Tectonic Study of Al-Thirthar, Al-Habbaniya, and Al-Razzazah Depressions, West of Tigris River, Iraq

Abstract

The neotectonics studied by using remote sensing data that showed some tectonic activities. They are represented by two features of extension, the first feature is the development of the four depressions and the second is the deflection of the axes of each Al-Thirthar and Al-Razzazah depressions. The axis deflects from north-south to the N35°W-S35°E and N45°W-S45°E respectively due to sinistral strike slip movement of the transversal faults during Early Quaternary. The extensional structures beneath the depression are grabens, horsts and normal faults. They are called The Lake Faults. They extend north-south and arcuated eastward. The Lake Faults control the development and location of the depressions. The four depressions represent one geological feature. It extends from Abu-Jir Fault System south of Dibddiba Depression in the south to the Al-Thirthar valley in the north. The uplifting in area between Al-Habbaniya and Al-Razzazah Depressions with no reactivation of the normal faults beneath Al-Habbaniya depression prevented the four depressions to become one depression. The reactivated faults play an important role in the development of the depressions due to the thinning of the sequence and raising the hydrogen sulfatebearing groundwater from deep formations to the upper ones through the soluble rocks, gypsum and limestone. These processes made collapses in the area of depression supported by the last stage of extension and the horizontal movement of the groundwater. Dibddiba Depression is filled by sediments of Dibddiba Formation (Pliocene- Pleistocene), and the deflection of the axis of Al-Thirthar and Al-Razzazah Depressions in Early Quaternary reflects that the age of the four depressions is the same age (Pliocene-Pleistocene).