The Undercutting of Coral Reef Limestone on the Coasts of Some Islands in the Red Sea
The Undercutting of Coral Reef Limestone on the Coasts of Some Islands in the Red Sea
复制标题
红海一些岛屿海岸珊瑚礁石灰岩的底切
DOI：
10.2307/1783749
复制
发表时间：
--
期刊：
影响因子：
--
通讯作者：
W. A. Macfadyen
中科院分区：
文献类型：
--
作者：
W. A. Macfadyen
“本说明的目的是描述珊瑚礁石灰石的下切悬崖，这些悬崖构成了红海某些岛屿海岸部分地区的显着特征，并且似乎不是由波浪作用形成的，而是由海水对石灰石的溶解和厌氧生物的侵蚀相结合而形成的。由于溶解作为一个因素的旧观点近年来在美国受到了大力反对，以至于否认了其可能性，因此有必要在某些情况下考虑这种情况埃伦伯格（Ehrenberg）在那里度过了将近十二个月的时间，克罗斯兰（Crossland）和其他人也对红海的珊瑚礁进行了研究，达尔文（Darwin）也没有亲自访问过这些珊瑚礁，但是，本文中描述的事实是基于二月份对苏伊士湾口的阿什拉菲岛（Ashrafi）和朱巴尔岛（Jubal）的考察。 1925 年，以及 1926 年至 1927 年冬季在红海东南部的法尔桑群岛和卡马兰岛进行的四个月的工作，除了法尔桑群岛中的一些（可能）玄武岩和沙岛之外，上述所有岛屿几乎完全由凸起的更新世珊瑚礁石灰岩组成，并且周围生长着正在生长的珊瑚，阿什拉菲群岛的高度最高可达海平面以上 30 英尺。朱巴尔岛、法尔桑岛和卡马兰岛的高度较高（法尔桑岛最高可达 260 英尺），其中许多岛屿上发现了一些裸露的上新世泥灰岩和泥灰岩，构成了岛屿的大部分海岸，主要由贝壳及其铸件、间隙物质（胶结钙质砂）和岩石组成。大多数岛屿在水下的礁石石灰岩平台上突出，涨潮时水深从靠近海岸的几英寸到生长边缘的约 6 英尺不等，但通常是 1 至 3 英尺。 100 码，有些地方达到 1000 米。平台的大部分裸露在极低的水域中，通常覆盖着一层薄薄的泥浆，上面有各种生物；但岛屿外围的很大一部分都被低矮的海蚀悬崖所包围，J 值几乎不等。
'"T^HE object of this note is to describe the undercut cliffs of coral reef limeX stone which form a striking feature of parts of the coasts of certain islands in the Red Sea, and which appear to be formed, not by wave action, but by a combination of solution of the limestone by sea-water and erosion by boring organisms. Since the old view of solution as a factor has been energetically combated in America in recent years, to the extent of a denial of its possibility, it is necessary to consider the case in some detail. The coral reefs of the Red Sea have been studied by Ehrenberg,* who spent in all nearly twelve months there, and by Crossland and others, who dealt with more restricted areas of it. They are also considered by Darwin,f who had not personally visited them. None of these authors were, however, directly con? cerned with the aspect considered here. The facts described in the present paper are based on a fortnight's examination of the Ashrafi and Jubal Islands at the mouth of the Gulf of Suez in February 1925, and four months' work during the winter of 1926-1927 on the Farsan Islands and Kamaran Island in the south-eastern part of the Red Sea. With the exception of a few (probably) basalt and sandy islands in the Farsan group, all the islands mentioned above consist almost entirely of raised Pleistocene reef limestone, and are fringed with growing corals. The Ashrafi Islands rise to a maximum of 30 feet above high-water mark, and are com? posed completely of coral reef. The Jubal, Farsan and Kamaran Islands are higher in places (the Farsan Islands reach a maximum of about 260 feet), and some exposures of the underlying Pliocene marls and marly limestones are found on many of them. The Pleistocene limestone, which forms most of the coasts of the islands, consists largely of shells and their casts, interstitial material (cemented calcareous sand), and corals. Most of the islands project above a submerged reef limestone platform. The depth of water covering this at high tide varies from sometimes only a few inches near the shore up to some 6 feet at the growing edge, but is usually from 1 to 3 feet. The platform is often surprisingly even, and slopes very gently seawards; the outer edge is well defined, the depth of water increasing rapidly from 1 to 15 or 20 fathoms. The width of the platform is very variable, but is rarely less than 100 yards, and in places reaches 1000. Much of the platform is laid bare in exceptionally low water. It is often covered with a thin layer of mud, with various organisms; but pebbles and sand are rarely present. For a considerable portion of their periphery, the islands are bounded by low marine erosion cliffs of raised reef limestone, J varying up to nearly the