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Eocene to Miocene tectonostratigraphic evolution of northwest New Zealand

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thesis
posted on 2023-09-26, 23:58 authored by Orr, Damian

Reinga Basin is located northwest of New Zealand, along strike structurally from Northland and has a surface area of ~150,000 km². The basin contains deformed Cretaceous and Cenozoic strata, flat unconformities interpreted as sea level-modulated erosion surfaces and is intruded by volcanics. Persistent submarine conditions and moderate water depths has led to preservation of fossil-rich bathyal sedimentary records. This thesis presents the first seismic-stratigraphic analysis tied to dredged rock samples and recent International Ocean Discovery Program (IODP) drilling. The Cenozoic tectonic evolution of Reinga Basin comprises four main phases. (1) Folding and uplift from lower bathyal water depths occurred at 56-43 Ma along West Norfolk Ridge to produce wave ravinement surfaces. This phase of deformation in Reinga Basin pre-dates tectonic events onshore New Zealand. (2) Basin-wide 39-34 Ma compression and reverse faulting exposed early to middle Eocene strata at the seabed. This phase of deformation is also observed farther south in Taranaki. (3) Oligocene uplift is recorded by late Oligocene shallow-water fauna at Site U1508, and led to a 6 Myr hiatus (34-28 Ma) associated with flat wave ravinement surfaces nearby. The unconformity is temporally associated with: normal faulting near West Norfolk Ridge that created topography of Wanganella Ridge; onset of Reinga Basin volcanism; and emplacement of South Maria Allochthon. Thin-skinned deformation and volcanism post-date thick-skinned reverse faulting and folding. The end of reverse faulting near South Maria Ridge is determined from undeformed Oligocene strata that have subsided 1500-2000 m since 36-30 Ma. (4) During the final phase of Reinga Basin deformation, South Maria Ridge subsided ~900-1900 m from middle shelf to bathyal depths from 23-19 Ma. Deformation migrated southeastwards, culminating in Northland Allochthon emplacement (23-20 Ma) and onshore arc volcanism at 23-12 Ma. Eocene onset of tectonic activity in northern New Zealand is shown to be older than previously recognised and it was broadly synchronous with other events related to subduction initiation and plate motion change elsewhere in the western Pacific.

History

Copyright Date

2019-01-01

Date of Award

2019-01-01

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

CC BY-NC-ND 4.0

Degree Discipline

Geology

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Masters

Degree Name

Master of Science

ANZSRC Type Of Activity code

3 APPLIED RESEARCH

Victoria University of Wellington Item Type

Awarded Research Masters Thesis

Language

en_NZ

Victoria University of Wellington School

School of Geography, Environment and Earth Sciences

Advisors

Sutherland, Rupert