Evidenze morfologiche di campi di pockmarks e fuoriuscite di fluidi sui fondali del Mar Tirreno

Tyrrhenian Seafloor is characterized by presence of abundant fluids /gas escapes and morphologies witness- ing the occurrence of this phenomenon. The detailed analy- ses of middle resolution morpho-bathymetric data, make available to the entire community in the frame of the EMODnet European program, allowed of identifying the presence of sub-circular depressions, named pockmarks, along the peri-Tyrrhenian margin which witness the escapes of fluids at seafloor fed by deep levels. We identified thirteen fields of pockmarks and several hundred of single pock- marks belonging to them. Among these: a) six are located in the Northern Tyrrhenian, amongst the Sardinia-Corsica and Tuscany; b) four are located in the Southwestern Tyrrhenian, to North of Sicily; c) two are in the Eastern Tyrrhenian, off- shore Calabria region; and d) one is offshore Lazio in the Central Tyrrhenian sea. Pockmarks of both small and very large dimensions are present. The small pockmarks have cir- cular shape, with both random distribution and aligned along preferential directions. Generally, these have an average di- ameter and depth of 500 m and 15 / 20 m, respectively, and have random distribution at the top of sedimentary ridges or within volcanic systems. Sometimes they align along en- graves generated by deep water currents, forming "Gully", or generated by tectonic structures. The large dimension pockmarks, named "Giant pockmarks", result by merging of several (tow, three or more) small pockmarks forming coa- lescent and elongated structures. Giant pockmarks have av- erage diameter that frequently exceed 2 km and depth ranging from 60 to 120 m. These are mostly organized in swarm along engraves mainly controlled by tectonic processes and in minor part by deep water currents. In the Eastern Tyrrhenian Sea the fluids / gas escapes able to leave large depression on the seafloor are frequently associated with volcanic systems.