MIS Ⅳ 阶段较MIS5a末期海平面突然下降后趋于稳定,期间出现若干次小规模海侵事件,可能与东亚夏季风频繁变化有关。MIS Ⅲ 阶段至末次冰盛期海平面大幅度下降且存在周期性升降变化,并在46 ka BP左右出现大规模海侵事件。MIS Ⅱ 阶段较MIS Ⅲ 阶段海平面出现小幅度下降,为低海平面时期; 伴随15 ka BP左右冰盛期的结束,东亚夏季风增强,海平面开始上升。渤海海平面180 ka BP以来的变化记录与北半球乃至全球范围内的地质记录存在一致性,与太阳辐射波动引起的冰川消融及东亚夏季风变化密切相关。     

Sequence stratigraphy of the Dakota Formation (Cenomanian), southern Utah: interplay of eustasy and tectonics in a foreland basin

The Dakota Formation in southern Utah (Kaiparowits Plateau region) is a succession of fluvial through shallow-marine facies formed during the initial phase of filling of the Cretaceous foreland basin of the Sevier orogen. It records a number of relative sea-level fluctuations of different frequency and magnitude, controlled by both tectonic and eustatic processes during the Early to Late Cenomanian. The Dakota Formation is divided into eight units separated by regionally correlatable surfaces that formed in response to relative sea-level fluctuations. Units 1–6B represent, from bottom to top, valley-filling deposits of braided streams (unit 1), alluvial plain with anastomosed to meandering streams (2), tide-influenced fluvial and tide-dominated estuarine systems (3A and 3B), offshore to wave-dominated shoreface (4, 5 and 6A) and an estuarine incised valley fill (6A and 6B). The onset of flexural subsidence and deposition in the foredeep was preceded by eastward tilting of the basement strata, probably caused by forebulge migration during the Early Cretaceous, which resulted in the incision of a westward-deepening predepositional relief. The basal fluvial deposits of the Dakota Formation, filling the relief, reflect the onset of flexural subsidence and, possibly, a eustatic sea-level rise. Throughout the deposition of the Dakota Formation, flexure controlled the long-term, regional subsidence rate. Locally, reactivation of basement faults caused additional subsidence or minor uplift. Owing to a generally low subsidence rate, differential compaction locally influenced the degree of preservation of the Dakota units. Eustasy is believed to have been the main control on the high-frequency relative sea-level changes recorded in the Dakota. All surfaces that separate individual Dakota units are flooding surfaces, most of which are superimposed on sequence boundaries. Therefore, with the exception of unit 6B and, possibly, 3B, most of the Dakota units are interpreted as depositional sequences. Fluvial strata of units 1 and 2 are interpreted as low-frequency sequences; the coal zones at the base and within unit 2 may represent a response to higher frequency flooding events. Units 3A to 6B are interpreted as having formed in response to high-frequency relative sea-level fluctuations. Shallow-marine units 4, 5 and 6A, interpreted as parasequences by earlier authors, can be divided into facies-based systems tracts and show signs of subaerial exposure at their boundaries, which allows interpretation as high-frequency sequences. In general, the Dakota units are good examples of high-frequency sequences that can be misinterpreted as parasequences, especially in distal facies or in places where signs of subaerial erosion are missing or have been removed by subsequent transgressive erosion. Both low- and high-frequency sequences represented by the Dakota units are stacked in an overall retrogradational pattern, which reflects a long-term relative sea-level rise, punctuated by brief periods of relative sea-level fall. There is a relatively major fall near the end of the M. mosbyense Zone, whereas the base of the Tropic shale is characterized by a major flooding event at the base of the S. gracile Zone. A similar record of Cenomanian relative sea-level change in other regions, e.g. Europe or northern Africa, suggests that both high- and low-frequency relative sea-level changes were governed by eustasy. The high-frequency relative sea-level fluctuations of ≈100 kyr periodicity and ≈10–20 m magnitude, similar to those recorded in other Cenomanian successions in North America and Central Europe, were probably related to Milankovitch-band, climate-driven eustasy. Either minor glacioeustatic fluctuations, superimposed on the overall greenhouse climate of the mid-Cretaceous, or mechanisms, such as the fluctuations in groundwater volume on continents or thermal expansion and contraction of sea water, could have controlled the high-frequency eustatic fluctuations.     

四川盆地东部晚二叠世-早三叠世飞仙关期礁、滩特征与海平面变化

据四川盆地东部上二叠统-下三叠统飞仙关组沉积特征和储层分布规律,认为区内长兴组生物礁和飞仙关组鲕粒滩特征和分布与海平面升降有关。长兴期生物礁发育于海平面快速上升阶段的缓坡坡折地带和缓坡内的局部,当生物礁的生长速度低于海平面的上升速度时,形成海侵追补型生物礁,当生物礁生长速度大于海平面上升速度时,则构成海侵并进型生物礁;飞仙关鲕粒滩形成于海平面下降阶段的台地边缘和台内局部地区,单一台地边缘鲕粒滩分布广、厚度大,而台内鲕粒滩数量虽多,但单一厚度小,分布范围窄。总体来看,长兴生物礁发育层位逐渐向海侵方向升高,而飞仙关鲕粒滩随海退的进行,向台地增生方向迁移。区内上二叠统-下三叠统飞仙关组是一次较大规模海平面升降过程中的产物,海侵始于吴家坪初期,长兴期海平面快速上升,至飞仙关初期达到最高海平面,海平面开始下降,直至飞仙关末期。     

