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

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 sample