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 52·8 cm and are up to 970 cm deep (mean depth for sediment-free pipes is 1·38 m). They generally have smooth walls along their length, are perfectly vertical and taper out towards their bottoms. Their development is not infl uenced 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 infi ltration 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 infi ltrating waters towards these spots giving rise to the downward growth of gravitycontrolled 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 fi lling them may be transported elsewhere.
On the formation of dissolution pipes in Quaternary coastal calcareous arenites in Mediterranean settings / De Waele J.; Lauritzen S.E.; Parise M.. - In: EARTH SURFACE PROCESSES AND LANDFORMS. - ISSN 0197-9337. - STAMPA. - 36:(2011), pp. 143-157. [10.1002/esp.2022]
On the formation of dissolution pipes in Quaternary coastal calcareous arenites in Mediterranean settings
DE WAELE, JO HILAIRE AGNES;
2011
Abstract
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 52·8 cm and are up to 970 cm deep (mean depth for sediment-free pipes is 1·38 m). They generally have smooth walls along their length, are perfectly vertical and taper out towards their bottoms. Their development is not infl uenced 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 infi ltration 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 infi ltrating waters towards these spots giving rise to the downward growth of gravitycontrolled 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 fi lling them may be transported elsewhere.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
