RADIOCARBON DATING OF PALEOSOLS USING SOIL ORGANIC MATTER COMPONENTS

Soil organic matter components of classical humic acid and humic fractions were extracted from two paleosols using 0.1 M Na₄ P₃ O₂:0.1 M NaOH. These fractions were subjected to chemical treatment with 6 M HC1 or 70 per cent HNO, before radiocarbon assay, and their radiocarbon dates were compared with those of similar but untreated fractions, untreated buried soils, and previously published charcoal dates. Hydrolysis of humic acid and humin fractions with mineral acids, particularly 70 per cent HNO₃ led to older radiocarbon dates, comparable to, though slightly older than, those of charcoal derived from the same buried layers. In contrast, the dates of soils and their humic acid and humin fractions before acid hydrolysis were younger and therefore less reliable. The application of this procedure to studies of paleosols in New Zealand is discussed.