Palaeocurrent and facies analysis of Ajali Sandstone in Western Anambra basin, Nigeria

Outcrops of the Campanian - Maastrichtian Ajali Sandstone in Ayogwiri, Fugar and Orame in the Western Anambra Basin allow for the recognition of palaeocurrent fabric and facies characterization of the formation. Detailed outcrop logging was carried out and production of graphic logs was made for each outcrop location. The Ajali is extensively cross-stratified with different types of cross-bedding, such as the planar, trough, and herring-bone cross-beddings. Palaeocurrent directions of the cross-beds were taken using the compass-clinometer to elucidate the palaeocurrent direction of the environment of formation and rose diagrams were constructed for each bed. The Ajali Sandstone is made up of two basic facies. The basal facies, is made up of thinly laminated, heterolithic beds of the shoreface environment. The upper facies consists mainly of cross-bedded sandstones of a tidally influenced shallow marine environment. The major palaeocurrent direction of the Ajali Sandstone in the studied area was in the NE direction which infers the sediment provenance source to be the uplifted Abakiliki Anticlinorium. However, subordinate direction to the south occurs in Orame1.