Late Flandrian Shoreline Oscillations in the Severn Estuary: The Rumney Formation At Its Typesite (Cardiff Area)
Late Flandrian Shoreline Oscillations in the Severn Estuary: The Rumney Formation At Its Typesite (Cardiff Area)
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塞文河口的晚期弗兰德海岸线振荡：其打字地点的拉姆尼地层（卡迪夫地区）
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发表时间：
1987
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通讯作者：
J. Allen
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作者：
J. Allen
加的夫东北部前潮汐湿地的海岸被称为温特卢格水位，在罗马时期开垦，暴露出一系列以河口粘土为主的佛兰德晚期岩石地层单位。其中最主要的是(上部)Wentlooge组(厚达2.5米)和Rumney组(厚达2.7米)。(上部)Wentlooge组由略带青灰色的粉质粘土组成，顶部覆盖着一层未成熟的古土壤，产生了粘土幻影的迹象。从古土壤内的一个水平向下延伸是一个网状的深排水沟渠系统，其中一些沟渠在当地填满了罗马-英国文化碎片，被认为是他们挖掘的年代。这种填充物被土壤封住了。罗马时期之后但中世纪晚期之前的海洋侵蚀摧毁了上温特卢奇地层的大部分，以及假定的罗马海上防御。当时没有保护措施的排水沟在这段海岸撤退期间被入侵，并扩大形成了一系列大型海湾，这些海湾界定了平顶的海角，古土壤在这些海角上形成了一个盖子。上面的Rumney组是一系列粉红色河口粉质粘土，带有一些沙子和砾石。它淹没了在温特卢奇床上切割的海岸线的入海口，并将其海角覆盖到约1.4米厚。入海口的沉积始于15世纪，但在海角的沉积又被推迟了100-200年。由Rumney组早期的泥滩和沼泽沉积记录的海岸向外运动最终被逆转，形成了一个大胆的泥崖，继续向内陆撤退到现在的位置。在这个悬崖的上部是裸露的沙片，记录了在撤退过程中形成的砂体，在海湾的头部，作为袖珍海滩，以及在涨潮和风暴期间向陆地冲到盐沼上的沙洲。最近的两个较年轻的岩石地层单位，Awre组和Northwick组，具有与Rumney组相似的地层关系，并记录了链的进一步运动。岩石地层学记录的海岸波动可归因于海岸波浪的作用和强度的波动，这是由中期天气变化或近岸浅滩的位置或海岸本身的地形决定的。
The shore of the former tidal wetland northeast of Cardiff, called the Wentlooge Level and reclaimed during the Roman period, exposes a series of late Flandrian lithostratigraphic units dominated by estuarine clays. Chief among these are the (upper) Wentlooge Formation (up to 2.5 m thick) and the Rumney Formation (up to 2.7 m thick). The (upper) Wentlooge Formation consists of greenish grey slightly silty clays and is capped by an immature palaeosol yielding signs of clay illuviation. Extending down from a level within the palaeosol is a reticulate system of deep drainage ditches, some of which are locally filled with Romano-British cultural debris, regarded as dating their excavation. Such fills are sealed by the soil. Marine erosion after the Roman period but before late mediaeval times destroyed much of the upper Wentlooge Formation together with a presumed Roman sea defence. The then unprotected drainage ditches were invaded during this episode of coastal retreat and widened out to form a series of large embayments that defined flat-topped headlands on which the palaeosol formed a capping. The overlying Rumney Formation is a series of pink estuarine silty clays with some sands and gravels. It infills the embayments of the coastline cut in the Wentlooge beds and smothers its headlands to a thickness of about 1.4 m. Deposition in the embayments began in the 15th century, but on the headlands was delayed for a further 100-200 years. The outward movement of the shore recorded by the mudflat and marsh deposits of the earlier part of the Rumney Formation was eventually reversed with the formation of a bold mud cliff that has continued to retreat inland to its present position. On the upper part of this cliff are exposed sand sheets which record sand bodies formed during the retreat, at the heads of inlets, as pocket beaches, and as landward-facing bars cast up on to the salt marsh during high tides and storms. Two younger lithostratigraphic units of recent date, the Awre Formation and the Northwick Formation, have stratigraphical relations similar to the Rumney Formation and record further movements of the strand. The coastal oscillations recorded by the lithostratigraphy are attributable to fluctuations in the role and strength of waves at the shore, as governed by either medium-term weather changes or the positions of offshore shoals, or by the morphology of the shore itself.