古龙咀周围海区沉积物粒度特征及海底地形变化

对古龙咀周围浅海区沉积物的粒度进行了测试与分析，结合相关的地质水文资料，探讨了海岸形态对沉积物粒度的影响。研究区表层沉积物平均粒径在海湾浅海区呈带状由岸向海变细，中等水深和岬角处分布着细粒区，向外海粒径相对变粗；除险岛湾砂质区外，分选差；偏态多数为正偏或近正态；整体峰形极窄，峰型多样。底质类型以粘土质粉砂和砂质粉砂为主，由东北经古龙咀岬角向西南形成S形粘土质粉砂分布带，险岛湾地区沉积物呈带状由砂逐渐过渡到粉砂。潮汐和波浪是本区沉积物输运的主要水动力，岬角的存在影响了沉积物粒度的分布。粒度趋势分析表明沉积物整体有向岬角汇聚的输运趋势。 对收集到基于1954年、1969年、1982年测量绘成的地形图水深数据进行数字化，结合2005年测量的水深数据，分别建立各时期DEM图，在此基础上分析研究区的地形特征。四个时期海底DEM呈现出大体一致的趋势，在险岛湾及白沙口海湾内为浅水区，水深值在-1～-4 m之间，深水区主要分布在南黄岛南端至古龙咀连线以南区域，呈扇形展布，水深由南黄岛两侧向中间逐渐加深，水深值在-10～ -17 m之间。从整体上看，研究区海底地形呈NW-SE方向逐渐加深。 将数字化后的水深数据统一校正到1956黄海高程系，分别建立DEM，运用GIS的栅格计算分析得出冲淤变化图。相关结果表明：1954～1969年研究区整体近岸为冲（险岛湾除外），离岸海域为淤；1969～1982年研究区总体处于弱淤积状态；1982-2005研究区海域近岸为淤，外海以弱冲刷状态为主。

From the granularity analysis of surface sediment at shallow sea around the Gulong Headland, together with geological and hydrological data, the effect of coast shape on the sediment grain size has been discussed. The mean grain size of surface sediment is thinning from shore to the sea in shallow area of bay, but fined in the area of medium-depth and around the headland. The sorting cofficient is poor except sandy area in the Xiandao bay. Most of skewness is normal and near normal. Kurtosis is diversity and leptokurtic The Sediments are mainly clayey silt and sandy silt in the studied area. There is a S-shape distribution zone of clayey silt from north-east to south-west by Gulong Headland. Sediment gradually changes from sand to silt around Xiandao bay area. The main hydrodynamic of sediment transport are tide and wave. The headland affectes the distribution of sediment grain size .Trend analysis shows that the sediment has a headland gathering transport trends in the whole area. Based on the digital topographic maps of depth measurement in 1954,1969 and 1982, with the combination of the depth data of 2005. the DEM maps of study area are builted. The terrain characteristics of the area studied are analyzed. during the four period, the DEM maps generally show a consistent trend. There is shallow water in Xiandao bay and Bai Shakou bay, while deep water a fan-shaped distribution in the southern tip of South Huangdao and Gulong Headland. The depth of water increase from both sides to the middle of Nanhuang island. The digital data of depth will be adjusted to the yellow sea height system (1956). DEM maps are established respectively. The maps of erosion/deposition changes are obtained by raster analysis of GIS. The whole study area is erosion inshore (except Xiandao Bay) and deposition offshore during 1954 and 1969. From 1969 to 1982, the study area is in state of weak siltation. Between 1982 and 2005, the study area is deposition inshore and mainly in state of weak erosion offshore.