New Zealand’s offshore sedimentary basins

ABSTRACT

We present new interpretations and mapping that define the distribution, extent, and sediment thickness of 25 primarily offshore sedimentary basins within New Zealand’s Exclusive Economic Zone (EEZ) and Extended Continental Shelf (ECS). These basins cover ∼1.64 million km² of the ∼5.8 million km² (∼28%) of New Zealand’s offshore territory. The sedimentary basins formed in different tectonic settings. Most initially formed during the mid- to Late Cretaceous in either a rift-related setting during Gondwana break-up, or within or atop the paleo Gondwana subduction margin. Others formed due to the onset of mid-Paleogene sea-floor spreading, or are related to Neogene–Quaternary subsidence driven by subduction processes. Slight to significant late Paleogene to Quaternary tectonic overprints are pervasive in basins located within the Hikurangi subduction margin’s deformation zone. Knowledge of the distribution and extent of these basins was refined during the multi-year ‘Atlas of Petroleum Prospectivity’ research programme, which builds upon many decades of previous research. New digital structure, isochore, and paleogeographic maps, along with annotated seismic reflection profiles, have been developed where data coverage has allowed, using a consistent set of age-equivalent seismic horizons tied to the New Zealand Geological Timescale. Maximum total sediment thickness of ∼11 km occurs in Taranaki Basin.

KEYWORDS:

• Zealandia
• Gondwana
• seismic stratigraphy
• sediment thickness
• Cretaceous
• Paleogene
• Neogene
• Atlas of Petroleum Prospectivity
• Exclusive Economic Zone
• Extended Continental Shelf

Acknowledgements

This work draws on the research and outputs from many generations of New Zealand and international geoscientists, who have helped us to understand Zealandia’s place on Earth; we acknowledge their much-valued contributions. We particularly thank our colleagues and mentors Peter King, the late Mike Isaac, Greg Browne, and Chris Uruski for providing the inspiration for the APP research programme. Rob Funnell provided significant technical input and guidance throughout the APP programme. Thanks to Phil Scadden and Andrew Boyes for creating and uploading data to the APP programme area within the Petroleum Basin Explorer web portal. We thank Emerson Paradigm Holding LLC, for use of seismic interpretation software (SeisEarth^TM), and geological modelling software (SKUA-GOCAD^TM), and Zetaware for use of Trinity^TM software. Rinze Schuurmans is thanked for digitising paper copy seismic lines in southwest Zealandia. We are indebted to the many petroleum exploration companies who, over many decades, have provided seismic and well data for use in research programmes such as APP and Te Riu-a-Māui / Understanding Zealandia, and also to the open-file petroleum data system administered by New Zealand Petroleum & Minerals. We gratefully thank the numerous New Zealand Geological Survey, GNS Science, Crown Research Institute, university, and industry colleagues for their decades of much-valued insights and contributions towards understanding New Zealand’s offshore territory. We thank Julien Bailleul, Chris Uruski, and journal editor Lorna Strachan for their constructive reviews of the manuscript, which have improved the focus of this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The descriptions of Zealandia’s sedimentary basins presented in this study have utilised open-file and published datasets, which are cited through the paper. Digital (GIS) palaeogeographic maps, illustrated seismic transects, digital (GIS) seismic depth-grids, and technical reports describing methodologies used during the ‘Atlas of Petroleum Prospectivity’ (APP) programme, are accessible via download from https://data.gns.cri.nz/pbe/, via digital Petroleum Exploration Data Packs distributed by New Zealand Petroleum & Minerals (MBIE; https://www.nzpam.govt.nz/), or by contacting the authors. The APP datapacks include all data presented in figures throughout this paper. A supplemental file providing more detailed descriptions of the sedimentary basins presented in this paper, and ArcGIS shapefiles of sedimentary basin boundaries and sediment thickness (as shown in Figure 2), are available from figshare via https://doi.org/10.6084/m9.figshare.6025748.v1.

Additional information

Funding

The Atlas of Petroleum Prospectivity programme was funded via the New Zealand Government through the Ministry of Business, Innovation and Employment’s (MBIE) Energy and Minerals targeted research fund, Contract C05X1406, to GNS Science. We also acknowledge funding from the Te Riu-a-Māui / Understanding Zealandia programme (MBIE Strategic Science Investment Fund, contract C05X1702), and previously the SSIF-funded Sedimentary Basins, Petroleum Basins, and Geological Exploration of the EEZ research programmes at GNS Science.