Abstract:
The Reinga-Northland Basin is a mid-Late Cretaceous basin whose formation is associated with the southwest Pacific region-wide extension and rifting of the Cretaceous period. It is contiguous with the Taranaki Basin to the south and bound by the parallel Wanganella Ridge and West Norfolk Ridge to the west and the Reinga Ridge to the northeast. The basin extends to the edge of the New Zealand Extended Continental Shelf (ECS). Past studies have focused in detail on the Cretaceous to Miocene evolution of the Reinga-Northland Basin and its place in the regional evolution or its hydrocarbon potential. The aim of this thesis is to provide further understanding to the Miocene to Recent geologic evolution of the Reinga-Northland Basin. Nine high resolution, industry standard 2D seismic reflection surveys and 3 exploration wells are used to perform a seismic stratigraphic interpretation including a seismic facies analysis. Four key horizons (Early Miocene, End Miocene, Mid-Pliocene and Seafloor) have been mapped using the loop-tie method. This created three sequences RN-1 (Miocene), RN-2 (Early Pliocene) and RN-3 (Mid-Pliocene to recent). Architectural elements are identified from the seismic facies analysis. These elements are Gradient change (i.e. a break in slope), Erosional Slides, Canyons/Channels and Levees, Mounds/Lobes, Contourite drifts, Sheets, Hiatuses/Erosional plains, and Tectonic features. The main source of sediment into the Reinga-Northland Basin is terrigenous/clastic with fluctuating volcaniclastic input from Miocene and Early Pliocene volcanoes. Miocene depocentres move from the western side of the basin to the southern section of the basin in the Mid-Pliocene to Recent. All of these elements are used to interpret relative sea level changes and a local sea level curve is created. In the Miocene, the sea level follows a similar trend to the global curve but Pliocene to Recent deposits show local variation indicating the influence of subsidence, climate and tectonic activity increased in the younger units.