Tectonic subsidence and uplift within Canterbury Basin, South Island, New Zealand

Abstract

ABSTRACT The Canterbury Basin is a portion of the mostly submerged continent of Zealandia that formed along the eastern portion of the Gondwanan front. Based on tectonic subsidence analyses of IODP Expedition 317 boreholes and Clipper-1 well data, we argue for a rapid subsidence event (∼84 Ma to ∼76 Ma) which we interpret as transit away from a region of mantle upwelling. Breakup was followed by thermal subsidence between 76 Ma and 20 or 10 Ma. Sea-level estimates based on our data are consistent with eustatic estimates in the literature between 76 and 30 Ma. From about 7 Ma to 3.8 Ma, there is evidence that over a kilometre of uplift could have occurred within the basin. This uplift event is consistent with earlier suggestions of lower mantle delamination based on local volcanism and the thickness of the lithosphere. Isostatic calculations are consistent with the hypothesis that delamination of some dense mantle lithosphere could account for the uplift seen in our tectonic subsidence analyses.