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11DT02孔位于南黄海辐射沙脊群东北部里磕脚沙脊南坡,通过沉积相分析、粒度统计,结合年代地层数据,重建晚更新世以来里磕脚沙脊的长周期环境演化,分析沙脊成因、厘定沙脊发育年代。研究表明:里磕脚沙脊从下至上由潮滩相、硬黏土相、潮滩相和潮流沙脊相组成。潮流沙脊和潮滩由粉砂、细砂和少量黏土组成,两者均成正偏态分布。潮流沙脊和潮滩在概率累积曲线上分别表现为三段式和四段式分布,以跳跃次总体为主,并呈双跳跃特点。研究区晚更新世经历海平面下降发育潮滩环境,到完全暴露形成标志性的“硬黏土”层;全新世初期经历海侵,研究区复又开始潮滩沉积,随后被海水完全淹没,潮流作用渐强,改造下伏潮滩和“硬黏土”,逐渐堆积成高差最大达30 m的脊槽地形。 相似文献
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黄河口近期环境演变与河口治理 总被引：4，自引：0，他引：4
本文分析了近几年来尾闾河道及河口滨海区实测资料，认为尾闾河道河相关系趋向于转好，河口变化造成的溯源冲淤作用影响范围仅有２０几ｋｍ，并且只有在汛期水流强度较大时，才发生溯源调整作用，非汛期淤积严重。由于河口砂咀向海凸出，三角洲前缘形成强流带，加上波浪作用及异重流发育，河口砂咀延伸速度明显减缓。最后，作者对目前河口治理中存在问题的解决提出了建议，尤其指出不应轻易放弃目前良好的河口行水环境。 相似文献
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华南大陆沿岸不乏造礁石珊瑚生长,但能成礁的仅在西部广西涠洲岛、斜阳岛和广东雷州半岛西南海岸,均为岸礁,累计礁体长约63 km,约占华南大陆(含近岸岛屿)岸线的1%,礁厚1~4 m,总面积约45 km2。礁体在全新世中期形成,胶结程度差,内礁坪部分已被沿岸泥沙覆盖,活珊瑚种类较少。进入全新世晚期,环境条件发生变化,冬季表层平均水温略低,沿岸泥沙运动活跃,人类生产活动对水质的影响等,珊瑚礁发育受到制约。但在西部海岸局部地方造礁珊瑚仍然顽强地生长,礁体向海拓展。预测未来冬季水温升高,更有利于珊瑚礁自然恢复。 相似文献
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渤海湾北岸表层沉积中的有孔虫群及其生态环境 总被引：2，自引：0，他引：2
我们对渤海湾北岸177个表层沉积物样品进行了有孔虫分析。经鉴定,未发现浮游有孔虫,底栖有孔虫共计82种,其中包括一新种Jadammina planata He et Li sp.nov.根据不同的环境中沉积物内有孔虫群属种组合不同,大体可归纳为二种组合:一是河口、海滩、泻湖、滨海平原等滨海边缘环境组合,在南堡以东该组合称为厚壁转轮虫——显孔鼓室希望虫组合,南堡以西称为厚壁转轮虫——多变假小九字虫组合,二是分布在水深10米以内的近岸浅海环境组合,称为厚壁转轮虫——缝裂希望虫组合。在不同环境中,有孔虫壳体数量的变化是有规律的,一般在泻湖中有孔虫含量最多,滨岸沙坝处最少,沙坝脊部有时为零,向海方向至近岸浅海共含量又有逐渐增多的趋势。 相似文献
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碳酸盐是黄土中的主要矿物,是黄土—古土壤序列中含量变化最显著的矿物之一,其在表生环境下极易移动,并且它的迁移变化受大气降水、温度等古气候因素制约,在黄土高原风尘堆积序列的古气候研究中具有极其重要的意义,其变化能够较好地反映古季风的演变规律。黄土—古土壤中碳酸盐的含量变化和东亚夏季风降水的强度密切相关,碳酸盐矿物中白云石和方解石的存在与否及淋失深度对夏季风演变同样有很好的指示意义。稳定同位素δ18O可以作为夏季风的代用指标,指示成壤时期环境中的古温度;δ13C值表现出在黄土层中高,而在古土壤层中低,因此碳酸盐δ13C值可能更多反映了植被发育程度。碳酸盐中Sr同位素能够反映风化作用的强弱,而去除碳酸盐后的Sr同位素则能更好地反映成壤作用的强度和判别风尘物质的来源。与其它季风气候替代性指标相比,酸溶相中的δ11B值变化与降水有直接关系,可以很好地作为夏季风降水指标。非传统稳定同位素Li、Ba和Fe有应用于黄土研究中,但目前的研究表明它们对气候环境暂无较好的指示意义。 相似文献
