Identification of possible active tectonics at al-Ajeej valley drainage basin, nw Iraq, using GIS technique

Abstract EN

Al-Ajeej valley drainage basin is located in the northwestern part of Iraq.

Tectonically, it is in the Al-Jazira Subzone, within the Mesopotamian Foredeep of the Unstable Shelf of the Arabian Platform.

This basin is filled by the soft sediments of the Quaternary Period overlie the clastics of the Injana Formation of Late Miocene age.

The entire Al-Ajeej basin is comprised of three contiguous sub-basins namely; Al-Badee, Al-Khazrajia and Al-Hamal sub-basins which occupy 80% of the northern and southeastern parts of the basin.

The drainage network of the entire Al-Ajeej basin is delineated using the Digital Elevation Model (DEM) 30 m resolution of Iraq, to examine the influence of tectonic activity through an analysis of the geomorphic characteristics by the benefit of the hydrology tools in the geographic information system (GIS).

The analyzed indices are; the Asymmetry Factor (Af), Stream Length, Gradient Index (Sl), Hypsometric Integral (Hi), Basin Shape (Bs), Valley Floor Width to Valley Height ratio (Vf) and Mountain Front Sinuosity (Smf).

These six indices were classified and combined to yield the “Relative Active Tectonics” Index (Iat).

According to the (Iat) results, the entire Al-Ajeej basin and its three subbasins were classified as “High” to “Moderate” active tectonics.

These results are due the effects of the existence of Sinjar Anticline in the northern most part of the basin and the subsurface extensional structural features.

The tectonic activity of Al-Ajeej basin and its sub-basins are reduced to the class of "Moderate" active tectonics, because most of the basin area (about 90%) are filled by soft sediments of the Quaternary Period and the low-resistance clastics of the underlying Injana Formation, in addition to the plain topography and arid climate conditions, despite the effects of Sinjar structure and the subsurface structural features.