SEDIMENTOLOGY AND GEOCHEMICAL EVALUATION OF MARL DEPOSITS ASSOCIATED WITH EZEAKU FORMATION IN AFIKPO AREA, SOUTHEASTERN NIGERIA

Abstract

The use of marl deposit as construction materials has recently attracted some attention, to both government and its citizens. Hence the evaluation of the sedimentological and geochemical assessment of the deposit in the Afikpo area was conducted to determine its suitability as aggregate. The Marl deposit belong to the Ezeaku Formation, this was confirmed from the field observations and description which shows that they are of dark grey to black shale, sandstone, subordinate limestone and siltstone deposited by shallow marine environment. Petrographic examination of the marl reveals the presence of allochem components, micrite and sparite corresponding to grain, matrix and cement respectively. Modal composition classify the rock as Carbonate Type II which consists of considerable proportion of allochems where current action was not enough to completely winnow away the microcrystalline ooze. Major oxide geochemistry of the rock samples showed a dominance of SiO2, CaO, Al2O3 and depletion in Na2O, K2O and Fe2O3. The high SiO2 content and inverse correlation with CaO describe the rock as impure limestone making the aggregate more chemically stable than pure limestone when used as components of building materials especially in subsurface constructions where materials may be exposed to water.