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| Títol: |
Morfologia i vegetació d'un grup de dolines de la serra de Tramuntana : Mallorca |
| Autor/es | Ginés Gràcia, Àngel ; Fiol, Lluís Antoni ; Pol, Andreu ; Rosselló, Josep Antoni |
| Matèries en català: | Geologia ; Biologia. |
| Matèries en anglès: | Geology ; Biology. |
| Resum-Abstract: | [spa] Se exponen los resultados de una serie de observaciones botánicas realizadas en 14 dolinas de la Serra de Tramuntana durante los últimos años. Las dolinas estudiadas se localizan dentro del término municipal de Escorca, entre Bini Gran y el Torrent de Pareis, en una zona donde las formas kársticas alcanzan un desarrollo excepcional. El trabajo ha sido estructurado en tres partes: en la primera se describen las características topográficas y geomorfológicas de las dolinas; en la segunda se indican las especies de líquenes, briófitos, pteridófitos y fanerógamas más abundantemente representadas en estas depresiones kársticas, comentando los rasgos más significativos de su poblamiento vegetal; y en la tercera se discute la interferencia de las actividades humanas en la conformación de estas comunidades vegetales. Entre los resultados obtenidos, destaca la presencia de algunos taxones de carácter calcífugo en un terreno kárstico caracterizado por los procesos de disolución de la roca caliza (como Acarospora schleicheri, Phaeoceros laevk, Polytrichum juniperinum, Ophioglossum lusitanicum, Aira caryophyllea, Centaurium maritimum, Logfia gallica y Erica arborea). También se ha puesto en evidencia el efecto que tiene la quema periódica de “càrritx” como condicionante de la vegetación actual de estas dolinas, y el riesgo que puede suponer esta rudimentaria práctica de explotación ganadera para la degradada cubierta vegetal de la Serra de Tramuntana. [eng] The present survey length of Cova de sa Gleda is 10,500 m and its maximum depth is -25 m. These figures make this cave the largest in Europe for a litoral mixing-zone cave. Cova de sa Gleda has a stratified hydro-profile, with up to five different saline layers. Three of the five sectors of the cave have been studied and with this preliminary view we can say that the cave is a series of breakdown chambers which are connected with each other either by phreatic galleries, circular, elliptic, or irregular in section, or by structurally controlled galleries. Throughout the cave different and varied types of corrosion morphologies can be found. The distribution of areas with primary formations and areas of breakdown are opposed. The most interesting formations are the corrosion notches, being both clearly and well marked, and which have affected wall bedrock and the speleothems equally. One of the best places for them is found along 150 m of the most central passages belonging to the Haloclines gallery, at a depth between -13.5 and -14 m, and they cut into the walls and speolothems between 0.3 and 1 m. A good place for illustrating the present corrosion processes in the mixing zone is the Francesc Ripoll chamber where a halocline, lying approximately between the -10 and -12.3 m (the depth depends on the season and the rainfall), has left the columns very deteriorated in a band between -10 and -12.3 m. Likewise the secondary formation have an important narrowing round them caused by dissolution. Most of the cave floor is covered by muddy sediment which are marked by two very different characteristics. On the one hand we have the red mud materials with a silicic composition which are related to the external entrances of the cave, and on the other hand we have yellowish carbonate mud from either the accumulation of Miocene calcarenitic rock following its granular decomposition, or the accumulation of floating calcite in the parts of the cave where air bells have been seen. The mixing of all the materials is also frequent as well as the accumulation of large blocks following roof and wall breakdown. Another noteworthy aspect of the cave are the phreatic speleothems, which are related to previous levels of stability and are precipitation of the grounwaters, which were in turn controlled by Quaternary sea-level oscillations. These are found as crystal coatings on walls and vadose speleothems forming ring-shaped overgrowths round stalactites, stalagmites and columns. The presence of these overgrowths caused by epiaquatic precipitation is very noticeable and has led to often impressive precipitation morphologies which characterise many of the cave’s chambers and galleries. |
| Font: | Endins 1989, Vol. 14-15, pp. 43-52 |
| Identificador: | e-ISSN: 2386-7299 |
| Tipus de document: | info:eu-repo/semantics/article ; info:eu-repo/semantics/publishedVersion |
| Avís legal: | all rights reserved ; info:eu-repo/semantics/openAccess |