Environments during the Kaihinu Interglacial and Otira Glaciation, coastal north Westland, New Zealand

Abstract

Shoreline gravel of a 47 m raised beach 15 km north of Greymouth, north‐west South Island, is overlain by 6 m of lagoonal deposits, beginning with fine organic silts from which pollen records the replacement of an early podocarp‐hardwood forest by Nothofagus‐podocarp and then by Nothofagus forest. Plant macro‐remains, including Dacrydium cupressinum (rimu), Nothofagus menziesii (silver beech), N. truncata (red beech), and N. solandri var. cliffortioides (mountain beech), clarify the nature of these forests. Radiocarbon dates >50 000 ¹⁴C yr BP and comparison with other north Westland sequences lead to correlation with the early Kaihinu (Last) Interglacial, and assignment to MIS5e and 5d. Locally overlying are 12 m of interbedded slope deposits and alluvial gravel, together with seven organic silt layers (Bed A down to Bed G). Leaves of Nothofagus menziesii were recovered from Bed G and N. solandri var. cliffortioides from higher layers. Bed B shows a significant Poaceae maximum. Radiocarbon dates from Beds G and E are 42700 ± 1300 and 22280 ± 150 ¹⁴C yr BP, respectively. The sequence represents much of the Otira (Last) Glaciation, MIS3 and MIS2. The persistence of trees and shrubs at this coastal site is consistent with the inference of closed canopy forest from a site near Westport, but contrasts with the dominance of Poaceae and Cyperaceae at previously studied inland Otira Glaciation sites.

Keywords:

• Kaihinu Interglacial
• Otira Glaciation
• raised beach
• pollen
• vegetation history
• radiocarbon dates
• north Westland