Spatial investigation of Ghezel Ozan basin alluvial terraces in relation to tectonics and climate changes

The study of the river basins’ terraces is one of the major issues related to river geomorphology. River basins are widely studied by geomorphologists as one of the alluvial and continental stratigraphic landforms to understand the tectonic time and climatic changes. Ghezel Ozan River has well responded to the climatic, lithological, and tectonic conditions as one of the longest river systems in Iran. To study the effects of the climate on alluvial terraces, present isothermal and isohyet maps are mapped using the topographic and geological maps of the area with the help of computer software such as ArcGIS, global mapper, and Excel, and climatic data. From the remaining evidence of quaternary glacial cirques in Zanjan topographic maps, Qaranghochai and Kordestan, the permanent snowline has been reconstructed using Porter’s Cirque - Floor Method with the help of thermal and humidity anomaly. The study of alluvial terraces above and below the Quaternary snowline altitude using field evidence suggests that the effect of the glacier on the formation of the terraces depends on the elevation of the basin. The estimated height using Porter's Cirque - Floor Method in Ghezel Ozan basin suggests that about 7.5% of the basin has been influenced by the glacial process during the cold quaternary periods. The elevation of the water and ice equilibrium line indicates that 65 percent of the basin has been affected by the adjacent glacier process and could have been affected by tongues secreted from glacial cirques, but field evidence suggests that only glaciers fed from high mountains have contributed to the formation of U-shaped valleys and alluvial terraces. The adaptation of the canals and glaciers tongues to the faults of the region has created water- glacial- tectonic valleys in Zanjanrood sub-basins. Although the depth of these valleys is less than the valleys in the Ghezel Ozan headwaters, their elevation difference compared to the plains of the region is such that they are symbolic of disturbances in the plains of the region.