Late Holocene Depositional Episodes in Coastal New Zealand
- Science and Research Directorate, Department of Conservation, P.O. Box 10-420, Wellington, New Zealand
During the Late Holocene (1800 years BP to the present day) there have been three depositional episodes in coastal sand dune areas: Tamatean (1800 to 450 years BP), Ohuan (450 to 150 years BP) and Hoatan (150 years BP to the present day). Each episode comprised two phases: an unstable phase with a high rate of deposition, followed by a stable phase with a low rate of deposition and soil formation.
For the last 1000 years sand dune areas have been favoured places for human settlement. Despite a growing population, unstable dunes have twice become stable. Soils formed on them at the same times as on river alluvium. During that 1000 years, three quarters of the forest cover was progressively cleared by burning, but there was no apparent correlation with increased instability in sand dune areas. The depositional episodes are therefore considered to be independent of human influence. Their principal cause appears to be climatic, with unstable phases being windy and dry and stable phases less windy and moist.