Processes and mechanisms of dynamic channel adjustment to delta progradation: the case of the mouth channel of the Yellow River,China

This paper analyses the processes and mechanisms of a three‐stage channel adjustment over a cycle of the Yellow River mouth channel extension based on data comprising hydrologic measurements and channel geometric surveys. Rapid siltation in the mouth channel takes place in the young stage when the channel is being built by deposits and in the old stage when the channel cannot further adjust itself to keep sediment transport in equilibrium. It is disclosed that the bankfull width–depth ratio, bed material size and slope decrease in the young and mature stages but do not change in the old stage. The reduction of bankfull width–depth ratio and bed material size during the young and mature stages is found to be able to offset the effect of the slope reduction on sediment transport due to continuous mouth progradation. They reach their limits in old stage, and a constant slope is kept by unceasing sediment accumulation. The grain size composition of incoming sediment and the fining mechanism are responsible for the occurrence of lower limit of bed material size. The reason for the existence of a limit of bankfull cross‐sectional shape is that the large flows can fully transport the sediment load they are carrying, and siltation in the channel in the old stage takes place mainly in the low flows. It is suggested that the bankfull discharge plays an important role in shaping the channel but that the entire channel form is the product of both the large and low flows plus the effects of interaction between them. Channel pattern change shows a process from a braided pattern in the young stage to a straight pattern in the mature and old stages, and the straight channel becomes gradually sinuous. The occurrence and transformation of the channel patterns are supported by two planform predictors, but are also facilitated by some other conditions. Copyright © 2003 John Wiley & Sons, Ltd.     

东营三角洲高频旋回划分与浊积砂体预测

笔者运用高分辨率层序地层学理论和分析方法,利用钻井、测井及三维地震资料对三角洲内部基准面旋回的各种界面识别,进行基准面旋回的划分和对比研究,最后分析三角洲各期基准面旋回和浊积砂体的分布规律,从而对东营三角洲的岩性油气藏进一步勘探提供一些科学依据.     

Stable isotopic compositions of sulfur in PIRLA sediment cores

Stable isotopic compositions of total sedimentary sulfur were determined for cores from eight of the PIRLA study lakes. Preindustrial sulfur deposited prior to 1800 had roughly constant isotopic compositions within a 1–2 range in each core. In more recent sediments, large 5–10 decreases in ³⁴S content occurred and likely resulted from the addition of anthropogenic sulfur. These isotopic changes began at the same time that lead concentrations increased in sediments, suggesting a close linkage between lead and sulfur deposition in the mid and late 1800s.This is the ninth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

山东省东部海岸湾岛资源旅游潜力分析

本研究范围北起山东半岛的成山角 (37°24′N ,122°42′E) ,南至苏鲁交界处的绣针河口(37°24′N ,122°42′E)。研究区东临南黄海 ,是我国北方主要的基岩港湾海岸分布区 ,海岸岩石特征为燕山期花岗岩为主 ,间有胶东元古代古老变质岩分布。海岸线全长300km多。海岸地貌特征是湾岛众多、海域开阔、生态环境优美。面积大于1km2的海湾有37个 ,大于500m2的海岛142个。海岸跨越威海、青岛和日照3个旅游区。区内具有丰富的海岛与海湾地学旅游资源 ,优美的风光、迷人的阳光沙滩、宜人的气候是本区主要的旅游资源特点。独特的生态环境和优越的区位条件决定了本区是一个具有巨大潜力的滨海旅游业发展区域。本文将其分为威海东南部、青岛近海和日照近海3个区 ,对各区地貌特征及旅游资源进行了研究 ,并针对各区旅游资源开发现状和特色 ,对其旅游开发潜力作了布局分析 ,提出了相应的旅游设计建议     

