Environmental Reconstruction and Maturity Assessment of Beach Sand: Insights from the Sapele Bypass, Benin Region, Nigeria

Abstract

The Beach sand, Obedoluogbeyi and Idogbo communities along Sapele bypass in Benin Region, Nigeria were studied for environmental and maturity indices. Forty (40) samples were collected and experimentally analysed for textural characteristics heavy minerals composition, pebble morphology and petrographic thin section.
The examination of heavy minerals showed that the major deposit of heavy minerals was opaque. The graphic mean (average 1.542) revealed that medium to coarse sand size sediments predominated which are moderately to well sorted (average 1.141), typical of Continental paleo-environment. The graphic skewedness (average 3.445) typifies a period of a balance between erosion and deposition of the sediments with the majority of the sediments being substantially coarsely skewed and a small amount of strongly finely skewed sediments. In the graphic kurtosis (3.64), are consistent with mesokurtic to leptokurtic sand grains, characteristic of an intermediate to high energy ancient fluvial depositional environment. The sand was compositionally mature (Qtz >90%), mineralogical mature (MMI average = 18.66) and chemically immature sub-mature (ZTR = 70.10). The ancient environment of the deposition from the average of the sorting value is typical of a continental origin. This finding is authenticated by the environmental discrimination plots which also confirm a continental environment of deposition for the coastal plain sand. The fluvial or continental origin indicates past river processes, which helps to reconstruct regional paleoenvironment. Textural and compositional maturity suggests significant transport and sorting by water. The mineralogical maturity provides insights to source rock weathering or recycling. Overall, understanding the origin and maturity, guides exploration strategies