Geomorphological features of the Jurassic Granites in NE Nigeria (Southern Sahara)

ABSTRACT This study investigates the spectacular geomorphological features of Jurassic (Younger) Granites in NE Nigeria by using field observations and some structural (i.e. joints) analyses. The study area is in the Sahel region of the Subsaharan of Africa as a transition zone between the Sahara Desert and Equatorial region, where many studies have focused on the loess deposits, ergs, climate change, and Saharan Desert boundary changes. Morphological features of rocks in the study area have not been widely discussed in the literature. However, inselbergs, ruwares, and pillar structures are the major landforms in this vast plain with an arid environment. Boulders, blocks, mushrooms, and corestones, tafoni, shelter caves, flared slopes, polygonal cracks, and weathering pits are minor features. Weathering products consisting of white-colored, granular quartz-bearing grus and red clayey laterite surround the granite masses. Subsurface weathering has favored the formation of major geomorphological features; however, subsequent superficial weathering leading to hydration and stripping occurred mostly under the humid climatic conditions with seasonal variation of dry and humid climatic conditions. Local paleoenvironmental – paleoclimatic conditions would have prevented excess weathering and erosion in the study area.