Understanding rates of tectonic-magmatic deformation at Lake Taupō and the Taupō-Reporoa Basin

In December 2020 a team of ECLIPSE scientists spent a week in the field examining faults and displaced paleoshorelines north of Lake Taupō. As part of a broader investigation examining magmatic-tectonic deformation in the region over the last ~25,000 years, the purpose of this research was to ground-truth the locations of newly interpreted faults and paleoshorelines from recently acquired high-resolution Lidar data, and identify key sites for future trenching and ground penetrating radar analyses. In all, this project will provide revised constraints on the rates of faulting in the Reporoa basin and in the Taupō Fault Belt, while also deconvolving the extent to which vertical ground displacements in the region are controlled by magmatic and/or tectonic processes.

Two key field sites were identified, which will form a critical component of the MSc dissertations for Yaasameen Shalla (Victoria University of Wellington) and Madisen Stewart (University of Auckland). A potentially active fault close to Reporoa township was identified using a 1 m digital elevation model derived from Lidar data, and landowner permission has now been granted to build high-resolution digital surface models and undertake ground penetrating radar analyses and paleosesimological trenching of this fault in May. Additional investigations of a N45°E-striking fault in the Kaingaora area will help confirm fault activity in this area and understand the kinematics of the Reporoa-Kaingaroa tectonic block with respect to the Taupō Rift and the North Island Dextral Fault Belt.

Whakaipo Bay was identified as a key locality for examining the relative displacement histories of the Taupō paleoshoreline that formed immediately after the 232 AD eruption. Analysis of this shoreline will reveal fault displacements along the Taupō fault belt and potential ground deformation associated with the changing state of the Taupō magma system for the last ~1,800 years. Drone surveys and ground penetrating radar analyses are currently planned for Whakaipo Bay in 2021, and the investigations at Reporoa Basin and Whakaipo Bay will be led by Pilar Villamor (GNS Science) and James Muirhead (University of Auckland).