Reassessment of Neogene tectonism and volcanism in North Island, New Zealand

Abstract

Reassessment of North Island Neogene tectonism identifies three shorter, vigorous, tectonic events, which separate three longer periods of relatively consistent tectonic activity and volcanism.

Waitemata Tectonic Event (26–25 Ma) established southwestward subduction beneath Greater Northland, creating the Northland Allochthon, and two belts of subsequent volcanism (23–16 Ma) with the Waitemata sedimentary basin between.

Kiwitahi Tectonic Event (15–14 Ma) terminated Northland volcanism and triggered Coromandel and Kiwitahi volcanism, which migrated southwards in the same two belts. Migration coincided with 200–300 km of transcurrent movement along a now‐abandoned Alpine Fault trace, which also transferred the subduction system, Cretaceous sediments, the East Coast Allochthon, Miocene pumiceous beds, and the East Coast region southward. Before 5 Ma, c. 25° of dextral curvature was imposed on the North Island, and relative tectonic quiescence (with consequent intraplate volcanism) extended southwards through Northland and South Auckland.

Kaimai Tectonic Event (5–2.5 Ma) halted volcanic migration and imposed another 40° of curvature. That caused the rotational rifting of the Central Volcanic Region, which initially tore away progressively along the Alpine Fault trace, creating three successive volcanic zones ‐ newly proposed Mangakino (2+ Ma to 950 ka), newly proposed Manawahe (950 to 400–350 ka), and previously named Taupo (400–350 ka to today).

Keywords:

• Alpine Fault
• North Island
• tectonics
• volcanism
• Northland Allochthon
• East Coast Allochthon
• Central Volcanic Region
• Mangakino Volcanic Zone
• Manawahe Volcanic Zone
• Taupo Volcanic Zone
• Marshall Volcanic Belt
• Searle Volcanic Belt
• North Island Dextral Fault Belt
• new structural names