The Geochemical Assessment of Sub Surface Coastal Plain Clastic Deposits of Eastern Dahomey, Basin around Lagos Area, South West, Nigeria

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Author(s) Fakolade, O. R | Obasi, R. A.
Pages 300-307
Volume 1
Issue 6
Date June, 2012
Keywords Coastal Plain Sand, Dahomey Basin, Provenance, Lithofacies, Geochemical composition

The subsurface coastal plain clastic deposits of Eastern Dahomey Basin around Lagos area was studied using the geochemical analytical method. The investigation determined the distribution pattern of the facies, identified their provenance, and depositional history. Ditch cut samples were collected at every three [3] meters from five [5] different boreholes with their depth of drilling as follows: [AGB – 162.0 meters, KJA – 168.0 meters, VI – 210.0 meters, IKY – 222.0 meters and AJ – 225.0 meters respectively]. Each borehole was subdivided into litho units. Field studies and geochemical composition were conducted to characterize each unit identified. Based on the above parameters, four lithofacies and subfacies were recognized as follows: Sandstone, Siltstone, Mudstone and Clay facies. Geochemical studies revealed that Sio2 has high content [ 80%] and chemical maturity index [CMI] of 12.5% for both sandstone and siltstone facies. This is attributed to the acidic plutonic igneous rocks. The mineralogical analysis revealed an average of 95.8% of quartz, 2.64% of feldspar and 1.5% of rock fragments an indication that the sandstone and siltstone facies are of quartz arenite. The lithostratigraphic facies established the correlation of various units and delineation of the environment of deposition as fluvitile.

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