第三章海岸带.ppt

障壁岛和障壁岛海滩 滨、浅海地区的潮汐沉积 Modern tidal flats are primarily sites of siliciclastic deposition; however, carbonate sediments and, in a few areas, evaporites accumulate on some modern tidal flats such as those in the Bahamas, the Persian Gulf, Florida Bay, and the western coast of Australia. Modern tidal flats have been studies intensively in many parts of the world since the 1950s, particularly in Germany; the North Sea coastline of the Netherlands; England; the Bay of Fundy, Nova Scotia; the west coast of Korea; and the Gulf of California. 潮坪沉积研究的进展 二次世界大战前德国Senckenberg 研究所从事北海潮坪沉积的研究， 至1973年发表关于潮坪沉积的文章500篇，其中90%发表于二次世界大战之后。 荷兰，德国，英国都是研究潮坪沉积最早的国家。 中国淤泥质海岸研究始于1960s 中国潮坪的分布 Depositional setting Tidal currents may operate in the ocean to depth of 2000 to 2500m. Vertical distance between the high- and low-tide line in most modern tidal environments commonly ranges from 1 to 4m (mesotidal coasts). The total width of tidal flats may range from a few kilometers to as much as 25 km. Topographic relief is generally rather small, except for tidal channels, and slopes of the tidal flat are gentle. 沉积滞后作用 代表人物：Van Straaten 和 Kunen(1950s) 主要理论概念： 沉积滞后作用(Settling lag) 推移质与悬移质在搬运和沉积上的的差异（颗粒启动流速和沉积临界流速差异）；淤泥质海岸堆积前展的问题。 潮坪分带和潮坪层理 代表人物：Reineck （1960s – 1980s） 潮上带，潮间带，潮下带 潮间带：高潮坪泥质带（泥坪）；中潮坪沙泥混带（混合坪）；低潮坪砂带（砂坪）。在潮下带有一个与之相反的相带分布。 Subdivision of a tidal flat lithofacies Muds predominate in the supretidal and upper intertidal zones, and the deposits of supretidal marshes are further characterized by abundant plant debris, which may eventually form peat. Mixed mud and sand characterize the middle part of intertidal zone, and sand dominates the lower intertidal zone as well as the channel and bar deposits of the shallow subtidal zone. Muds may be deposited between channels in the subtidal zone below wave base. The proportion of mud and sand in modern tidal flats varies considerably. 潮成沉积构造的特征和组合 高潮坪 中潮坪 低潮坪 低潮坪 潮坪层序的特征及形成 微型层序（层偶）：古代潮坪 微型层序（层偶）：现代潮坪 实际观测的微型层序（层偶） 小型层序：现代潮坪 古代小型层序 Tidal