Présentations Colloques

Karst formation depends on several external and internal factors such as lithology, porosity, permeability, environmental conditions, and the couplings between fluid flow and carbonate dissolution into heterogeneous rocks. It has often been proposed that water circulation in karsts is controlled by the presence of extensional faults, assuming that they are more favorable to water circulation than other geological structures. However, the permeability of fault zones is large only in the early stages their formation because, after a short period, deposition of minerals (e.g. calcite) precipitated from underground waters. These minerals fill the empty spaces and therefore generate dramatic porosity and permeability reduction. The question arises then if other geological heterogeneities initially present in the rock, such as stylolites, do have a stronger control on karst formation.**We present here a field study of karts in the region of Fasano (South Italy) where karst features are more abundant and present along compressional features, such as tectonic stylolites, rather than faults. These field observations suggest that karst formation is controlled by several kinds of heterogeneities initially present in the formation or created during tectonic processes. The data allow characterizing which among these heterogeneities (faults, stylolites) have a larger control on karsts development. For this, the regional direction of the various tectonic structures (faults, stylolites, joints) are compared with those of the main caves. In a conclusion, it can be demonstrated that even small heterogeneities such as stylolites control partly the formation of karst.**