THE GENETIC ORIGINS OF FOUR REGOLITH PROFILES IN THE GRAHAMSTOWN AREA, EASTERN CAPE, SOUTH AFRICA

The genetic origins of four regolith profiles in the Eastern Cape, South Africa, were explored and defined through field observation and laboratory-based geochemical and mineralogical analyses. Somewhat of a complex evolution is evidenced, with discussion of the findings focusing on two main issues: the formation of distinct soil and weathering horizons, and the formation of stone-lines within the profiles.

The regolith has undergone in situ weathering and pedogenesis in a humid to temperate climate with marked seasonality, resulting in broadly similar 'A-B-C-R' profiles. Generally speaking, eluviation in the upper solum and illuviation in the lowerlying B-horizons is evident. Beneath lies mildly oxidized saprolitic material, which passes down into largely unaltered substratum.

Stone-lines lying at depth within the profiles appear to be polygenetic in nature, with both autochthonous and allochthonous material present. Variations in the nature of the stone-lines are seen to result from the differing intensities of a number of processes, including sheetwash, bioturbation, soil creep and the subterraneous removal of material.

The study's findings are important with regard to landscape analyses and the implications raised by these. Understanding the origins of material as inherent as regolith is crucial in the elucidation of a landscape's development.