Geodynamic evolution of the Pacific margin of West Antarctica based on apatite thermochronology

• Main Author: Zundel, Maximilian
• Other Authors: Spiegel, Cornelia, Najman, Yani
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2018
• Subjects: Thermochronology; West Antarctica; Gondwana break-up; upper crustal evolution; basin development; West Antarctic rift system; thermal history modeling; 550; 550 Earth sciences and geology; ddc:550; Antarctic; Byrd; Drake Passage; Elephant Island; Marie Byrd Land; Pacific; Scotia Sea; South Orkney Islands; Thurston; Thurston Island; Antarc*; Antarctica
• Online Access: https://media.suub.uni-bremen.de/handle/elib/1441; https://nbn-resolving.org/urn:nbn:de:gbv:46-00106584-15

The West Antarctic continent formed during most of the Palaeozoic and Mesozoic era by accretion of crustal blocks to form the palaeo-Pacific margin of Gondwana. In the mid Cretaceous, Gondwana break-up was associated with a major change from convergence to extension along the palaeo-Pacific margin, which opened the West Antarctic rift system (WARS) and the Southern Pacific Ocean by separating Zealandia from West Antarctica. Further disintegration of Gondwana led to the separation of West Antarctica from South America by opening of the Drake Passage and the development of the Scotia Sea. Thus, Gondwana break-up and ensuing tectonic movements brought geographic isolation to Antarctica and potentially favoured the onset of glaciation. Extensive ice-cover of West Antarctica is itself one of the main challenges when trying to better constrain the geodynamic evolution since Gondwana break-up that remains poorly understood. This study focussed on western Marie Byrd Land (MBL) and the Thurston Island area which both form parts of the conjugate continental margins of Zealandia. Further investigation was carried out in the area of the South Orkney Islands and Elephant Island group (southern Scotia Sea). To comprehensively reconstruct the thermo-tectonic evolution of the upper 2-5 km of the crust, the main methods utilised in this study were apatite fission track (AFT) and apatite (U-Th-Sm)/He (AHe) thermochronology. Thermal history modelling of both AFT and AHe data was also carried out. For a better understanding of the geodynamic history, selected samples were analysed by means of U-Pb zircon geochronology and hornblende thermobarometry. The oldest thermochronological record was obtained from Carboniferous to Early Cretaceous (meta)igneous rocks of the Thurston Island area. Their AFT ages of 145-92 Ma and AHe ages of 112-43 Ma were integrated in thermal models and show episodes of cooling and reheating since the Late Palaeozoic. These episodes refer to exhumation and back-arc basin development between the Permian and ...