ALLUVIAL FANS OF THE HAB'BARIYAH DEPRESSION, IRAQI WESTERN DESERT

Abstract

The Hab'bariyah Depression is one of the largest depressions in the Iraqi Western Desert, its length in Iraq is 230 Km; extends southwards into Saudi Arabia, whereas its width ranges from (5.1 –16.5) Km, covering an area of about 2530 Km2. Its depth; on the surface ranges from (22 – 51) Km, along the eastern and western rims, respectively. The depression is filled by Quaternary sediments derived by tens of valleys that drain very large area in the Western Desert, east of longitude 40° E (east of Wadi Hauran), and some of them drain farther southern areas; in Saudi Arabia. Only two of the main valleys cross the depression, others drain in it.The Quaternary sediments that fill the Hab'bariyah Depression include gravels; called "Hab'bariyah Gravels" (Pleistocene), alluvial fan sediments (Pleistocene – Holocene) and depression fill sediments (Holocene). The development of alluvial fans needs a drop in gradient, beside many other factors. However, the drop in the gradient of the valleys and the present gradient of the depression is not sufficient to develop the studied alluvial fans. Therefore, the development of the alluvial fans had occurred in different conditions than those are present nowadays. The Hab'bariyah Depression was developed due to a structural reason accompanied by karstification. However, neotectonic activity also has contributed in the development of the depression, consequently contributed in the development of the alluvial fans, in the depression.