DRAINAGE EVOLUTION ALONG THE NORTH ANATOLIAN FAULT ZONE, EASTERN MARMARA-TURKEY

Recent drainage of the eastern Marmara region is discharged to the Sea of Marmara and Black Sea. Physiographic prolongations in the region are E-W under the structural control of the North Anatolian Fault Zone (NAFZ). The NAF bifurcates in two strands in the eastern Marmara as the northern and southern strands characterized by trough morphology. Samanlý Mountain is an east-west, 165 km long isolated uplift between two strands. Average elevation of the massif is 800-1000 m. At the east, it is traversed by Geyve antecedant gorge drained by Sakarya River. NW-SE trending Orhangazi fault separates the massif as the Iznik and Armutlu blocks. Regional geologic and geomorphologic data indicate that whole of NW Anatolia including Sea of Marmara basin was a highland drained to Black Sea during the Late Pliocene period. The paleo-geomorphology of this period characterized by a denudational surface including mature valley forms filled with fluvial deposits. Late Pliocene paleo-morphology is distinctive on the Kocaeli Peninsula, situated in the northern block of the NAF between Central Marmara bend and Sakarya Basin. Average elevation of the surface is 200 m on the peninsula and slightly tilted toward north and paleo-valleys hanged along the northern margin of the Izmit Bay. On the other hand, the same surface on the Samanlý Mountain is observed between 500-1000 m. Late Pliocene valleys are hanged both strand of the NAF. Armutlu Block is tilted toward north. However, perturbated valley forms on the Iznik Block indicate a domal uplift at the central part of the massif. Geomorphologic and plaeo-drainage correlations between Kocaeli peninsula and Samanli Mountain revealed: (1) The NAF propagated into Marmara Region in latest Pliocene (2) Total displacement of the NAF is about 70+/-10 km based on Sakarya river’s offset. (3) In the Marmara region large scale vertical motion occurred along with strike slip motion of the NAF. Samanlý Mountain uplifted about 800 m relative to Kocaeli peninsula since latest Pliocene. Amount of relief inversion between summit flatness of Samanlý Mountain and bottom of Cinarcik basin in the Sea of Marmara is more than 2000 m in the Quaternary. (4) Tectonic relief inversion mainly occurred south of the northern strand NAF, however, slightly tilting developed on the north of the northen strand.