Cenozoic

Cretaceous

Neoproterozoic

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Nanka Formation

Nanka Fm

Period:

Paleogene

Age Interval:

Eocene

Province:
Niger Delta - Outcrop

Type Locality and Naming

The Ameki Group was given early attention by the Geological Survey of Nigeria but then affirmed by Nwajide (1979, 1980) and eventually nominating three component members that are laterally equivalent. It is an upward succession of the Ameki Fm, the Nanka Fm, and the Nsugbe Fm. The Nanka Fm name is derived from the Nanka town, an extensive area of which has been so deeply gullied as to expose the bedrock which is elsewhere covered by thick lateritic soil development (Nwajide, 2013).

Synonym: Nanka Sandstone Fm

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

[Fig 1. Stratigraphic successions in the Benue Trough and the Nigerian sector of the Chad Basin]

Lithology and Thickness

Nanka Fm lithology is overwhelmingly loose, flaser-bedded, and fine to medium sand, with a few mudrock breaks (Nwajide, 2013). The thickness of the formation is estimated to be about 305m.

Lithology Pattern:

Fine-grained sandstone

Relationships and Distribution

Lower contact

Overlies the Ameki Fm

Upper contact

Overlain by the Nsugbe Fm

Regional extent

Niger Delta outcrop to Anambra Basin

GeoJSON

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Fossils

Whale remains (Pappocetus lugardi), Nautiloid (Deltoidnautilus nwajidei), gastropods (Siphonochelus nigeriensis, Turritella sp.)

Age

Paleogene. Underlying Ameki Fm is Lutetian – Early Bartonian (Whiteman, 1982); therefore Nanka Fm placed here for display purposes as Late Bartonian.

Age Span:

Beginning stage:

Bartonian

Fraction up in beginning stage:

0.5

Beginning date (Ma):

39.37

Ending stage:

Bartonian

Fraction up in the ending stage:

1.0

Ending date (Ma):

37.71

Depositional setting

The Nanka Fm has a Continental/coastal plain deposit to a shoreface setting (Nwajide, 2013)

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.