Pseudokarstic cavities in pyroclastic rocks: some examples from North Sardinia

This paper reports on some small pseudokarstic features oççurring in Tertiary pyroclastic rocks outcropping in Sardinia. The cave of Su Niarzu (Bultei, Northern Sardinia) is the best example of this pseudokarst, but other smaller tube-like features have been noted in the same area, all between 10- 20 m above the present altitude of the small streamlet Riu Cugadu.A detailed morphological and minero-petrographical study has been carried out to unveil the genesis of these peculiar pseudokarst morphologies. Su Niarzu cave seems to have formed through physical and chemical weathering of the tufaceous rock and subsequent piping phenomena. A speleogenetic model for these pyroclastic caves and their relative dating is given in this paper.