Pascucci, Vincenzo (2005) The Tuscan shelf south of the Elba Island (Italy) as imaged by the Crop M12A line. Bollettino della Società geologica italiana, Vol. 3 , p. 167-178. ISSN 0037-8763. Article.
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The North Tyrrhenian Sea separates Corsica from the Tuscany coast and it is subdivided into three sectors with different morphological and geological characteristics: the Corsica Basin, the Elba-Pianosa Ridge and the Tuscan Shelf. The North Tyrrhenian Sea is considered to be an extensional basin formed during the post-collisional phases of the Northern Apennines. It is filled by up to 8.5 km of Eocene to Recent deposits unconformably lying on Cretaceous or older strata. The aim of this work is to present the main features of the seismic line CROP-M12A and provide a linkage between this line and the inland CROP-03 profiles. The M12A line crosses the Tuscan Shelf from SW-NE, south of Elba Island from the Elba-Pianosa Ridge to the Punta Ala promontory. The Corsica Basin is bounded to the west by an east-dipping master fault (the Solenzara fault) active in Oligocene times and reactivated in the Late Miocene. To the east the basin is flanked by the Elba-Pianosa Ridge. Industrial and deep seismic profiles indicate that the sedimentary fill of the Corsica Basin is up to 6.5 sec (TWT) thick, and that it is composed of Oligocene to Quaternary poorly deformed strata resting on Eocene deformed strata, in turn resting on the acoustic basement, probably composed of calcschists. The Elba-Pianosa Ridge has been drilled by the two wells Martina 1-Mimosa 1 and it is crossed by the CROP line M12A. The submerged part of the ridge is mainly composed of a thick Eocene-Early Miocene siliciclastic succession. Only at Pianosa Island, where the top of the ridge is emerged, are Lower Miocene-Quaternary deposits exposed. The Oligocene deposits are well-imaged on seismic line CROP M12A and have been penetrated by the two wells; their thickness reduces towards the Tuscany coast from 2.0 sec TWT (about 3000 m) to 0.7 sec TWT (about 800 m). Industrial seismic profiles across the Tuscan Shelf show that Oligocene deposits are folded and thrusted eastwards and that Burdigalian-Langhian sedimentary fill occurred the thrust-top basins. Evidence of a post-Oligocene deformational phase has recently been documented by the stratigraphic revision of the Mimosa 1 well, where the tectonic repetition of the Eocene series has been recognised. A suite of basins filled by about 2500 m of Late Miocene-Quaternary deposits, resting unconformably on the acoustic basement, characterise the eastern part of the Tuscan Shelf. Basins formed as half-grabens during Late Miocene-Early Pliocene times, and hilly post-rift conditions occurred in the Pleistocene. East-dipping basin master faults show listric geometry and can be followed down to 3.0 sec TWT. The acoustic basement of the eastern part of the Tuscan Shelf is represented by the Mesozoic carbonate rocks of the Tuscan Nappe. CROP-M12A analysis underlines that the Montecristo High is one of the major structures of the Tuscan Shelf. Similarly to the Middle Tuscany Ridge, it is bounded by opposite verging faults. The western NE-verging thrust was reactivated as a normal fault in the Late Miocene. The thrust can be followed throughout the whole Tuscan Shelf and affects the crust down to about 15 km. The prominent reflections at depths of 7.0 and 8.0 sec TWT are interpreted to be the Moho. The shallow reflection is interpreted to be the Apenninic Moho, and the deep reflection to be the Tyrrhenian Moho.
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