Abstract
Detailed sedimentology and petrographic studies of outcrop sections of the Eocene Ameki formation exposed in the Northern depobelts of the Niger Delta was done to, characterize the sediment facies, determine the depositional environment and also to development a depositional model for the study area. Three facies associations were have been identified in the study area based on lithology, primary sedimentary structures, fossil content, geometry, lateral and vertical succession of beds and the nature of bedding contacts,and they include; brackish swamp, braided fluvial channels and Tidal creek environments. Results from polished section study showed the percentage distribution of the maceral groups as Huminite = 58.25%, Liptinite = 34.35%, Inertinite = 7.5%. The lignites are mainly Duroclarite in nature, deposited in swamp vegetation with preserved cell structures in a slightly oxic to anoxic condition. Furthermore results from petrographic studies of representative sandstone samples showed that the predominant mineral is quartz with a greater number of them showing Monocrystalline features, while the feldspars are mostly of the plagioclase type. Ternary diagram plots for the sandstones suggest a subarkose to lithic subarkose, and Arkose to lithicarkose for the sandstones, a mixed provenance of plutonic, metamorphic and recycled sedimentary sources which are consistent with humid climatic conditions.   Â
Highlights
The Niger Delta occupies an area of about 75,000 km2
Facies code Shale facies (Sh) is used for shale facies, SS is for sandstone, Lg is for Lignite, Cs for Claystones while Slt is for Siltstone
The lithofacies identified in the study area were further grouped into facies associations in order to interpret the environments of deposition
Summary
The Niger Delta occupies an area of about 75,000 km. Geographically, the basin is situated at the Gulf of Guinea continental margin in equatorial West Africa. The frontiers of Niger Delta are defined by the Anambra basin to the north, the Cameroun volcanic line to the east, Dahomey basin lies westerly while Gulf of Guinea barricades its southern end. The outcrops occurs in a broad belt running in a southeast trend from NW of Onitsha, Awka and Orlu Divisions to Umuahia/Bende area in Southeastern Nigeria. This Formation consists of two lithological units; a lower part of fine to coarse grain sandstones interbedded with calcareous shales and thin shelly limestone and an upper part dominated by fine of fine, grey-green sandstone, siltstone, sandy fossiliferous clays, and sandstones. This paper seeks to develop a depositional model and characterize the sediment facies based on pertrographic analysis and observed sedimentological properties
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