Textural and Depositional Environment Analyses of Maastrichtian Ajali Sandstone Outcrops at Igbere-Abiriba Area Afikpo Basin South Eastern Nigeria

Abstract

The study presents the Textural characteristics of the Ajali sandstone at Igbere-Abiriba area in Afikpo basin, southeastern Nigeria. The intent is to highlight possible constraints of the environment of deposition of the source material on one hand and to infer the provenance on the other hand. The investigation approach includes field studies involving grain size analysis. Field studies shows that the Ajali Sandstone is friable at all location and range in colour from white in freshly cut stone, to reddish brown on weathering. In addition, the Ajali Sandstone units are cross-bedded and show graded bedding, exemplified by fining upward sequence. Textural examination indicates that the sandstone ranges from fine to medium grain and few coarse grain sizes constituting about 76-99% sand fraction, with graphic mean grain size of 0.93-2.60. Standard deviation (sorting) ranges from 0.71-1.48 and implies poor – moderately sorted sediments, also symmetrical, mesokurtic to leptokurtic were observed in skewness and kurtosis. Bivariate plot from the grain size parameter combination gives a more satisfactory approach toward predicting the sedimentary environment. General studies inferred from the Textural index, the depo-environmental description of the Ajali Sandstone revealed a Fluvial-river system-dominated sedimentary process.