A mid Otira Glaciation palaeosol and flora from the Castle Hill Basin, Canterbury, New Zealand

Abstract

A section exposed at the Broken River road cutting in Castle Hill Basin revealed a palaeosol resting on reddish, rusty gravel and beneath 30 m of fresh-looking, grey, glacio-fluvial outwash gravel deposited by a meltwater stream during the Black-water advances of the Waimakariri Glacier. A radiocarbon date >37 000 ± 200 yr B.P. (NZ 7518) was obtained for the palaeosol. Pollen spectra from it are dominated by a herbaceous plant assemblage indicating cold climatic conditions. Redeposited pollen from adjacent Tertiary rocks is also present. The soil appears to have been formed in a marshy habitat soon after the onset of the Blackwater 1 glacial episode (the first cold phase of the middle part of the Otira Glaciation).

Keywords:

• glacial advance
• glacio-fluvial outwash
• radiocarbon date
• herbaceous pollen flora
• cold climate