The distribution of red, yellow and grey earths in the Torrens Creek area, central north Queensland

Abstract

Red, yellow, and grey earths mantle extensive plains in northern Australia. They have been studied in a semiarid, tropical area at Torrens Creek, some 200-300 km south-west of Townsville, Queensland. An examination of boreholes drilled along transects across these soils shows that the red earths usually occupy the lower slope sites and broad, non-channeled, drainage lines. The yellow and grey earths generally occur at midslope sites or over broadly convex upper regions of the low undulations that rise 10-30 m above the non-dissected parts of the plains. The distribution patterns of the red, yellow, and grey earths cannot be explained by differential weathering of the gently dipping Mesozoic sedimentary rock substrates. Nor can they be attributed to simple, topography-controlled, hydrological regimes in the soils. The distribution patterns of the different soils depend on factors related to the geology and the late Cainozoic geomorphic history of the area. These include the transported or sedentary nature of the soil parent materials, the hydrological regimes of the soils and of the weathered rock substrates, and the depth to the underlying, weathered rock.