The crustal evolution of the Chatham Rise: Mid-Cretaceous Hikurangi Plateau collision and breakup between Zealandia and Antarctica

• Main Author: Riefstahl, Florian
• Other Authors: Gohl, Karsten, Krastel, Sebastian
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2020
• Subjects: Geophysik; Geosciences; Seismics; Gondwana breakup; 550; 550 Earth sciences and geology; ddc:550; New Zealand; West Antarctica; Antarc*; Antarctica; Antarktis*
• Online Access: https://media.suub.uni-bremen.de/handle/elib/4317; https://doi.org/10.26092/elib/102; https://nbn-resolving.org/urn:nbn:de:gbv:46-elib43171

The breakup of supercontinents is often associated with the changing polarity of tectonic forces from lithospheric convergence to lithospheric divergence. The initiation of the last supercontinent disintegration occurred simultaneously with the breakup of Gondwana. During the mid-Cretaceous, the East Gondwana margin underwent a remarkably fast transformation from a long-lived active subduction margin to a passive continental rifted margin, which led to the separation of southern Zealandia from West Antarctica. Recent studies suggest that the cessation of subduction and onset of extension in southern Zealandia was initiated by the collision and subduction of the thick oceanic Hikurangi Plateau with the East Gondwana subduction zone. However, little is known about the crustal structure of the Chatham Rise, east off New Zealand, although the Chatham Rise played a central role in change in tectonic forces. In particular, the nature of the southern Chatham Rise margin and the SE Chatham Terrace, an area of anomalously shallow seafloor hosting abundant seamounts and guyots, is poorly constrained. To investigate the role of the Hikurangi Plateau collision and subduction on the onset of extension and rifting in southern Zealandia, geophysical data including wide-angle reflection and refraction seismic, multi-channel seismic reflection, and potential field data were acquired during RV Sonne cruise SO246 in 2016. Geophysical data were collected along four profiles across two sub-provinces of the Chatham Rise, the SE Chatham Terrace and adjacent oceanic crust. P-wave velocity and gravity modelling of the new geophysical data yield insights into the crustal structure and therefore the breakup mechanism of the southern Chatham Rise margin, constrain the extent of the Hikurangi Plateau underthrusted beneath the Chatham Rise, and enhance our understanding of the driving forces behind the abrupt change from subduction to rifting along the East Gondwana margin. Along the Chatham Rise, the P-wave velocity models highlight ...