GROUND MAGNETIC SURVEY OF PLIOCENCE – PLEISTOCENCE SEDIMENTS IN BAHR AL-NAJAF DEPRESSION, CENTRAL IRAQ
ABSTRACT The present study aims to verify the aeromagnetic shallow source anomaly that appears at Bahr Al-Najaf depression and to determine its source. The studied area is completely covered by Quaternary sediments, which are, almost, composed of sandy sediments. A ground magnetic survey includes 557 magnetic measuring points, distributed mainly on five profiles ranging in their lengths from (0.7 – 16) Km, have been measured in the area. The comparison between aeromagnetic profile and geomagnetic profile has shown a coincidence between them in the regional field. On the other hand, local magnetic anomalies (LMA) have been well recognizable on geomagnetic profiles. The combination of the effect of these LMA seems as similar as that of the aeromagnetic anomaly. Accordingly, the residual aeromagnetic anomaly of Bahr Al-Najaf, which appears related to deep source, can be interpreted as due to accumulations of sediments containing few amounts of magnetic minerals. The source of the LMA has been defined by collecting samples from three separated sites. Results of XRD identifications and heavy minerals laboratory showed the presence of magnetite particles among the sandy sediments.