Podzol development in a holocene chronosequence .1. Moruya Heads, New South-Wales

Abstract

Calcareous sands (Fluvisols/Regosols) and Podzol soils of at least seven different ages (0, 2500, 3000, 5000, 5800, 6200 and 6500 calendar years) form a soil chronosequence in the prograded beach-ridge plain near Moruya Heads, on the south coast of New South Wales. Ages of the soils were determined by radiocarbon dating of marine shell deposited with the sediment. The soils range from undifferentiated quartz sand mixed with marine shell debris at the youngest site, to well developed podzols with pronounced AI, A2 and iron-humus B horizons at the oldest sites. Age trends are evident in a range of physical and chemical soil properties, the most significant of which are: an increase in the thickness of the A2 and B horizons with a concomitant decrease in C horizon thickness; a decrease in Munsell colour chroma in the A1 and A2 horizons and an increase in B horizon chroma; a fall in the pH of all horizons (particularly in the younger soils); an increase in depth to the leaching front of marine shell carbonate; the progressive leaching of HC1-extractable manganese, calcium, magnesium and sodium from the soil profiles; and the progressive development of the A2 and B horizons in terms of HC1-extractable iron and aluminium.