55 Geo-Eco-Marina 25/2019 1. INTRODUCTION The change of palaeoenvironment settings during a basin history is a common fact. In turn, the basin evolution is related to diferent tectonic forces that created, developed and fnally closed it (Allen & Allen, 2005). After its closure, as the tectonic forces disappeared, only the deformed basin fll and associated structures remains. Therefore, the basin fll analysis provides useful lithostratigraphic information, as the lithology can be deducted from wells and extrapolated on seismic data. The age of diferent lithological units, is commonly based on biostratigraphic elements and/or sequence stratigraphy models for basin wide age propagation, allowing a proper understanding of its kinematics from creation to closure. The macro- and micropalaeontologic contents usually refect the palaeoenvironment settings and any changes, such as salinity, temperature and nutrient input, afected the faunas and foras during geological time. The accurate identifcation of fossil assemblages are very useful in the age assignment and paleoenvironmental reconstruction. In a long run, deciphering the biostratigraphy is essential in elaborating the scenario of the basin evolution in diferent tectonic regimes. These principles may be successfully applied to any basin analysis as is the case for Istria Basin (IB), a sub-basin located in the Western Black Sea Basin (WBSB) (Fig. 1). The IB opened during the Early Cretaceous (Barremian- Albian), extended within the Late Cretaceous-Early Eocene interval and inverted during the Middle Eocene- Miocene (Fig. 2) (Görür, 1988, 1997; Nikishin et al., 2003, 2015; Hippolyte et al. 2010; Munteanu et al., 2011). Hence, the Eocene deposits of the IB recorded the transition from extension to compression of the WBSB and provide useful keys for deciphering the basin evolution, including palaeoenvironmental and palaeogeographic settings. The IB sedimentary flling comprises a Cretaceous-Cenozoic successions, mirroring a polyphase deposition and subsidence (Boote, 2017). Main geological events of this LITHO- AND BIOSTRATIGRAPHY OF THE EOCENE DEPOSITS FROM ISTRIA BASIN NORTHERN EDGE (WESTERN BLACK SEA) ELIZA M. ANTON 1,2 , IOAN MUNTEANU 3 , CORNELIU DINU 2 , MIHAELA C. MELINTE - DOBRINESCU 1 1 National Institute of Marine Geology and Geo-Ecology (GeoEcoMar), 23-25 Dimitrie Onciul St., 024053 Bucharest, Romania e-mail: antoneliza@geoecomar.ro 2 University of Bucharest, Faculty of Geology and Geophysics, Traian Vuia 6, Bucharest, Romania 3 Repsol S.A., UK Exploration team, Mendez Alvaro 44, Madrid, Spain Abstract. This study aims to bring new constraints on the Eocene stratigraphy of the northern edge of Istria Basin, located in Western Black Sea. For achieving our goal, we have studied several core reports containing the description of the lithology and microfossils assemblages (foraminifera, ostracods and calcareous nannofossils) from 3 wells drilled in the northern Istria Basin. Thus, we were able to identify lithological and biostratigraphic constraints, allowing to generate a coherent correlation scheme for the Eocene deposits, with precise age assignment and advanced models of the IB evolution during the Eocene. The lithology of the 3 wells, situated in the Sinoe, Lebăda West and Lebăda East areas, is mainly represented by calcareous sandstones and siliciclastic ones. The biostratigraphy indicates that the deposits of the Sinoe and Lebăda West wells are Middle Eocene in age (mostly the upper part), while in the Lebăda East well a late Early to Middle Eocene age was assigned. Key words: Western Black Sea Basin; Palaeogene; wells; calcareous nannofossils; foraminifera