A QUANTITATIVE PALYNOSTRATIGRAPHY OF THE MIOCENE MANUHERIKIA GROUP, NEW-ZEALAND

A quantitative palynostratigraphy is presented for the Manuherikia Gro up, New Zealand. Six stratigraphic sections were studied from the nort hern Manuherikia basin where the relative proportions of six pollen ta xa were compared: Nothofagus 'brassii type', Nothofagus 'fusca type', Casuarinaceae, Myrtaceae, Arecaceae, Asteraceae, and Chenopodiaceae. A consistent order of dominance is apparent and zone boundaries are ere cted based on dominance of the latter five taxa over that of Nothofagu s 'brassii type'. Four new zones are proposed: the Nothofagus 'brassii type' Zone, the Arecaceae-Myrtaceae Zone, the Casuarinaceae Zone, and the Asteraceae-Chenopodiaceae Zone. The latter is essentially a redef inition of the Chenopodipollis chenopodiaceoides Zone of Mildenhall an d Pocknall. Correlation with the International time scale is attempted : the N. 'brassii type' Zone is Early Miocene, while the base of the C asuarinaceae Zone or the Asteraceae-Chenopodiaceae Zone may correlate with major global cooling recognised at approximately 14 Ma.