An interpretation of the occurrence of diverse types of soils on basalt in Northern NSW and Queensland.

Abstract

This study is confined to a consideration of the genesis of soil patterns formed on basalt in four districts in northern New South Wales and Queensland. The chief features of five distinct groups of soils — probably of great soil group status — recognized in these soil patterns are described. It is concluded that any interpretation based solely on the present climatic conditions is inadequate. It is submitted that, in the patterns described, the different soil groups represented commenced to form during different climatic eras, on a new basalt flow or on a new basalt surface exposed by erosion. In each case the newly initiated soil would be in conformity with the pedogenic environment of the era. For instance, under high rainfall the red soils would be initiated; under low rainfall the black soils would be expected to form. These soils tend to persist unless removed by erosion in spite of subsequent changes in the pedogenic environment. This points to the importance of the time factor in the form of past climatic eras and of geologic erosion in the development of these soil patterns. It is suggested that these pedogenic factors may be important in the development of many soil patterns.