One hundred pollen grains and spores, recovered from a single sample of in situ silica sinter from the Te Kopia geothermal field, include some from a podocarp forest that grew in a temperate, frost-free climate, unlike that of today, as indicated by the presence of Ascarina. Also present are pollen From taxa introduced within the last 100 years. Ascarina has been absent from the area since at least 1800 B.P. and its presence in the sinter indicates that alkali chloride waters discharged at the surface of Te Kopia before 1800 B.P., and possibly before 3500 B.P. Although palynology is a powerful tool to place age limits on fluctuations in the shallow hydrology of geothermal fields, interpretation must be moderated by considering the present flora and also changes in both local and regional flora, habitat and climate. (C) 2000 CNR.