The subsurface structure of Ar'ar-al-Bireet area, south Iraq, from geophysical analysis

الملخص EN

The area includes the locations of Ar'ar, Ma'ania and Al-Bireet in southwest Iraq.

The area is bounded by 30o 40' – 31o 40' northing and 41o 40' – 42o 50' easting.

The available gravity and aeromagnetic maps are analysed with the aim of producing a geological picture of the subsurface.

The gravity map is filtered to produce a smooth regional map that amplifies the broad anomalies over Ar'ar area and Ma'ania area.

The filter also gives a residual map that shows sharp local anomalies over Ar'ar area such as, Khaliga and Ashoria as well as a series of long anomalies trending N – S in the Bireet area.

Over Ar'ar area, both the magnetic and the regional gravity anomalies are interpreted together so as to have a better constrain on the solution.

The interpretation shows that the anomalies are related to a single source within the basement.

A sheet of possible basic igneous rock occurs mainly within the basement but its top penetrates the overlying sediments by about 0.5 Km.

Such model is seen to satisfy the gravity and magnetic observations at the surface.

The residual anomalies over Ar'ar area are explained by up warping of Lower Cretaceous rocks in addition to probable faulting on top of the upwarp.

The residual elongated undulations that trend N – S in Bireet area are explained by correlation with the seismic section in the southwest as due to parallel folds in the lower Cretaceous and older strata.

The difference in the trend of these residual anomalies in Bireet area from that of Ar'ar area is explained in that the latter folds are to some extent influenced by the deeper sources trends.