Journal of Petroleum Geology, Vol.10,
No.3, pp. 283-294, 1987
©Copyright 2000 Scientific Press,
Ltd.
DEPOSITIONAL ENVIRONMENTS
AND DIAGENESIS OF ALBIAN CARBONATES ON THE CALABAR FLANK, SE
NIGERIA
T. J. A. Reijers* and S. W.
Petters+
* Shell Petroleum Development
Company of Nigeria Limited, EPDE/3, Port Harcourt, Nigeria.
Present address: KSEPL, Rijswijk, Netherlands.
+ Department of Geology,
University of Calabar, Calabar, Nigeria.
Abstract
Lithostratigraphic interpretations are here
presented of a carbonate body which rims the exposed basement on
the SE hinge zone of the Niger delta, and which thickens to over
450 m on a nearby subsurface basement horst. This faulted margin,
which is known as the Calabar Flank, was occupied by carbonate
platforms similar to those in the Gabon and Angola Basins, during
the pronounced South Atlantic Albian transgression.
Stromatolitic, oncolitic/pisolitic, oolitic and fossiliferous
coralline algal lithofacies are well displayed both in outcrop
and in the subsurface of the carbonate body (the Mfamosing
Limestone). These lithofacies suggest a facies progression from
tidal flats, through restricted marine bays and lagoons to a
possible reef front, with ooid bars and encrusting and ramose
coralline algae. In the subsurface, the Mfamosing Limestone,
which is gas-bearing and oil-impregnated, exhibits fair to good
porosities in which calcarenitic bars and chalkified lagoonal,
calcarenitic and extensively dolomitized limestones are the
potential reservoirs.
