Components of saturated zone thickness in a Nigerian Basement Complex regolith / Les constituants de l'épaisseur de la zone saturée dans un complexe très altéré du socle au Nigeria

Abstract

ABSTRACT This study reveals that the thickness of the saturated zone in the regolith of the Middle Osun Valley, a deeply weathered Basement Complex area in southwestern Nigeria, consists of three components: regional, local and random. The regional component, optimally described by a quadratic trend surface equation, constitutes about 83% of the gross spatial distribution. Residuals from the quadratic surface are separable into predictable “local deviations” and unpredictable random residuals. The irregular contour of the basal rock surface and the differential erosion of the regolith account largely for the occurrence of the local deviations. The local component, about 16% of the gross spacial distribution, is adequately described by a conventional regression equation in which the independent variable is weathering depth. A linear combination of the quadratic trend surface equation and the ordinary regression equation yields the optimum prediction equation for the gross spatial distribution. About 99% of...