SEDIMENTOLOGY AND STRATIGRAPHY OF THE CAMPANO – MAASTRICHTIAN SUCCESSION, NORTHEASTOF IDAH TOWN, NORTHERN ANAMBRA BASIN
SEDIMENTOLOGY AND STRATIGRAPHY OF THE CAMPANO – MAASTRICHTIAN SUCCESSION, NORTHEASTOF IDAH TOWN, NORTHERN ANAMBRA BASIN
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Date
2017-04
Authors
ADAMU, Lukman Musa
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Abstract
The Campano-Maastrichtian successions in the northern Anambra Basin comprises
theNkporoFormation, Mamu Formation and Ajali Sandstone.An extensive geological field
work was carried out, where lithostratigraphic sections were studied and described. Features
such as textures, physical and biogenic sedimentary structures (facies variations and
associations) were documented. Some selected representative samples of the sedimentary
depositional facies were also subjected to grain size analysis.The NkporoShale is made up
ofsandy shale, silty clay, grey mud, bioturbatedsiltstone which graded into Mamu Formation
which is made up ofcross-massive bedded sandstone with bioturbation structures, siltstone,
dark grey to light grey fissile shale, mudstone and milky white claystone which often
displays a fining upward trend. It passes upward into Ajali Sandstone which is made up of
fine to coarse-grained, cross-bedded sandstone and fissile shale with bioturbation
structures.The sandstone facies of the Mamu Formation is coarse to fine-grained, poorly to
moderately sorted, leptokurtic and negatively skewed possibly deposited from fluvial source.
The bioturbated lower sandstone beds contain burrows of Ophiomorphawhich belong to
skolithosichnofacies that typifies littoral environment while the Ajali Sandstone is pebbly
coarse to medium-grained, poorly to moderately sorted, predominantsmesokurtic
toplatykurtic orvery platykurtic and negative to near symmetrical.The linear discriminate
function scatter plots results reveal shallow marine deposits forthe sandstone facies of Mamu
Formation and AjaliSandstone.
The fissility of shale suggests that it was deposited in a low energy environment.
However, the textural studies of the Nkporo Formation and the siltstone facies of the Mamu
Formation suggests the sediments to be deposited in a low energy environment which
favoured deposition of fine to medium size sediments, that is, deltaplain to prodelta
environment. Field and textural studies of the sandstone facies of the Mamu Formation
suggest the sediments to be deposited in a relatively high energy environment with tidal
influence of transport and deposition with two main facies association, that is, subtidal and
intertidal.The cross-beddings, unimodal paleocurrent of Ajali Sandstones also indicates
fluvial or fluvial-dominated deltaic environment while the bimodal oblique paleocurrent
pattern obtained for Mamu Formation shows that the formation was deposited in
environment such as shoreline (beach) or fluvio-deltaic where tidal effect is
significant.Paleocurrent studies and textural characteristics indicate that the paleocurrent
direction is northeast while the provenance is southwest suggesting that the sediments were
mainly sourced from the Santonian Okigwe-AbakalikiAnticlinorium and partly from the
nearby Oban Massif for the Ajali Sandstone in the study area while the sediments of the
sandstone facies of Mamu Formation were sourced from more than one source.The results
obtained from the textural, structure and statistical analyses revealed that the sediments in the study area were deposited in fluvial, deltafront through deltaplain to prodeltain shallow
marine environment.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE
STUDIES, AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF
MASTER OF SCIENCE DEGREE IN GEOLOGY
DEPARTMENT OF GEOLOGY
FACULTY OF PHYSICAL SCIENCE
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
SEDIMENTOLOGY,, STRATIGRAPHY,, CAMPANO MAASTRICHTIAN SUCCESSION,, NORTHEAST,, IDAH TOWN,, NORTHERN ANAMBRA BASIN