IOSR Journal of Applied Geology and Geophysics (IOSR-JAGG) e-ISSN: 2321–0990, p-ISSN: 2321–0982.Volume 8, Issue 3 Ser. II (May – June 2020), PP 11-30 www.iosrjournals.org DOI: 10.9790/0990-0803021130 www.iosrjournals.org 11 | Page Facies analysis and depositional environment of conglomeritic deposits in the northeastern part of the Niger Delta Basin, Nigeria UDO, ITORO GABRIEL 1 , ETUKUDO, NSIKAN JACKSON 2 ,ABIA, UWEM BASSEY 3 ,IBANGA, IFIOK MFON 4 1 Department of Geology, Faculty of Physical Sciences, AkwaIbom State University, AkwaIbom State, Nigeria 2 Department of Geology, Faculty of Physical Sciences, AkwaIbom State University, AkwaIbom State, Nigeria 3 Department of Geology, Faculty of Physical Sciences, AkwaIbom State University, AkwaIbom State, Nigeria 4 Department of Geology, Faculty of Physical Sciences, AkwaIbom State University, AkwaIbom State, Nigeria Abstract: The Niger Delta Basin is an extensional rift basin located in the Niger Delta and the Gulf of Guinea on the passive continental margin near the western coast of Nigeria. Lithofacies analysis was carried out in order to ascertain the environment of deposition of the conglomeritic deposits. Ten lithofacies were delineated in the northeastern part of the Niger Delta Basin and grouped into three facies associations: facies association 1 comprising matrix-supported conglomerate (Cm), clast-supported conglomerate (Cc), massive sandstone (Sm), planar cross-stratified sandstone (Sc), trough cross-stratified sandstone (Tc) and horizontally stratified sandstone (Sp); facies association 2 comprising claystone (Ct) and variegated mudstone (M); facies association 3 comprising grey-green shale (Sh) and black shale (Sb). Facies association 1 was deposited in a braided fluvial channel because of the presence of unimodal paleocurrent pattern, organic matter, fining upward succession, subrounded to rounded and poorly sorted clasts ranging from granules to boulders. Facies association 2 represents braided fluvial floodplain deposit due to the presence of claystone and mudstone with organic matter. Facies association 3 is characterized by the following dinoflagellates cysts: Andalusiella sp., Paleocystodinium sp., Deflandra sp., Apectodiniumhomomorphum and pollen such as Spinizonocolpitesehinatus, Spinizonocolpitesbaculatus, Psilatricolporitescrassus, Proxapertitesoperculatus and Proxapertites cursus suggesting that it was deposited in estuarine environment. The occurrence of fluvial conglomerate on top of marginal marine grey green shale was triggered by a gradual progradation of a river over the shale as the sea level fell during the Eocene period. Keywords: Facies analysis, conglomerate, depositional environment, Niger Delta, progradation --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 01-06-2020 Date of Acceptance: 16-06-2020 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction The Niger Delta Basin is a progradational depositional complex within the Cenozoic era. It is located in the southern part of Nigeria and covers an area of about 75,000 square kilometers. It is among the World’s largest petroleum Provinces and has been rated as the sixth largest oil producer and twelfth giant hydrocarbon Province. The origin of the Niger Delta Basin is traced to the the separation of the Afro-Brazilian plate during Early Cretaceous. The Niger Delta is the failed arm of a Y-shaped triple junction that initiated the opening of the south Atlantic Ocean and is thus regarded as an aulacogen (Olade, 1975; Hoque and Nwajide, 1984). Conglomeritic deposits abound in the northeastern part of the Niger Delta Basin (figure 1, 2) where they are being quarried for construction purposes.In the past, inadequate access routes and poor exposure related to thick subequatorial vegetation prevented previous researchers from thorough and sustained investigation of the rocks. Consequently, little is known about the conglomeritic deposits. Recently, extensive road construction and quarring have provided excellent exposures of the deposits. Hence, the need for a thorough research works to be carried out in the area in order to characterize the deposits. The aim of this research work is to undertake a detailed lithofacies analysis of the conglomeritic deposits in order to reconstruct the depositional environment of the deposits.