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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >On the formation of dissolution pipes in Quaternary coastal calcareous arenites in Mediterranean settings
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On the formation of dissolution pipes in Quaternary coastal calcareous arenites in Mediterranean settings

机译：关于地中海地区第四纪沿海钙质球面中溶解管的形成

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A large number of uniform cone-shaped dissolution pipes has been observed and studied in Quaternary coastal calcareous arenites in Apulia and Sardinia (Italy) and Tunisia. These cylindrical tubes have a mean diameter of 52·8cm and are up to 970cm deep (mean depth for sediment-free pipes is 1·38m). They generally have smooth walls along their length, are perfectly vertical and taper out towards their bottoms. Their development is not influenced by bedding nor fractures. Sometimes their walls are coated by a calcrete crust. Their morphology has been studied in detail and their relationships with the surrounding rocks and with the environment have been analysed. The perfectly vertical development is a clear evidence of their genesis controlled by gravity. The depth of the dissolution pipes can be described by an exponential distribution law (the Milanovic distribution), strongly suggesting they developed by a diffusion mechanism from the surface vertically downward. We believe dissolution pipes preferentially form in a covered karst setting. Local patches of soil and vegetation cause infiltration water to be enriched in carbon dioxide enhancing dissolution of carbonate cement and local small-scale subsidence. This process causes the formation of a depression cone that guides infiltrating waters towards these spots giving rise to the downward growth of gravity-controlled dissolution pipes. A change of climate from wetter phases to drier and hotter ones causes the formation of a calcrete lining, fossilizing the pipes. When the pipes become exposed to surface agents by erosion of the sediment cover or are laterally breached the loose quartz sand filling them may be transported elsewhere.
机译：在普利亚和撒丁岛（意大利）和突尼斯的第四纪沿海钙质沉积物中，已观察到大量均匀的圆锥形溶出管并进行了研究。这些圆柱形管的平均直径为52·8cm，深达970cm（无沉淀物管的平均深度为1·38m）。它们通常沿其长度具有光滑的壁，完全垂直且朝着其底部逐渐变细。它们的发育不受层理或裂缝的影响。有时它们的壁上覆盖着一层硬壳。对它们的形态进行了详细的研究，并分析了它们与周围岩石和环境的关系。完美的垂直发育是它们成因受重力控制的明显证据。溶解管道的深度可以通过指数分布定律（米兰诺维奇分布）来描述，强烈暗示它们是通过扩散机制从表面垂直向下发展而来的。我们认为溶蚀管优先在有盖的岩溶环境中形成。当地的土壤和植被斑块使入渗水富含二氧化碳，从而增强了碳酸盐水泥的溶解和局部的小规模沉降。该过程导致形成一个下沉锥，该下沉锥将渗透的水引向这些斑点，从而导致重力控制溶出管的向下生长。气候从湿润的阶段转变为较干燥和较热的阶段，导致形成钙质衬砌，使管道化石。当管道由于沉积物覆盖层的侵蚀而暴露于表面介质或横向破裂时，填充的疏松石英砂可能会被运送到其他地方。

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