GNGTS 2014 - Atti del 33° Convegno Nazionale

56 GNGTS 2014 S essione 3.1 The main feature involving the sedimentary sequences of the studied area is the presence of the evaporite units (Messinian Trilogy) deposited in the deep basin during the Messinian post- drifting phase. The salt tectonics developed due to the lower density of salt in relation to loaded adjacent sediments and differential compaction of adjacent and overlying sediments due to the incompressibility of the salt. This process forms domes, diapirs, sliding on deepening basement and compressive deformations. Halokinetic deformation developed mainly during the Lower Pliocene, but continues until Present, as testified by some circular structures piercing the sea bottom. Some growth strata have been evidenced also in the UU, testifying that local halokinetic processes started as early as the late Messinian, probably due to the UU load and the start of the re-flooding. As shown by the generated structural maps, the favourable conditions for halokinetic tectonics are: large thickness of salt, sedimentary (and water) loading, deepening of the underlying basement and the presence of faults (which make only a local contribution). Integration of the different seismic datasets used in this work allowed identification of the probable presence of a halite layer within the UU in the deep basin. The deep basin reaches its maximum depth at the toe of the West-Sardinian slope, but the deep horizons show that the original basin depocentre was in a western position: this is due to the abundant sedimentary supply from the Rhône river, unlike the sparse input from the Sardinia Isle. Acknowledgements. We would like to thank TGS and OGS for permission to disclose seismic data. References Aslanian D., Moulin M., Schnurle P., Klingelhoefer F., Leroux E., Rabineau M., Gailler A., Bache F. Gorini, C. Carminati E., Lustrino M. and Doglioni C.; 2012: Geodynamic evolution of the central and western Mediterranean: Tectonics vs igneous petrology constraints. Tectonophysics, doi:10.1016/j.tecto.2012.01.026. Carminati E. and Doglioni C.; 2005: Mediterranean Geodynamics: Encyclopedia of Geology . Elsevier, 135–146. CIESM; 2008: The Messinian Salinity Crisis from Mega-Deposits to Microbiology- A consensus report . In:Briand, F. (Ed), CIESM Workshop Monographs, 33, 168. Clauzon G., Suc J.P., Gautier F., Berger A., Loutre M.F.; 1996: Alternate interpretation of the Messinian Salinity Crisis: controversy resolved? . Geology 24, 363–366. Finetti I.R., Del Ben A., Fais S., Forlin E., Klingelé E., Lecca L., Pipan M. and Prizzon A.; 2005: Crustal tectono- stratigraphic setting and geodynamics of the Corso-Sardinian Block from new CROP seismic data . In: Finetti I. R. (Ed.): CROP PROJECT: Deep Seismic Exploration of the Central Mediterranean and Italy . Atlases in Geo- science, 1, Elsevier B.V., 430-446. Finetti I.R. and Morelli C.; 1973: Geophysical Exploration of the Mediterranean Sea . Bollettino di Geofisica Teorica ed Applicata, 15, 263-341. Geletti R., Zgur F., Del Ben A., Buriola F., Fais S., Fedi M., Forte E., Mocnik A., Paoletti V., Pipan M., Ramella R., Romeo R. and Romi A.; 2014: The Messinian Salinity Crisis: new seismic evidence in the West-Sardinian Margin and Eastern Sardo-Provençal Basin (West Mediterranean Sea) . Marine Geology, 351, 76-90. Gennesseaux M. and Vanney J.R.; 1979: Cartes bathymetriques du Bassin Algero- Provençal. Somm. Soc. Geol. Fr., 4, 191-194. Krijgsman W. and Meijer P.Th.; 2008: Depositional environments of the Mediterranean “Lower Evaporites” of the Messinian Salinity Crisis: constraints from quantitative analyses . Marine Geology , 253, 73-81. Krijgsman W., Hilgen F.J., Raffi I., Sierro F.J., Wilson D.S.; 1999: Chronology, causes and progression of the Messi- nian Salinity Crisis . Nature, 400, 652–655. Kuroda, J. Eguchi, N., Droxler A., Alain K., Roure F. and Haq B.; 2012: Structure and evoultion of the Gulf of Lions: The Sardinia Seismic Experiment and the GOLD (Gulf of Lions Drilling) project . The Leading Edge - Special Section: Mediterranean Region, 786-792. Lofi J., Déverchère J., Gaullier V., Gillet H., Gorini C., Guennoc P., Lonke L., Maillard A., Sage F. and Thinon I.; 2011: Atlas of the Messinian seismic markers in the Mediterranean and Black Seas. Mem. Soc. Geol. Fr., n. s. 179 and World Geological Map Commission, 72. Lofi J., Gorini C., Berné S., Clauzon G., Dos Reis A.T., Ryan W.B.F. and Steckler M.S.; 2005: Erosional processes and paleo-environmental changes in the Gulf of Lions (SW France) during the Messinian Salinity Crisis . Marine Geology, 217, 1-30. Montadert L., Letouzey J. and Mauffret A.; 1978: Messinian event: seismic evidence . In: Hsü K. J., Montadert L., et al. (Eds), Initial Reports of the Deep Sea Drilling Project, 42, part I, US Government Printing Office, 1037-1050.