Crustal evolution of the submarine plateaux of New Zealand and their tectonic reconstruction based on crustal balancing

• Main Author: Grobys, Jan
• Other Authors: Miller, Heinrich, Gohl, Karsten, Huhn, Katrin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2007
• Subjects: Tectonics; marine geophysics; plate-tectonic reconstruction; new zealand; antarctica; seismic refraction/wide-angle reflection; Gondwana break-up; 550; 550 Earth sciences and geology; ddc:550; Bounty Trough; Campbell Plateau; New Zealand; Antarc*; Antarctica
• Online Access: https://media.suub.uni-bremen.de/handle/elib/2433; https://nbn-resolving.org/urn:nbn:de:gbv:46-diss000108692

The last supercontinent fell into pieces with the break-up of Gondwana. In this context, the separation of the microcontinent of New Zealand from Antarctica is a jigsaw puzzle of many pieces. Its parts lay at the convergent margin of East Gondwana, which changed into a divergent margin within a geologically short time. That is why the microcontinent of New Zealand experienced different tectonic regimes and phases of the Wilson cycle. Although it is a good object of investigation due to its changing history, remarkably little is known about the submerged parts of the microcontinent. Knowledge of the magmatic-tectonic development of the submarine plateaux such as Campbell Plateau and Chatham Rise will improve the understanding of the processes that led to the late Gondwana break-up, and, in turn, lead to better reconstructions of East Gondwana, as Zealandia is a key piece in plate-kinematic reconstructions of this part of Gondwana.The central part of this thesis deals with the separation process of Zealandia from Antarctica leading to an improved reconstruction of New Zealand with emphasis on the submarine plateaux. Bounty Trough separating Chatham Rise from Campbell Plateau, and the Great South Basin separating Campbell Plateau from the South Island are investigated with seismic refraction and reflection methods. They are interpreted jointly with magnetic and gravity data. The results of crustal thickness modelling based on satellite gravity data are combined with existing information about crustal thickness of Zealandia. With these data, a crustal thickness grid is calculated which creates the basis for a novel technique for plate-kinematic reconstructions in areas of crustal thinning and in the absence of magnetic seafloor anomalies. This reconstruction consists of crustal balancing to compensate for extension within basins and troughs.The seismic refraction and reflection survey across the Bounty Trough shows a strongly thinned crust in the trough. Zones of high P-and S-wave velocities were found in the lower ...