胶州湾及邻近海区沉积动力学

IOCAS-IR > 海洋环流与波动重点实验室

	胶州湾及邻近海区沉积动力学
	汪亚平
学位类型	博士
	2000
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋地质学
关键词	沉积动力学沉积物搬运粒径趋势分析悬沙浓度回声强度沉积速率胶州湾
摘要	本文通过在胶州湾及邻近海区的野外调查，其中包括海底表层沉积物采集、海水样采集、浊度测量、ADCP走航式测量，获得大量数据；结合历史资料，用如下方法研究了胶州湾及邻近海区的沉积动力学：（1）以地貌单元完整性和特征距离一致性为依据，将研究区划分为若干小区；采用Gao-Collins粒径趋势分析模型提取海底沉积物净搬运方向的信息，并寻找天然示踪沉积物方面的证据；（2）通过现代声学理论分析，获得了用ADCP进行走航式悬沙浓度测量的方法；（3）用~(210)Pb方法和沉积物平衡法计算百年尺度的沉积速率；（4）通过对原始水槽试验数据的重新分析，获得了用于沉积物搬运率计算的经典公式之一－Bagnold型方程的系数校正公式。胶州湾及邻近海区海底沉积物种类繁多，而且呈现斑状分布特征。沉积物粒径趋势结果显示，胶州湾内的大型垄脊和口门延伸至外海的深槽尾部是两个主要的沉积物汇聚区，这不仅与地貌及水动力相吻合，还与根据重矿物扩散趋势一致；与颗石藻化石空间分布型式变有一定的相关性。对于相同的沉积物样品来说，基于不同粒度分析方法所获得的粒径趋势矢量具有一致性。因此，粒径趋势分析模型不仅可用于采样间距不一致、沉积物类型复杂的深水海湾；也可用于传统方法获得的历史粒度资料的处理。胶州湾沙滩供沙的主要机制是通过风暴潮期间强烈的动力作用，使沙滩沉积物以悬移质、底移质形式向深水区扩散或搬运。胶州湾悬沙浓度的时空变化主要与水动力状况、陆地径流和天气状况有关。野外实测悬沙浓度和用卫星图像遥感算法获得的结果均表明，胶州湾西北部潮滩外缘海域悬沙浓度较高，海湾东部和邻近海区悬沙浓度较低。悬沙浓度的年变化、季节变化均较为显著。春季、冬季风浪大，悬沙浓度较高；夏季风暴潮通常导致悬沙浓度急剧升高。理论分析获得了海水中悬沙浓度与ADCP输出的回声强度之间的函数关系式；在胶州湾口门进行走航式测量，同步采水样进行现场校正来率定相应的ADCP声学信号，获得了计算悬沙浓度的半经验公式；进而得到走航断面准同步的悬沙浓度剖面。结果发现，胶州湾口门断面流速沿水深呈垂向均匀分布的特征较显著；悬沙浓度具有一定的水平成层分布特征，水流流速的增大有利于悬沙浓度的提高。在普通大潮潮周期内，胶州湾悬移质输向外海。多种研究方法表明，胶州湾沉积速率较小，其量级为10~0mm yr~(-1)；这主要与胶州湾沉积物来源较少有关。
其他摘要	Sediment transport and deposition patterns of Jiaozhou Bay and adjoining areas, Shandong Peninsula, are investigated in the present study. The approaches adopted are as follows. (1) Grain size trends are identified to delineate sediment transport pathways on the basis of the Gao-Collins model, which are consistent with evidence from natural tracer dispersal patterns. (2) A technique is developed to measure suspended sediment concentrations using ADCP mounted on a moving vessel, based upon contemporary acoustic theory. (3) Rates of sediment accumulation are derived, by ~(210)Pb dating and sediment balance calculations on a temporal scale of 100 years. (4) A formula for the calibration coefficient contained in Bagnold-type bed-load equations is modified and improved, on the basis of re-analysis of original flume experiment data. The data sets used for the study are obtained from analyses of sediment and water samples and turbidity and ADCP measurements, and collation of historical data. The patchy distribution patterns of seabed material, with many sediment types, indicate a multi-source nature of sediment supply and complex hydrodynamic conditions in the study area. Grain size trends show sediment transport towards the central sandbank within the embayment and the seaward end of the deep channel at the entrance. Such patterns are highly consistent with the characteristics of current velocities and geomorphology; they are also in good agreement with heavy mineral movement and spatial distribution patterns of calcareous nannofossils. The surficial sediment samples are analyzed using a laser particle analyzer and pipette/sieving method to obtain grain size data. It is found that grain size trend patterns derived from the two methods are compatible with each other. The grain size trend model is not only applicable for coastal areas with complex sediment distributions and irregular sediment sampling grids, but also for the use of historical grain size data (which are not obtained with laser techniques), which a potential for studies in the evolution of the embayment. The nearby beaches may supply sediment for the embayment during storm surges, by causing bed-load and suspended-load transport of the beach material towards deeper waters. Suspended sediment concentrations, obtained by field measurements and estimated by a remote sensing algorithm using TM satellite images, are high in the waters of northwestern Jiaozhou Bay and low in its eastern part. Variations in suspended sediment concentrations are significant on annual and seasonal scales; this is associated with local weather, hydrodynamics and river discharges. Strong wind waves during spring and winter result in high concentrations, and the concentration can increase rapidly in response to resuspension during summer storm surges. An equation is derived by theoretical analysis, to establish a relationship between suspended sediment concentrations and ADCP echo intensity output. For the survey at the entrance to Jiaozhou Bay, an ADCP is mounted on a moving vesslel; the calibration coefficient in the equation is determined by in situ measurement. Then, a semi-empirical formula is obtained and used to calculate suspended sediment concentration profiles along several cross sections. Stratification in terms of the concentration is observed, which is probably in response to sediment settling processes. The current velocities are similar within the water column, due to the tidal barotropic force and the shape of the narrow entrance to Jiaozhou Bay. Here, suspended sediment concentrations increase due to high current velocities. In general, net suspended sediment transport is directed to seaward during a tidal cycle. Within the embayment, the sediment accumulation rates are relatively low, with an order of magnitude of 10~0 mm yr~(-1), due to a small sediment supply.
页数	205
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/721
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	汪亚平. 胶州湾及邻近海区沉积动力学[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,2000.

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