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Geotectonic Evolution of the Eastern Tyrrhenian Sea

Alfonsa Milia and Maurizio M. Torrente

The Tyrrhenian Sea is a Neogene back-arc basin formed at the rear of the eastward migrating Apennine thrust belt. It is characterized by two large bathial basins, Vavilov and Marsili Basins, covered by few ten of meters of sediments, and a number of peri-Tyrrhenian basins filled by thousands of meters of clastic and/ or volcaniclastics sediments. The stratigraphic record of these basins offers the opportunity to study the timing and kinematics of the basin-forming faults.

Active extensional faulting and sedimentation are linked during basin evolution because tectonics controls the creation of the accommodation space, the sediment supply and the variation of the rate between subsidence and sedimentation. Depositional sequence mapping is a powerful technique that assists the interpretation of basin evolution on continental margins. By contrast, the detailed geometry and sequence of movements on the linked fault system directly controls the dip and strike development of the sedimentary fill and its facies.

The geologic evolution of the Eastern Tyrrhenian Sea has been reconstructed on the basis of a large amount of multichannel and single-channel seismic reflection data with different resolution and penetration, exploration wells, core data and onshore data. We interpreted this seismic grid using a seismic and sequence stratigraphy approach in a dedicated GIS environment and generated: isochron maps, 2-D models of relevant geological surfaces and 3-D digital models linking stratigraphic horizons and faults.

The stratigraphy of these basins clearly records a poly-phased history of subsidence. Each episode of basin formation gives rise to a distinctive stratigraphic signature and to tectonically-enhanced unconformities. We reconstructed different tectonic stages in the evolution of the Eastern Tyrrenian Sea that featured a progressive change in the direction of extension.

The reconstructed tectono-sedimentary evolution of the Eastern pery-Tyrrhenian basins can integrate our knowledge of the Tyrrhenian Sea crustal fabric and dynamics, plate kinematics, and timing of back-arc opening.

AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013