青岛海滩表面磁性特征分析及其指示意义

发布时间：2019-04-23 18:22

【摘要】：海滩是大自然赋予人类的珍贵的自然资源，是海陆作用最活跃的地区，其宜人的景致能够作为人们的休闲旅游场所而产生经济效益，其特殊的地理位置能够阻隔海浪对陆地建筑、农田和道路的冲击，保护人类的生存空间。但目前海滩侵蚀是一个普遍存在的问题，海滩侵蚀是一个源到汇的过程，那掌握海滩沉积地貌特征、正确认识海滩的沉积动力环境和过程并予以科学的防护就显得尤为重要。沉积物磁性特征一般可通过磁性矿物的含量、种类和颗粒大小等因子来反映，而这些因子与沉积物源、搬运迁移、沉积动力作用以及沉积后次生变化等条件密切相关，因此沉积物的磁性特征蕴含着丰富的环境信息。本文选择青岛前海著名海滩一浴海滩、二浴海滩和石老人海滩作为研究对象，通过对研究区海滩磁性特征、沉积物粒度特征和磁性矿物成分分析，结合该区水动力条件，探讨海滩沉积物磁性与粒度的关系，以及所反映的沉积指示意义和环境意义。对一浴、二浴及石老人海滩表层沉积物进行体积磁化率原地测量分析，发现海滩体积磁化率空间分布具有一定的规律性：在平行海岸方向上，高磁化率值出现在侵蚀区，相对低值出现在沉积区；在垂直海岸方向上，高磁化率值出现在滩肩顶附近的冲流带区域，向海向陆两个方向都减小，且在滩面区域磁化率值最小最稳定。两个由于受冬夏季季风气候影响，冬季西北向的风将海滩表层低密度的细颗粒沉积物搬运至海水中，密度高的重矿物（如磁性矿物）滞留原地，夏季则方向相反。所以冬季西北区出现小范围磁化率高值区，而夏季东南区域出现小范围磁化率高值区。而受自东向西向沿岸流的作用，海滩东侧为侵蚀区，磁化率值较高；西部为沉积区域，磁化率值较低。石老人海滩沉积物的粒度特征为：滩面下部沉积物粒度比滩面上部、滩肩区域更细。沉积物粒度从海滩西南区域向中间区域逐渐变小，再向东北区域又逐渐变大，分选性从西南区域向中间区域逐渐变好，而由中间区域向东北区域逐渐变差。整个海滩粒度变化大致呈带状分布。冬季海滩沉积物颗粒以中粗砂为主，沉积物颗粒分选中等，而夏季以中细砂为主，沉积物颗粒分选较好。不同粒级砂样品的磁化率值有明显差异，其中粒径为0.063~0.125mm的细颗粒磁化率值远高于其他粒级（高1~2个数量级），这是由于控制海滩磁性的磁性矿物（如磁铁矿）颗粒主要集中于粒径为0.063~0.125mm的细颗粒中。通过是石老人海滩磁性矿物的提取，显微镜下鉴定和电子探针分析发现，海滩磁性矿物主要为磁铁矿，其次为钛铁矿，还有少量的赤铁矿。
[Abstract]:The beach is the precious natural resource that nature endows mankind, is the most active land and sea function area, its pleasant scenery can be used as people's leisure tourism place and produces the economic benefit. Its special geographical location can prevent the impact of waves on land buildings, farmland and roads, and protect the living space of human beings. However, beach erosion is a common problem at present. Beach erosion is a process from source to sink. So it is very important to master the characteristics of beach sedimentary landform, correctly understand the dynamic environment and process of beach sedimentation and protect it scientifically. The magnetic characteristics of sediments are generally reflected by such factors as the content, species and particle size of magnetic minerals, which are closely related to the conditions of sediment source, transport and migration, sedimentary dynamics and post-deposition secondary changes. Therefore, the magnetic characteristics of sediments contain abundant environmental information. In this paper, one-bath beach, two-bath beach and Shigao beach are selected as the research objects in Qingdao Qianhai famous beach. Through the analysis of the magnetic characteristics, sediment size characteristics and magnetic mineral composition of the beach in the study area, combined with the hydrodynamic conditions in this area, The relationship between magnetic properties and grain size of beach sediments, as well as the sedimentary indication and environmental significance reflected in this paper are discussed. Through in situ measurement and analysis of the surface sediments in one bath, two bath and Shielderly beach, it is found that the spatial distribution of bulk susceptibility in the beach has certain regularity: in the direction of parallel coast, the high magnetic susceptibility value appears in the eroded area. The relatively low value appears in the sedimentary area; In the vertical coastal direction, the high magnetic susceptibility value appears in the alluvial zone near the top of the beach shoulder, and decreases in both directions towards the sea and land, and the lowest and most stable magnetic susceptibility value is found in the beach surface region. Due to the monsoon climate in winter and summer, the northwest wind in winter carries the low density fine grain sediment on the surface of the beach into the seawater, and the dense heavy minerals (such as magnetic minerals) stay in situ, but the direction is opposite in summer. Therefore, a small range of high value region of magnetic susceptibility appears in the northwest region in winter and a high value region of small range magnetic susceptibility in the southeast region in summer. However, due to the action of the coastal current from east to west, the east side of the beach is eroded, and the magnetic susceptibility is higher in the eastern part of the beach, while the magnetic susceptibility is lower in the western part of the beach. The grain size characteristics of the beach sediment in Shigao beach are as follows: the sediment size in the lower beach surface is smaller than that in the upper beach surface and the beach shoulder area is finer. The grain size of sediment gradually decreases from the southwest of the beach to the middle, and then to the northeast, and then to the northeast. The separability of the sediment becomes better from the southwest to the middle, and from the middle to the northeast. The grain size change of the whole beach is about zonal distribution. In winter, the beach sediment particles are mainly coarse sand, and the sediment particles are medium-sized, while in summer, the sediment particles are mainly medium-fine sand, and the sediment particles are better sorted. The magnetic susceptibility values of different grain size sand samples are obviously different, in which the magnetic susceptibility value of fine particles with 0.063~0.125mm particle size is much higher than that of other grain grades (1 ~ 2 orders of magnitude higher). This is due to the fact that the particles of magnetic minerals (such as magnetite) which control the beach magnetism are mainly concentrated in the fine particles with the size of 0.063~0.125mm. It is found that the beach magnetic minerals are mainly magnetite, followed by ilmenite and a small amount of hematite by extraction, identification under microscope and electron probe analysis.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P748

【参考文献】