莱州湾海洋沉积物粒度特征及其环境响应分析

Grain size characteristics and environmental response of marine sediments in Laizhou Bay

基于20个柱状样粒度信息,文章对山东莱州湾海域1~3 m厚度的沉积环境展开了研究。莱州湾海域沉积物粒度组分以砂质和粉砂质为主,整体上分选性偏差,在沉积过程中受周边环境改造明显。莱州湾海洋沉积动力环境在粒度方面有较好的响应,柱状样粒度分布图反映不同海域沉积物所处的外力作用阶段各有不同,但总体上随着搬运距离增大,至中部浅海平原,概率累积曲线斜率逐渐变大,阶段分化愈发明显。莱州湾浅部海域共同环境敏感组分为3≤φ≤4,沿岸河流性质和泥沙输运路径对粒度组分影响明显。综合前人关于沉积速率的研究成果,表明莱州湾东部海域粒度组分阶段性变化与1855年黄河改道在时间上存在一定的对应关系。就沉积物形成环境而言,莱州湾中部海域沉积环境水动力较强,物质来源多样。屺坶岛—刁龙嘴海域沉积物的颗粒略粗,需要的临界起动速度较大,发生再悬浮的几率相对较小。黄河水下三角洲沉积环境比较动荡,能量不稳定,处于重力流后期,能量衰减并向牵引流转化。南部的水下岸坡在波浪、潮流作用下有一定量的泥沙淤积。

This paper studied the 1~3 m thick sedimentary environment in the Laizhou Bay based on the grain size information of 20 core samples.Sand and silty sand are the main components of the sediments in Laizhou Bay,and their sorting degree is poor on the whole,indicating significant influence on the formation of the sediments exerted by surrounding factors.The grain size characteristics of the sediments in Laizhou Bay obviously reflect the environment.The distribution of grain size in cores indicate different stages of forces acting on the sediments in different sea areas.In general,from the coast of Laizhou Bay to the plain under middle shallow sea,the slope of the probability accumulation curve increases gradually and the periodic differentiation becomes more and more distinct.The environmentally sensitive component of Laizhou Bay sediment is 3≤φ≤4,and coastal river properties and sediment transport path have significant effects on grain size and components.Combined with the previous research on sedimentation rate,the periodic changes of grain size and components in the eastern area of Laizhou Bay is temporally corresponding to the diversion of the Yellow River in 1855.The sedimentary environment in the middle sea area of Laizhou Bay has strong hydrodynamics and diverse material sources.The grain size of sediments in Qimudao-Diaolongzui sea area is slightly coarse,requiring a higher critical starting speed and a relatively small probability of resuspension.The Yellow River submerged delta is relatively turbulent with unstable energy.It is in the late stage of gravity flow,with energy attenuation and conversion to traction and drainage.The underwater bank slope in the southern Bay has a certain amount of sedimentation under the action of waves and tidal currents.