On the origin of the Bosphorus

Abstract

Abstract The Palaeozoic-Upper Cretaceous basement palaeomorphology of the Bosphorus (the Strait of Istanbul) bears the evidence of a valley of a palaeostream running to the Black Sea in the north, a palaeobasin deeper than —160 m opening to the Sea of Marmara in the south, and a barrier between these two features. This suggest that the northern part of the Bosphorus was formed mainly by fluvial activity, whereas the southern part developed as a basin by faulting. The recent sediment thickness exceeds 130 m in the basin, indicating that the southern part of the Bosphorus was once essentially depositional rather than an erosional. The present form of the Bosphorus was established in Holocene time by the connection of the basin in the south with the stream in the north. The barrier and the stream valley in the north have been deepened by erosion and faulting to form a strait connecting the Black Sea and the Mediterranean.