No abstract

<p>It has long been recognized that the central Adria Plate, as well as the Dinaric-Hellenic sector, contains a vast volume of Triassic salt associated with diapirism and it is well know that Triassic evaporites developed in the Mediterranean Sea region over epicratonic platforms. Nearby the Apennines and Dinaric-Hellenic front, several authors highlighted the presence of Triassic salt structures such as pillows, diapirs and salt walls, mostly triggered by Neogene tectonic shortening associated with the accretion of these opposite Chains. Nevertheless, in the Apulian foreland, representing the southernmost termination of the Adria plate the Northern Ionian Sea, Triassic evaporitic deposits have never been mapped due to the lack of explorative wells in this deepwater offshore sector. Based on seismic reflection profiles, we illustrate new evidences of Triassic evaporites in the Apulian foreland subsurface associated with two squeezed diapirs as evidence of regional shortening episodes, probably enucleated from inherited Mesozoic salt structures such as pillows and/or salt domes, thus implying new constrains on the paleogeographic reconstruction of the Northern Ionian Sea. The identification of halokinetic-related sequences up to the Plio-Quaternary foreland shallow sediments allows to constrain the evolution of the two diapirs. It results that they are reactivated till Plio-Pleistocene times in response to  the compressive stress trasmitted by the Southern Apennines/Calabrian Arc and Hellenides to the Apulian foreland. Later, after Middle Pleistocene, they were  dismembered by extensional tectonics related to Adria plate flexuring, as they represent areas of weakness. These observations make the regional geological contest one of the foundamental features controlling the Plio-Pleistocene Triassic evaporitic squeezing in the southern Adria Plate.</p>

<p>The Sicily Channel, located in the foreland area of the African plate, is a very interesting geological area in the Western-Central Mediterranean, as it has undergone different tectonic processes because of its proximity to the convergence zone with the European plate. Extension and opening of a rift zone (Sicily Channel Rift Zone, including the Pantelleria, Malta, and Linosa grabens) occurred in the lower plate of the subduction zone marked by the Gela Thrust System and the Calabrian Accretionary Wedge, respectively located south and south-east of Sicily, and the Maghrebian chain to the west. We analyzed geological and geophysical data, such as variable penetration seismic reflection profiles integrated with borehole data; these allowed us to investigate subsurface structures down to the crust-mantle boundary. The crustal profile shows a Moho deepening down to 11.8 s/(TWT) under the Gela Thrust System and going up to 8 s/(TWT) under the Linosa Graben. Moreover, the presence of several hyperbolae zones and signal anomalies have been linked to a rise of deep fluids associated with mantle uplift and, upward, to magmatic intrusions. The sub-surface also shows evidence of a N-S oriented zone, from the Gela Thrust System to the Malta and Linosa grabens, which has undergone contractional tectonic events superimposed on previous extensional structures. Throughout this area, from the Early-Middle Miocene to the Early Pliocene, an extensional event occurred in association with the slab roll-back of the African Plate. In this phase, several volcanic intrusions concentrated near the grabens’ rims suggest a relation between the extension, the Moho rising, and the magmatic manifestations.  Afterward, a compressional event in the Madrepore and Malta Grabens was registered. This event has been correlated to the advance of the Gela Thrust Front, which, according to literature bio-chronostratigraphic analysis, had three stages of advancement in Zanclean, Piacenzian and Chibanian. Furthermore, a recent contractional event caused the folding of the seafloor in the central part of the Malta Graben. This latter phase has been related to a potential change in the subduction polarity. These results provide new insights into the regional kinematic setting of the Sicily Channel, suggesting that strain located within the African Plate can be explained through the overlapping of both intra-plate (localized asthenospheric rise) and inter-plate (compression transmitted from surrounding mountain belts) processes ongoing between Europa and Africa. Indeed, the Sicily Channel structural setting resulted from the interplay of the rollback of the African slab, the consequent changes in the asthenospheric flow that caused extension and local magmatic intrusions, and the active subduction front and its potential polarity reversal that caused local and polyphased compressional pulses.</p>

<p>The central Mediterranean is a geodynamically very complex area included in the convergence zone between the European plate and the African plate. We investigated the western sector of the Sicily Channel , which shows, according to literature data, different deep and shallow tectonic structures than the eastern sector.  Structural data show the presence of a crustal-scale discontinuity that has generated major seismic events such as the Belice earthquake of 1968. This structure has been identified as a wideband roughly oriented N-S from the San Vito Lo Capo to the Sciacca area (SVCS band, San Vito Lo Capo - Sciacca band) (Di Stefano et al., 2015) and continuing offshore to the Pantelleria area. In this work, through multidisciplinary data analysis, we aim to investigate the correlation between the surface structures highlighted onshore and the offshore continuation. For this purpose, we considered offshore data from the Sicily Channel including: gravimetric data, which show negative anomalies in the Pantelleria graben (Palano et al., 2020) and in the Sciacca offshore and velocity models showing the lateral variation of the Moho with values ranging from 30 to 33 km depth and values ranging from 20 to 23 km depth respectively west and est of the Pantelleria graben (Finetti, 2005). These data were compared with our interpretation of crustal reflection seismic profiles and seismic events (since 2005 with M≥2). The results show an alignment of seismic events with roughly N-S direction from offshore Sciacca to Lampedusa. Moreover, the seismic profiles show a lateral variation of the Moho depth deepening estward. From the joint analysis of these data we obtained a geological model of the investigated sector defining the offshore prosecution of the SVCS band present onshore. The present work may be useful for understanding the geodynamic evolution and for studying the seismic hazard of this area.</p> <p> </p> <p><strong>References</strong></p> <p>Di Stefano P., Favara R., Luzio D., Renda P., Cacciatore M. S., Calò M., Napoli G., Parisi L., Todaro S., Zarcone G. (2015). A regional-scale discontinuity in western Sicily revealed by a multidisciplinary approach: A new piece for understanding the geodynamic puzzle of the southern Mediterranean, Tectonics, 34, 2067–2085, doi:10.1002/2014TC003759.</p> <p>Finetti I. R. (Ed.). (2005). CROP project: deep seismic exploration of the central Mediterranean and Italy. Elsevier.</p> <p>Palano M., Ursino A., Spampinato S., Sparacino F., Polonia A., Gasperini L. (2020). Crustal deformation, active tectonics and seismic potential in the Sicily Channel (Central Mediterranean), along the Nubia–Eurasia plate boundary. Scientific reports, 10(1), 1-14.</p>