PALEOGEOGRAPHIC AND TECTONIC POSITION OF THE CARBONIFEROUS ROCKS OF THE WESTERN PONTIDES (TURKEY) IN THE FRAME OF THE VARISCAN BELT

The Carboniferous rocks situated between Istanbul and Zonguldak coal b asin belong to a fragment of the Hercynian chain of problematic origin , known as the ''Palaeozoic of Istanbul''. The Carboniferous rocks of the ''Palaeozoic of Istanbul'' are part of a well-developed passive co ntinental margin which is totally exotic with respect to the surroundi ng units in Turkey, but shows many similarities with the Palaeozoic se quence of the Moesian Platform and the European coal basins. It is sug gested that the ''Palaeozoic of Istanbul'' was part of the East Europe an Platform and has drifted southwards during the opening of the weste rn Black Sea basin. The original position of this unit within the Herc ynian chain is tentatively shown in a global reconstruction during Car boniferous.