摘要
中国大陆东南沿海自杭州湾以南,大体上属于港湾式基岩海岸,濒临热带亚热带海洋,众多的河流于此人海,沿海的港湾式海岸为海岸地貌学研究的重要课题之一。吴尚时、罗开富以及曾昭璇等先后对粤中海岸进行过地貌研究。笔者等也曾对粤中海岸作过动力地貌调查。本文以崖门至漠阳江间海岸为例,探讨港湾式海岸地貌发育问题。
In the investigated area,the general coastal features have been controlled by the Mesozoic fracture systems.The X-type systems have divided the terrain into several blocks,and the vertical movements of the latter have resulted in positive landforms as well as negative ones.Along the NE-trending fractures,which are best developed here,extend first a series of granitic low mountains and then,landward of and parallel to the latter,another series of metamorphic ones with folds and faults,both forming the coastal range.The successive upheavals of the mountains have produced 3 levels of erosional surfaces at 500 m,200 m,and 120 m respectively plus 4 steps of terraces at 80-60 m,40 m,20 m,and 10-5 m respectively.The general features of the coast were shaped in the period of Atlantic transgression.The emergence of the sea resulted in the ria-type of shore,with promontories alternating the bays.Erosion formed a promontory and sand bars surrounded the bay.It was the neotectonic upliftings that during an early stage elevated the abra-sional platforms to 10-12 and 3 m respectively and two or three rows of ancient sand bars between dried lagoons,the bars inclining toward the sea.The sedimentary flow of suspended materials,originating from the mouth of Zhujiang River,travels westwards along the coast all year round and represents the most important force shaping the coast of this section.For the last thousand years,a higher percentage of silt and mud supply has been accumulated and,finally by flood tidal currents,transported to the bays,Mangroves and molluscs have actively participated in the process of deposition.Muddy plains and mud flats have grown on the bay heads,especially since the fifteen century,when the plains might have extended seawards as much as 10 m a year.The bays will be finally filled up and the coast be straightened,not by erosion,but by deposition.
作者
赵焕庭
Zhao Huanting(The South China Sea Institute of Oceanology,Academia Sinica)
出处
《海洋与湖沼》
1980年第2期121-133,共13页
Oceanologia Et Limnologia Sinica
