High energy coastal sedimentary deposits; an evaluation of depositional processes in Southwest England
High energy coastal sedimentary deposits; an evaluation of depositional processes in Southwest England
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DOI：
10.1002/esp.3290160407
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发表时间：
1991-06
影响因子：
3.3
通讯作者：
I. Foster;A. Albon;K. Bardell;J. Fletcher;T. C. Jardine;R. Mothers;M. Pritchard;S. E. Turner
中科院分区：
文献类型：
--
作者：
I. Foster;A. Albon;K. Bardell;J. Fletcher;T. C. Jardine;R. Mothers;M. Pritchard;S. E. Turner
全世界都观察到沿海洪水留下的沉积物，并将其归因于风暴潮和海啸波的作用。到目前为止，还没有研究试图明确地建立在地层学，沉积学和古生态学的理由，这两个不同的过程可能是在沿海沉积序列区分的手段。本文探讨了历史上的风暴潮和海啸的证据，并表明，这两个高震级的事件已被记录在过去的250年在英格兰西南部。锡利群岛几个浅湖的全新世泻湖和泥炭序列中存在不同厚度的砂层。对圣艾格尼丝大水池的详细分析表明，基底泥炭可追溯到公元前1000年左右。底部泥炭内有许多薄砂层。在底部泥炭之上是一个15至40厘米厚的广泛的砂层。后一层的基础可能可以追溯到世纪早期到中期。颗粒大小、颗粒表面形态、硅藻和矿物磁性研究用于尝试和确定最可能的沉积模式。所有分析的结果都是不确定的，但证据的重量表明，在底部泥炭的上部薄砂层的频率增加可能与小冰期期间叠加在海平面上升之上的大西洋风暴的频率和强度增加有关。厚沙层可能是1755年11月1日里斯本地震产生的海啸波沉积而成。由于在沿海环境中已知已受到风暴潮和海啸波的影响，在区分沉积过程的困难，它建议，普遍接受的沉积学技术是不够的，在沿海环境中的沉积过程的歧视。
Sediments left by coastal flooding have been observed worldwide and have been variously ascribed to the action of storm surges and tsunami waves. To date, no study has attempted to unequivocally establish on stratigraphical, sedimentological, and palaeoecological grounds the means by which these two different processes might be distinguished in coastal sedimentary sequences. This paper examines the evidence for historical storm surges and tsunamis and shows that both high magnitude events have been documented over the past 250 years in southwest England. Sand layers of varying thickness are present within Holocene lagoonal and peat sequences of several shallow lakes of the Scilly Isles. Detailed analysis of Big Pool, St Agnes, indicates that the basal peats date from around 1000 BP. Within the basal peats are numerous thin sand layers. Above the basal peat is an extensive sand layer 15 to 40 cm thick. The base of this latter layer probably dates from the early to mid 18th century. Particle size, grain surface morphology, diatom, and mineral magnetic studies are used to try and determine the most likely mode of deposition. The results of all analyses are inconclusive, but the weight of evidence suggests that the increasing frequency of thin sand layers in the upper part of the basal peat may be related to the increasing frequency and intensity of Atlantic storms during the Little Ice Age superimposed upon a rising sea level. The thick sand layer may have been deposited by the tsunami wave generated by the Lisbon earthquake of November 1,1755. Due to the difficulties in distinguishing depositional processes in coastal environments known to have been affected by storm surges and tsunami waves, it is suggested that generally accepted sedimentological techniques are inadequate for discriminating depositional processes in coastal environments.