تحريات جيولوجية موقعية بين سدي الموصل وبادوش (شمال العراق) في ضوء مقاطع التصوير المقاومي
Abstract
The studied area is located between Mosul and Badoosh dams, 35 Km northwest of Mosul city, in north Iraq. The area is covered by rocks of the Fatha Formation, which are marl, gypsum and limestone, in addition to the Quaternary sediments (fluvial, alluvial and Tigris river terraces). The area is distinguished by the presence of two anticlines extending E – W, the first is Masarra anticline with western plunge located across Tigris River. The second one is Taira anticline, whose western plunge represents the eastern embankment of Mosul dam.For the detection and delineation of subsurface defects, seven sites were chosen in the studied area. Deep and shallow geophysical investigations using Electrical Resistivity Tomography (ERT) via Winner – Schlumberger system was conducted along 31 electrical profiles with lengths ranging between (290 – 3075) m and (4 – 13) levels. The continuous rolling-along technique was applied with new procedure in covering the triangular segments.The ERT results of "Wana" site display four suggested channels and a fault. The profile of Mosul dam, points out two contiguous channels, which are being the most significant defects that have caused the development of the sinkholes, which are grouted nowadays. In the other sites (Dawasa, Kirj, Mostah, Sheheya, Filfale), many features of karst caverns were identified, beside dissolution channels and faults within rocks of the Fatha Formation. Those defect zones may lead to serious problems and developments, which could not be controlled and consequently the remedy may be costly as it is the case in Mosul dam project. Those problems must be taken into consideration in Badoosh project dam, where the up-stream lake will cover the studied area; leading to the importance of the present site investigation. Moreover, the seven profiles of the ERT (100 m spacing) covering the studied sites, have shown weakness zones extending from the ground surface to a depth of 99 m (the Quaternary sediments and Fatha Formation). Six profiles, indicated the homogeneity of the deep horizontal stratified rocks within Euphrates – Jeribe Formation (Lower – Middle Miocene respectively), while the seventh profile (ERT19) of "Dawasa" site, displays deeper changes (Heterogeneity) below 134 m, within the rocks of the Euphrates – Jeribe Formation.
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