Structural Interpretation of the Basement beneath the Southern Desert of Iraq based on Aeromagnetic Data.

Abstract

The Southern Desert of Iraq is located on the stable part of the Arabian Platform. The area has a considerable thickness of Phanerozoic sediments overlying a basement. The basement has neither been seismically imaged nor drilled. Accordingly, magnetic method can help identify and map deep structure of the basement. The aeromagnetic data are used to determine the structure and approximate depth of the basement. We have used the combined results of the Tilt derivative and Phase Preserving Dynamic Range Compression (PPDRC) methods to qualitatively delineate the main basement structures and then used the Source Parameter Imaging (SPI), Tilt-depth and finite SPI (FSPI) methods to determine basement depths. The qualitative interpretation of the Tilt derivative and PPDRC methods identifies three N-S to NE-SW trending linear negative anomalies that could represent extensional grabens in the basement surface. These grabens divide the basement into three blocks, the NW block, central block, and SE block. The magnetic anomalies over the basement blocks suggest the NW and Central blocks are cut by a set of N-S to NNW-SSE and NE-SW faults. Depth estimation methods over the uplifted blocks have minimum depths of between 4 km to 5 km, while over the graben the depths range from 7 km to in excess of 12 km. The FSPI method, unlike the SPI and TD methods that use an infinite depth source body, gives depths generally deeper by up to 1.1 km if the assumed Curie point depth is at 21 km. A more realistic Curie point depth of 32 km is used in the final interpretation model. These inferred basement blocks, grabens and sub-basin structures agree in a general way with the regional structures associated with the Arabian Peninsula and could provide an important framework for developing future hydrocarbon exploration strategies of the Southern Desert.