GRANOMETRIC AND MORPHOMETRY ANALYSIS OF SANDSTONE DEPOSITED WITHIN AWKUNANAW AND ENVIRONS IN ENUGU AREA SOUTHEASTERN, NIGERIA

ABSTRACT: An intensive field mapping covering a total of nineteen locations was carried on. This study aimed at determining the geology and depositional environments of sandstone deposited within Awkunanaw and environs in Enugu area. Based on litho-facies the study area is underlain by five lithological units. Integrated granometric (textural analysis) was carried out on eight (8) friable sandstone samples collected from two locations based on their stratigraphic positions. An application of pebble
morphometric analysis was also carried out in an attempt to reconstruct environment of deposition of
the study area. A total of 100 unbroken fresh quartz pebbles were picked at randomly from a distinct
pebble horizon, washed, numbered and analyzed. Morphometric parameters such as size, flatness index,
elongation ratio, maximum projection sphericity, form geometry and oblate-prolate index were
computed. Histogram results of grain size analysis reveal a unimodal and bimodal distribution, which
indicate a strong population mix provenance for the sandstones. Statistics reveals a graphic mean range
from 1.10 to 4.27, sorting range from 0.55 to 1.29, skewness range from -0.07 to 0.29, and kurtosis
between 0.76 and 1.76. The sandstones are false bedded and burrowed, fine to medium grained, poorly
to moderately sorted, positively to strongly negatively skewed and platykurtic to very leptokurtic.
Bivariate and multivariate results reveal that the sediments where deposited in a fluvial to shallow
marine environment. Results show that the coefficient of flatness for the area range from 28.42 to 76.37
while mean values of sphericity and oblate prolate index ranges from 0.52 to 0.89 and -0.009 to 1.116
respectively. These values suggest fluvial origin for the pebbles. Bivariate scatter plots of coefficient of
flatness versus sphericity and sphericity versus oblate-prolate index suggest that the pebbles were
formed in a fluvial environment.