MORPHOMETRY AND GENESIS OF THE MAIN TRANSVERSAL GORGES IN NORTH AND NORTHEAST IRAQ

Abstract

The north and northeastern parts of Iraq are mountainous region with very rugged topography that attains to about 3600 m (a.s.l.). Hundreds of streams, of different sizes and types, and few rivers dissect these areas, some of them form gorges along their courses, partly are of canyon type. The main lithology, in the area involved, is very hard carbonate rocks that form the carapace of the mountains (almost anticlines) with soft clastic rocks, filling the synclines in between, rarely clastic rocks occur as intercalations with the carbonates. Some of these streams and rivers dissect the anticlines, oriented almost perpendicularly to the trend of the anticlines that is NW – SE and E – W, forming gorges of different sizes with different characters and origins.This study is an attempt to reveal the morphometry and genesis of the main gorges in the northern and northeastern parts of Iraq. Twenty two gorges were selected; the selected gorges are the main ones that dissect the whole mountain or the whole anticline (a topographic barrier). Those which exist within part of a mountain and/ or an anticline are not included in this study.For each of the 22 gorges, the lithology, exposed formation(s) and genesis are given. Moreover, the morphometry of each gorge is given too. These include the longitude and latitude of the inlet and outlet; with their heights, beside the height difference between the highest and lowest points along the gorge, length, gradient and sinuosity of the streams along the gorges.To achieve this study, geological and topographical maps of different scales were used. Moreover, Landsat images were used to select the main gorges, beside other characters that were acquired from GIS applications and remote sensing techniques. The study revealed that the origin of the main gorges is mainly due to structural effect, one is due to karstification and others are due to blockage of the stream either; by mass movements or alluvial fans. They are of superimposed – posterior type.