THE GUANO HOLES: A NEW CORROSION FORM FROM NATUTURINGAM CAVE (PALAWAN, PHILIPPINES)

Travaux de l'Institut de Speologie Emile Racovitza

卷:57

TOMMASO SANTAGATA¹  JO DE WAELE²  PAOLO FORTI³  JOSE MARIA CALAFORRA³  MARCO VATTANO³ 

[1] BIGEA Dept., University of Bologna, Italy;

[2] University of Almeria, Spain;

[3] La Venta Esplorazioni Geografiche, Italy;

关键词: Corrosion form;    climatic control;    genetic mechanism;    cave minerals;   

DOI  :  

来源: DOAJ

【 摘 要 】

A totally new corrosion form has been recently observed inside theNatuturingam cave (better known as Puerto Princesa Underground River) in Palawan (Philippines): the guano holes. They consist of perfectly rounded holes, 4–5 cm wide and up to 10–15 cm deep, developing over a flat limestone surfaces covered by a thin layer of fresh guano. In the same cave larger guano-related corrosion forms have also been encountered, but are not presented in detail here (guano pots). A 3D photogrammetric survey has been carried out on a series of guano-holes to make some morphometric measurements. Their development is controlled by the peculiar Palawan climate, which is characterized by short but heavy rainfalls followed by rather long dry periods. During rainfalls each water drip drills a perfectly rounded hole into the fresh guano reaching the limestone surface which is then corroded by the acids produced by guano digestion. The corrosion process on the exposed limestone surface continues during the whole subsequent dry period and causes the deepening of the initialdepression with respect to the surrounding area. At the end of the dry period the drilled holes are partially refilled by fresh guano, and the process restarts at the beginning of a new rainstorm. Subsequent cycles of wet and dry periods cause a progressive deepening of each hole. When two or more drops and their splashing areas interfere, their holes coalesce thus giving rise to relatively larger and complex forms. Finally, during the dryperiods, capillary rise and evaporation of the solution trapped within the hole may cause the deposition of small aggregates of different minerals (mainly hydroxylapatite, with minor quantities of calcite). During the next rainstorm, sometimes dripping may not be able to wash away all these minerals, so that they progressively accumulate inside thehole developing a layered speleothem.

【 授权许可】

Unknown