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近期长江北支口门圆陀角附近潮滩地貌动态变化 总被引：2，自引：0，他引：2
圆陀角位于长江北支岸线与江苏海岸线的交会处,独特的互花米草潮滩、淤泥质光滩环境和复杂的河海沉积动力,决定了潮滩地貌对海洋环境变化的响应具有敏感性。由于大规模的围垦,圆陀角附近过去40年来海岸线向东推进了6km。根据2006年以来多次的野外调查和室内粒度与钻孔岩芯的137Cs分析, 2006年以来圆陀角附近潮滩淤积明显加强,由137Cs时标估算的互花米草滩多年平均沉积速率为2.3cm/a, 2006~2008年观测到的互花米草滩淤积速率>4cm/a,粉砂淤泥质光滩的淤积速率更高;圆陀角风景区内互花米草滩前缘陡坎在风暴潮影响下侵蚀后退,并因粉砂淤泥质光滩的快速淤长而消亡,圆陀角附近潮滩地貌动态是对人类围垦活动、风暴潮与潮汐海洋动力的综合响应,互花米草与光滩快速淤积是近期圆陀角附近潮滩地貌演化的主要特点。 相似文献
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古尔班通古特沙漠树枝状沙丘沉积物粒度和微形态特征的空间分异 总被引：3，自引：3，他引：0
树枝状沙丘是古尔班通古特沙漠独特的沙丘地貌类型。分析了古尔班通古特沙漠树枝状沙丘表层沉积物的粒度和微形态特征。结果表明：（1）树枝状沙丘以中砂为主,其次是细砂和粗砂;平均粒径与分选系数有较好的线性关系,平均粒径越小,分选系数越好;沉积环境以河流湖泊环境为主;石英颗粒形态以圆形和长形为主,磨圆度适中,碟形坑分布广泛,同时伴有硅沉淀现象,表明沉积作用以机械作用为主,同时还伴有化学作用。（2）整体上,粗砂和极粗砂含量西部最多,细砂含量南部最多,受风力分选作用的影响明显。西部的分选较其他区域好,东部分选较差;西部磨圆度最好,南部磨圆度最差。坡顶的中砂含量最多,迎风坡丘间地粗砂含量高于背风坡丘间地;迎风坡坡脚的细砂和中砂含量远远高于背风坡坡脚;沙丘的两翼部位粒级占比相对一致。（3）粒度和微形态特征都表明树枝状沙丘沉积物特征主要受风力分选作用的影响,同时受物源和植被的影响,共同揭示出河流湖泊的沉积环境。 相似文献
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小浪底工程修建对黄河河口淤积影响 总被引：3，自引：1，他引：2
本文在整理、分析黄河小浪底工程建成后 ,坝下游来水来沙条件变化的基础上 ,利用若干经验关系式 ,就小浪底工程修建后对黄河河口区清水沟流路的淤积特征和变化趋势进行了研究 ,得到了 :在小浪底水库初期蓄水拦沙运用阶段 ,淤积减少、河口砂嘴发展速度变缓 ;在后期正常调水调沙运用阶段 ,淤积又有所恢复 ,河口砂嘴发展加快的认识。 相似文献
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废黄河三角洲的演变* 总被引：20，自引：1，他引：19
本文主要根据历史文献,论述1194～1855年的古黄河口泥沙堆积形式、速率及其沉积特点,并探讨了废黄河三角洲形成机理和类型,以及尾闾变迁对下游河道的影响。认为在黄河南流夺准入黄海过程中,河口和三角洲发育具有明显的阶段性;前、后两期形成不同类型的三角洲,前期为径流一潮汐型,后期转化为径流一波浪型;后期河口迅速延伸,河口基准面相对抬升所引起的溯源淤积可达河南境内。 相似文献
11.
