THE DEPTH TO BASEMENT IN THE WESTERN DESERT OF IRAQ FROM A POWER SPECTRUM ANALYSIS OF GRAVITY AND MAGNETIC DATA

The depth to the basement of sedimentary basins is an important factor in the exploration of hydrocarbons and for tectonic analyses. The Western Desert of Iraq is a part of the northern Arabian Platform, where relatively thin Phanerozoic sediments cover the Precambrian continental basement complex which contains north- and northeast-trending fractures. The Arabian platform can be divided into two parts: 1) a stable part to the west (within which the Western Desert is located) and 2) an unstable one to north and east. The stratigraphy of the Iraqi Western Desert includes the oldest exposed rocks being Permian in age, belonging to the Ga`ara Formation, with the youngest formations being Pliocene to Pleistocene units, including the Zahra Formation. Since the Western Desert region has few seismic reflection surveys and wells to basement, an analysis of regional gravity and magnetic will provide useful constraints on the structural makeup of the basin. One useful technique is the power spectrum method where gravity and magnetic data can be used to estimate the depth to the Precambrian. The region was divided to fifty five one-half a degree windows to determine the two-dimensional power spectra and then the depths to density and magnetic susceptibility interfaces can be determined. The estimated depths to the basement ranged to from 4 to 11.5 km with the gravity depth estimates being shallower in several locations which may be caused by intrabasin density boundaries. The estimated depths show a series of north-trending basement highs probably caused by Paleozoic orogenic events.