Journal of Earth Sciences and Geotechnical Engineering

The Regional Geology of Dokan Area, NE Iraq

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• Abstract

  The northern and northeastern part of Iraq, which includes the Iraqi Kurdistan Region, is characterized by mountainous area with very rugged relief. The difference in relief may reach up to 1000 m and locally more when the height reaches up to 3600 m (a.s.l.). The mountains usually represent anticlines, whereas the depressions are represented by synclines. The Lower Cretaceous rocks usually form the carapace of the mountains, whereas the soft clastics of Upper Cretaceous and Paleocene form the synclines. However, some exceptions occur when the area is affected structurally by main faults. The main trend of the anticlines in the study area is NW – SE, which are dissected by either NE – SW normal faults or by reverse and/ or thrust faults oriented in NW – SE trend; however, some exceptions occur too. The Dokan area is characterized by a large depression in which the Lesser Zab River was flowing; before construction of Dokan dam (1954 – 1959). The depression is a big one with surface area of about 260 Km2. The height at the surface of the reservoir when filled to normal operational level is 511 m (a.s.l.); however, the depression is surrounded; almost from all sides by high mountains that range from (800 – 1300) m (a.s.l.). he depression is believed to be structurally controlled, a normal fault with NE – SW trend had dissected the southwestern limb of Ranya anticline, the eastern block being the down thrown one that had formed the depression, besides the exposure of soft rocks of Sarmord, Chis Gara, Barsarin and Naokelekan formations that form the core of Ranya anticline. The regional geology of Dokan area including structure and tectonics, stratigraphy and geomorphology is discussed aiming to explain the development of the large and wide depression in a mountainous area.