The study area is between latitude N04o59’0”and N04o 59′ 30” North and longitude E005o47’0”and E005o 48′ 30” East of the primemeridian and is within the freshwater swamps, back-swamps, deltaic plainalluvium and meander belt of the recent Niger Delta (Fig. 1). The area is lowlying with dense vegetation, criss-crossed by an anastomosing network of riversand creeks. The rivers and creeks arecharacterised by the occurrence of natural levees on both banks, behind whichoccur vast areas of back-swamps.
The banks of the creeks and rivers comprisefirm sandy silty clay soil, and are generally less than 3 m in height. Atspring tide, the swamps are submerged by up to 0.5 m in places.
At neap tides,however, the high water barely covers the top of the banks. The present day Niger Delta is due to build-up of fined grainedsediments eroded and transported by the River Niger and its tributaries,a process which started in the Eocene. The geologic sequence of the NigerDelta consists of three main Tertiary subsurface lithostratigraphic units 10namely from bottom to top are Akata, Agbada and Benin Formations. The BeninFormation consists of either a relatively uniform lithology or an alternatingsequence of sand, silt, clay-peat or sand-silt-clay mixtures, with the clay andpeat increasingly more prominent seaward. These lithostratigraphic units areoverlain by various types of Quaternary deposits. Sand and gravel depositsoccur within the Quaternary deposits of the Niger Delta 11. Studies by 12,13and 14 revealed that the sediments were deposited under the influence offluctuating Pleistocene eustatic sea levels.
Existing borehole records show awide occurrence of sand in the Niger Delta 11. Sand deposits are usuallyoverlain by clayey sand or peaty clay that vary from less than 1 to 10 m thick.11 reported that the boundary is usually sharp but may be occasionallygradational.