New Zealand’s offshore sedimentary basins

Abstract

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.