Interpretation of Gravity and Magnetic Data in the Erbil Plain (Iraqi Kurdistan Region)

Abstract

Gravity and magnetic anomalies create because of the lateral change in density and susceptibility of rocks underneath a certain datum. Gravity data in the form of Bouguer anomaly map of Erbil plain is subjected to quantitative interpretation by means of 2-D modeling by the assistance of some magnetic data in the form of profiles. Magnetic anomalies were interpreted qualitatively because of lack of magnetic properties of rocks. Seven gravity profiles in different directions from the Bouguer map were chosen to construct geological models which satisfy the situation. The residual anomaly of each profile was obtained by hand smoothing technique. It is shown that the main gravity low is attributed to thick Neogene sediments which are thrown against the Paleogene sediments by two major NW-SE faults which give rise to a density contrast of 0.3 gm/cm 3 , while local anomalies were interpreted as reflections of local and shallow structures and depressions within the upper part of the Neogene sediments. The shallower anomalous bodies are less than two kilometers in depth while the main anomalous body of Erbil so-called trough reaches four kilometers in depth. Magnetic anomalies indicate both suprabasment and intrabasement anomalies. It is revealed that at least a part of the Pirmam anticline (NW of the Gomspan NE-SW trending fault) is underlain by basic igneous rocks in the basement.