Spatial distribution of chemical weathering intensity on an acid hillslope

This paper investigates the spatial distribution of soil pH, clay content, and clap mineralogy on a hillslope (Bicknoller Combe, Somerset, UK) in orde r to identify lateral and vertical variation of chemical weathering intensi ty associated with a podzolic catena. Despite a steep slope gradient and a clear catena on the study slope, active chemical weathering is mostly limit ed to upper soil horizons down to about 40-50 cm soil depth, below which th roughflow causes lateral differentiation of soil pH and clay content along hillslope profiles. The depth of the active weathering zone becomes deeper along the upper part of a hillslope hollow in which acid throughflow conver ges from adjacent spurs, while an accumulation of clay is observed in the s ubsurface layers of the lower hollow. The intensity of chemical weathering identified Ly the transformation sequence of mica correlates well with the evolutionary sequence of podzolisation in the upper soil horizon; this enab les the spatial variation of chemical weathering across the slope to be ass essed. The results show chat more adequate consideration of both catena and horizon development is necessary in order to understand the longterm patte rn of chemical denudation on hillslopes.