Geoconservation in Sicily (Italy): the Example of the Isola delle Femmine (Palermo)

The Regional Administration of Sicily recently erected Isola delle Femmine-a small island of the Tyrrhenian Sea, close to Palermo-as a geosite. A detailed geological survey has been carried out in order to define the most important geological features of the island together with the development of a new geological map based on topographic data and a digital model at 1:2.000 scale specially processed. Finally, a geological pathway through the island has been traced and illustrated. The geological substrate of Isola delle Femmine consists of a Mesozoic carbonate succession belonging to the Panormide Carbonate Platform. Two lithostratigraphic units have been differentiated. The lowest one consists of dolomitic limestones cropping out in the intermediate and northern part of the island. Despite the absence of biostratigraphic constrains, analogies with comparable deposits from the Palermo Mountains suggested to ascribe this unit to the Upper Triassic. The overlying unit consists of well-bedded rudist and stromatolitic limestones organized in peritidal cycles. The macro- and micro-facies analysis of these Cretaceous limestones allows to attribute this unit to the Lower Cretaceous (i.e., Aptian). Patches of upper Pleistocene skeletal calcarenites rich in benthic foraminifers and calcareous algae overlap the Mesozoic units. Spectacular speleothems such as stalagmites, ray crystals ("raggioni") of calcite, and mammillary calcite suggest a relative long-lasting exposure of the Mesozoic carbonate substrate to groundwater. This is not surprising since glacio-eustatic oscillations caused sea-level to fall up to 125 m during the Pleistocene thus exposing and linking to the mainland (Sicily) Isola delle Femmine and the surrounding area.