New Zealand Journal of Geology and Geophysics abstracts

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

David Kear

34 West End, Ohope
Whakatane, New Zealand
email: kear@xtra.co.nz

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

G03035; Received 10 December 2002; accepted 17 September 2003; Online publication date 7 September 2004
New Zealand Journal of Geology & Geophysics, 2004, Vol. 47: 361-374
0028-8306/04/4703-0361 © The Royal Society of New Zealand 2004

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