鲁北贝壳滩脊沉积特征及发育环境分析

Characteristics and evolution of sedimentary environment of shell ridge in the coast north of Shandong Province

渤海西南岸贝壳滩脊发育典型 ,贝壳含量高、规模大 ,不仅作为古岸线标志 ,还是抵御风暴潮的天然屏障。作者通过对鲁北贝壳滩脊的沉积结构 ,发育环境分析 ,将贝壳滩脊分为堤梗和堤内充填两个亚相。前者以贝壳和贝壳碎块为主 ,具有平行层理和高角度斜层理 ,后者以贝壳细碎屑为主 ,亦含细粉沙 ,具有向陆倾的平行层理。贝壳滩脊的形成和发育受多种因素的控制 ,其中贝壳物质的大量富集、较强的暴风浪、风的吹积作用及入海河流的改道效应等均与其有密切关系。当黄河从鲁北入海时 ,潮滩快速加积 ,贝壳贫乏 ,当黄河远离本区时 ,鲁北岸滩相对侵蚀 ,利于贝壳滩脊的发育。

Shell ridge is a long ridge-like form of deposit formed by wave actions when coastline is eroded.It lo-cates commonly on silty or clayey tidal flat deposits.The shell ridges on southwestern coast of Bohai Bay in north Shandong Province is not only the largest but also the highest contents of shell and its fragments in the world.The shell ridge can be divided into two sedimentary subfacies———ridge subfacies and infilled subfacies in terms of sedimentary structure.The former consists of primarily shells and its fragments with parallel beddings and high angle oblique beddings;the latter consists of small shell clasts and silty sand with parallel beddings dipping to the land.Evolution of the shell ridge is con-trolled by the accumulation of substantial shelly matters,strong storms,wind and the shift of river channel.When the Huanghe(Yellow)River debouched into Bohai Bay,the muddy tidal flat progradated seaward quickly,resulting in the ab-sence of shelly materials.On the contrary,when Huanghe(Yellow)River shifted to the north of Jiangsu,old river delta was eroded,which benefited the development of shell ridges.