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Home  >  Volume 25 (2013)

Distinction between Lithogenic and Anthropogenic Sources of Magnetic Susceptibility Enhancement in Urban Soil Profiles from Jalingo, Taraba State, N-E Nigeria by Kanu M. O., Meludu O. C., Oniku S. A. and Abong A. A. Vol. 25 ( Nov. 2013). pp 191-202
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Magnetic properties of soils reflect different effects of soil mineralogy. The minerals present in soils due to either natural (lithogenic or pedogenic) or anthropogenic (human activities) origin. The distinction between natural and anthropogenic magnetic signal is crucial for interpretation of the source of magnetic signature. In order to discriminate between both sources, magnetic measurements, basically low field mass specific magnetic susceptibility and its frequency dependence have been performed on samples from seven vertical soil profiles (labeled AWQ1, AWQ2, ABF1, STI, MYG, SGR and MGM) within the same geological setting. Results showed that all the samples in all the profiles had moderate to high magnetic susceptibility values indicating magnetic enhancement in the study area. Varying sources of magnetic enhancement was observed with profiles AWQ2, STI and MGM showing lithogenic magnetic enhancement as the magnetic susceptibility values increased with depth. Profiles ABF1 and SGR showed anthropogenic magnetic enhancement with high magnetic susceptibility values on the surface which decreased with depth, profile AWQ1 displayed varying magnetic susceptibility values with depth while, MYG profile indicated a combination of lithogenic and anthropogenic magnetic enhancement. The results of frequency dependence of susceptibility measurement indicated that most of the samples contained a mixture of ultrafine superparamagnetic grains and coarse multidomain magnetic grains as their values varied between 2 and 10%. Profiles AWQ1, AWQ2 and ABF1 are dominated by the presence of ultrafine superparamagnetic grains while only a few samples had completely multidomain characteristics.