Reston, Timothy J., Fruehn, J. and von Huene, Roland and IMERSE Working Group (2002) The structure and evolution of the western Mediterranean Ridge. Marine Geology, 186 (1-2). pp. 83-110. DOI 10.1016/S0025-3227(02)00174-3.

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Abstract

The Mediterranean Ridge is a unique accretionary complex, consisting of five key elements: the frontal slope, the upper slope, the crest of the Ridge, the Cleft area, and the Inner Plateau. The IMERSE data show that these correspond roughly to the locus of frontal accretion, of underplating, of a pre-Messinian wedge, of complex faulting and possible strike-slip tectonics, and of a backstop of Hellenic nappes covered by a Messinian forearc basin. The frontal portion of the complex is a post-Messinian accretionary wedge (composed of Messinian evaporites and overlying tightly folded Plio–Quaternary sediments), underlain by pre-Messinian sequences attached to the African Plate. The basal detachment at the front of the wedge occurs at the base of the evaporites. Moving further to the northeast (the upper slope), the basal detachment cuts to deeper levels leading to the development of duplex structures where pre-Messinian units are subcreted beneath the Messinian evaporites. Just behind the subcreted units, the evaporites thin and may be absent on the crest of the Ridge. This region we interpret as the site of a pre-Messinian accretionary wedge: we suggest that following the deposition of thick evaporites in the Messinian, the pre-Messinian accretionary tectonics continued as subsurface accretion (subcretion) beneath the evaporites. Although the crest of the Ridge is largely devoid of evaporites, local deep evaporite basins observed here formed as local closed basins on top of the pre-Messinian wedge. We infer that the Messinian sealevel was at about the level of the Ridge crest, that is 3000 m below present. Allowing for isostatic adjustment to the removal of the water load, this would imply a sealevel drop of at least 2000 m. The Cleft basins mark the northeast limit of the accretionary complex. Thick evaporite deposits to the northeast (beneath the Inner Plateau) may have been deposited in a Messinian forearc basin. The evaporites of the Inner Plateau are underlain by a thin pre-Messinian sequence and by crystalline basement of the Hellenic nappes. This basement forms the backstop to the accretionary complex.

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