Some aranuian (postglacial) organic deposits in the south eastern Ruahine Range, North Island, New Zealand, investigated by palynological methods : a thesis presented in partial fulfilment of the requirements for the Degree of Master of Science in Geography at Massey University

Abstract

Palynological methods have been used to investigate Aranuian organic deposits in the south eastern Ruahine Range. The relevant literature was reviewed. Six profiles from five sites ranging in altitude from 80 to 1050 metres and from 13,300 years B.P. to present were sampled and the pollen analysed. Investigation of the palaeoecology of each site included the geomorphology, stratigraphy, present vegetation and pollen rain where relevant. The pollen data as percentages of several pollen sums was presented in pollen diagrams, statistically analysed and an interpretation suggested. An investigation of pollen rain in the Kahuterawa Valley in the Tararua Range and on Mount Ruapehu was made to obtain information on present podocarp-broadleaf forests and about Weinmannia racemosa in particular. The results indicated a succession of dominants, including W. racemosa over a period of up to 1000 years. This information was used in interpreting the pollen spectra of the fossil sites. All sites were reviewed as part of an Aranuian series. It was concluded that a climatic change from a drier cooler climate to a warmer moister one occurred between 13,300 ± and 10,650 (provisional date only). A more equable climate than at present possibly occurred between 3200 ± and 3770 ± with fewer frosts and droughts.These findings are in general agreement with those of palynologists at sites in other parts of New Zealand. Other aspects of climatic change erosional history, plant-land relationships and species representation have been discussed. The decline of W. racemosa at the West Tamaki site was part of a natural stage in the life cycle and not caused by the browsing of the opossum.