Abstract: Thirty - six sediment samples were gathered from two off - shore drills in the Golden Horn between Eminönü and Karaköyowing to the construction of a bridge 55 genera and 88 species belonging to 31 families were discriminated and named. Each sediment sample was environmentally interpreted according to dominant species, and the geological evolution of the area is explainedduring Holocene.Sediments of the Golden Horn, were divided in four main levels, according to environmental conditions, as of fluvial, marine,brackish water and again marine. The ages of these levels were found by dating of mollusc shells using t lie ESR (Electron Spin Resonance) technique.Evidence suggests the Golden Horn was a river 8.000 years ago, then it was invaded by the Mediterranean water about 7.400years ago. About 1.400 years later it become brackish due to regional regression. About 5.700 years ago, it gained the present condition.