The distribution and pedology of soil mosaics, Barossa District, South Australia

Abstract

Black earths and Australian brown earths occur in ways contrary to normal expectation in the red brown earth zone of southern Australia. The soil pattern is an intimate fine-grained mosaic of the three great soil groups changing within a few yards from one to another in an erosional landscape and quite out of accord with the underlying Precambrian metamorphic rocks. Field studies reported here ascribe the black earths to thin intermittent remnants of a lacustrine Tertiary clay as parent material, and the brown earths to a mixture of the clay with the normal weathering products of the underlying rocks. A substantial part of the evidence for this is derived from their distribution as a horizontal lamina tracing out a contour band in the mid and upper mid slope topography. There is a nice accordance between the elevations of this band and of an adjacent, elevated, dissected black clay plain. The three soils are everywhere found in places which are consistent with the postulate that their parent materials were put there by processes of erosion, dissection, and redistribution of distinctly separate hill and high plain landscapes.