Subduction zones of the western Mediterranean.

Subduction zones of the western Mediterranean have been extensively studied during the last three decades, through their geologic, petrologic, geophysical, kinematic, and structural features. A synthesis of available data, along with their tectonic interpretation, has been published by FACCENNA et alii (2001). In this paper we propose a new model of subduction in the western Mediterranean since the early Cretaceous, based upon recently published plate tectonic reconstructions for the central Atlantic and the Mediterranean regions (SCHETTINO & TURCO, 2008). We present geologic and kinematic evidences that an early subduction zone formed during chron M10 (131.9 Ma, Hauterivian) along the eastern margin of Iberia, which predates by about 50 Myr the timing proposed by FACCENNA et alii (2001). This trench accommodated the subduction of Ligurian Tethys during the eastward escape of Iberia, which accompanied the formation of the Valais Ocean until the early Albian (110 Ma). Next, from ∼110 Ma to 83.5 Ma (early Campanian), the counterclockwise rotation of Iberia relative to Eurasia led to the opening of the Biscay Bay to the West and further compression in the Ligurian Basin. Moreover, a westward motion of Adria relative to Apulia and Africa contributed itself to the subduction of Ligurian Tethys lithosphere beneath Iberia until the Paleocene. The subsequent evolution of this Iberian subduction zone was mainly controlled by the opening of the Liguro- Provençal Basin and the rotation of Corsica and Sardinia during the Oligocene and early Miocene. Starting from chron M0r (early Aptian, 120.4 Ma), another important subduction zone established at the northern margin of Adria. This Alpine subduction zone extended progressively to the West, reaching the North Pyrenean Fault in the Gulf of Lion. Close to the northern tip of Corsica this trench formed a TTT triple junction with the Iberian subduction zone (Fig. 1). A third subduction zone established at the southern Eurasian margin during chron C34n (83.5 Ma, early Campanian). Apart from a Paleocene standstill, the eastern part of this trench accommodated subduction of Valais oceanic lithosphere beneath Eurasia until the early Oligocene. The relative timing for the onset of these subduction processes, the shape of the three oceanic basins, and the directions of convergence are the important factors which constrained the tectonic style of subduction and the geometry of the subducted slabs.