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The Formation of the Northern Tyrrhenian Basin in a Back-arc Rift Context: Interaction Among Faulting, Magmatism and Mantle Exhumation

César R. Ranero, Valenti Sallares, Ingo Grevemeyer, Manel Prada, Montserrat G. Vendrell, Stefan Moeller, and Nevio Zitellini

We present new data collected in the Tyrrhenian basin to study the processes that controlled the extension of the continental lithosphere related to the retreat of a Ionian slab across the mantle.

The basin is not currently actively extending, but its preserved crustal structure gives information of the temporal evolution of rifting processes. The structure displays two conjugate margins with asymmetric architecture that form a natural laboratory to study rifting processes. The basin opened from north to south with different extension factors. The northern region stopped opening after a relatively low extension factors, but towards the south extension increased up to full crustal separation that produced magmatism in one region and mantle exhumation in another region. Different transects across the basin permit to trade space –where transects map different extension factors- for time, so that different transects provide information of the evolution of extension up to break up.

We present data collected in two legs of a two-ship seismic experiment carried out in spring 2010. In the first leg, the Spanish R/V Sarmiento de Gamboa and the Italian R/V Urania collected five several-hundred-km-long E-W trending wide-angle seismic (WAS) profiles crossing the entire basin at different transects to image the conjugate margins. The marine profiles were extended with land stations that recorded the marine airgun shots. During a second leg the R/V Sarmiento de Gamboa collected 16 Multichannel Seismic Reflection (MCS) profiles. MCS profiles were acquired coincident with WAS profiles, and a number of additional MCS lines concentrated in the basin center where mantle exhumation has taken place.

Each transect crossing the basin provides the tectonic structure, the geometry of sedimentary deposits, and P-wave seismic velocity distribution. This information allows to interpret the mechanisms of deformation, infer the importance and potential role of magmatism in the rifting process, and estimate the region of mantle exhumation, currently inferred from one drill site. The analysis of the data provides insight in the process of formation of the asymmetric structure of conjugated margins.

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