Cenozoic

Cretaceous

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Nkporo Shale Formation

Nkporo Shale Fm

Period:

Cretaceous

Age Interval:

Campanian – Maastrichtian

Province:
Anambra Basin

Type Locality and Naming

The Nkporo Gr includes an upward succession of the Nkporo Shales Fm (or equivalent), Owelli Sandstone Fm and Enugu Fm (or equivalent). Type section is located near Nkporo Village in Abia State.

Synonym: Upper Grits and Sandstones (Falconer, 1911)

References: Reyment, 1965; Adeleye, 1975; Dessauvagie, 1975; Kogbe, 1976; Petters, 1978; Offodile, 1980; Whiteman, 1982; Benkhelil,1989; Okosun, 1992; Guiraud, 1993; Akande et al., 1998; Zaborski et al., 1998; Jauro et al., 2007; Obaje, 2009; Nwajide, 2013

Lithology and Thickness

Nkporo Shale Fm: Consists chiefly of blue or dark grey shales with occasional thin beds of sandy shale and sandstone. Reyment (1965) gave a thickness of 3280ft to the Nkporo Shale but varies with location (Whiteman, 1982). The formation consists of dark grey to black, fissile, friable and soft shales and mudstones with occasional thin beds of sandy shale, fine sandstone and marl with coatings of sulphur. The Leru Section of the Nkporo Shale has dolerite boulders occupying the first 2m of the section at the base and said to be of hypabyssal bodies emplacement mode.

Lithology Pattern:

Sandy claystone

Relationships and Distribution

Lower contact

Thinly overlies the Awgu Fm in the Southeast and rests directly on the Basement Complex to the North and Northwest.

Upper contact

Locally overlain by the Owelli Sandstone Fm

Regional extent

Anambra Basin

GeoJSON

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Fossils

The Nkporo shale contain the following; Ammonites (Lybicocerasafikpoense, Innoceramussp., Sphenodiscus, Bostrychoceras, Pachydiscus, Cirroceras), Foraminifera (Afrobolivina, Gabonella, Bolivinaexplicata, Bulimina fang, B.prolixa), Skolithos, Thalassinoides, Ophiomorpha, Palynomorphs.

Age

Early Cretaceous

Age Span:

Beginning stage:

Campanian

Fraction up in beginning stage:

0.3

Beginning date (Ma):

80.21

Ending stage:

Campanian

Fraction up in the ending stage:

0.5

Ending date (Ma):

77.91

Depositional setting

Marine environment characterized by a brackish lagoonal and lower delta plain setting (Nuhu, 1992; Petters, 1995). Campanian transgression to Maastrichtian withdrawal (regression)

Depositional pattern:

Additional Information

Compiler:

Enam O. Obiosio, Solomon Joshua Avong and Henry Nasir Suleiman (2024)- Stratigraphic Lexicon compiled from the following books:

Nigeria: Its Petroleum Geology, Resources and Potential, by Arthur Whiteman, 1982; (Volume 1) Published by Graham and Trotman Ltd.

A review of the Cretaceous System in Nigeria by P. M. Zaborski (1998) In Africa Geoscience Review, Vol.5, No.4, pp385-483.

Geology and Mineral Resources of Nigeria by Nuhu George Obaje, Published by Springer-Verlag Berlin Heidelberg 2009; http://www.springer.com/series/772.

Geology of Nigeria Sedimentary Basins, Nwajide C. S., 2013; Published by CSS Bookshops Limited, Lagos Nigeria.