Lithology and economic potential resource of Igumale-Nsukka area, SE Nigeria

Abstract

The Maastrichtian Mamu and Nsukka Formations in the Anambra Basin (SE Nigeria) consist of a cyclic succession of coals, carbonaceous shales, silty shales and siltstones interpreted as deltaic deposits. The studied area is located in the northern part of Nsukka within the Anambra Basin southeastern Nigeria. The aim of this investigation is to examine the litholologic and economic aspect of some rocks in this area. Four main stratigraphic units belonging to the Enugu Shale, the Lower and Upper Mamu Formation and the Ajali Sandstone were identified. The Enugu Shale is the oldest unit which forms the base of the sequence and could be subdivided into subunits; carbonaceous shale, grey shale and sandy shale. The carbonaceous shale consists of dark, soft bluish shales-thinly laminated. The grey comprises laminated shales alternating with sandstones and the sandy shale consists of alternating shale, fine sandstones and siltstones. The Mamu Formation succeeded the Enugu Shale and two members of this formation; Lower and Upper Mamu Formation are identified. The Lower Mamu Formation is made up of three subunits, carbonaceous shale, grey shale, and sandy shale. The Upper Mamu unit consists of friable fine white sandstones. The Ajali Sandstone overlain the Upper Mamu Formation and consists of whitish to pinkish red, poorly consolidated medium grained sandstones. It is well cross-bedded and contains plant impression, and burrow-fills as ichno-fossils. The sandstones are used in the manufacturing of glass while laterites are used for various construction purposes such as roads, buildings and bridges. The clays are for pottery, glazed tiles, in ceramics industry. The coal has a future prospect for industries, such as iron and steel industry as cooking coal, cement industries and raw materials for chemical industries and also use locally for cooking. The alternation of shales and sandstones in the Enugu Shales, Mamu Formation and Ajali Sandstones provide a good petroleum system.

Key Words: Lithofacies, sandstone, shale, mineralogy, depositional environment potential resource.