珠江三角洲生物埋葬群与环境变迁 总被引：6，自引：0，他引：6
本文将珠江三角洲第四纪环境与现代环境的生物埋葬群进行对照，重建晚更新世中期和全新世中期的古沉积环境，划分出两期的海侵区、海侵波及区、海侵影响区。并对中更新世海侵期表示存疑。 相似文献
12.
Asymmetry in the tide (unequal ebb and flood duration) is a dominant factor in causing residual sediment transport and morphological changes in estuaries. The evolution of estuarine morphology is a process of dynamic equilibrium in the short-term, while these features are ephemeral in the long-term. In this study we investigate the spatial distribution of tidal distortion and asymmetry in the Dee estuary, UK, by 3-dimensional numerical modelling methods. High resolution LIDAR surveys are used to underpin and explain our numerical modelling results in terms of basin hypsometry and areas of recent erosion and deposition. Harmonic analysis of the numerical modelling results showed that the shallower intertidal areas (sand and mud banks) were the most tidally asymmetric, showing flood dominance. The main navigation channels showed some ebb dominance but the tides here were relatively undistorted. This overall flood dominance is likely to induce net sediment import to the Dee, which explains known historical morphological changes (large scale accretion over the last two centuries) and also recent morphological changes as seen from the LIDAR surveys (which show predominantly net accretion between 2003 and 2006). Hypsometrical analysis suggests the Dee may be approaching equilibrium, and that the flood dominance and sedimentation rate may therefore decrease in the future. In an infilling estuary, an increase in the area and elevation of tidal flats can eventually shift an estuary towards ebb dominance, as shown by previous research and by ‘idealised estuary’ modelling results presented in this study. The large tidal amplitude to hydraulic depth ratio of the Dee, however, suggests that the tidal flats would have to be very extensive indeed for this to occur. 相似文献
13.
中国河口盐淡水混合特征研究 总被引：4，自引：0，他引：4
河口盐淡水混合受河口潮差、几何形态及淡水流量等诸多因素影响,并有着大小潮和洪枯季变化周期。本文在分析中国众多河口实测盐度分布资料的基础上,首次归纳了中国河口盐淡水混合的基本特征,给出数十个河口盐淡水混合的基本图式。并从高度分层型、部分混合型和强混合型三个类型,分别选择较典型的几个河口进行具体阐述。 相似文献
14.
本文从河口塑造与输沙关系、流域泄沙与输移模式,以及口外来沙与潮流输移特征等三方面,探讨河口区的泥沙运移规律和补给来源。并在此基础上,提出粗细不同粒级的造床泥沙按不同方式治理的设想。 相似文献
15.
基于前期工作,采取粒度端元分析方法,结合沉积物粒度参数、研究区水深以及水动力等对福建省泉州湾海域采集的65个表层沉积物样品进行了沉积动力学解析判别,量化研究区表层沉积物复杂的沉积动力特征。结果表明：样品粒度数据中可以至少分离出4个不同的端元组分,其粒径范围大致分布在0.2~200、20~30、50~500、80~1 000 μm,可能分别代表了水动力较弱的滞流沉积作用环境、台风作用下的改造作用、潮汐作用下的较强的水动力以及人类活动作用下的扰动作用。由于沉积动力的持续进行及分选沉积作用,可能掩盖了粒度的物源效应,所以只呈现出不同的沉积动力学特点。 相似文献
16.
