Determination of Variation in Current Energy and Sediment Dispersal Patterns Using Grain Size Statistical Parameters in Ajali Sandstone

Grain size statistical parameters derived from Ajali Sandstone outcropping in Ayogwiri, Fugar and Orame in the Western Anambra Basin were used to determine the variation in current energy and sediment dispersal pattern. The sandstone was logged in the three locations: Ayogwiri, Fugar and Orame, and samples collected for grain size analysis. Statiscal parameters such as the mean, sorting and skewness were derived to enable the study. The average mean value for Ayogwiri is 4.29 (coarse silt), Fugar has an average of 3.63 (very fine sand) and Orame with an average of 3.78 (very fine sand). The variation of the mean grain size shows a decline in grain size from Orame, through Fugar towards Ayogwiri, giving a NE – SW trend. The current energy was high enough to sort the sediments, despite the intermittent waning of the current. The sorting values range from moderately well sorted to moderately sorted with few samples that are poorly sorted and only one that is very poorly sorted.. The average sorting value at Ayogwiri is 0.94 (moderately sorted), Fugar is 0.98 (moderately sorted) and Orame is 0.91 (moderately sorted). Skewness reflects the sorting and energy of deposition. The skewness of the studied samples range from negatively skewed to very negatively skewed (indicating coarseness) with just one exception: that is, AY6 from the mud drape overlying the heterolithic Bed B in Ayogwiri, which is positively (fine) skewed. Grains in Orame are coarser, more negatively skewed than those in the other two locations, which implies decline in grain size from Orame through Fugar to Ayogwiri giving a NE – SW trend decline of grain size and invariably decline in depositional current energy in the same direction. The good sorting and coarseness of the Ajali Sandstone has highly favoured its exploitation in the construction and allied industries.