Summary of the age and paleoecology of the miocene Manuherikia Group, Central Otago, New Zealand

Abstract

Pollen analyses of ten sections through the Miocene Manuherikia Group of Central Otago have confirmed the presence of a number of paleoenvironments previously determined by sedimentological studies. The depositional environments include peat swamps, levees, flood plains, braided channels, permanent and ephemeral lakes, inter- distributary bays, beaches and back swamps. Most localities contain a complex mixture of sedimentary types and a great diversity in the spore-pollen assemblages reflecting a dynamic, constantly changing, local environment caused by a combination of tectonic activity, changing climatic patterns, fire, soil parent material and sedimentary sources. The climate was warm temperate, probably never subtropical, moist and humid, although subject to periodic droughts. Fire played a significant role in some areas as indicated by the abundance of charcoal in some samples. The oldest sediments occur in the east of the study area around Gimmerburn. These sediments fall into the upper part of the Proteacidites isopogiformis Zone of early Miocene (Otaian-Altonian) age. All other sequences through the Manuherikia Group fall into the Tricolpites latispinosus Zone of early Miocene (Altonian and possibly slightly younger) age. Sediments of late Miocene (Taranaki Series) age at some localities are assigned to the Maori Bottom Group.