A late Miocene marine, massive fossil-rich, rock-fall/avalanche deposit, >42 m thick (base unexposed) and mud-flow and debris-flow deposits, commonly 0.2–4 m thick, are present adjoining and near to either margin of a 12 km long segment of the NE-trending Waihoki Fault/fault zone, near Pongaroa, North Wairarapa, North Island, New Zealand. The Waihoki Fault/fault zone lies in the outboard part of the onland part of the forearc. It forms the western margin of the Tawhero Basin, a forearc basin overlying a subducting Pacific plate, during 6.6–25 Ma. The basin had a partly dextral transpression history (especially in the Late Miocene) but the amount of dextral displacement along the Waihoki Fault/fault zone is unknown. It is likely that lightly indurated fossil-rich, rock-fall, mud-flow and debris-flow deposits were derived from the tops of fault slivers that were pushed upwards along the Waihoki Fault/fault zone during dextral faulting to reach the neritic zone.
