The lower Miocene Waitemata Group on Puketotara Peninsula has been formally divided into three formations: (a) the proposed Timber Bay Formation (?Waitakian-Otaian) composed mainly of thinly interbedded sandstones and mudstones, an intraformational conglomerate, and a channel-fill deposit; (b) the Pakaurangi Formation (Otaian-?Hutchinsonian) containing sandstones and pebble bands of the Hollands Member, richly fossiliferous silty sandstones locally intruded by basalts, all belonging to the Pakaurangi Member, and sulphurous, sandy siltstones of the Funnel Member; and (c) the proposed Motuouhi Formation (?Hutchinsonian) consisting of dark brown vitric tufts. Also included in the Waitemata Group is the informal Waipahihi formation which overlies the Motuouhi Formation.