SERIES OF GEOMORPHOLOGICAL MAPS OF IRAQ,ERBIL&MAHABAD QUADRANGLES

Abstract

Detailed gravity and ground magnetic surveys have been executed in a mostly agricultural area, which covers (28×40) Km and lies between Al-Nasiriya and Wasit governorates, nearby Al-Gharraf River and to its west. The aim of this work is to follow-up a magnetic anomaly by high resolution gravity and ground magnetic surveys, which is almost related to supra basement magnetic body and this in turn might result anomalous structures within the deeper part of sedimentary column that could be of interest in hydrocarbons exploration. A net of polygons, includes 868 gravity and magnetic stations with spacing interval 0.5 Km, has been measured. The accuracy of gravity and magnetic measurements is ±0.033 mGal and ±0.9 nT, respectively. After applying the necessary corrections on the acquired data, Bouguer anomaly and total magnetic intensity (TMI) maps have been constructed. Filters for enhancing shallow and deep source anomalies and high gradient areas have been applied on Bouguer anomaly and TMI maps also. The Bouguer anomaly map showed two prominent regional zones: The first is a gravity low trending NNW–SSE and composed of two negative anomalies; a northern, which is circular in shape with amplitude of -2 mGal and has an extension towards SE, whereas the second anomaly partially appeared in the southeastern edge of the studied area. The negative zone is supposed to be related to the negative background that dominates the Arabian Plate. The second zone is a gravity high, which has a direction of ENE – WSW and it seems to be a part of a regional positive anomaly that extends eastwards; out of the studied area. On the other hand, NNW – SSE, NNE – SSW and E – W residual anomalies that could reflect antiforms and synforms or faults have been assigned on the map, too. The TMI map showed a magnetic high, which has the same direction, extension, length and location of the gravity high. The magnetic high is, essentially, related to basement intrusion, and it could be contributed as a causative source for the gravity high. However, local magnetic anomalies (LMA), which are related to Quaternary gray sand sediments, can easily be recognized throughout the area. The LMA were effective to disturb the earth magnetic field. Upward continuation filter has been applied to remove the effect of these anomalies. In addition, the upward continuation map shows two impressive residual negative anomalies, which are probably related to two faults, bound the magnetic high. Recommendations for using the available seismic reflection information, as a support data to integrate interpretations, and adopting quantitative interpretations by using the well known Geosoft programs, have been submitted for future studies, too.