【作者】 李建芬；

【导师】 方念乔；

【作者基本信息】 中国地质大学（北京） ， 海洋地质， 2010， 博士

【摘要】 本文主要进行了两方面的研究工作。第一,对渤海湾西部潮间带及浅海区不同亚环境下采集的110个底质沉积物样品,分别进行了有孔虫活体和死体(埋藏)种群的鉴定、统计和分析,其中包括:现代有孔虫群的组成,优势种和常见种的分布特征及现代有孔虫对地质环境和海面的指示意义,高程/水深、沉积物底质粒径和现代沉积作用等因素对有孔虫生态的影响;第二,在现代有孔虫特征区域研究的基础上,进行了地层中应用实例的个案研究,逆推了全新世地质环境与海面的历史变化。活体和死体(埋藏)有孔虫都显示了渤海湾西部及浅海区的有孔虫主要优势种有: Ammonia beccarii vars.、Ammonia limbatobeccarii、Protelphidium tuberculatum、Ammoboculites sp.、Elphidium simplex、Pseudogyroidina sinensis、Quinqueloculina akneriana rotunda、Cribrononion porisuturalis、Ammonia granuloumbilica等,常见种有Elphidium magellanicum、Elphidium advenum、Cribrononion subincertum、Ammonia maruhasii等。有孔虫的分布特征和主成分分析均表明,研究区主要受到近岸浅海环境、潮间带环境和高潮线附近的盐沼、河口漫滩的影响,其它环境如河口闸下、潮间带的潮道等环境影响不明显。通过对优势种的聚类分析,探讨了现代有孔虫的组合特征。共分为五5个组合7个亚组合,各组合区几乎平行于岸线分布,分别对应于潮间带及浅海区不同的亚环境。筛选出的8个优势种有孔虫随水深(高程)变化的垂直分布特征表明,高程/水深是现代有孔虫的主要影响因素。讨论了不同属种、不同有孔虫垂直组合带与地质环境及海面的定量关系。结果表明,有孔虫属种及组合的垂直分布范围决定了其作为地质环境及海面变化指标的灵敏性和精度,C. porisuturalis和E. simplex等及组合I、II和IIIa带的精度较高。讨论了环境参数对有孔虫的影响。不同种属及组合带与底质沉积物组成的分析表明,除了Protelphidium tuberculatum外,底质沉积物粒径组成对研究区的有孔虫分布没有明显的影响。有孔虫个体数量与沉积作用具有相关性,现代沉积速率高的区域,有孔虫个体数量少,沉积速率低的区域,有孔虫个体数量多。按照海相性分布指数(Ic)的计算方法,确立研究区各参数的有孔虫分类方案,结果表明,研究区受陆地影响的下限为0.5、受海洋影响的上限指数为0.3。在现代有孔虫研究的基础上,通过渤海湾西岸及浅海区5个钻孔,对全新统地层中有孔虫进行了详细分析。恢复了全新世以来区域性相对海面变化曲线,认为全新世以来海面主要为7500~6200 a BP的快速上升期和之后的缓慢上升期,中间存在海面波动,但没有出现高于现代海面的高海面期。揭示了现代海区及陆区在全新世经历的不同地质环境演变过程。更多还原

【Abstract】 Identification, statistics and analysis of the living and necro (taphonomic) foraminifera assemblages of 110 surficial sediment samples, taking from the various subenvironments on subbottom of the intertidal zone and shallow sea, west Bohai Bay, have been systematically carried out in this study. Principal results of this thesis include:(1) Modern foraminifera assemblages of the surficial sediments in the intertidal zone and shallow sea area;(2) Distributions of their dominant species and common species, the indication of modern foraminifera assemblages for geoenvironment and sea level;(3) Elevation/depth influence (ie. the sampling positions, changing from the upper tidal flat to the shallow sea, each of which occupies an exclusive and definite elevation/depth relative to the msl, mean sea level) for the foraminifera composition;(4) Grain size and modern sedimentation rate influence for the foraminifera composition.The major living and dead (buried) dominant species in the intertidal zone and shallow sea, west Bohai Bay, consist of Ammonia beccarii vars., Ammonia limbatobeccarii, Protelphidium tuberculatum, Ammoboculites sp., Elphidium simplex, Pseudogyroidina sinensis, Quinqueloculina akneriana rotunda, Cribrononion porisuturalis, Ammonia granuloumbilica and so on. The common species are composed of Elphidium magellanicum, Elphidium advenum, Cribrononion subincertum and Ammonia maruhasii.The distribution characteristics and main-composition-analysis indicate that foraminifera in the studying area is influenced by a number of subenvironments including neritic sea, intertidal zone, salt marsh near high tides and washland near estuary. Nevertheless, the other subenvironments such as channels off estuary-sluice and tidal channels are obviously less important.By using the cluster-analysis for the dominant species, the modern foraminifera assemblages have been separated into 5 groups and 7 subgroups. Distribution of each group almost parallels the shoreline and corresponds to the various subenvironments from the intertidal zone to shallow sea, respectively.8 selected dominant species indicate that depth (elevation) is a major factor controlling the foraminifera vertical distributions. Detailed discussions include quantitative relationships of the vertical distributions of different genera and/or species with geoenvironments and sea level changes. Sensitivity and precision indices, indicating geoenvironmental and sea level changes, are determined by the vertical distributions of certain single species and their assemblages, in which C. porisuturalis and E. simplex and their Assemblages I, II and IIIa are much more precisely.Also, the environmental factors influencing foraminifera composition have been discussed in this thesis. Comprehensive analyses on the different genera, spices and their different assemblages indicate that, except Protelphidium tuberculatum, grain sizes of the subbottom sediments do not give obvious influences to the foraminifera distribution. Amount of individuals negatively correlates with the vertical accretion of sediments. Area with high modern sedimentation rate has a less amount of individuals while the amount increases when the rate decreases.Based on the classification principle of Marine-Influence-Distribution Index (Ic), regional classification has been established as 0.5 for the lowermost limit determining the terrestrial influence and 0.3 for the uppermost marine influence.As the second portion of this thesis, five case-studies have revealed profound information of the Holocene geoenvironmental and sea level changes from the strata recorded by foraminifera.Based the aforementioned results and discussions, 5 cores, drilling in the intertidal zone and shallow sea, have been thoroughly analyzed for their foraminifera composition. As a result, a local Holocene relative sea level curve has been reconstructed revealing that a rapid-rising period in 7500~6200 cal BP and ensuing slow-rising period. Sea level fluctuations have also been found during the second period without any stand obviously higher than the present level. As a proper paradigm, this approaching effort shows various changes in the modern geoenvironments as the Holocene strata as well by foraminifera study.更多还原