Rocky coasts ― their role as depositional environments

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• 作者：Alan Trenhaile
• 关键词：Rock coasts ; Sediments ; Boulders ; Beaches ; Model ; Climate change
• 刊名：Earth Science Reviews
• 出版年：2016
• 出版时间：August 2016
• 年：2016
• 卷：159
• 期：Complete
• 页码：1-13
• 全文大小：1865 K

文摘

The role of rocky coasts as depositional environments has been generally neglected by rock- and depositional-coast workers. Although rock coasts can be hostile sedimentary environments, they frequently host a variety of deposits consisting of mixes of boulders and megaclasts to sand and cobbles. These deposits include pockets of sand and pebble trapped in topographic depressions or at the foot of scarps and cliffs, isolated boulders, pocket beaches trapped between headlands, and sand to boulder beaches in shallow bays exposed to strong wave action. The tectonic setting, which is reflected in the degree of geological heterogeneity alongshore, together with the wave regime and other elements of the morphogenic environment, help to determine the amount and mobility of the sediment, and consequently whether it plays an essentially abrasional or protectional role. Many beaches have a resistant rock foundation which will modulate their response to rising sea level and possibly increased storminess during this century. Wave refraction and temporal and spatial changes in sediment abrasional and protectional efficacy influence the development of crenulated planforms on coasts with a high degree of geological heterogeneity, and possibly on more geologically homogeneous coasts with longshore variations in cliff height or in the amount of sediment. Theory suggests that these coasts may develop equilibrium planforms with uniform rates of erosion in bays and on headlands, or they may undergo a series of cyclical transformations involving alternating increases and decreases in the depth of the bays relative to the headlands.