The architecture and Neogene to Recent evolution of the W Calabrian continental margin: an upper plate perspective to the Ionian subduction system (Central Mediterranean)

Abstract

The W Calabria continental margin forms the transition between the Pliocene to Recent Marsili spreading centre and continental Calabria, all parts of the upper plate of the Ionian subduction zone. Integrating high-resolution and crustal seismic images constrained by gravity modeling we provide a detailed reconstruction of the architecture of the margin and develop a new scheme for its Miocene to Present evolution. This time span encompasses the continent-continent collision between Africa and Eurasia, subsequent orogenic collapse and rifting apart between the two continental masses and the Pliocene to Recent emplacement of oceanic crust in the Vavilov and Marsili basins. The crust of the margin thins from the Calabria coast (~25 km) to the Marsili continent-ocean transition (~12 km). On the whole, upper and lower crust thin proportionally with pure shear geometry. The continental margin is covered by an Oligocene (?) to Present sedimentary succession reaching a maximum thickness of ~ 6.0 km in the Paola Basin. During the Miocene the continental margin experienced regional shortening accommodated by a large number of mainly W-vergent thrusts possibly associated with the late stages of the Kabilo-Calabrian chain. Shortening continued through Pliocene to Recent, but was accommodated by a limited number of W-vergent thrust faults located in the western part of the margin and by a few tens of kms wide syncline located in the eastern part of the profile. The accommodation space created in the syncline core hosted a ~4.5 km thick, Plio-Quaternary sedimentary succession, the Paola Basin. No significant extensional fault is observed along the profile. Miocene to Recent subsidence was controlled by i) a short wave length component related to shortening and responsible for the formation of the Paola Basin syncline and, possibly, contributing to the uplift of onshore Calabria, and ii) a long wavelength component responsible for the regional subsidence and ocean-ward tilting of the Calabria margin. Short wavelength subsidence ended in the late Pliocene but long wavelength downward movements persisted and even accelerated during late Pliocene (?) to Quaternary times when the present day bathymetry was achieved. Both horizontal deformations and vertical movements are difficult to explain in the context of a normal back-arc basin without taking into consideration patterns of secondary mantle flow generated by the retreat of the subducting slab.