Geological and Erodibility Investigations of Rafin Gora area of Niger State, Northern Nigeria

Abstract

Geological, geotechnical and geochemical studies were carried out in Rafi Gora area to ascertain the erodibility of the soils. Medium and coarse-grained sandstone and clay stone were mapped with structures like joints, cross bedding (120/18E and azimuth of 190S), Herringbone, clay clasts, lamina and bioturbation. The sand content of the soils is between 59% and 90%, silt ranges from 18% to 1% and clay constitutes between 9.9% and 32%). Using USDA textural classification, the soils were classified into sand (S), Loamy Sand (LM), Sandy Clay (SC) and Sandy Loam. The soil has a mean pH value of 4.73, average Organic Matter (OM) content of 2.72 and the Coefficient of permeability (K) of 0.90 cm/sec. This k is classified to be within moderately rapid flow (FAO, 2010), an indication of base flows which could result in the collapse of river bank and consequently advance the growth of gullies. Erodibility index (EI) ranges between 0.01 and 0.16 with a significant positive relationship with silt content (0.96), clay content (0.30) and organic matter content (0.20) but significant negative relationship with sand content, pH and permeability. It was advised that excavation of vulnerable claystones by the locals for building construction be totally discouraged.