Shallow structures at the outer Calabrian accretionary wedge (NW Ionian Sea): new insights from recently migrated reflection data

Abstract

Terra Nova, 00, 000–000, 2010 Abstract Post-stack time migration of a set of seismic reflection profiles reveals details of the stratigraphic–structural setting of the outermost Calabrian accretionary wedge, in the NW sector of the Ionian Sea, with particular emphasis on the Messinian stratigraphy and the deformation style of the thin frontal portion of this wedge. A structural style and seismic facies analysis, calibrated by refraction data, images a general bipartition of the Messinian evaporite deposits: the `lower subunit', consisting mainly of salt, appears to have undergone ductile-flow deformation, and the `upper subunit', consisting mainly of gypsum and marls, appears to be characterized by brittle deformation. Lateral variations in evaporite composition and/or thickness reflect a change in the deformation style of the accretionary wedge, with the development of double-verging imbricated thrust sheets of the whole Messinian sequence. Gravitational-slide tectonics of the unstable accretionary wedge, too steep to support a skinny evaporite-based top layer, characterize the outermost wedge, indicating here a near-surface `olistostrome' from the Late Messinian.