The predominantly siliclastic Eze-Aku Formation (Turonian) located in the southeastern Nigerian Basin contains scattered lenses and layers of bioclastic limestone which show three distinct facies: Facies 1 — Beds (0.2-1 m thick) of sparite-cemented grainstones grading laterally into cross-bedded medium sandstones, Facies 2 — Lenses (1–2 m thick, 0.1–2 km wide) of grainstones and wackestones within fine bioturbated silty sandstones. Facies 3 — Tabular units (1–2 m thick, 2–6 km wide) of wackestone within laminated black shale.Grainstones are interpreted as storm-lag deposits accumulated either at the margins of offshore bars (facies 1) or on the wide platform of bioturbated muddy sand located below the wave base (facies 2). Wackestones of facies 3 are believed to be deposited by high-density turbidity currents carrying shallow-water shells into the deeper basin. Wackestones of facies 2 are difficult to interpret but might have been deposited by smallscale storm-generated debris flows on a shallow platform.
Sedimentary Geology 10/1981; 30(1-30):133-147. DOI:10.1016/0037-0738(81)90016-6