Weathering and soil development on a sequence of river terraces

Abstract

Five soil profiles on alluvial terraces in the Macleay River Valley, N.S.W., have been studied to determine changes in soil development with increasing age. The criteria used were mainly macromorphology, micromorphology (basic fabric, evidence of weathering of lithorelicts and biotite, and depth functions of illuviated clay), depth functions of grain-size distributions, and clay mineralogy. The evidence suggests that the four youngest soil profiles represent successive stages of profile development by weathering for the most part and, to a lesser extent, formation of an horizon of illuviated clay; data for the oldest soil indicate a different history of profile development.