摘要
本文仅以1984年10号风暴为例,讨论了风暴前后的水动力条件及路径变化.重点阐述了该次风暴对西沙珊瑚礁区的潮间和潮上带现代砾堤和海滩的影响.描述了珊瑚礁区的砾堤沉积物的空间分布及垂向序列,并对沙质海滩的风暴搬运过程进行了适当的讨论.西沙砾质砾堤和沙质海滩无论从沉积序列上还是从沉积物的结构成份上,都存在着较大的差异,它们是在一种水动力条件下形成的两种不同的沉积体,在沉积过程中各有自身的沉积特点.本文尝试性地从上述角度提出一种沉积序列的空间格局,以便为古代沉积物的研究提供一些滨岸风暴沉积的信息.
Modern coastal storm deposits widely exist in the region of coral reefs especially in the Xisha Islands of China, which is a good site to stuty and observe the modern coastal storni deposits. This paper mainly describes the characteristics and vertical sequences of the coral sands and gravels in the sandy beach and pebble-bars formed when Typhoon 8410 passed through the Xisha Islands.
Two kinds of modern storm deposits were found in the Xisha Islands, One is sandy sediment and the other is gravelly one. They are different in pattern, texture and structure. Our incomplete statistics show that the gravelly depositis are much more abundant than sandy deposit in the coral reef area. The latter has two structure units: one is in the upper part of the section, showing hummock cross-beddings; the other is in the lower and bottom part, characterised by graded beddings and scour-and-fill structures.
Four deposit zones can be distinguished by the grade and species of cora. Is in the pebble-bar. The first zone is huge disc Porties and Diploria zone, which is composed of large coral pebbles (about 10-20cm in diameter) and located in the supertide; the second is middle-^graded coral gravel (about 5-10cm in diameter) zone, showing imbricate arrangements and deposited above high-tide level; the third, branch coral gravel zone, is composed of Cladopora, Acropora palmate and so on, which are located near the high-tide level; the fourth, fine coral gravel zone, containing coarse sand sediments, is in the tide zone. These features mentioned above are the same as those of Zh-oushan Islands studied by G.D. Zhang and other areas of coral reefs in the world, especially in correspondence with those of the storm gravel bank pro-posed by Bluck, B.J.
The study purpose of modern storm deposits is to find out similar sequences of storm deposits in ancient sediments. Therefore, it is necessary to fu-rther perfect the facies model.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1991年第1期83-91,共9页
Marine Geology & Quaternary Geology
关键词
风暴沉积
西沙群岛
滨岸
沉积构造
Modern storm deposits coral reefs Xisha Islands storm pebble-bar storm beach
