From foreland to forearc domains: New multichannel seismic reflection survey of the Mediterranean ridge accretionary complex (Eastern Mediterranean)

Abstract

The Mediterranean Ridge of the Eastern Mediterranean Sea is a huge accretionary wedge emplaced as a consequence of the Africa-Aegean plate convergence, that has a rate estimated at ~40 mm/yr. Processing of recent multichannel seismic data and integration with previous results (seismic profiling, swath bathymetry, sonar) have facilitated the study of the overall deformation pattern of the area which includes three distinct major structural domains facing various forelands: 1. (1) The outer domain is bounded southward by the present-day wedge toe and towards the north by topographic slope breaks and clear changes in deformational style. Beneath the Ionian and Levantine Mediterranean Ridge branches the base of Messinian evaporites seems to act as a major décollement level. 2. (2) The central, or crestal, domain, the shallowest one, shows evidence of mud diapiric and mud volcano activity and is overthrusting northward over the inner domain. Facing the Libyan margin, this area, which displays spectacular mud volcano fields, appears much wider and shallower. 3. (3) The less-deformed inner domain is bounded northward by the Hellenic trench system. Beneath its Ionian inner area, seismic velocities characteristic of continental crust have been recorded, while within its Levantine region, it is made of a series of disconnected and uplifted basement blocks (Strabo seamounts). Along the Matapan and Pliny trenches structures which could be caused by transpressive deformation are locally observed. We believe that both the north-south structural arrangement and the clear west—east lateral variations of the Mediterranean Ridge relate to its progressive collision against the Libyan margin promontory. This event, which may have initiated ~5–6 Myr ago, may have induced: (a) a differentiated paleogeography of Messinian evaporites (later available for tectonic accretion) leading to the further lateral structural variations of the outer domain; and (b) strain partitioning between the central Mediterranean Ridge and the Hellenic trench system.