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Failles actives et structures profondes de la Marge Est-Sicilienne

Abstract : In the Ionian Sea (central Mediterranean) the slow convergence between Africa and Eurasia results in the formation of a narrow subduction zone. The nature of the crust of the subducting plate remains debated and could represent the last remnants of the Neo-Tethys ocean. The origin of the Ionian basin is also under discussion, especially concerning the rifting mechanisms as the Malta Escarpment could represent a remnant of this opening. This subduction retreats toward the south-east (motion occurring since the last 35 Ma) but is confined to the narrow Ionian basin. A major lateral slab tear fault is required to accommodate the slab rollback.This fault is thought to propagate along the eastern Sicily margin but its precise location remains controversial.This PhD project focussed on the deep sedimentary and crustal structures of the eastern Sicily margin and the Malta Escarpment (ME). Two two-dimensional P wave velocity models were modelled by forward Modelling of wide-angle seismic data, acquired onboard the R/V Meteor during the DIONYSUS cruise in 2014.A 3D gravity model of the region was also performed to constrain the depth of the subducting slab bellow the Calabro-Peloritan backstops. The seismicity of the three structures identified in the velocity models (ME, Alfeo fault System, Ionian Fault System) permits to study their recent activity. The results image an oceanic crust within the Ionian basin as well as the deep structure of the Malta Escarpment, which presents characteristics of a transform margin. A deep and asymmetrical sedimentary basin is imaged south of the Messina strait and seems to have opened between the Calabrian and Peloritan continental terranes. In the western lobe of the Calabrian accretionary prism, the southern velocity model allows to observe the indentation of the internal clastic wedge into the external evaporitic wedge, thus showing the recent activity of this lobe. The interpretation of the velocity models suggests that the major STEP fault is located east of the Malta Escarpment, along the Alfeo Fault System.
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Submitted on : Friday, March 22, 2019 - 5:57:16 PM
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  • HAL Id : tel-02077449, version 1



David Dellong. Failles actives et structures profondes de la Marge Est-Sicilienne. Sciences de la Terre. Université de Bretagne occidentale - Brest, 2018. Français. ⟨NNT : 2018BRES0065⟩. ⟨tel-02077449⟩



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