Pollen analysis of predominantly Last Glaciation samples from the Wainuiomata Drillhole, Wainuiomata, Wellington, New Zealand

Abstract

Pollen analysis of 15 samples from a drillhole sequence at Wainuiomata, near Wellington, has shown that the sediments below the valley floor are predominantly of Last Glaciation age, with only a thin veneer of Holocene preserved. Radiocarbon dates with a maximum age range between 18 700 and 25 200 yr B.P. at 25.7–27.1 m below ground level, and the Kawakawa Tephra (22 600 yr B.P.) at 4 m depth, together suggest either rapid sedimentation (possible) or spurious radiocarbon dates (more likely). A pollen zonation suggests that the sequence is similar to those reported from elsewhere in the Wellington area and that the ages should be well beyond the limit of C‐14 dating. The younger of two major discon‐formities occurs immediately above the Kawakawa Tephra and represents an estimated 8000–10 000 years (late Last Glaciation and most of the Holocene). The older discon‐formity is of unknown duration but occurs above a red‐weathered horizon at 50.9 m, and possibly represents the early part of the Last Glaciation, the Last Interglacial, and probably several other glacial/interglacial cycles. Below the red‐weathered horizon, an enigmatic 10.7 m sequence of highly weathered gravel, with interbedded silt, produced very sparse palynofloras, two of which contain abundant Casuarina pollen. The age and environment are uncertain but the sequence could be as old as late Pliocene and represent a glacial environment.