长江三角洲晚第四纪古土壤的古环境及古气候信息

运用孢粉、藻类、有孔虫等古生物综合分析方法，对比土壤微形态、沉积磁组构分析结果，研究长江三角洲地区晚第四纪古土壤层记录的古环境信息。结果表明，古土壤是海平面变化、气候、环境综合作用的产物，它的发育具有明显的阶段性。古土壤堆积阶段，海水已退出本地区，气候温暖而湿润，河漫滩经常受洪水淹没积水，多次滞水与暴露环境的交替，形成了淡水藻类与陆生植物互为消长的特殊生物组合特征。这一时期沉积与暴露成壤作用反复交替，古土壤形成了多个粘粒胶膜淀积层。此期相当于未次间冰阶向未次盛冰期过渡及海平面下降的时期，沉积后进入了持续成土阶段，海平面变得更低，气候变干，地下水面降低，古土壤已不能被淹没，持续暴露成壤，这一时期逐渐接近末次盛冰期。     

厦门市无居民海岛植被生态保护方案与规划

本文分析了厦门市无居民海岛植被生态现状与存在的问题,阐述了海岛生态功能定位,提出3种海岛生态保护方案,拟定了海岛生态保护措施及植被绿化规划,并得到当地政府的采纳.     

黄河断流对黄河三角洲生态环境的影响

介绍了黄河断流的特点和原因，分析了黄河断流的变化趋势及断流在黄河三角洲地区造成的影响，指出断流不仅加重三角洲地区今后防洪的负担，而且对三角洲环境变化将产生重大影响，研究表明，黄河断流的原因是多方面的，流域降雨量的减少，水土保持减水是黄河流域水资源不足的主要原因；但人为用水如城乡工农业用水和居民生活用水量增加加剧了黄河的断流；人为引水过程中的水资源不合理利用乃至严重浪费，流域引水管理混乱，水资源统一调配的机构和机制不健全，缺乏具体有效的控制引水措施和手段是导致近年来黄河断流加剧的根源，黄河断流对三角液地区的生态环境影响是严重的而且涉及到多个方面，包括造成了三角液地区水资源的极度匮乏，影响三角洲地区水质质量，造成地下水质恶化，区域植被生态系统良性循环变差，陆区农业及海区渔业生态系统失调，湿地生态系统退化，生物多样性减少等多方面的影响。     

辽河三角洲潮道软土及其工程灾害研究

辽河三角洲潮道沉积物为软弱淤泥质土，管桩在波流荷载作用下的弹性变形或振动，可以导致潮道软土强度衰减并发生变形位移，随着悬臂段加长和波流荷载振动作用，下部扮土会自上而下发生液化。简单管桩的抗倾验算可以按照波流力与被动土压力的作用力矩分析，并考虑到海底的冲刷淘空深度。管桩打入下卧高强度粉土时，在保证打入深度的同时，应适当增大管桩的强度，加大管桩自振周期与波浪周期的差值。     

黄河三角洲整体冲淤平衡及其地质意义

海岸侵蚀、三角洲面积减小已成为世界上关注的热点问题。三角洲造陆的趋势及速度制约着三角洲地区经济的持续发展和生态环境的演变。本文以1976、1986、、992、1996－1998年黄河三角洲卫星遥感照片及海区水深等实测资料为依据，通过其高潮线的对比分析，研究整个黄河三角洲面积变化的趋势。结果表明，黄河三角洲在整体淤进的同时伴随着蚀退，三角洲的造陆面积呈逐渐减小的趋势。通过对1950－1998年黄河利津站实测来水来沙资料的分析，发现近年来水沙呈递减趋势，这可能是三角洲造陆面积减小的重要原因。研究了黄河三角洲造陆面积与流域来水来沙的关系，从而得出当来沙量为2．45亿t/a时，三角洲面积整体趋于不冲不淤的平衡。若来水来沙量继续减少，黄河三角洲将走向全面蚀退，趋于消亡。     

Studies on island intertidal benthic ecology in Fujian

lNreomicrlowIntertidal zone is an important type of wetIand easystem on the earth as it is in the tranai-tion zone between 1and and the and subject to frequent human interferences. Since the inter-tidal sone is subject to a1ternative physical and chemical actions of land and as, the intertidalzone has a compticated and changeable environment. The studies on intertidal zon ecobeyhave always attracted much attention for the past decades (Stephensons, l972; MOrtons,l983: Huang and Zhu, l998; Y…