COMPARATIVE SEDIMENTOLOGICAL STUDIES OF THE LAFIA, KEANA AND AWE FORMATIONS WITH REFERENCE TO THE AWGU AND ASU RIVER FORMATIONS

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Date
1980-05
Authors
OHIKERE, CHRISTIANA
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Abstract
The area under investigation is part of the Middle Benue, this region is made up of Cretaceous sediments of marine to fluvio~deltaic environments,, Sedimentation in the Benue valley is believed to be related to the breaking up of South America from Africa, parting the way for a northward transgression of marine waters from the great atlantic The sediments studied are represented by the Lafia, Keana and Awe Formations respectively and also by the Awgu and Asu river shales; these sediments are thought to range in age from Cenomanian to Maastrichtian (Offodile, 1976). Petrological and sedimentological analysis were carried out on the data and samples collected from the field work. The results of sedimentological analysis included granulometric, heavy and light minerals and clay mineral analysis. From granulometric analysis, it was observed that the sandstones were deposited in one as more depositional cycle (Lafia and Awe Formations) or were reworked after deposition (Keana Formation) in certain parts of the studied area. Generally, the sandstones are medium to coarse grained, poorly sorted, and positively skewed. Heavy mineral analysis shows the presence of assemblages of zircon, tourmaline, rutile, staurolite and kyanite, and opaques (iron oxides?). This indicates an igneous-metamorphic source rock for the sandstones. The light mineral analysis shows the presence of quartz and mica, with quartz grains generally being the most dominant mineral. Their morphology indicates a relatively strong weathering conditions and short distance of transportation. Results from the clay mineral analysis shows the presence of kaolinite, illite and chlorite in decreasing order of abundance relatively. These results prove that these sediments under study in the Benue basin owe their origin to the Nigerian basement complex, which is composed of granites, gneisses, and migmatites. These are found to the north and south of the mapped area.
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PRESENTED TO THE GEOLOGY DEPARTMENT OF AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF BACHELOR OF SCIENCE (HONOURS) DEGREE IN GEOLOGY MAY, 1980
Keywords
COMPARATIVE,, SEDIMENTOLOGICAL,, STUDIES,, LAFIA,, KEANA,, AWE,, FORMATIONS,, REFERENCE,, AWGU,, ASU,, RIVER,, FORMATIONS,
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