Morphometric and Sedimentological Features of Terrace Systems in the Middle Sakarya Valley (Inhisar-Gemicikoy, Bilecik)

Abstract

Sakarya River, which is the largest river in northwest Anatolia, drains waters from a large area known as the Middle Sakarya Plateau. The most striking geomorphological features of the Sakarya River, and its tributaries in this area, are the joining gorges which connect the basins and terrace systems together. This study aims to reveal the morphometric and sedimentological features of the terrace systems in the area between the Sakarya River, the Inhisar, and the Gemicikoy settlements. The Sakarya River, which has settled in the region from the Upper Pliocene, has formed terrace systems that can be monitored in several steps throughout the valley. They are monitored under the control of the climatic changes during the Quaternary, the sea level changes in the Black Sea, and the cyclical regional/local tectonic movements. Multiple terraces determined in this study area including the following. Starting from the valley floor of the Sakarya River, two terraces (+19 m and +11 m height) are determined around Gemicikoy, three terraces (+36 m, +24 m and +12 m height) are determined around Hamitabat village, and four terraces (+52 m, +34 m, +18 m and +10 m height) are determined in Yakacik village. These terrace formations, which are distributed irregularly along the valley of the Sakarya River, are mostly semi-rounded from large gravel at the high elevations, and at the lower elevations, terrace formations are made of small gravel and floodplain sediments.