Modern Diatom Assemblages in Surface Sediments from Estuarine Systemsin the Southeastern Buenos Aires Province, Argentina 总被引：1，自引：0，他引：1
Paleoecological reconstructions of Holocene sea-level changes in Argentinean coastal regions were based mainly on ecological
data gathered from other regions, as there was a lack of information on modern estuarine diatom distributions. The aim of
the present work was to assess the spatial variation of diatom assemblages in two representative estuaries of Argentina in
order to gather ecological information for paleoecological reconstructions in the region. The two selected estuaries have
different geomorphologic features and salinity regimes: Mar Chiquita Lagoon is shallow, which prevents the development of
a stable salinity gradient as it occurs in the Quequén Grande River. Surface sediment samples were taken from selected stations
representative of the environmental gradient from the inlet to the inner reaches of both estuaries. Cluster analysis defined
three diatom zones at Mar Chiquita: marine/brackish assemblages dominate the inlet (zone I), where salinity, tidal range and
current speed are higher. The brackish/freshwater tychoplankton Staurosira construens var. venter and Staurosirella pinnata dominate the inner lagoon (zone II), where environmental conditions are very variable and concentrations of suspended sediments
are higher. Brackish/freshwater euryhaline diatoms dominate the headwaters (zone III). On the other hand, the Quequén Grande
River was divided into three diatom zones: coastal taxa are distributed at the inlet (zone I), while the middle estuary (zone
II) is dominated by brackish/freshwater euryhaline taxa. At the upper estuary region (zone III), freshwater diatoms dominate,
and the halophobous Nitzschia denticula increased in abundance values. Diatom distributions were most closely related to the salinity gradient at Quequén Grande
River than at Mar Chiquita Lagoon. Fossil data of a sequence from Mar Chiquita Lagoon (Las Gallinas Creek) were compared to
the modern data set in order to search for analogies between fossil and modern diatom assemblages. DCA results showed that
fossil diatom assemblages have modern counterparts. Most diatom assemblages of Las Gallinas Creek fall within Mar Chiquita
zone III, representing a shallow brackish/freshwater environment, with low salinity fluctuations
(~1–9‰) and no tidal influence. Therefore, our modern diatom data provide useful analogs to interpret paleoenvironments in
the region. 相似文献
17.
I. C. Potter D. Tiivel F. J. Valesini G. A. Hyndes 《International Journal of Salt Lake Research》1996,5(4):337-358
Leschenault Estuary consists of a large lagoonal-like water body, which opens into Koombana Bay through a short and deep entrance channel at its southern end. Since the only major tributary discharges into the estuary opposite the entrance channel, much of the freshwater discharge in the winter passes directly out to sea. Consequently, during the year of the present study, the mean monthly salinities in the main body of the estuary remained above 20 per mil. This presumably accounts for the fact that the ichthyofaunal composition in the shallows of the estuary did not undergo the type of marked changes that are exhibited in other south-western Australian estuaries, in which salinities often fall below 10 per mil in winter. Despite the maintenance of high salinities in Leschenault Estuary and a close proximity to Koombana Bay, the estuary contained a far greater density and markedly different species composition of fish than that found in that marine embayment. This difference reflected, in part, the high abundance in Leschenault Estuary of some species whose entire life cycle is confined to estuaries,e.g. the atherinidsAtherinosoma elongata andLeptatherina wallacei and the gobiesPseudogobius olorum andAfurcagobius suppositus, and the fact that the juveniles of several marine species,e.g. Hyperlophus vittatus, Sillaginodes punctata, Mugil cephalus andGymnapistes marmoratus were also largely or entirely restricted to the estuary. In contrast,Lesueurina platycephala, which was by far the most abundant species in Koombana Bay, was absent in the estuary. Furthermore, the relatively protected region of Koombana Bay contained a greater density and different composition of fish than the more exposed region of this embayment. This reflected the greater use that was made of the protected region as a nursery area by certain marine species,e.g. Aldrichetta forsten andSillago bassensis. Our data, when taken in conjunction with those collected on the fish fauna in other south-western Australian estuaries, demonstrate that, within this geographical region, some fish species are specifically adapted to the estuarine environment, and that certain marine species apparently have a strong preference for using the highly protected and productive waters of this type of environment as a nursery area. 相似文献
18.
