Collision-related break-up of a carbonate platform (Eratosthenes Seamount) and mud volcanism on the Mediterranean Ridge: preliminary synthesis and implications of tectonic results of ODP Leg 160 in the Eastern Mediterranean Sea

This paper is included in the Special Publication entitled 'Geological evolution of ocean basins: results from the Ocean Drilling Program', edited by A. Cramp, C.J. MacLeod, S.V. Lee and E.J.W. Jones. Drilling of the Eratosthenes Seamount south of Cyprus documented incipient collision of the African and Eurasian plates. The oldest sediments recovered, mid?-Cretaceous shallow-water limestones, are overlain by Upper Cretaceous to Lower Oligocene pelagic carbonates, with several hiatuses. Following uplift, a carbonate platform was established in the Miocene; Eratosthenes was then below eustatic sea level during the Messinian desiccation crisis. The platform subsided to bathyal depths during the Lower Pliocene, associated with localized breccia deposition. Further subsidence occurred in Late Pliocene-early Quaternary, coeval with strong surface uplift of southern Cyprus. Subsidence and break-up of Eratosthenes was achieved by a combination of flexural loading and normal faulting. In addition, the Milano and Napoli mud volcanoes were drilled on the northern flank of the Mediterranean Ridge accretionary complex, south of Crete. A mainly extrusive, sedimentary origin is indicated. Multiple debris flows include clasts of sandstone and limestone of at least partly Miocene age. Both mud volcanoes are dated as >1 Ma old and have been active episodically. Hydrocarbon gas is associated with both mud volcanoes, while methane hydrates (clathrates) exist locally at Milano. The driving force of mud volcanism is overpressuring caused by incipient plate collision. Messinian evaporites may have acted as a localized seal. Material escaped through a zone of backthrusting against rigid Cretan crust to the north.