Cenozoic

Cretaceous

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Imo Formation

Imo Fm

Period:

Paleogene

Age Interval:

Paleocene – Lower Eocene

Province:
Niger Delta - Outcrop

Type Locality and Naming

The type unit is identified as a series of exposures along the Imo River near Okigwe – Umuahia road by (Reynment, 1965).

Synonym: Imo Shale Fm, Imo-Anambra Shales (Tattam, 1944), Imo Clay-Shales (Grove, 1951; Simpson, 1955; Reynment and Barber, 1956), Imo Clay-Shale Group (GSN older maps)

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

the Imo Formation consists of blue-grey shales with sand lenses, marls and fossiliferous limestones, sandstone members (Ebenebe, Umuna and Igbaku Sandstones). Its maximum thickness is given as 1,000m according to Reynment (1965) but Dessauvagie (1975) gave a total thickness of 490m for the type area.

Lithology Pattern:

Claystone

Relationships and Distribution

Lower contact

Nsukka Fm of the Anambra Basin from the Beinin Flank in the West and stretching eastwards (Nwajide, 2013).

Upper contact

The Ameki Fm in the Ameki Gr

Regional extent

Niger Delta outcrop

GeoJSON

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Fossils

Ichnofossils, vertebrates (Rhynoptera sp., Myliobatis sp), foraminifera, pelecypods, Gastropods (Haustator nigeriensis, Clinuropsis sp.), cephalopods, ostracods

Age

Paleocene and earliest Eocene. Assumed a short K/T hiatus as in Benue Trough deposits for the strat column.

Age Span:

Beginning stage:

Danian

Fraction up in beginning stage:

0.2

Beginning date (Ma):

65.16

Ending stage:

Ypresian

Fraction up in the ending stage:

1.0

Ending date (Ma):

48.07

Depositional setting

Neritic depositional setting (Arua, 1980)

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.