Studies in pedogenesis in NSW. 5. The Euchrozems.

Abstract

A study has been made of certain red soils overlying basalt around Inverell, N.S.W., that are distributed in a complex manner amongst the black soils of chernozemic character considered to be the climax soils from basalt under the present climate. The red soils are sufficiently distinct from related soils to merit separation as a new soil group — the euchrozems. The euchrozems are shown to be affected by residual leached soils of a previous wetter climate, but are not merely relics. Laterite residuals, which are relics of a former period, are found in perched positions as a capping on most of the euchrozem catenas. The euchrozems are considered to be derived partly from basalt weathering under present-day conditions and partly from the relics of the former soils, the latter distributing sesquioxide by movement down the catena. Evidence for the conversion of euchrozems to chernozemic soils is shown, and the term "reversion" applied to this process, since it constitutes a reversal of the weathering sequence. A series of stages from the euchrozem catena to the chocolate/chernozem catena is described, which together with the occurrence of two distinct basalt flows, the upper overlying laterite on both basalt and other rocks, affords an adequate explanation of the complex distribution of the soils.