Inaha Terrace deposits: A late Quaternary terrestrial record in South Taranaki, New Zealand

Abstract

A 38 m thick stratigraphic section is exposed in cliffs near Inaha on the South Taranaki coastline. At the base, Quaternary deposits overlie a subhorizontal erosional surface which truncates gently dipping Pliocene muddy sandstones about 2 m above present high–water mark (HWM). This erosional surface is interpreted as a wave–cut surface and forms the Inaha Marine Terrace; its age is estimated to be c. 100 000 years. Immediately verlying the wave–cut surface are marine and beach sands, formally designated as the Inaha Formation. These pass upwards to a thick sequence of volcaniclastic beds with interbedded lignites in which 6 distinct palynological zones (informally named Inaha A–F) are recognised. One of these (Inaha C) contains pollen indicative of a full forest cover dominated by Dacrycarpus dacrydioides and Podocarpus spicatus. The other lignites contain pollen spectra dominated by grasses and shrubs. The lignite containing the microflora representing Inaha C is formally named the Mania Lignite. It represents a warm interstadial period estimated to be c. 80 000 years old.