GRAVITY ANALYSIS OF THE OGADEN BASIN, ETHIOPIA

The Ogaden Basin of eastern Ethiopia is a major structural feature east of the East African Rift. The evolution of the rift is related to the breaking up of Gondwanaland. Jurassic rifting in northeast Kenya and southwest Somalia that separated Madagascar from Africa the southwestern portions of the Ogaden basin. Continued rifting in northeastern Somalia that separated India from Madagascar formed the northern Ogaden sub-basin. Additionally, rifting in the Neogene where the northern Somalia margin was separated from Arabia created additional structures and sediments within the northern Ogaden. While the Ogaden Basin has been studied by seismic reflection profiles and drill hole data, the proprietary nature of these data, has inhibited the determining the nature of the deeper structure of the basin. To aid in determining, the crustal structure of the Ogaden Basin, recent airborne gravity data will be used. These data which cover the entire basin with flight lines are spaced approximately 10 km. The data were terrain corrected and an isostatic residual gravity anomaly map was created to aid in crustal structure interpretation. These maps will be further analyzed using horizontal derivatives, power spectral analyzes and wavelength filtering. Preliminary interpretation of the isostatic residual gravity anomaly map indicates several distinct anomalies including gravity minima in the central and southern portions of the basins, and gravity maxima in the western and northern portions. The gravity minima are related to the deepest portions of the basins while the gravity maxima are related to edges of sub-grabens. Additional analysis will include the construction of two-dimensional gravity models across anomalies of interest.