Browsing by Author "Adepoju, S.A., Ojo, O.J., Akande, S.O. and Sreenivas, B."

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    Provenance of the Campanian-Maastrichtian Sandstone, Northern Bida Basin: Evidence from Facies Analysis, Detrital Zircon Morphology and Whole-Rock Geochemistry
    (2020) Adepoju, S.A., Ojo, O.J., Akande, S.O. and Sreenivas, B.
    The sediments in the northern Bida Basin, Nigeria were investigated on the basis of facies analysis, architectural elements, sandbody geometry and paleocurrents, whole-rock geochemical and zircon cathodoluminescent studies. The aim was to interprete the depositional environments and provenance as well as a platform for further reservoir characterization. Regional distribution, architecture and morphology of the sandstone were interpreted through the identification of ten distinctive sub-facies that were classified within four facies associations; intraformational conglomerate, braided fluvial channels, meandering channels and fluvial overbank/floodplain. Six identified architectural elements within the study area; channels (CH), gravelbars and bedforms (GB), lateral accretion (LA), laminated sand sheet (LS), sandy bedforms (SB) and overbank fines (OF) showed a river system settings ranging from floodplains to more high energy, braided fluvial systems of low sinuosity. Sheet and blanket Sandbody geometry that characterizes sandstone reservoir heterogeneity by their vertical and lateral connectivity of sand bodies are common in the central and northern part while wedge and lobate types are common in the southern and eastern parts. Paleocurrent data obtained indicate dominant influence of southwestern and minor southeastern paleocurrent transport directions across basin axis. Detrital zircon morphological studies reveal changes in the primary sources during depositional history; prismatic and lamellar detrital zircon types with a well-developed oscillatory zoning typical of magmatic crystallization were observed in Bida Formation whereas distinct populations of short and acicular types in Enagi Formation characterizes preservation of crustal rocks. The geochemical proxies; Al O /TiO , SiO /Al O , K O/Al O , 2 3 2 2 2 3 2 2 3 La/Th, La/Co, Th/Co, La/Sc, Cr/Th, Zr/Nb and Zr/Th with chondrite-normalized REE patterns, light REE enrichment, heavy REE flat pattern and negative Eu anomalies revealed sediments' derivation mainly from felsic source rocks. A higher Zr/Sc and Zr/Hf ratio with Th/Sc and Zr/Sc binary plot reflects considerable zircon enrichment in the source areas. Discrimination plots; log(K O/Na O) versus SiO , TiO versus (Fe O +MgO), Al O /SiO versus (Fe O +MgO) and 2 2 2 2 2 3 2 3 2 2 3 SiO /20-(K O+Na O)-(TiO +Fe O +MgO), La/Y versus Sc/Cr, La-Th-Sc, Th-Sc-Zr/10 indicate passive continental 2 2 2 2 2 3 margin paleotectonic settings. In conclusion, this integrated study revealed that fluvial sediment input in the northern Bida Basin Nigeria is sourced from Precambrian Basement Complex with possible mixing from two igneous source materials.