Late Otiran sedimentation and glacial chronology in the Warwick valley, southeast Nelson

Abstract

Approximately 14 m of sediment are exposed in a road cutting beneath a landslide deposit in the Warwick valley, southeast Nelson, New Zealand. Three radiocarbon dates and 5 pollen spectra were obtained from organic horizons in these sediments. The dates indicate that lacustrine sedimentation predominated from before 17 500 until 14 450 years ago. This was interrupted by a brief period of gravel aggradation between 17 500 and 16 650 years ago, which is attributed to a glacial advance. Vegetation at the site was consistently dominated by Cyperaceae, with some Gramineae, suggesting a bleak, treeless landscape. Correlation of this information with other radiocarbon-dated sites indicates the need for some revision of the chronology of the late Otira Glaciation. A late phase of the Kumara 2₂ advance occurred between 17 000 and 16 000 years ago, and the Kumara 3₁ advance did not occur until after about 15000 years ago. The end of the Otira Glaciation probably occurred between 13 000 and 12 500 years ago.