The late Messinian Lago-Mare episode in the Mediterranean Basin: Preliminary report on the occurrence of Paratethyan ostracod faunafrom central Crete (Greece)

Dans l’ıˆle de Cre`te, les facie`s du Lago Mare du Messinien supe´rieur ne sont pas bien connus. Actuellement, la pre´sence dans l’Iˆle de Cre`te des de´poˆ ts post-e´vaporitiques du Messinien supe´rieur est une question qui fait de´bat. Dans ce travail, on pre´sente les re´sultats pre´liminaires des analyses biostratigraphiques re´alise´es sur des e´chantillons pre´leve´s dans des affleurements de la Plaine de Messara`. Pre`s de Faneromeni et Ano Akria, la limite Mioce`ne/Plioce`ne est bien observable. Ici, les de´poˆ ts e´vaporitiques du Messinien sont caracte´rise´s par des argiles contenant du gypse, du gypse microcristallin lamine´ et des gypsorudites. Dans ces zones, on a trouve´ au-dessus des e´vaporites du Messinien des argiles polychromes finement lamine´es. Les argiles grises et les conglome´rats du Plioce`ne se trouvent discordants sur les de´poˆts post-e´vaporitiques du Messinien supe´rieur a` Faneromeni comme a` Ano Akria. Dans les deux coupes, l’e´chantillonnage a e´te´ re´alise´ tous les 20 cm (total de 100 e´chantillons). Les re´sultats des analyses micropale´ontologiques montrent la pre´sence des ostracodes suivants : Loxocauda limata (Schneider in Agalarova et al.), Loxocauda sp., Cytherura pyrama Schneider, Cyprideis anlavauxensis Carbonnel, Cyprideis agrigentina Decima, Amnicythere palimpsesta (Livental), Amnicythere propinqua (Livental), Amnicythere accicularia (Olteanu), Amnicythere costata (Olteanu), Amnicythere multituberculata (Livental), Amnicythere sp. D (Miculan in Bassetti et al.), Amnicythere sp. 2 Gliozzi and Grossi, Amnicythere sp., Euxinocythere (Maeotocythere) praebaquana (Livental in Agalarova et al.), Mediocytherideini indet., Pontoniella pontica (Agalarova), Camptocypria sp. 1 Gliozzi and Grossi, Caspiocypris sp., Zalanyiella venusta (Zalanyi), Tyrrhenocythere sp., Loxoconcha rhombovalis Pokorny, Loxoconcha eichwaldi Livental, Loxoconcha sp. A (Miculan in Bassetti et al.), Loxocorniculina djafarovi (Schneider in Suzin). On a trouve´ aussi dans les e´chantillons analyse´s des foraminife`res planctoniques remanie´s et des gyrogonites de Characeae bien conserve´s. Les associations d’ostracodes trouve´es dans la Plaine de Messara` appartiennent a` la Zone a` Loxocorniculina djafarovi (sensu Carbonnel, 1978), qui caracte´rise les de´poˆ ts du Messinien supe´rieur dans tout le bassin me´diterrane´en. A cette pe´riode, le facie`s bien connu du Lago Mare existait aussi dans l’Iˆle de Cre`te. La pre´sence des ostracodes parate´thysiens dans les de´poˆ ts post-e´vaporitiques du Messinien, a` Faneromeni et a` Ano Akria, sugge`re que des conditions de se´dimentation sous-aquatique en milieu saumaˆtre se sont de´veloppe´es en Cre`te pendant le Messinien supe´rieur.In the Crete Island, late Messinian Lago-Mare facies are not well known. At present, the occurrence in Crete of the uppermost Messinian post evaporitic deposits is a matter of debate. According to several authors, the well-known late Messinian Lago-Mare facies does not occur in Crete. In this paper the preliminary results obtained from the biostratigraphical analysis of some sections sampled in the Messara` Plain will be shown. Nearby Faneromeni and Ano Akria villages, the Miocene/Pliocene boundary is well exposed. There, gypsum-bearing clay, laminated microcrystalline gypsum and gypsum-rudites characterize the evaporitic deposits of the Messinian stage. In these areas, above the Messinian evaporite, post-evaporitic fine-laminated polychrome clays, with intercalations of sandstones and conglomerates, have been found. In both the Faneromeni and Ano Akria area, the Pliocene grey clays and conglomerates rest unconformably on the uppermost Messinian post-evaporitic deposits. A 20 cm-spaced sampling has been performed in both the sections, for more than 100 samples collected. The results of the micropaleontological analysis performed on the Faneromeni and Ano Akria sections point to the occurrence of ostracod assemblages containing: Loxocauda limata (Schneider in Agalarova et al.), Loxocauda sp., Cytherura pyrama Schneider, Cyprideis anlavauxensis Carbonnel, Cyprideis agrigentina Decima, Amnicythere palimpsesta (Livental), Amnicythere propinqua (Livental), Amnicythere accicularia (Olteanu), Amnicythere costata (Olteanu), Amnicythere multituberculata (Livental), Amnicythere sp. D (Miculan in Bassetti et al.), Amnicythere sp. 2 Gliozzi and Grossi, Amnicythere sp., Euxinocythere (Maeotocythere) praebaquana (Livental in Agalarova et al.), Mediocytherideini indet., Pontoniella pontica (Agalarova), Camptocypria sp. 1 Gliozzi and Grossi, Caspiocypris sp., Zalanyiella venusta (Zalanyi), Tyrrhenocythere sp., Loxoconcha rhombovalis Pokorny, Loxoconcha eichwaldi Livental, Loxoconcha sp. A (Miculan in Bassetti et al.), Loxocorniculina djafarovi (Schneider in Suzin). In the analysed samples, reworked planktonic foraminifers and well-preserved charophyte gyrogonites have been also found. The ostracod assemblages found in the Messara` Plain belong to the Loxocorniculina djafarovi Zone (sensu Carbonnel, 1978), which characterizes the uppermost Messinian deposits of the whole Mediterranean Basin. At that time, the well-known Lago-Mare biofacies was also widespread on the Crete Island. The presence of Paratethyan ostracods in the post-evaporitic Messinian deposits of both Faneromeni and Ano Akria sections suggests that in the Crete Island the latest Messinian sedimentation took place in brackish water palaeoenvironments