Late Miocene ostracod assemblages from eastern Mediterranean coral-reef complexes (central Crete, Greece)

Dans ce travail, les ostracodes trouv´es dans dix complexes coralliens du Mioc`ene sup´erieur construits par Siderastrea, Tarbellastrea et Porites, localis´es dans la plaine de Messara (zone m´eridionale du bassin de l’Iraklion, Cr`ete centrale) sont ´etudi´es et illustr´es. Cinq diff´erentes associations caract´eristiques des divers environnements marins ont ´et´e reconnues par : (1) association des couches silteuses basales, caract´eris´ee par des esp`eces typiques des eaux marines du domaine infralittoral sup´erieur, parmi lesquelles Cyamocytheridea meniscus, Cyamocytheridea obstipa, Cyamocytheridea dertonensis, Cytheretta semiornata et Nonurocythereis seminulum sont tr`es repr´esent´ees ; (2) association des couches r´ecifales avec Grinioneis haidingeri, Aurila cicatricosa, Cimbaurila diecii, Tenedocythere cruciata, Pokornyella italica et Callistocythere quadrangula dominants qui indiquent un environnement marin infralittoral sup´erieur stable, caract´eris´e par des eaux chaudes et bien oxyg´en´ees ; (3) association des couches silteuses interpos´ees entre les complexes coralliens, parmi lesquelles Neomonoceratina laskarevi, Cytheridea acuminata, Phlyctenophora farkasi, Aurila albicans Callistocythere spp., Xestoleberis communis et X. dispar sont dominants. Ces esp`eces indiquent des eaux peu profondes avec v´eg´etation aquatique ; (4) association des couches silteuses sup´erieures, domin´ee par la pr´esence du genre Xestoleberis, caract´eristique des environnements marins moins profonds et tr`es riches en flore aquatique et (5) association des couches argilosilteuses terminales, domin´ee par Hemicytherura defiorei,

Ostracods from ten Late Miocene coral reef complexes built by Siderastrea, Tarbellastrea and Porites, cropping out in the Messara Plain (southern Iraklion basin, central Crete), have been investigated and five assemblages have been recognised, which point to different marine environments: (1) assemblage from the basal sandy silts, dominated by very shallow inner-infralittoral species, such as Cyamocytheridea meniscus, Cyamocytheridea obstipa, Cyamocytheridea dertonensis, Cytheretta semiornata and Nonurocythereis seminulum; (2) assemblage from the coral reef complexes within which Grinioneis haidingeri, Aurila cicatricosa, Cimbaurila diecii, Tenedocythere cruciata, Pokornyella italica and Callistocythere quadrangula are dominant and point to a stable inner-infralittoral environment characterised by warm, quiet and well-oxygenated waters; (3) assemblage from the silts intercalated among the coral reef complexes, mainly characterised by Neomonoceratina laskarevi, Cytheridea acuminata, Phlyctenophora farkasi and Aurila albicans together with Callistocythere spp., Xestoleberis communis and Xestoleberis dispar, which points to a very shallow marine environment rich in aquatic vegetation; (4) assemblage from the upper silts, which records the absolute dominance of Xestoleberis species, reflecting a very shallow and highly-vegetated environment and (5) assemblage from the uppermost silty clays, dominated by Hemicytherura defiorei, Xestoleberis spp. and Palmoconcha dertobrevis, accompanied by Acanthocythereis hystrix, Cytherella scutulum, Bairdoppilata conformis, Semicytherura spp., Krithe sp., Cytheropteron alatum, Bythocypris sp. and Pseudocythere caudata, which suggest deeper marine environments probably located in the outer infralittoral/inner-circalittoral zones. The studied section has been dated by means of calcareous nannoplankton to be not younger than Zone MNN9 (Early Tortonian), which is the biostratigraphical datum recorded in the fine-grained deposits that overlie the coral reef complexes. An age not older than Tortonian can be inferred by the stratigraphical distribution of the recognized ostracods. Thus, the coral reef complexes have been tentatively referred to the Early Tortonian.