Born in a maritime bay, meaning also the Delta and the Razim-Sinoe lacustrian territory following the deposits of mud brought in here by the Danube, or over deposited by the Black Sea's circular drafts, the Danube Delta is nowadays a bank, bordered by the sand banks arise from deposits of overlapped mud.
According to the studies made by Romanian and foreign scientists, the Danube Delta was formed in a golf of the Black Sea, beginning from the Upper Pleistocene. At this stage, an offshore bar appeared, the so called "initial bar", which is estimated to have been formed in its central part with approximately 11,000 years B.C. and to have continued its development until 7,500 B.C. The formation of this initial bar, which corresponds to the central axis of the alignment of Jibrieni, Letea, Caraorman and Crasnicol bank ridges, closed the golf, transforming it into a firth. The Danube Delta evolved in close connection with the three branches: Sfantu Gheorghe, Sulina and Chilia. These three arms are of different age, Sfantu Gheorghe in the South being the oldest, and Chilia, in the North the youngest.