Seismic stratigraphy and structure of the Northland Plateau and the development of the Vening Meinesz transform margin,SW Pacific Ocean |
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| Authors: | R H Herzer B W Davy N Mortimer P G Quilty G C H Chaproniere C M Jones A J Crawford C J Hollis |
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| Institution: | (1) GNS Science, 1 Fairway Drive, Avalon, Lower Hutt, 5040, New Zealand;(2) GNS Science, 764 Cumberland Street, Dunedin, 9016, New Zealand;(3) School of Earth Science, University of Tasmania, Hobart, TAS, 7001, Australia;(4) Research School of Earth Sciences, The Australian National University, Acton, ACT, 0200, Australia |
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| Abstract: | The Northland Plateau and the Vening Meinesz “Fracture” Zone (VMFZ), separating southwest Pacific backarc basins from New
Zealand Mesozoic crust, are investigated with new data. The 12–16 km thick Plateau comprises a volcanic outer plateau and
an inner plateau sedimentary basin. The outer plateau has a positive magnetic anomaly like that of the Three Kings Ridge.
A rift margin was found between the Three Kings Ridge and the South Fiji Basin. Beneath the inner plateau basin, is a thin
body interpreted as allochthon and parautochthon, which probably includes basalt. The basin appears to have been created by
Early Miocene mainly transtensive faulting, which closely followed obduction of the allochthon and was coeval with arc volcanism.
VMFZ faulting was eventually concentrated along the edge of the continental shelf and upper slope. Consequently arc volcanoes
in a chain dividing the inner and outer plateau are undeformed whereas volcanoes, in various stages of burial, within the
basin and along the base of the upper slope are generally faulted. Deformed and flat-lying Lower Miocene volcanogenic sedimentary
rocks are intimately associated with the volcanoes and the top of the allochthon; Middle Miocene to Recent units are, respectively,
mildly deformed to flat-lying, calcareous and turbiditic. Many parts of the inner plateau basin were at or above sea level
in the Early Miocene, apparently as isolated highs that later subsided differentially to 500–2,000 m below sea level. A mild,
Middle Miocene compressive phase might correlate with events of the Reinga and Wanganella ridges to the west. Our results
agree with both arc collision and arc unzipping regional kinematic models. We present a continental margin model that begins
at the end of the obduction phase. Eastward rifting of the Norfolk Basin, orthogonal to the strike of the Norfolk and Three
Kings ridges, caused the Northland Plateau to tear obliquely from the Reinga Ridge portion of the margin, initiating the inner
plateau basin and the Cavalli core complex. Subsequent N115° extension and spreading parallel with the Cook Fracture Zone
completed the southeastward translation of the Three Kings Ridge and Northland Plateau and further opened the inner plateau
basin, leaving a complex dextral transform volcanic margin. |
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| Keywords: | Northland Plateau Southwest Pacific tectonics Vening Meinesz Fracture Zone New Zealand continental margin South Fiji Basin Three Kings Ridge Transform margin |
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