Application of Radiometric Surveys to Delineate between Sedimentary Terrain and Basement Complex: A case study of Sagamu and Abeokuta, South Western Nigeria

Abstract

NaI (TI) detector crystal coupled to a Canberra series 10 plus multichannel analyser (MCA) was used to analyse the soil samples collected from Sagamu (Sedimentary terrain) and Abeokuta (Basement complex) in South Western Nigeria. The use of the soil samples is to determine the activity concentrations due to radium, thorium and potassium so as to delineate between the two terrains using radiometric survey. From the result of the activity concentrations of these radionuclide, the mean value of the activity concentrations of ⁴⁰k (72±48) in sedimentary terrain is higher than in ²²⁶Ra (35± 20) and ²³²Thorium (43 ±26) respectively. In the basement complex, the average value of the activity concentration of ⁴⁰k (80 ±46) was also higher in ²²⁶Ra (44±18) and ²³²Thorium (53 ± 25) respectively. The relatively high value recorded ⁴⁰k radionuclide may be attributed to the perceived variations in the environment resulting from past activities. The results shows that the activity concentration of the radionuclides is higher in basement complex than in sedimentary terrain thus, delineate between the two terrains since it is well know that in basement complex, granites contain high concentrations of uranium, thorium and potassium.

Keywords: key words: Activity concentrations, Basement complex, Radiometric survey, Sedimentary terrain, Soil samples