Rift to Drift on the Edge of Gondwana: Two-Phase Cretaceous–Paleocene Rifting In The Taranaki Basin, New Zealand

Abstract

The Taranaki Basin, located predominantly offshore of western North Island, New Zealand, has a complex geological history. This study focuses on the pre- and syn-Tasman Sea opening rift history through the mid-Cretaceous to Paleocene, utilising new seismic mapping, biostratigraphy, basement cooling ages and paleogeographic reconstructions. Three phases of basin evolution are recognised through the Cretaceous–Paleocene. An early ‘mid’ to early Late Cretaceous rift phase has long been recognised in the Deepwater Taranaki Basin. For the first time, sub-basins with fill related to this rift-phase, are recognised as being widespread in the proximal Taranaki Basin and on the Challenger Plateau. Extension was orientated NE–SW, and related to initial Tasman Sea rifting. Evidence for rapid uplift associated with this rift event may be seen in cooling ages (c. 99 Ma) seen in basement rocks in well Taranga-1. The timing of the end of this phase is not well constrained, but it had ceased prior to 80 Ma, and the onset of seafloor spreading in the Tasman Sea. The orientation and timing of this extensional event is comparable to that observed in the West Coast and Great South-Canterbury basins, consistent with suggestions that this was a Zealandia-wide tectonic event associated with Gondwana breakup. A brief period of uplift and erosion occurred in the proximal Taranaki Basin, and appears to coincide with the deposition of the Taranaki Delta in Deepwater Taranaki. This uplift event led to only small erosional remnants, often tilted and folded, of the early rift-related sub-basins being preserved in the proximal basin beneath Late Cretaceous to Paleocene strata. A later, Late Cretaceous–Paleocene rift phase (c. 80–55 Ma) affected only proximal, especially southern, parts of the Taranaki Basin. This rift phase, also observed in the basins of the West Coast and Western Southland, was mainly confined to western New Zealand and did not affect more distal areas, such as Deepwater Taranaki. Extension was orientated NW–SE to E–W, roughly orthogonal to the first rift phase. This second, more minor, phase of extension led to the formation of a failed rift arm associated with seafloor spreading in the area between the Ross Sea and Zealandia, and was followed by passive thermal subsidence during the Eocene (c. 55–40 Ma). Implications for the regional tectonic evolution, breakup of Gondwana and for petroleum systems are also considered.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015