The Santa Ninfa cave (Belice Valley): hydrogeochemical features and relationships with neotectonics

The Santa Ninfa Cave (SNC) develops in an outcrop of Messinian gypsum, located in the heart of the zone struck by the 1968 seismic sequence of the Belice valley. It is composed of different levels of sub-horizontal galleries, the lowest of which is characterized by perennial flowing water, running along the water table. From the hydrogeological point of view, it configures as an open circuit, both inflowing and outflowing from/to neighboring aquifers. The geochemical facies of groundwater collected in the SNC is compatible with a meteoric recharge chemically interacting with evaporitic deposits. The most relevant geochemical feature is the mixing between a small tributary of sulfur water with the main stream flowing in the lowest passage. The mixing between groundwater of different origin, flowing in aquifers with different permeability, can give rise to geochemical transients linked to seismogenic processes. Under this light, SNC could be of potential interest in the framework of a monitoring system of neo-tectonic activity in southwestern Sicily.