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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Lithological control on the elevation of shore platforms in a microtidal setting
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Lithological control on the elevation of shore platforms in a microtidal setting

机译：微潮环境下岸台高程的岩性控制

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The shore platforms on Shag Point, southern New Zealand, are quasi-horizontal surfaces and are developed between supratidal and low water spring levels. A range of morphologies occur, with more exposed platforms having a distinct low-tide cliff, in contrast to low-tide surfaces where the seaward edge is buried beneath rubble and macro-algal growth. The platforms range in width from 20 to 80 m and are eroded into Late Cretaceous/Early Tertiary fine marine sandstones and mudstones. Shore platforms have formed in two principal lithological units: a homogeneous unit that is characterized by few discontinuities, and a fractured unit with joints spaced about 0.5 m apart. Rock hardness is low in both units (L-type Schmidt hammer rebound values of 31 +/- 4), and there is little systematic variation in values between the two units in which platforms have developed. Case-hardened concretions within the sandstone are significantly harder than surrounding rock and cause local relief of metre scale as the spherical diagenetic features are eroded from the bedrock. They do not, however, appear to affect broad-scale platform geometry. Joints within the bedrock are a primary control on platform elevation. Platforms formed in jointed rock occur at the lower portion of the intertidal zone, in contrast to platforms formed in unjointed bedrock, in which horizontal surfaces occur at or above mean high water spring tide level. Rock structure, therefore, appears to be the primary determinant factor of platform geometry at Shag Point. Copyright (c) 2006 John Wiley & Sons, Ltd.
机译：新西兰南部沙格波因特（Shg Point）的海岸平台是准水平的表面，在水上和低水位之间发展。与低潮表面相比，低潮表面将海向边缘掩埋在碎石和大型藻类的生长之下，形成了一系列形态，更多的裸露平台具有明显的低潮悬崖。平台的宽度从20到80 m不等，被侵蚀成晚白垩纪/第三纪的精细海洋砂岩和泥岩。岸台形成了两个主要的岩性单元：一个均一的单元，具有很少的不连续性;一个破裂的单元，节理间隔约0.5m。两种单位的岩石硬度都很低（L型施密特锤的回弹值为31 +/- 4），并且在开发平台的两个单位之间，值几乎没有系统的变化。砂岩中经过表面硬化处理的混凝土比周围的岩石坚硬得多，并且由于球形成岩特征从基岩中侵蚀而导致米级局部起伏。但是，它们似乎不会影响大规模平台的几何形状。基岩内的节理是对平台标高的主要控制。与在节理岩层中形成的平台相比，在节理岩层中的下部出现在潮间带的下部，而在非节理基岩中形成的平台中，水平面出现在等于或高于平均高水位潮汐水平的水平面上。因此，岩石结构似乎是Shag Point平台几何形状的主要决定因素。版权所有（c）2006 John Wiley＆Sons，Ltd.

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