The Middle Pleistocene Maitahi Formation, Taranaki, New Zealand: a new formal lithostratigraphic unit

The Maitahi Formation is a regionally extensive, lithologically and texturally distinctive Middle Pleistocene volcanogenic‐sedimentary deposit in western Taranaki, New Zealand that warrants recognition as a formal lithostratigraphic unit. Maitahi strata blanket >360 km 2 of the Taranaki peninsula with up to 270 m of poorly sorted debris‐avalanche, debris‐flow and fluvially reworked andesitic, basaltic–andesitic, quartzo‐feldspathic and pyroclastic deposits. These deposits accumulated on an incised, pedogenically altered Tertiary bedrock surface and are dominated by heterolithologic megaclasts, clasts and matrix derived from subedifice bedrock, Pouakai and possibly Kaitake cone and ring plain sources. Widespread incorporation of subedifice bedrock megaclasts and clasts is attributed to a deep‐seated edifice collapse or collapses that may have been triggered by seismic activity, spontaneous failure or eruptive activity. The Maitahi Formation is defined and characterised using a composite stratotype constructed from exposed surface and subsurface (borehole) reference stratotypes located near the coastal township of Oakura.