Crustal structure of the North Tyrrhenian Sea: first results of the multichannel seismic LISA

Abstract: During a deep-penetration multichannel seismic cruise, the North Tyrrhenian basin was investigated. This basin has a shallow Moho along the Italian coast. Two kinds of dipping reflections were identified in the crust. The westward-dipping reflections are interpreted as Apennines or/and Alpine thrusts whereas the eastward-dipping reflections may be the seismic expression ofextensional detachments. The deep part of the 10 km thick Corsica Basin is well imaged on the continental shelf. This basin was formed before or during the opening of the Balearic-Ligurian basin and is related to the collapse of the Alpine Corsica belt. We emphasize the active role of plutonic bodies that rise from a 3 km depth during the mid-Pliocene. The thinning of the North Tyrrhenian crust could be explained by a delamination f the Adriatic lithosphere that re reats towards the east. The formation of extensional basins in conver-gent setting is a major problem of Earth sciences (Faccena et al. 1996). In the past years formation of marginal basins behind subduction zones was the best explanation for extensional tectonics. Indentation theory was an alternate hypothesis to explain extension in the collided plate. In recent years several studies highlighted the col-lapse of former orogens to explain the extension. The Mediterranean Sea is an ideal place to study the formation of extensional basins that were fully developed in the Western Mediterranean basins (Balearic and Ligurian Seas) with early Miocene emplacement of oceanic crust. The North Tyrrhenian Basin is underlain by conti-nental basement and its evolution is very recent (late Miocene to Pliocene). Consequently in this region we can study the young extensional pro-cesses that are inactive in the others basins of th