The 7,700-km2-area Federal Capital Territory, Nigeria, is underlain by crystalline igneous and metamorphic rocks of Precambrian age. Sandstone and claystone of Cretaceous age overlie Precambrian rocks in the southwestern part of the Territory. Laterite caps many hills of Cretaceous rock, some hills of Precambrian rock, and crops out near stream banks in the east and northeast. The most conspicuous structural features are a broad “J”-shaped fold traversing the eastern and central part of the Territory and a north-trending shear zone along the eastern boundary. The soils of the Territory are lateritic and belong to the SW-SP-SM (Unified Soil Classification System) groups covering Precambrian migmatites gneisses and granites and the SC group covering Cretaceous sediments and Precambrian mica-rich schists. The average penetrometer shear strength of the soil is 3.11 bars. The engineering characteristics of the rocks are (1) medium- to high-strength massive and gneissic rock, (2) low-to medium-strength bedded rock, and (3) low-strength foliated and sheared rock. An area of at least 800 km2 is free from apparent geological hazards and should be suitable for construction of a capital city, its environs and supporting facilities.
