Abstract-- The main physiographic features of the Eastern Mediterranean basin result a long evolution presently marked by the convergence of the African and Eurasian plates which tend to reduce and close the oceanic space. Since the Messinian salinity crisis, about 5 my BP, the eastern basin is separated from the Central Mediterranean domain by an orographic axis linking the Nile delta to the Cyprus island through a prominent submarine relief, the Eratosthenes seamount which reaches a water depth of -810 m and towers the surrounding basins of about 2000 m. The present configuration of the seafloor of this area is under a tight control of two major factors active during the Pliocene- Quaternary and even now. It is firstly, the influence of tectonics related to the convergence of the African/Eurasian blocks which generates important scarps on the Eratosthenes seamount. The second factor corresponds to the sedimentary transfer and accumulation through the Nile deep sea fan which spreads largely northward wrapping the Eratosthenes seamount. A major consequence of this important sedimentary accumulation is the remobilization of the Messinian evaporitic layer, buried under the Nile sediments, which tends to upraise as diapiric structures resulting in a rugged morphology of the seafloor. Index Terms-- EM12 echosounding, Eratosthenes, Levantine basin, seafloor morphology. I. INTRODUCTION he physiography of Eastern Mediterranean seafloor is complex being under various geodynamic regimes resulting mainly from the convergence of the African and Eurasian plates since -60 my. The bordering margins of this almost closed basin are of several types : passive to the East with the Levantine Margin, passive and fed by the Nile delta to the South, active and complex to the North with the Turkey margin and the convergent zone of the Cyprus arc (Fig. 1). After the great salinity crisis of the Mediterranean during the Messinian (-5.3 my), a thick Pliocene-Quaternary sedimentary cover, widely coming from the Nile river but also from the bordering relieves of the Levantine margins, was deposited above the evaporite layer. The slow closing of the Mediterranean due to the convergence has effects on the Manuscript received September 28, 2000. J. Benkhelil is with the Laboratoire de Sédimentologie Marine, Université de Perpignan, Av. de Villeneuve, 66860 Perpignan, France (telephone: (33)- 468662059, e-mail: jb@univ-perp.fr). L. Nguyen is with Laboratoire de Sédimentologie Marine, Université de Perpignan, Av. de Villeneuve, 66860 Perpignan, France (telephone: (33)- 468662049, e-mail: nguyen@univ-perp.fr). J. Mascle is with the Géoscience Azur, 06230Villefranche-sur-France (e- mail: mascle@vlfr.fr). seafloor through the deformation of the recent to present deposits. A second cause of the seafloor disturbances is the uprising of the Messinian salt through the Pliocene-Quaternary sediments resulting in a rough morphology especially on the Nile deep sea fan. Major fault Trancurrent fault Deformation front Extension Collision Anatolia/Eurasia pole of rotation STP : Sinai Triple Point KTP : Karlovia Triple Point 20¡ 25¡ 30¡ 35¡ 40¡ 45¡ 30¡ 35¡ 40¡ Arabic Plate Anatolian Plate African Plate Eurasian Plate Florence Ridge Herodote Abyssal plain Levantine basin North Anatolian Fault East Anatolian Fault KTP STP Zagros M e d ite r r a n e a n Eratosthenes seamount A natolia/E urope rigid rotatio n Hellenic Arc Cyprus Arc Sinai Israel Nil Egypt N ile D e e p S e a F a n ANA/EUR Fig. 1. Geodynamic sketch in the Eastern Mediterranean (Modified after [1], [2]) II. THE MAIN FEATURES OF THE GEODYNAMICS IN EASTERN MEDITERRANEAN The present configuration of the Levantine basin and the Eastern Mediterranean in general, results from a geodynamic history which have started during the Triassic with the breakup of the Pangea supercontinent formed during the Paleozoic orogeneses [3]. Because of the divergence between the African and Eurasian plates, an ocean was formed in-between, the Tethys ancestor of the Mediterranean. During the early Cretaceous, the margins of the African continent underwent a strong extension and due to this stretching a block was individualized forming a carbonate platform being the future Eratosthenes seamount. A kinematic inversion occurred at the end of the Cretaceous resulting in a convergent movement between the separated African and Eurasian continents. An a northward verging intra-oceanic subduction was responsible, during the Lower Cenozoic, of the formation of the Troodos ophiolitic complex, while eastward an incipient continent collision was operating along the margin of the Arabic plate. During the Cenozoic, there was an accentuation of the convergence with the emersion of the Troodos and the Effects of the Africa-Europe Collision on the Seafloor Morphology in Eastern Mediterranean after the Data of the PRISMED II Survey J. Benkhelil, L. Nguyen, and J. Mascle. T 29 0-7803-7117-8/01/$10.00 (C) 2001 IEEE