Seismic and heat flow study of the southern Adriatic Basin

From the interpretation of a large number of regional seismic reflection lines it is seen that the Southern Adriatic basin is an old depression, generated in the Mesozoic, when huge widespread riffing phases took piace in the central-castern Mediterrancan Sea. An initial stretching occurred in the Middle Triassic with extensional deformations that thinned the crust of the Ionian Sea - Eastern Mediterranean and began to detach the Adria plate (Apulia) from the North African plate. In the Middle-Upper Jurassic (178 to 150 m.a.) a second rift phase produced the most impressive and important extensional deformations, with generation of oceanic crusts such as in the Ionian and Eastern Mediterranean Seas, and drastic crustal thinning with deep basins. The Southern Adriatic is one of these Mesozoic deep continental basins that now constitutes a foredeep at the contact between the Southern Dinarides and Northern Hellenides orogenic systems. Seismostratigraphic information shows that the sequenee from Trias to Lias thins notably from the Apulian margin to the deep basin, and is affected by numerous distensive faults. The succession dating from Dogger to Oligocene, in the deep basin, is very thin, continuous and of deep basin deposition. Stretching processes begun at about 178 m.a., confinued very active until 150 m.a. with some terminal, less important movements until 120 m.a., thinning the crust from the 30 km of the Apulian Platform to the approximately 19-20 km of the Southern Adriatic Basin. Miocene and Plio-Pleistocene sediments thicken considerably into the basin. At the castern side of the Southern Adriatic Basin are the buried front of the Dmarides thrusts to north and those of the Hellenides to the south, generated from late Oligocene to Middie Miocene. Mesozoic evaporites are involved in the thrusting tectonics. Using all data furnished by scismic exploration, the Authors give a full explanation of the high heat flow values, according Io time and rate of lithospheric stretching processes and associated thermal evolution. At about 150 m.a. the lithosphere reduced Io about 35 km by thinning. Subsequent rethickening of the LID caused by cooling has led to an increase in the lithosphere to about 80-90 km al present.