THE PREVAILING DIRECTION AND MECHANICS OF BEACH DRIFT INFERRED FROM VARIATION SERIES OF BEACH SEDIMENTS ALONG THE SAGAMI BAY COAST, JAPAN
THE PREVAILING DIRECTION AND MECHANICS OF BEACH DRIFT INFERRED FROM VARIATION SERIES OF BEACH SEDIMENTS ALONG THE SAGAMI BAY COAST, JAPAN
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日本相模湾沿岸海滩沉积物变化系列推断的海滩漂移的主导方向和机制
DOI：
10.4157/grj.35.17
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发表时间：
1962
期刊：
影响因子：
--
通讯作者：
Takasuke Suzuki
中科院分区：
文献类型：
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作者：
M. Aramaki;Takasuke Suzuki
对海滩沉积物的岩石学研究有望大大有助于了解其来源、运输和沉积。因此，我们检查了沿海岸线采集的沉积物样品的砾石和矿物含量，以努力确定海滩漂移的主要方向，并弄清沿海运移的机制。实地调查是在日本太平洋沿岸的相模湾地区进行的。海湾沿岸的海岸线被暴露在公海中的大约40英里的连续海滩所标志。海滩的东端是三浦半岛，西端是伊豆半岛。在这片海滩上，每隔一英里选择了38个采样点。然后，将采集的样品作为岩相学分析的基础数据。研究的主要结论如下：1)主要河口沿岸及其邻近地区的滩涂沉积岩性组成与河流沉积的岩性组成相似。这种相似性导致了海滩沉积与河流输送物质密切相关的结论。此外，这一沿海地区的海滩沉积物大量来自佐伽米河、萨哈瓦河和玛雅河。2)根据面积分布和系统变化序列，认为该海湾的滨岸带主要受沿岸流的影响而东移。(3)随着距源区距离的增加，滩涂砾石的粒度减小。这种尺寸的减小可能是由于砾石磨损的结果，而不是选择性地输送砾石的波的分选作用。此外，海滩砾石似乎间歇性地沿着海岸线移动，一旦这些砾石沉积在海滩上，它们应该被磨损并根据当地海岸力的强度变形成不同的形状。4)在这片海滩的一些地方，在近海有岛屿或礁石的地方，存在着许多圆形的、极其平坦的砾石。此外，重矿物含量和石英与长石的比值都大幅度增加。这些现象可能是由于海滩沉积物一旦沉积，在岛礁阻挡引起的近海折射波的作用下长期保留的事实。
A petrographic study of beach sediments can be expected to contribute much to the understanding of their source, transportation and deposition. Therefore, we examined the gravel and mineral content of sediments samples taken along the shoreline in an effort to determine the prevailing direction of beach drift and to make clear the mechanics of littoral transport. Field work was done in the Sagami Bay area, on the Pacific coast of Japan. The shoreline along the coast of the Bay is marked by some 40 miles continuous beach which is exposed to the open sea. At the eastern end of beach, there lies Miura Peninsula and at the western end, Izu Peninsula. 38 sampling stations were selected at one mile intervals along this stretch of beach. Then, those samples collected were used as basic data for petrographic analyses. The major conclusions of this investigation are as below : 1) The lithological composition of beach deposits in the coast of major river mouths and their neigh borhood are similar to that of fluvial deposits of those rivers. This similarity led to the conclusion that beach deposits have a close relationship to river-transported materials. In addition, the beach sediments deposited in this coastal region are in a great quantity derived from the rivers of Sagami, Sahawa and Maya. 2) Based on the areal distribution and systematic variation series, it is believed that littoral brift in this Bay prevailingly moves eastwards by longshore currents. 3) There is decrease in grain size of the beach gravels with increase in distance away from the source areas. This decrease in size is probably due to the result of abrasion of gravels rather than the sorting action of waves which transports gravels selectively. Moreover, beach gravels seem to move intermittently along the shoreline and once these gravels deposit on the beach, they should be abraded and deformed to various shapes in accordance with the strength of local littoral force. 4) In some places of this stretch of beach, where are islands or reefs in the offshore, numerous wellrounded, extremly flat gravels are present. In addition, both the amount of heavy mineral contents and the ratio of quartz to feldspar increase materially. Those phenomena might be explained by the fact that the beach sediments once deposited remain for a long time under the effect of the refracted offshore waves caused by the hindrance of islands or reefs.