Shore platform downwearing in eastern Canada: The mega-tidal Bay of Fundy
Shore platform downwearing in eastern Canada: The mega-tidal Bay of Fundy
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加拿大东部的岸台下沉：芬迪湾的巨潮
DOI：
10.1016/j.geomorph.2009.12.002
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发表时间：
2010
期刊：
影响因子：
3.9
通讯作者：
Jacob I. Kanyaya
中科院分区：
文献类型：
--
作者：
N. J. Porter;A. Trenhaile;Kyle J. Prestanski;Jacob I. Kanyaya
进行了实验室和现场工作，以确定加拿大芬迪湾两个地点岸上平台的表面磨损率；需要这些数据来评估和模拟贬低机制对平台演化的影响。使用去离子水或人造海水，将砂岩和玄武岩样品 (900) 暴露在半日潮汐周期中超过 3 年。在每个 12 小时的潮汐周期中，它们被浸入水中 1、6 或 11 小时，分别代表最低潮位 (LHT)、中潮位和最高潮位 (HLT)。每1、2或3周将另外600个样品浸入去离子水或人造海水中90分钟，代表LHT水平以上的海拔逐渐升高，或每1、2或3周暴露90分钟，代表HLT水平以下的海拔逐渐降低；这些实验持续了 12 个月。在现场，我们在 2 至 6 年期间在 108 个横向微侵蚀仪 (TMEM) 站测量了表面磨损情况。在实验室中，砂岩中 LHT 和 HLT 水平之间的平均磨损率为 0.61–1.80mmyr−1，玄武岩中为 0.01–0.18mmyr−1； LHT 级别的比率最高。比率随 LHT 水平以上升高而下降，低于 HLT 水平则一致较低。 LHT水平以上盐风化作用占主导地位。盐风化和湿润和干燥对于 LHT 和 HLT 水平之间的砂岩很重要，但盐会抑制玄武岩中的岩石破裂。在现场，砂岩的平均磨损率为1.254mmyr−1，与实验数据相似；玄武岩的平均磨损率为0.722mmyr−1，远高于人工海水实验，但与去离子水实验相似。在现场，磨损率与岩石硬度或 TMEM 站高程之间没有关系。
Laboratory and field work was conducted to determine rates of surface downwearing on shore platforms at two sites in the Bay of Fundy, Canada; these data are needed to assess and model the effect of downwearing mechanisms on platform evolution. Sandstone and basalt samples (900) were exposed to semidiurnal tidal cycles over 3years, using de-ionized water or artificial sea water. They were immersed for 1, 6, or 11h over each 12h tidal cycle, representing the lowest high (LHT), mid-, and highest low (HLT) tidal levels, respectively. A further 600 samples were immersed in de-ionized water or artificial sea water for 90min every 1, 2, or 3weeks, representing increasingly higher elevations above the LHT level, or exposed for 90min every 1, 2, or 3weeks, representing increasingly lower elevations below the HLT level; these experiments ran for 12months. In the field, surface downwearing was measured at 108 transverse micro-erosion meter (TMEM) stations over 2 to 6year periods. In the laboratory, mean downwearing rates between the LHT and HLT levels were 0.61–1.80mmyr−1in sandstones and 0.01–0.18mmyr−1in basalts; rates were highest at the LHT level. Rates decreased with elevation above the LHT level and were uniformly low below the HLT level. Salt weathering was dominant above the LHT level. Salt weathering and wetting and drying were important in sandstones between the LHT and HLT levels, but salts inhibited rock breakdown in basalts. In the field, the mean downwearing rate was 1.254mmyr−1in sandstones, which was similar to the experimental data, and 0.722mmyr−1in basalts, which was much higher than in the experiments with artificial sea water but similar to the experiments with de-ionized water. There was no relationship in the field between downwearing rate and rock hardness or TMEM station elevation.