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Sandclass
classification scheme for Ajali sandstone units in Ohafia
area, Southeastern Nigeria
K. K. Ibe and C. C. Z. Akaolisa
Department of Geosciences, Federal University of Technology,
Owerri, Imo State, Nigeria.
*Corresponding author. E-mail:
casakaolisa@yahoo.com.
Accepted 22 December, 2009 |
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Twenty six (26) sandstone samples from the Ajali
Formation in Ohafia area of southeastern Nigeria and two
samples from the Gombe Formation in the Upper Benue valley,
northeastern Nigeria, have been analysed for major elements
and the results used in sandclass classification scheme. In
the scheme, Log ratios of SiO2 /Al2O3
and Fe2O3/K2O, which
express and relate geochemical fractions of sands to the
existing sandstone classification scheme have been used to
re-classify the Ajali sandstone units from Ohafia area.
Results of this method show that the Ajali sandstone in the
area can be classified as Fe-rich quartz arenitic sandstone
when taken as one unit. However, field and geochemical data
indicate two major sandstone units grouped as quartz arenite
and ironstone. About 50% of the samples from the area plot
in the Fe-rich class, 41% in the quartz arenite class and 9%
in the sub-arkosic class. In comparison with two samples
from a similar Maastrichtian Formation, one of the samples
in the sub-arkosic class belongs to the upper Benue valley
Maastrichtian Gombe sandstone. These results indicate that
the Ajali sandstone Formation in the area is made up of two
units. The lower unit is composed of an Fe-poor variety,
while the upper unit is Fe-rich.
Key words:
Geochemical, petrographic, sandclass, classification scheme,
Ajali sandstone. |
