A soil catena on weathered basalt in Queensland

Abstract

Deep weathering in the upper layers of basalt flows in central Queensland led to the deveIopment of lateritic profiles with a surface cover of leached red clay soils overlying ferruginous and mottled zones. Subsequent erosion and bevelling of the weathered mantle left small residuals of the old surface and exposed the underlying weathered zones. In places the mantle was completely removed to uncover fresh rock. A soil catena comprising six zones with associated discrete plant communities developed in these landscapes. Soil differences are related to variations in the intensity of weathering of parent materials and the leaching, translocation, and precipitation of differentially soluble and mobile constituents of the parent rock. The sequence of clay minerals is kaolinite -->kaolinite + randomly interstratified material + montmorillonite --> montmorillonite. The distribution of the plant communities is closeIy associated with variations in soil properties, particularly those which affect water relationships.