ON THE ORIGIN OF THE BOSPORUS

The Palaeozoic-Upper Cretaceous basement palaeomorphology of the Bosph orus (the Strait of Istanbul) bears the evidence of a valley of a pala eostream running to the Black Sea in the north, a palaeobasin deeper t han -160 m opening to the Sea of Marmara in the south, and a barrier b etween 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 e xceeds 130 m in the basin, indicating that the southern part of the Bo sphorus was once essentially depositional rather than an erosional. Th e present form of the Bosphorus was established in Holocene time by th e connection of the basin in the south with the stream in the north. T he barrier and the stream valley in the north have been deepened by er osion and faulting to form a strait connecting the Black Sea and the M editerranean. (C) 1997 Elsevier Science B.V.