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The Neogene seismic stratigraphy and uplift history of the Otago Shelf, New Zealand

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posted on 2021-11-14, 12:31 authored by Clark, Michael

The Otago continental shelf is a prospective petroleum area on the east side of the South Island New Zealand. During the Neogene it evolved from a post-rift to passive margin as giant progrades extended eastward across the shelf, fed by tectonic uplift and erosion of the Southern Alps to the west. Seismic reflection profiles reveal an uplifted limestone horizon near the Dunedin Volcano. This may be caused by a buoyant load under the lithosphere and can be spatially and temporally linked to the Dunedin Volcano and geophysical anomalies in the area.  This thesis utilises 2D and 3D seismic data to map Neogene sequence boundaries over the Otago Shelf. Seven such sequence boundaries have been mapped based on distinctive seismic characteristics above and below these surfaces. These surfaces have been tied to nearby petroleum and Integrated Ocean Drilling Project wells using biostratigraphic data and then used to generate a series of isopach and depth maps that document the Neogene evolution of this margin. The maps depict the deposition of Neogene sediment and provide age constraints to structural events in the basin such as the uplift near Dunedin and fault movement on the Endeavour High.  The maps are then used to develop a lithospheric flexure model where uplift is interpreted to have been caused by asthenospheric upwelling beneath Dunedin. The model provides insight into the conditions that led to the flexure of the lithosphere, specifically the elastic thickness of the plate and the magnitude and depth distribution of buoyant intrusive material that fed the Dunedin Volcano. Asthenospheric upwelling explains elevated heat flow around Dunedin and would result in enhanced petroleum maturity. This highlights the potential for petroleum generation in source rocks immediately offshore from Dunedin.

History

Copyright Date

2014-01-01

Date of Award

2014-01-01

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Petroleum Geoscience

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Masters

Degree Name

Master of Science

ANZSRC Type Of Activity code

970104 Expanding Knowledge in the Earth Sciences

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

Stern, Tim; Browne, Greg