Use of macro‐ and micromorphological data in soil stratigraphy to elucidate surficial geology and soil genesis

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Abstract
Recognition of time as an important soil‐forming factor suggests the importance of soil stratigraphy in studies of soil genesis and history of landscape development. Some of the principles of recognizing and ranking soil‐stratigraphic units are considered especially in the context of Butler's (1959) K cycle theory. Soil‐ (and rock‐) stratigraphic units are recognized in vertical sections by interpretation of the form of depth functions of morphological features or analytical data, or the presence of characteristic soil features, in terms of hypotheses of soil formation and of sediment transport, deposition and diagenesis. Confirmation, and sometimes modification of units recognized in this way may depend on laterally extensive studies, applying accepted stratigraphic criteria concerning superposition and relationships of units. The technique for recognition in a vertical section is illustrated by a number of Australian examples. The aim in soil‐stratigraphic studies is to recognize and rank soil‐stratigraphic units, not individual soil profiles, so, since soils vary laterally, care is needed in selecting type sites and the soil variation within a unit must be recognized. Some of the aspects of recognizing and ranking soil units are illustrated by studies from a number of situations involving different sequences of soils for each of which different criteria are used. At present there is no sound basis for correlation between these different sequences by comparative morphological or analytical data, so correlation depends on field data and/or isotopic dating. Within each sequence, however, and even between some sequences, there is reason to believe that soil‐stratigraphic units can be ranked broadly on their ‘degree of development’.