Stratal stacking patterns and termination relationships of Upper Cretaceous and Paleogene strata of Aotea Basin, which is at the southern end of New Caledonia Trough and adjacent to Taranaki Basin, are used to infer vertical movements before, during, and after Tonga‐Kermadec subduction initiation. Regional 2D seismic‐stratigraphic units are tied to petroleum exploration wells, including recently drilled Romney‐1. We identify: (a) an uppermost Cretaceous to Paleocene (70–56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea‐level falls; (b) a diachronous deepening of the basin from shelfal to bathyal environments, that progressed northwest to southeast during the early to middle Eocene (53–46 Ma); (c) that was contemporaneous with small‐scale volcanism; (d) a brief phase of middle to late Eocene (46–35 Ma) delta development at the western basin margin (Challenger Plateau) that is evidence for local uplift; and (e) an onlapping sequence deposited since the latest Eocene (35–0 Ma) that requires ∼1,300 m of subsidence at the western margin. Paleogeographic maps and a generalized stratigraphic chart summarize our observations. The Eocene phase of tectonic subsidence, uplift, and diffuse volcanism (53–46 Ma) was a precursor to plate motion at the Cenozoic plate boundary through New Zealand and suggests a causal relationship between prearc subsidence, Tonga‐Kermadec subduction initiation, and plate motion change. Delamination of lower crust beneath Aotea Basin during initial subducted slab formation might explain our observations.

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>