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Cave formation initiated by dissolution of carbonate cement in qartzose sandstones
Adamovič, Jiří ; Mikuláš, Radek ; Navrátil, Tomáš ; Mertlík, J.
Besides cavities of irregular shape, European sandstones also feature symmetrical cavities of spherical, ellipsoidal or teardrop shapes. Most of them are tens of centimetres across but some reach as much as 2–3 m in diameter and may coalesce into large caves tens of metres in length. Their origin has not been clearly explained yet. Based on the field comparison between such cavities in quartzose sandstones and incompletely developed cavities in carbonate-cemented sandstones, it can be demonstrated that the symmetrical cavities form by carbonate dissolution within the limits of former carbonate concretions. The diagnostic features of post-concretionary cavities include their circular or elliptical cross-section, a uniform orientation of their long axes across the region, and the presence of a set of parallel vertical joints or grooves/ribs on their inner walls. In some sandstone areas (e.g., Petite Suisse area in Luxembourg, Kokořín area in the Czech Republic), a wide variety of transitional forms can be found between the cavities and concretions forming positive relief on a vertical cliff face, depending on the position of the carbonate dissolution front in the present landscape.
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