利用长江口现代潮滩沉积硅藻建立海平面转换函数的尝试

在高精度海平面定量重建研究中,有孔虫、硅藻等海洋微体古生物转换函数技术是近10余年随着计算机技术发展而快速兴起的一项新技术,已成为欧美地区研究海平面变化的不可或缺的定量手段之一,而其在中国沿海地区全新世海平面定量重建中的应用却屈指可数。以硅藻为例,详细介绍了建立其与海平面之间的转换函数的过程,包括现代表层样采集、统计学分析、误差的可能来源和减小误差的方法。通过在对崇明岛四滧港SY剖面潮滩表层样品的环境因子分析和对硅藻属种的CCA排序分析发现,高程对潮滩硅藻属种排序有着很高的解释贡献。随后通过WA和WA-PLS建立模型,四滧港SY剖面全样WA-PLS模型的相关系数(R²_Jack)达到0.9004,预期误差(RMSEP)为12.622,若不考虑潮上带样品SY1后的转换模型其精度更能达到±10cm。本研究以期带动此项技术在国内的发展,促进高精度海平面定量重建,从而能为沿海地区海岸带管理提供更详实、更具现实指导意义的地质记录。     

New relative sea-level curves for the southern Scott Coast,Antarctica: evidence for Holocene deglaciation of the western Ross Sea

Here we present new relative sea-level (RSL) curves developed from Holocene-aged raised beaches along the southern Scott Coast of the western Ross Sea, Antarctica. Fifty-four dates of marine shells, seal skin and elephant seal remains incorporated within raised beaches during storms afford a chronology for these curves. All of the curves show the same pattern and timing of RSL change within a small range of error. The best-dated curve suggests that final unloading of grounded Ross Sea ice from the southern Scott Coast and McMurdo Sound region occurred shortly before 6500 ¹⁴C yr BP. This age is consistent with glacial geological evidence that places deglaciation between 5730 and 8340 ¹⁴C yr BP. Our data strongly suggest that grounding-line retreat of the Ross Sea ice sheet southward through the McMurdo Sound region occurred in mid- and late Holocene time. If this is correct, then rising sea level could not have driven ice recession to the present-day grounding line on the Siple Coast, because global deglacial sea-level rise was essentially accomplished by mid-Holocene time. Copyright © 1999 John Wiley & Sons, Ltd.     

Holocene sea-level changes and crustal movements in Morecambe Bay,northwest England

Holocene stratigraphy from Skelwith Pool, on the northern side of Morecambe Bay, is described. Diatom and pollen analyses and radiocarbon dating have been undertaken for three sampling sites, from which eight sea-level index points have been obtained. These index points come from a small homogeneous area and similar palaeoenvironments. Some published sea-level index points from Morecambe Bay have been re-evaluated and validated by means of diatom analysis. An enhanced sea-level database with 28 index points has been used for the reconstruction of Holocene sea-level history. Relative sea-level rose rapidly around 6870–6510 BC at a maximum rate of +36.7 mm yr⁻¹. Subsequently, the rate of sea-level change has varied between −8 mm yr⁻¹ and +12 mm yr⁻¹. The rate of relative sea-level changes for the last 3500 years is not clear. Uplift driven by deglaciation is believed to have been interrupted in the early Holocene by a rapid rise in relative sea-level. Uplift restarted at 6510 BC but soon declined as glacio-isostatic recovery ended around 3800 BC in the Morecambe Bay area. Since then, crustal movements in the Morecambe Bay area have been minimal. Factors affecting the attitudes of the index points such as sediment compaction of the basal peat and variations in palaeotidal range during the Holocene have been considered. © 1996 John Wiley & Sons, Ltd.     

压实作用下广西典型红树林区沉积速率及海平面上升对红树林迁移效应的制衡

气候变化造成的海平面上升是迫使红树林向陆迁移的主要驱动力, 而其自身通过捕沙促淤不同程度的减缓了海平面上升速率的影响。基于广西典型红树林区8根短柱的210Pb测年和含水率分析, 以考虑/未考虑沉积物压实作用为研究情景, 通过对比研究红树林区潮滩地表高程抬升速率和相对海平面上升速率的大小关系, 揭示当前海平面上升对广西红树林向陆/向海迁移的驱动机制。研究发现:未考虑压实作用下的沉积速率约是考虑压实作用下沉积速率的1.00~1.34倍(平均1.12倍), 压实作用明显;压实沉积速率介于0.16~0.78 cm/a, 其底层压实沉积速率与潮滩地表高程抬升速率相等。压实作用下, 英罗湾和丹兜海红树林区的地表高程抬升速率小于相对海平面上升速率;与未考虑压实作用得到的结论相悖。由于广西红树林海岸大都建有防波堤, 限制了红树林向陆的迁移;表明英罗湾和丹兜海的红树林正面临海平面上升的威胁。压实作用校正与否对地表高程抬升速率与相对海平面上升速率相当的区域尤为重要。     

Variations in the pattern and rate of isostatic uplift indicated by a comparison of Holocene sea-level curves from Scotland

Differences in the timing of maxima and minima and shape between sea-level curves from the western Forth valley, lower Strathearn, inner Moray Firth and eastern Solway Firth areas of Scotland are interpreted as being due to differences in isostatic uplift and different methodologies used to interpret the basic data. Possible changes in the relative rates of uplift between areas suggest that the practice of applying the western Forth ‘model’ of relative sea-level change to other parts of Scotland must be questioned.