Geology 499 POTENTIAL DATA INTERPRETATION AND 2¾D MODELLING AIMING TO DECIPHER AN ELEVATED STRUCTURE REVEALED BY 3D SEISMIC ON THE ROMANIAN OFFSHORE Dr. Radu G. Dimitriu 1 Prof. Dr. Corneliu Dinu 2 Dr. Ioan Munteanu 3 PhD student Irina M. Stanciu 1 1 National Institute of Marine Geology and Geoecology - GeoEcoMar, 23-25, Dimitrie Onciul St., Bucharest, Romania 2 University of Bucharest, Faculty of Geology and Geophysics, 6 Traian Vuia St., Bucharest, Romania 3 Repsol Exploration, 44 Mendez Alvaro St., Madrid, Spain ABSTRACT The 2¾D modelling of marine gravity and magnetic data was carried out on the Romanian offshore, along two lines which cross the elevated structure of interest. 3D seismic and well data are also integrated in models. Although the regional morphology of the marine magnetic field strongly sustains the existence of Hercynian intrusions in the deep of the study area, the amplitude and wave-length of magnetic anomaly mapped and subsequently modelled above the elevated tectonic block do not comply with the existence of any such magnetic source within it, but accept the deeper presence of magmatic rocks (depth over 10 km to the top of the intrusion), within the crystalline basement. The hypothetical existence of a interpreted reef structure build-up within the uplifted block was also modelled considering a maximum density contrast of -0.15 g/cc between the reef and the surrounding geological environment. The alternative model resulted is theoretically possible but its rightness should be strengthened by other complementary data prior to undertaking concrete actions aiming the structure’s check and validation. The most likely model of the studied structure, resulted from the gravity and magnetic data 2¾D modelling, accept that this positive feature of the sedimentary basement corresponds to a tilted tectonic block, around 5.5 km thick, bordered by faults, consisting of Palaeozoic sedimentary rocks of Măcin-type. Below it, the crystalline basement is situated at depths from over 10 km and hosts a complex of Hercynian age intrusions. Keywords: Black Sea, tectonics, gravity & magnetics, interpretation, modelling. INTRODUCTION A 3D seismic survey conducted in 2012 on the Romanian offshore, covering the surface of Muridava and East Cobălcescu blocks (Fig. 1), led to the identification of a promising elevated tectonic structure of the deep pre-Oligocene sedimentary basement, located on the northern margin of the initial Cretaceous rift of the Western Black Sea Basin. In order to enhance the knowledge of the regional and local deep geological structure, beyond the limits reached in depth by seismic and well driling and also to