MORPHOLOGY AND EVOLUTION OF INSELBERGS ON A PART OF THE BASEMENT COMPLEX OF WESTERN NIGERIA

Afolabi, M.R.* and Ogunkoya, O.O.

This study examined the morphological properties of ten selected inselbergs in Igbajo District of Central Western Nigeria in a bid to draw useful inferences on the long-term evolution of the landscape. Topographic and geologic sheets of the study area provided the basic information for the study. Additional data were acquired on the field using land surveying method (with Digital Global Positioning System and Total Station). The equipments facilitated the determination of the geographic coordinates of the landforms. The data were processed using ArcGIS 10.3. Triangular Irregular Network (TIN) in ArcGIS was used to generate the morphology of the landscape from the topographic data. Morphometric data pertaining to basal area and perimeter; relative relief and elevation (above the sea level); and slope length and maximum slope angle of the inselbergs were determined on the TIN generated. The morphometric data of the inselbergs showed 41.4% variation in basal area and 63.9% variation in perimeter. There were also 41.9% variation in slope length, and 47.4% in relative relief. There was however relative uniformity in the results for angle of maximum slope as well as the elevation of inselbergs above the sea level with the values of 17.1% and 13.1% as their variation indices respectively. The study showed that morphology of inselbergs studied was variable and concluded that the evolution of the inselberg landscape was via two stage process of deep weathering and stripping.

Key words: Etchplanation, Inselbergs, Landforms, Landscape evolution, Morphology.