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Pyrex Journal of Geology and Mining Research (PJGMR)

November 2015 Vol. 1(1), pp. 007-017

Copyright © 2015 Pyrex Journals




Original Research Article


Lithofacies, Petrology and Depositional Environment of Limestone in Ohafia–Ozu Abam Area in Southeastern Nigeria


O.S. Okon1* and M.U. Uzoegbu2

1Department of Geology, Federal University, Oye-Ekiti, Ekiti State, Nigeria.
2Department of Geology, University of Port-Harcourt, Choba, Nigeria.

Corresponding Author E-mail: nekyx@yahoo.com

Accepted 12th November, 2015



Abstract


Lithofacies and petrological studies of the limestones in the Nsukka Formation were carried out so as to understand their diagenetic history and depositional environments. The Nsukka Formation in the study area consists of two facies associations; shale-limestone and cross bedded sandstone. The limestone-shale facies association consists of the following lithofacies; rippled clayey sandstone, carbonaceous shale, heterolithic sandstone-shale, laminated grey shale, fossiliferous limestone, fine grained sandstone, silty shale, medium grained sandstone and carbonaceous sandstone. The cross bedded sandstone facies association consists of only cross bedded sandstone, which is made up of fine to coarse grained sandstones. Petrological analysis of the limestones shows that the limestones consists of allochemical biosparites or bioclastic packstones and grainstones. The textural and mineralogical characteristics of the limestones show that the limestones have undergone some diagenetic processes such as cementation, neomorphism, micritization, compaction and dissolution. Dolomitization is almost absent in the limestones. The shale-limestone facies association is interpreted as sediments from a lagoon / swamp, mixed tidal flat and shoreface to shallow marine shelf environments. The crossbedded sandstone suggests deposition in a moderate to high energy, upper shoreface shallow marine environment.

Keywords: Lithofacies, Diagenesis, Afikpo sub-basin, micritization.

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