The Burrum River estuary: identifying reference sites for Australian sub-tropical estuarine systems using paleolimnological methods 总被引：1，自引：0，他引：1
There is a pressing need to obtain historical information on estuaries so that levels of natural variability and ecosystem
thresholds can be identified. Once these factors are known, estuaries that exhibit high conservation value and minimal impact
from anthropogenic activity can be acknowledged and protected. In order to understand and quantify the level of change that
may have occurred due to human impact, near pristine estuaries that have the potential to act as reference sites need to be
identified. However, this is often difficult due to a lack of documented knowledge of estuary variability. This paper retrospectively
assesses environmental conditions in the Burrum River, a sub-tropical east Australian estuary on the coast of Queensland,
using diatom and stable isotope analyses. These techniques were combined with AMS 14C dating methods to determine if this system has undergone any natural or anthropogenically induced change. Diatom assemblages
have shown very little variation over the past 5,000 years, indicating minimal changes to water quality. Upper and lower limits
for δ13C and δ15N stable isotope results also infer that the sources of carbon and nitrogen to the Burrum River estuary have remained constant
over this time period. Carbon inputs have been dominated by marine autotrophic production, whilst nitrogen inputs are indicative
of terrestrial sources. Hence, the Burrum River has not been altered by anthropogenic activities and is a suitable reference
site for benchmarking impacted sub-tropical estuaries. This paper demonstrates that paleolimnological techniques can be applied
successfully to identify estuaries that are suitable as reference sites. 相似文献
19.
认识珠江,保护珠江--试论广州至虎门潮汐水道的特性和保护问题 总被引：8，自引：2，他引：6
广州城下的珠江（广州至虎门）下属河成水道,而是潮道－潮成水道。论述了这一水道的成因和动力地貌特点,强调指出了这一潮道体系中潮滩和潮汐汊道存在的重要性。认为洙江的保护必须首次注意保护好潮滩（潮道中的近岸浅滩）,即不要再缩窄江面;其次是不能随意将潮道四周平原上的潮汐汊道堵塞或消灭 相似文献
20.
Sediment-rich estuaries typically exhibit considerable dynamicity, with channel shifts and shoreline erosion/deposition occurring over timescales of years to decades. Contemporary behaviour is usually attributed to the immediate effect of short-term events (such as storms), longer-term forcing (such as sea-level change) or anthropogenic modifications to system controls (such as wave–tidal–fluvial regime and sediment supply). In this context, geological control is understood to provide an inherited framework within which an estuary will evolve. This paper examines the morphodynamics of two sand-filled, but sediment-limited, mixed-energy estuaries of Loughros Bay in northwest Ireland. Analysis of ebb channel morphometry shows that estuaries can be divided into upper and lower estuary components, which appear to represent a down-valley increasing energy gradient. Examination of historical ebb channel migration reveals three morphodynamic zones delimited by a significant spatial variability in channel mobility that reflects the distribution of specific structural controls along the estuary and their influence on the changing energy gradient. Based upon analysis of low tide channel migration over the last 172 years, three phases of geomorphic response are identified. In Loughros More, the behaviour is characterised by a 19th century phase of steady-state equilibrium; a subsequent period of dynamic response to extrinsic (storm) forcing; and, most recently, adjustment to intrinsically forced changes in structural control. In Loughros Beg, the phases are comparable, but contrast specifically in inlet and ebb-tidal behaviour. This analysis illustrates discontinuities in decadal- to century-scale forcing and morphological response, identified here as complex response. It suggests that the sedimentary evolution of coastal systems that have no appreciable external sediment supply is potentially more strongly determined by local variability in system character than climate or sea-level driven mechanisms. 相似文献