Paleoclimate Reconstruction during Mamu Formation (Cretaceous) Based on Clay Mineral Distributions

Abstract

Paleoclimate was reconstructed by the clay mineral assemblages within the age of Cretaceous (Campanian-Maastrichtian) of the Mamu Formation. To compare with clay mineral assemblages in this formation, selected samples were collected from sections along the road cuts from the King Petrol Station up the Miliken Hills and at the left bank of River Ekulu near the bridge to Onyeama mine, around Iva Valley and along Enugu Port-Harcourt road in Enugu State. Collected samples were prepared using standard clay mineral methodology. Their identification was made on X-Ray diffractographs, Kaolinite covered a range of 22-45%, its variation style in this formation could be a marker of climate changes from wet to dry which is supported by the lithological changes. Illite percentage varies from 5-10 and increases from Enu.1.1-1.5 to Enu.2.1-2.5. This may be due to dominant dry climate. Montmorrilonite ranges from 7-10% and its presence is due to terrestrial depositional condition. It seems thus, the present results can be indicated a possible procedure for ancient climate changes evaluation.